Background
In the past, various molding systems have typically been provided, including the formation of parts of thermoplastic resins or thermoplastic composites. In vacuum forming, a heated sheet of thermoplastic material (slab) (sheet) of constant thickness is placed over a vacuum mold and a vacuum drawn between the mold and the heated plastic material, wherein the vacuum draws the plastic material onto the mold. Similarly, in compression molding, a block (bump) or sheet of preheated material is pressed between two forming dies that compression mold the material into the desired part or shape.
Previous U.S. patents that use material thermoforming can be seen in four Winstead patents, namely US 4,420,300, US 4,421,712, US 4,413,964, and US3,789,095. Winstead patents US 4,421,712 and US 4,420,300 relate to an apparatus for continuous thermoforming of sheet material, said apparatus comprising: an extruder (extruder) together with a stretching device and a wheel with a die thereon; and a plurality of plug-assist plugs (plug-assist) interconnected to form a rail arrangement having plug-assist features that engage the sheet about a generally circular arc of the wheel surface. The Winstead patent US 4,413,964 teaches an apparatus for continuously extruding and forming molded products from a web of thermoplastic material while continuously separating, stacking and handling the products from the web and regenerating the selvage of the web for further extrusion. The apparatus uses a multi-mode cavity in the configuration of a rotating polygon, on the outer peripheral surface of which the biaxially oriented web is continuously positioned by a biaxially orienting apparatus by means of follower rollers (follower rollers) interfaced with said polygon. Winstead U.S. Pat. No. 3,789,095 is an integrated process for continuously extruding a low density form of thermoplastic material and producing three-dimensional shaped articles from the material.
Howell, U.S. Pat. No. 3,868,209, is a two-sheet thermoformer for making hollow plastic objects from a pair of heat-fusible thermoplastic sheets that are sequentially moved within a common horizontal plane from a heating station to a molding device at a forming station. The hell, jr patent, US3,695,799, is an apparatus for vacuum forming a hollow article from two sheets of thermoplastic material by passing the sheets through a heated zone in spaced relation while positioned between two mold halves. As vacuum is pulled on each sheet to cause the sheet to conform to the shape of its respective mold, the mold halves are brought together, molding a hollow article. U.S. patent No. 5,551,860 to Budzynski et al is a blow molding apparatus for making bottles having a continuously rotating rotary mold while aligning one mold at a time with an extrusion die handle to load the mold. The Hujik patent, US3,915,608, is an injection moulding machine for multi-layer shoe soles, comprising a turntable for rotating a plurality of moulds through a plurality of work stations in order to mould the sole continuously. The Ludwig patent, i.e. U.S. Pat. No. 3,302,243, is another device for injection molding of plastic shoes. The Lameris et al patent, US3,224,043, teaches an injection molding machine having at least two molds that can be rotated to align with a plastic material injection nozzle. The vismura patent, US patent 4,698,001, is a machine for manufacturing molded plastic motorcycle helmets that uses compression-type molds in which a pair of mold halves are switched between a plurality of positions. The Krumm patent, US 4,304,622, is an apparatus for producing thick thermoplastic synthetic resin slabs (slab) that includes a pair of extruders, each of which extrudes a strand of half-sheet into a respective roll assembly. The roll assembly has a final roll forming a consolidation nip (nip) therebetween within which the two half-plates are joined together.
Composite materials and other processes
Composite materials (composite) are materials formed from a mixture of two or more components that result in a material having properties or characteristics superior to those of a single material. Most composite materials comprise two parts, namely a matrix component and a reinforcement component. Matrix components refer to materials that hold the composite together, and they are generally not as stiff as the reinforcement components. These materials are molded at elevated temperatures under pressure. The matrix encapsulates the reinforcements in place and distributes the load among the reinforcements. Since the reinforcement is generally harder than the matrix material, the reinforcement is the primary load-bearing component within the composite. The reinforcement may take many different forms ranging from fibers to fabrics, to particles or rods embedded within a matrix forming a composite material.
Composite structures have existed in nature for millions of years. Examination of the microstructure of the bioceramic of wood or shell reveals the presence of composite materials found in nature and indicates that modern composite materials have essentially developed into a mimic structure found in nature. One desirable example of a composite material is concrete. How the reinforcement functions can be appreciated by different forms of concrete. The cement acts as a matrix holding the elements together, while at the same time, the sand, gravel and steel act as reinforcement. Concrete made with only sand and cement is much less strong than concrete made with cement, sand and stone, which is not as strong as concrete reinforced with steel, sand and stone. The matrix material and the reinforcement material of concrete are typically mixed, poured and molded in a forming structure. In the production of parts made of other composite materials, the shape of the composite structure or part depends on the shape or geometry of the mold (mold), die, or other tool used to form the composite structure.
There are many different types of composite materials, including plastic composites. Each plastic resin has its own unique properties that, when mixed with different reinforcements, result in composites with different mechanical and physical properties. The number of possible composites is surprising if the number of plastic polymers present today is considered and this number is multiplied by the number of available reinforcements. Plastic composites are divided into two main categories: thermoset composites and thermoplastic composites.
In the case of thermoset composites, after application of heat and pressure, the thermoset resin undergoes a chemical change that crosslinks the molecular structure of the material. Thermoset parts cannot be remolded once cured. Thermosets are more temperature resistant and provide greater dimensional stability than most thermoplastics because of the tightly cross-linked structure found in thermosets. The thermoplastic matrix composition is not as constrained as a thermoset material and can be recycled and remolded to create new parts.
Common matrix components for thermoplastic composites include polypropylene (PP), Polyethylene (PE), Polyetheretherketone (PEEK) and nylon. Thermoplastics reinforced with high strength, high modulus fibers to form thermoplastic composites have significant improvements in both strength and stiffness as well as toughness and dimensional stability.
Composite materials are used in a wide variety of applications in many industries. Typically, composite materials are used in place of products or multi-component metal structures made of metal alloys incorporating reinforcements or other connectors. The composite provides sufficient strength while reducing weight. This is particularly important in industries like automotive and aerospace where the use of composite materials results in lighter, faster, more energy efficient and environmentally friendly aircraft and automobiles. Composites can also be designed to replace wood, fiberglass and more other traditional materials. The following is a partial list of industries that may have applications using large parts made from thermoplastic composites: aerospace, automotive, construction, home appliances, marine, materials handling, medical, military, telecommunications, transportation, and waste management.
In general, thermoplastic composites, among other attributes, are resistant to corrosion and provide long fatigue life, which makes them particularly attractive to many manufacturers. Fatigue life refers to the time that a part lasts before exhibiting material wear or significant stress and reaching a level that compromises the part's ability to meet specification work. Typically, composite materials are used in applications where it is desirable to reduce the weight of a particular part while providing the strength and other desirable characteristics of existing parts. There are many very expensive parts made of thermoset composite materials. These types of parts are commonly referred to as advanced composite materials and are most used in the military and aerospace industries.
Product development engineers and production engineers believe that thermoplastic composites will play an ever increasing role in modern technology development. New thermoplastic resins have been conventionally developed and more innovative manufacturing methods have been introduced to reduce the costs associated with manufacturing parts made from composite materials. As the cost of manufacturing parts made from thermoplastic composites decreases, the use of thermoplastic composites has become a more viable solution for many commercial and industrial applications.
Existing forming method of thermoplastic composite material
Most commercially available thermoplastic composite manufacturing techniques have evolved from methods for processing thermoset composites. Because these processes are designed for resin systems with much lower viscosity and longer cure times, certain inefficiencies and difficulties continue to plague thermoplastic manufacturing processes. There are several manufacturing methods currently in use that utilize thermoplastic composites, some of the most common processes including: compression molding, injection molding, and autoclaving, all of which can be used to produce "near net shape" parts, i.e., parts that substantially conform to a desired or designed shape after molding. Less common methods for processing thermoplastic composites include pultrusion, vacuum forming, film forming (diaphragm forming), and hot pressing techniques.
Compression molding
Compression molding (compression molding) is by far the most common method now used to commercially manufacture structural thermoplastic composite parts. Typically, compression molding uses a Glass Mat Thermoplastic (GMT) composite comprising a polypropylene or similar matrix blended with continuous or chopped, randomly oriented glass fibers. GMT is made by third party material manufacturers and sold as standard or custom sized flat blanks to be formed. Using such pre-impregnated composites (or prepregs, which is more commonly referred to as such when using their thermosetting equivalents), a sheet of GMT is heated in an oven and then placed on a moulding tool. The two mating halves of the mold tool are closed under great pressure, forcing the resin and fibers to fill the entire mold cavity. Once the part is cooled, it is removed from the mold with the aid of a release mechanism.
Generally, the counter mold tools used for GMT forming are machined from high strength steel to withstand the continued application of high molding pressures without degradation. These molds are often actively heated and cooled to speed cycle time and improve surface finish quality. GMT molding is considered one of the highest-yielding composite manufacturing processes with cycle times between 30 and 90 seconds. Compression molding does not require high capital investment, however, in order to purchase a high load press (2000-3000 tons pressure) and a high pressure die, compression molding is only effective for large production volumes. In the case of lower throughput of smaller parts, the production can be carried out on existing presses with aluminium moulds, saving some costs. Other disadvantages of this process include low fiber percentage (20% to 30%) due to viscosity problems, and the ability to obtain only moderate quality surface finishes.
Injection molding
Injection molding is the most common manufacturing method for non-reinforced thermoplastic parts and is more commonly used for short fiber reinforced thermoplastic composites. Using this method, thermoplastic pellets are impregnated with short fibers and extruded into a closed two box hardened steel tool at an injection pressure typically between 15,000 and 30,000 psi. The mold is heated to obtain high fluidity and then instantaneously cooled to minimize deformation. Using hydrodynamic analysis, a mold can be designed that produces specific orientations of the fibers at different locations, but the injection molded part is typically isotropic. The fibers in the final part are typically no longer than one-eighth (1/8) ", with the maximum fiber volume content being about 40%. This method is called Resin Transfer Molding (RTM) with a slight modification. RTM manufacturing utilizes woven fibers (mattedfiber) placed in a mold that is then filled with resin under high pressure. This method has the advantage of being able to manually orient the fibers and use longer fiber lengths.
Injection molding is the fastest thermoplastic process and is therefore commonly used in high-volume applications such as automotive and consumer goods. The cycle time is between 20 and 60 seconds. Injection molding can also produce highly repeatable near net shape parts. Another advantage is the ability to form around the insert, the bore and the core material. Finally, injection molding and RTM generally provide the best surface finish in all processes.
The process discussed above presents problems due to the size of the required molds and the capabilities of the injection molding machine, with practical limitations on the size and weight of the parts that can be produced by injection molding. Therefore, this method has been dedicated to small to medium size production of parts. From the point of view of structural reinforcement, the most problematic is the limitation on the length of the reinforcing fibers that can be used in the injection molding process.
Autoclave treatment
Autoclave processing is another thermoplastic composite manufacturing process used in the industry. Thermoplastic prepregs and unidirectional fibres or woven fabric are placed on a single-face tool. Several layers of bagging material are placed on the prepreg assembly for surface finishing, to prevent sticking and to enable evacuation when it is placed in an autoclave. Within the autoclave, the composite is heated and placed under pressure to consolidate and crosslink the layers of material. Unlike compression and injection molding, the tool is open-mold and can be made of aluminum or steel because the pressures involved are much lower.
Since the autoclave process is much slower and more labor intensive, it is used primarily for very large, low throughput parts requiring a high degree of accuracy, which is not conducive to being performed on a production line. Significant advantages of this approach include a high fiber volume fraction and the ability to control fiber orientation for specific material properties. This process is particularly useful for making prototypes because the tooling is relatively inexpensive.
Forming method for thermoplastic composite material requiring long fibers
None of the above processes is capable of producing thermoplastic composites reinforced with long fibers (i.e., greater than about 1/2 inches) that remain largely constant during the molding process itself, which is particularly true for the production of large and more complex parts. Historically, a three-step process was used to mold such parts: (1) a third party formulation of a pre-impregnated composite composition; (2) preheating the prepreg material in an oven, and (3) inserting molten material into the mold to form the desired part. This process has several drawbacks which limit the industrial versatility, making it inconvenient to produce more complex large parts with sufficiently enhanced structure.
One disadvantage is that the sheet forming process cannot produce parts with varying thicknesses, or parts that require "deep drawing" of the thermoplastic composite. The thicker the extruded sheet, the more difficult it is to uniformly remelt the sheet through its thickness to avoid problems associated with the structural formation of the final part. For example, a tray with feet projecting perpendicularly from the top surface is a deep-drawn portion of the tray that cannot be molded with a thicker extruded sheet because the formation of the tray feet requires deep drawing of the material in a "vertical plane" and, as such, will not be uniform in the horizontal plane of the extruded sheet. Other disadvantages associated with the geometric limitations of extruded sheets having uniform thickness are apparent and will be described in greater detail below in connection with the description of the invention.
The present invention is directed to a molding system that uses a vacuum or compression mold to produce thermoplastic resin for thermoplastic composite parts that are fed directly into the mold from an extrusion die while a thermoplastic sheet still retains the heat used to heat the resin to a fluid state to form a sheet of material through the extrusion die. The present invention relates to a thermoplastic forming process and apparatus, and in particular to a thermoplastic process and apparatus using a thermoplastic extrusion die having an adjustable gate (gate) for varying the thickness of the extruded material which is molded as it passes through the extrusion die.
A further object of the present invention is a continuous thermoforming system that is fed with a sheet of thermoplastic material coming directly from an extruder forming said sheet onto a mold that can rotate between tables. Thermoplastic material is extruded through an extrusion die that can be adjusted to provide a deviation from a constant thickness plastic sheet to a varying thickness across the surface of the plastic sheet. The varying thickness may be adjusted for any particular forming operation or may be continuously varied as desired. This allows for continuous molding or thermoplastic material having different thicknesses across the extrusion plate and through the molded part to control the mid-portion thickness of the molded part so that the molded part can have thick or thin locations throughout the molded part as desired. The invention is not limited with respect to the size, shape, composition, weight or strength of the desired part to be produced by the extrusion process.
Disclosure of Invention
A thermoplastic molding system includes a thermoplastic extrusion die for extrusion of a thermoplastic slab contoured by adjustable die orifice features, dynamic die settings, for varying the thickness of extruded material at different portions of the extruded slab. The thermoplastic extrusion die has a trimmer for cutting the extruded thermoplastic sheet from the thermoplastic extrusion die. A plurality of thermoplastic molds, which may be vacuum molds or compression molds, are each mounted on a movable platform, such as a rotating platform, for moving the molds one at a time into position to receive the thermoplastic sheets being cut from the thermoplastic extrusion die. Molded parts are formed of a heated sheet of thermoplastic material of varying thickness that is fed from an extrusion die while still hot. A plurality of molds are mounted to a platform that delivers one mold to a loading position for receiving the thermoplastic sheet from the extrusion die and a second mold to a release position for removing the formed part from the mold. The platform may be a shuttle or rotating platform and allows each molded part to be cooled as another molded part receives the thermoplastic sheet. A thermoplastic forming process is provided, the process comprising the steps of: the thermoplastic extrusion die settings are selected in accordance with means for adjusting the thermoplastic extrusion die to vary the thickness of the extruded material passing through the extrusion die at different portions of the extrusion plate. Thermoplastic material is heated to a fluid state and extruded through selected thermoplastic dies that have been adjusted to vary the thickness of the extruded material at different portions of the extruded sheet, cut the extruded thermoplastic sheet with varying thickness to predetermined dimensions, and direct each cut sheet of heated thermoplastic material onto a thermoforming die and mold predetermined parts within the die, whereby molded parts with varying thickness are formed from a sheet of material that is heated during material extrusion.
The "extrusion-forming" process also facilitates the formation of thermoplastic composite structures reinforced with long fibers (greater than about 1/2 inches) because the extruder dispenses the molten thermoplastic composite material through a dynamic die, depositing the material directly onto a lower die that is movable relative to the position of the dynamic die. As used herein, the term "lower mold" refers to the lower mold half of a matched mold into which a thermoplastic material is introduced. Similarly, the term "upper mold" refers to the upper half of a matched mold, in which the desired thermoplastic part is formed when the upper and lower mold halves are joined, i.e., closed. The lower mold may be moved by a trolley to fill the cavity of the mold with varying amounts of thermoplastic composite material. For example, if the cavity defined by the upper and lower dies is larger within a certain horizontal range, the lower die may be slowed to receive more molten thermoplastic composite material in that area. The dynamic die uses flow control elements that alter or regulate the flow of the molten extruded thermoplastic composite material to deliver different amounts of material from each flow control element to selectively deposit material across the width of the lower die in a direction perpendicular to the direction of movement of the lower die. The thermoplastic composite may be molded with as much long fibers (greater than about 1/2 inches) as at least ten percent (10%) to fifty to sixty percent (50% -60%) by weight and have a low fiber breakage. After the molten extruded thermoplastic composite material is deposited onto the lower mold, the trolley is automatically transported into a press that closes the upper mold onto the lower mold to form the composite part.
One embodiment in accordance with the principles of the present invention includes a system and method for forming an article from a thermoplastic material and fibers. The method comprises the following steps: the thermoplastic material is heated to form a molten thermoplastic material while being mixed with the fibers. The molten thermoplastic material and fibers are blended together to form a molten composite material having a desired concentration of fibers by weight and/or volume. The molten composite material is then extruded through a dynamic die to form a specified composite stream and is deposited into the lower portion of the die for forming the article. The lower mold may be discontinuously moved at varying speeds in space and time while receiving the flow of composite material to deposit thereon a predetermined amount of molten composite material that precisely conforms to the amount of material required within the mold cavity of the lower mold. An upper portion of the mold may be pressed against the predetermined amount of molten composite material and closed over a lower portion of the mold to form the article.
One aspect of the present invention provides a molded thermoplastic article comprising a fibrous material embedded in a thermoplastic resin matrix, said article being prepared by a process comprising the steps of:
a) melt mixing a mixture of a thermoplastic resin, a fibrous material and any optional additives using a single screw, wherein the fibrous material has a fiber length of 0.5 to 3 inches long prior to molding and the fibrous material comprises 5 to 55 percent of the total weight of the mixed mixture, and wherein the screw pitch of the single screw is greater than the length of the fiber;
b) extruding the mixture through a sheet extrusion die;
c) gravitating the extruded mixture onto a horizontally movable first mold half of a mating mold to form a molten near-net-shape layup of molded thermoplastic articles; and
d) compression molding the molten near-net-shape layup with the second mold half of the matched mold, the molten near-net-shape layup allowing completion of the compression molding, solidification, and molding of the thermoplastic article to be achieved with substantially less movement of the molten near-net-shape layup at pressures in the range of 100-,
wherein:
in the molded article, the fiber length of the fibrous material is greater than 60% of its pre-molded length;
less than 20% of the fibers in the fibrous material in the molded thermoplastic article are oriented in the same direction; and
the mechanical properties of the molded article in the x, y and z planes are within 20% of each other.
In one embodiment, the extrusion is performed by a multi-die, horizontally mounted sheet extrusion die with independently controlled die orifices capable of varying the thickness of the mixture extruded through each die orifice.
In one embodiment, the article further comprises conveying the resin/fibrous material mixture through a conveying tube prior to extrusion.
In one embodiment, the fibrous material is selected from the group consisting of glass fibers, glass filaments, carbon fibers, synthetic fibers, metal fibers, natural fibers, cellulose, and wood.
In one embodiment, the thermoplastic resin is selected from the group consisting of polyolefins, polyhaloolefins, polyaromatics, polyalkenyl aromatics, polystyrenes, acrylonitrile/butadiene/styrene resins, polyamides, nylons, polycarboxylic acids, polyamines, polyethers, polyacetals, polysulfones, polyorganosulfides, polyorganooxides, polyesters, polycarbonates, polyimides, polyurethanes, polyetheretherketone resins, styrene/maleic anhydride resins, and mixtures thereof.
In one embodiment, the thermoplastic resin is a homopolymer, copolymer, random copolymer, alternating copolymer, block copolymer, graft copolymer, liquid crystal polymer, or mixtures thereof.
In one embodiment, the thermoplastic resin is a virgin resin, a recycled resin, or a mixture thereof.
In one embodiment, the extrusion operation is performed at a temperature in the range of 300-700 ° F.
In one embodiment, the optional additive is a coupling agent that enhances bonding of the fibrous material to the thermoplastic resin.
In one embodiment, the mold is a metal mold, a non-metal mold, a ceramic mold, or a wooden mold.
In an embodiment, the tensile strength, tensile modulus and flexural strength of the article in the axial and transverse directions are within 20% of each other.
In an embodiment, the fiber length of the fibrous material in the molded article is greater than 70% of its pre-molded length.
In an embodiment, the fiber length of the fibrous material in the molded article is greater than 80% of its pre-molded length.
In an embodiment, the fiber length of the fibrous material in the molded article is greater than 90% of its pre-molded length.
In one embodiment, the mechanical properties of the article are substantially anisotropic.
In one embodiment, the length of the article is greater than 0.5 feet in at least one of the x, y, and z planes.
In one embodiment, the length of the article is greater than 1.0 foot in at least one of the x, y, and z planes.
In one embodiment, the length of the article is greater than 2.0 feet in at least one of the x, y, and z planes.
In one embodiment, the length of the article is greater than 3.0 feet in at least one of the x, y, and z planes.
In one embodiment, the weight of the article is greater than 10 lbs.
In one embodiment, the weight of the article is greater than 20 lbs.
In one embodiment, the weight of the article is greater than 25 lbs.
In one embodiment, the process is an insert molding process.
In one embodiment, the thermoplastic resin is a virgin resin, a recycled resin, or a mixture of both.
In one embodiment, the resin includes a coupling agent that enhances bonding of the fibrous material to the thermoplastic resin.
In one embodiment, the article further comprises one or more optional reinforcing inserts.
In one embodiment, the reinforcing insert is selected from the group consisting of a tube, a rod, a mesh, and combinations thereof.
In one embodiment, the article has one or more solid protruding three-dimensional features.
In an embodiment, the one or more solid protruding three-dimensional features are blind ribs, posts, mounting posts, or tabs.
In another embodiment of the present invention, a molded thermoplastic article is provided. The article comprises a fibrous material embedded in a thermoplastic resin matrix and is prepared by a process. The pre-molded fiber length is about 0.5-3 inches long, while the length of the fibers within the molded article is greater than about 60% of their pre-molded length. The fibrous material comprises 5-55% of the total weight of the compounded mixture. Less than 20% of the fibers in the fibrous material have the same orientation within the molded thermoplastic article, and the mechanical properties of the molded article in the x, y and z planes are within 20% of each other. The mechanical properties of the article are substantially anisotropic.
In another aspect of the invention, a process for preparing a molded thermoplastic article is provided. The process for preparing a molded thermoplastic article generally comprises the steps of:
a) melt mixing a mixture of the thermoplastic resin, the fibrous material, and any optional additives with a single screw;
b) extruding the mixture through a sheet extrusion die;
c) gravitating the extruded mixture onto a horizontally movable first mold half of a mating mold to form a molten near-net-shape layup of molded thermoplastic articles; and
d) compression molding the molten near-net-shape layup with the second mold half of the matched mold, the molten near-net-shape layup allowing completion of the compression molding, curing, and molding of the thermoplastic article to be achieved with substantially less movement of the molten near-net-shape layup at pressures in the range of 100-. Thus, the present invention can be distinguished significantly from vacuum forming processes and sheet forming processes.
Detailed Description
For many years, there has been a gap in the composite manufacturing industry that has failed to provide a process for large scale production of large thermoplastic composite structures or parts that is produced at the speed and labor efficiency of compression or injection molding and that has the accuracy and low pressure of autoclave molding. The principles of the present invention provide a process for closing this gap and producing such thermoplastic composite parts. The above process is suitable for medium to high volume part production and can produce large parts and structures with high reinforcement fiber concentrations at low forming pressures.
Referring to fig. 1 and 2 of the drawings, a thermoforming apparatus 10 for thermoforming a part from a thermoplastic resin or from a thermoplastic composite material is illustrated having an extruder 11, a die exchange station 12 and a compression die station 13. The extruder has a top mounted hopper 14, the hopper 14 being used to feed thermoplastic resin or composite material into an auger (auger)15 where a heater heats the thermoplastic material to a fluid material, while the auger feeds the material along the length of the extruder path to an extrusion die 16 at the end thereof. The material fed through the extruder and exiting the extrusion die is cut by a trimmer 17 mounted at the end of the die 16. The material is extruded in a sheet (slab) (not shown), typically a flat sheet, and is trimmed at predetermined points by edge trimmers 17 as it exits the extrusion die 16. The support platform 18 will support the moving mold half 19 directly below the extrusion die 16 for receiving the sheet of thermoplastic material. The moving mold half 19 has wheels 20, the wheels 20 allowing the mold half 19 to be moved from the platform 18 onto a rotating platform 21 (shown as mold half 19 '), wherein the rotating platform 21 is mounted on a central rotating shaft 22 for rotation as indicated by the double-headed arrow 21' in fig. 1. The rotary platform 21 will have a second mold half 23 thereon, the second mold half 23 being capable of being fed into the compression forming station 13 (shown as mold half 23') while the mold half 19 is on the platform 18. The mold half 23' may be supported on a stationary platen 24 within the compression molding station directly beneath a common stationary mold half 25 mounted to a movable platen 26 where the forming operation takes place. Thus, the mold halves 19 and 23 can be shuttled back and forth so that one mold can capture the thermoplastic sheet while the other mold half forms the part. Each of the moving mold halves 19, 23 has a motor 27, the motor 27 being used to drive the mold half from the rotating platform 21 onto the platform 18 or onto the stationary platform 24. To control the speed of moving the mold halves, a linear transducer 28 may be mounted on the platform 18.
It should be noted at this point that the extruder 11 produces onto the moving half-mould a heated extrusion plate still containing thermal energy, which is transported to the compression mould 13 and moulded into parts without reheating the sheet of thermoplastic material. It will also be noted hereinafter in connection with fig. 4 and 5 that the thermoplastic sheet may have a varying thickness across its width to reinforce the thermoformed part produced from the mold.
Turning to fig. 3A through 3E, a thermoplastic forming apparatus 10 is illustrated having mold halves 19, 19 'and 23, 23' in a series of positions in the press operation in accordance with the present invention. There is an extruder 11 in each figure, the extruder 11 having a hopper 14, the hopper 14 feeding the thermoplastic resin or composite material to a pusher 16 where the thermoplastic resin or composite material is heated prior to being extruded. In fig. 3A, the mold half 23' is empty and the mold half 19 is filled with hot melt directly from the extruder 11. In fig. 3B, the mold carrier moves the mold halves 19 and 23' on the rotating turret 21. In fig. 3C, the rotary turret 21 rotates on a central axis 22 (not shown) between the station for loading the sheet onto one of the mold halves 23 and the station for loading the loaded mold halves 19' into the compression or vacuum forming machine 13. In fig. 3D, the half mould 19' is moved into the press 13, while the empty half mould 23 is moved under the extrusion mould 16 in order to load the sheet of thermoplastic material. In fig. 3E, the mold half 19' is press cooled and the part is demolded, while at the same time it is filled with hot melt until fully full as the mold half 23 is moved by its carrier under the extrusion die 16.
Turning to fig. 4 and 5, an extrusion die 30 is illustrated having a die body 31, the die body 31 having a passageway 32, the passageway 32 for feeding a fluid thermoplastic material through an extrusion channel 33 using the impeller 15 shown in fig. 1 and 2 to produce a sheet or slab of thermoplastic extruded material from a nozzle 34. The die 30 has a plurality of die plates (gated plates) 35, each die plate 35 being connected to a threaded shaft 36 driven by a die drive motor 37, wherein the die drive motor 37 may be a hydraulic or pneumatic motor, and as shown is an electric stepper motor having a control line 38 fed to a remote controller 40, the remote controller 40 being capable of stepping the motor 37 to move the plate 35 in and out to vary the thickness of the thermoplastic plate passing through the channel section 41. It can be seen in fig. 5 that a plurality of any number of motors 37 drive a plurality of plates, where each plate is mounted next to the next plate and each plate is independently controlled so that the plates 35 can be varied in a variety of patterns within the channel 41 to produce plates from the output section 34 that can vary in thickness across the width of the extruded plate. It is also clear that the die ports 35 can be manually controlled to adjust the thickness of any portion of the extrusion die by individually threading or unthreading each die port, and that, optionally, the die ports 35 can be controlled by a controller 40 under remote control as needed, wherein the controller 40 can be a computer program for changing the thickness of any portion of the extrusion plate.
A thermoplastic forming process is provided that includes selecting a thermoplastic extrusion die 16 or 30 for extrusion of a thermoplastic slab, the extrusion die having adjustable die orifice features for varying the thickness of the extruded material at different portions of the extruded slab. The process includes adjusting a thermoplastic extrusion die for a plurality of thicknesses of extruded material passing therethrough at different portions of an extrusion plate and subsequently heating the thermoplastic material to a fluid, and extruding a sheet of fluid thermoplastic material through the selected and adjusted thermoplastic extrusion die. The thermoplastic sheet is then trimmed and directed onto a heated thermoplastic material into a hot forming die 19 or 23 and molded in a forming apparatus 13 to form a part in which the thickness is varied.
At this point it should be clearly seen that a thermoplastic forming process and apparatus have been provided which allows parts of varying thickness to be thermoformed using an extrusion die which can be continuously controlled to vary the thickness of different portions of the extruded sheet being molded and which completes the molding process while the thermoplastic sheet is still hot to take advantage of the thermal energy from the extrusion process. It is to be clearly understood that the same is not to be considered as limited to the forms shown, which are to be regarded as illustrative rather than restrictive. For example, although the extruded material is sometimes described as a generally flat sheet, the extruded material is also described as follows: (i) heat energy is contained to avoid reheating when delivered to the compression mold 13, (ii) to have varying thickness across the width, (iii) to be a hot melt when fed from the extruder 11 into the mold half 19, (iv) to use a plurality of die plates 35 to vary the thickness across the width of the extruded material and in different portions of the extruded material, and finally (v) to extrude the molten thermoplastic material through an extrusion die selected and adjusted to achieve varying thickness in the formed portions. Thus, an extruder typically provides a molten stream of thermoplastic composite material through a dynamic die that settles in varying amounts onto the mold half or lower die in a vertical plane and across two horizontal directions on the mold.
The above-described "extrusion-forming" process is ideal for the manufacture of medium to large thermoplastic composite structures that are reinforced with, for example, glass, carbon, metal, or organic fibers. The extrusion-forming process comprises: a computer controlled extrusion system that integrates and automates the material mixing or blending of the base and reinforcement components to dispense a shaped quantity of molten composite material that settles into the lower half of the mating mold, the lower half of which is controlled in its movement as it receives the material; and a compression forming station for receiving the lower half of the die to press the upper half of the die against the lower half to form a desired structure or section. The lower half of the matched mold moves discontinuously in space and time at varying speeds to enable the material to deposit thicker at low speeds and thinner at faster speeds. The thermoplastic apparatus 10 described above is one embodiment for carrying out the extrusion-forming process. The raw resin, which may be any form of regrind or pelletized thermoplastic or alternatively thermosetting epoxy resin, is the matrix component that is fed into the feeder or hopper of the extruder along with reinforcing fibers having a length greater than about 1/2 inches (1/2 "). The composite material may be blended and/or mixed by the extruder 11 and "intelligently" deposited onto the lower mold half 19 by controlling the output of the extruder 11 through the die 35 and controlling the movement of the lower mold half 19 relative to the position of the extruder 11, as will be described below using the embodiment shown in fig. 6A and 6B. In these embodiments, the lower part of the matched molds is fixed to a trolley that moves discontinuously under the dynamic molds. The lower section of the mating die receives a precise amount of extruded composite material and is then moved into a compression forming station.
As is understood in the art, thermoplastic matrix materials that may be used in the extrusion-molding process to form composite materials include thermoplastic resins. Thermoplastic resins that may be used in accordance with the principles of the present invention may include any thermoplastic resin that is capable of being melted and mixed by the extruder 11. Examples of such thermoplastic resins are provided in table 1 with the understanding that these examples are not intended to be a complete list and that other thermoplastic resins and materials may be used in the manufacture of structural parts using the extrusion-molding system. The thermoplastic resins in table 1 may be used alone or in any combination.
TABLE 1
Specific thermoplastic materials include polypropylene, polyethylene, polyetheretherketone, polyester, polystyrene, polycarbonate, polyvinylchloride, nylon, polymethyl (methacrylate), polymethacrylate, acrylic, polyurethane and mixtures thereof, which are particularly suitable for extrusion molding processes.
Fibers that serve as a reinforcing component for the thermoplastic composite generally include those materials that can be used to reinforce thermoplastic resins. Suitable fibrous materials in accordance with the principles of the present invention include, without limitation, glass, carbon, metal, and natural materials (e.g., flax, cotton), either alone or in combination. Other fibers not listed may also be used as is understood in the art. Although the diameter of the fibers is not generally limited, the diameter of the fibers used to mold larger structural parts is generally in the range between 1 and 20 μm. It should be appreciated, however, that the diameter of the fibers may be larger depending on factors including desired strength of the structural part, desired fiber density, size of the structural part, and the like. In particular, the improvement in mechanical properties is significant when fibers having a diameter of about one (1) to about nine (9) μm are used.
The number of individual fibers (filamentt) bundled within a fiber is also not generally limited. However, for handling considerations, a fiber bundle consisting of 10,000 to 20,000 filaments or monofilaments is generally desirable. Rovings of these reinforcing fibers may be used after surface treatment by silane or other coupling agent. In order to improve the interfacial bonding with the thermoplastic resin, for example, in the case of a polyester resin, surface treatment may be performed by a thermoplastic film forming polymer (thermoplastic film forming polymer), a coupling agent, a fiber lubricant, and the like. Such surface treatment may be performed before the treated reinforcing fibers are used, or the surface treatment may be performed just before the reinforcing fibers are fed into the extruder, so that the extrusion process to produce the molten thermoplastic composite is performed without interruption. The ratio between the thermoplastic resin and the fibers is not particularly limited, as any composition ratio can be employed to produce the thermoplastic composite material and the formed part according to the end use purpose. However, as is understood in the art, the fiber content is typically five percent (5%) to fifty percent (50%) by weight in order to provide sufficient structural support to the structural part. It has been determined that the fiber content is typically ten (10) to seventy (70) percent by weight, and preferably forty (40) percent by weight, to achieve the mechanical properties desired for the production of larger articles.
The fibers have an average fiber length greater than about one-half inch (1/2 "). However, typical structural parts produced by the extrusion-molding system 600a use fiber lengths greater than about one inch. It should be noted that when the average fiber length is less than one inch, it is difficult to obtain the desired mechanical properties for large articles. The distribution of these fibers in the thermoplastic composite is generally uniform so that the fibers and thermoplastic resin do not separate upon melting and compression molding. The distribution or distribution of these fibers includes the process by which the fibers are dispersed from the monofilament level to the multifilament level (i.e., a bundle of several tens of fibers). In one embodiment, bundles of about five fibers are dispersed to provide efficiency and structural performance. Further, "degree of combing" can be evaluated by observing a cross section of the structure with a microscope and determining the proportion (total number of reinforcing fibers in ten or more bundles/total number of reinforcing fibers × 100) (percentage) of the number of reinforcing fibers in bundles of ten or more in the total number of reinforcing fibers observed of 1000 or more. Typical values produced by the principles of the present invention result in no more than about sixty percent (60%), and generally less than thirty-five percent (35%).
Fig. 6A is an exemplary schematic diagram of an extrusion-molding system 600a, the extrusion-molding system 600a being operable to form a structural part. The extrusion-molding system 600a is comprised of several discrete components that are integrated into a single body to form a structural part from a composite material. These components include: a material receiving unit 602, a heater 618, an extruder 604, a dynamic die 606, a trolley 608, a compression press 610, and a controller 612. Other auxiliary components may also be included to form the extrusion-molding system 600 a.
The material receiving unit 602 may include one or more hoppers or feeders 614 and 615, the feeders 614 and 615 for receiving the materials M1 and M2, respectively, the materials M1 and M2 to be extruded to form the thermoplastic composite. It should be appreciated that additional feeders may be used to receive additional materials or additives to formulate different mixtures. In the present example, the materials M1 and M2 represent the starting materials, i.e. the reinforced thermoplastic material, preferably in the form of pellets. M1 and M2 may be the same or different reinforced thermoplastic materials. As is understood in the art, thermoplastic materials may be reinforced with fibers, such as glass or carbon fibers. It should be further appreciated that non-thermoplastic materials may be used in accordance with the principles of the present invention.
The heater 618 preheats the thermoplastic materials M1 and M2. Extruder 604 is coupled to feeder channel 616, and extruder 604 is operable to mix heated thermoplastic materials M1 and M2 by propeller 620. The extruder 604 further melts the thermoplastic material. The auger 620 may be helical or any other shape that can be operated to mix and flow the composite material through the extruder 604. An extruder output channel 622 is coupled to the extruder 604 and is used to carry the composite material to the dynamic die 606.
The dynamic die 606 includes a plurality of flow control elements 624a-624n (collectively 624). The flow control element 624 may be a separate die orifice (gate), valve, or other mechanism operable to control the extruded composite material 625 from the dynamic die 606, wherein at the dynamic die 606 the extruded composite material 625a-625n (collectively 625) varies the volumetric flow rate across the plane P at or below the flow control element 624. The different volumetric flow rate outputs are generally in the range between zero and 3000 pounds per hour. More preferred volumetric flow rates range between about 2500 and 3000 pounds per hour. In one embodiment, the flow control element 624 is a die that is raised and lowered, either individually or integrally, by a separate actuator, which may be, for example, a motor (such as a stepper motor), a hydraulic actuator, a pneumatic actuator, or other actuator that may be operated to vary the flow of composite material from the adjustable flow control element 624. The flow control elements 624 may be configured to be adjacent to provide a continuous separation of adjacent flow control elements 624. Alternatively, the flow control elements 624 may be individually configured such that the composite material flowing from adjacent flow control elements 624 remains separated until the composite material is spread on the mold. It should be appreciated that the flow control element 624 may suitably operate as a trimmer 17. In an embodiment of the present invention, the molten composite material may be delivered into an accumulator (accumulator) placed between the extruder 604 and the dynamic die 606, from which the composite material may be delivered into the lower die using a plunger or other actuation mechanism.
The trolley 608 may be moved under the dynamic die 606 so that the extrusion material 625 is deposited onto or onto the lower mold 626, wherein the lower mold 626 passes under the dynamic die 606 at a predetermined vertical distance, i.e., a "drop distance" (d). The lower mold 626 defines a cavity 630 for forming the structural part. Extruded composite material 625 is deposited on the lower mold 626 to fill the volume defined by the cavity 630 within the lower and upper molds 626 and 632 to form a composite part. In a two-axis controlled process, the composite material 625a may be deposited on the lower mold 626 at a substantially constant volumetric flow rate from the dynamic mold 606 or across the vertical plane (P) to form a composite material layer 628 having substantially the same thickness or volume along the vertical plane (P) to fill the cavities 630 in the lower and upper molds 626 and 632, based on the discrete movements and varying velocities. In a three-axis controlled process, composite material may be deposited on the lower mold 626 at different volumetric flow rates across the vertical plane (P) from the dynamic mold 606 to form a composite material layer 628 having different thicknesses or volumes along the vertical plane (P) to fill the cavities 630 in the lower and upper molds 626 and 632. It should be appreciated that a two-axis controlled process may be used to deposit composite material to a mold having cavities 630 with substantially constant depth in the vertical plane, and a three-axis controlled process may be used to deposit composite material to a mold having cavities 630 with varying depths.
The trolley 608 may further include wheels 634, the wheels 634 providing translational movement along the track 636. The rails 636 enable the trolley 608 to roll under the dynamic die 606 and into the press 610. The press 610 operates to press the upper mold 632 into the lower mold 626. Although the principles of the present invention provide for a reduction in the forming process forces as compared to conventional thermoplastic forming processes because composite material layer 628 is deposited directly from dynamic die 606 to lower die 626, the forces applied by press 610 may still be sufficient to damage wheel 634 if wheel 634 is left in contact with guide rail 636. Thus, the wheels 634 may be selectively engaged and disengaged with the upper surface 638 of the base 640 of the press 610. In one embodiment, the trolley 608 is raised by an inflatable tube (tube) (not shown) attached thereto, such that when the tube is inflated, the wheels 634 engage the tracks 636 so that the trolley 608 can move from beneath the die 606 to the press 610. When the tubes are deflated, the wheels 634 are disengaged, thereby seating the body of the trolley 608 on the upper surface 638 of the base 640 of the press 610. It should be noted that other drive features may be used to engage the wheels 634 and disengage the wheels 634 from support of the trolley 608, but the functionality of engaging and disengaging the wheels 634 is substantially the same. For example, an upper surface 638 of a base 640 of the press 610 may be raised to contact a base plate 642 of the trolley 608.
The controller 612 is electrically connected to the various components forming the extrusion-molding system 600. The controller 612 is a processor-based unit that operates to coordinate the shaping of the structural parts. In part, the controller 612 operates to control the composite material deposited on the lower mold 626 by controlling the temperature of the composite material, the volumetric flow rate of the extruded composite material 625, and the positioning and rate of movement of the lower mold 626 by the trolley 608 to receive the extruded composite material 625. The controller 612 is further operable to control the heater 618 to heat the thermoplastic material. The controller 612 may control the speed of the auger 620 to maintain a substantially constant flow of the composite material through the extruder 604 and into the dynamic die 606. Alternatively, the controller 612 may vary the speed of the auger 620, thereby varying the volumetric flow rate of the composite material from the extruder 604. The controller may further control heaters (not shown) within the extruder 604 and the dynamic die 606. Based on the structural part being formed, a predetermined set of parameters may be established for the dynamic die 606 to apply the extruded composite material 625 to the lower die 626. These parameters may be defined such that the flow control elements 624 may be selectively set to positionally synchronize the movement of the trolley 608 with the volumetric flow rate of the composite material, depending on the cavity 630 defining the structural part being produced.
The trolley 608 may further include a heater (not shown) controlled by the controller 612, and the heater may be operated to maintain the extruded composite material 625 in a heated or molten state. The controller may control the trolley 608 by varying the required speed of the trolley during the application of the extruded composite material 625 to the lower mold 626. Upon completion of the application of the extruded composite material 625 to the lower mold 626, the controller 612 drives the trolley 608 into the press 610. The controller then signals a mechanism (not shown) to disengage the wheels 634 from the rails 636 as described above so that the press 610 can apply a force to the upper mold 632 against the lower mold 626 without damaging the wheels 634.
Fig. 6B is another exemplary block diagram of the extrusion-molding system 600a shown in fig. 6A. The extrusion-molding system 600b is configured to support two presses 610a and 610b to form a structural part, where the presses 610a and 610b are operable to receive a trolley 608 that supports a lower mold 626. It should be appreciated that two trolleys 608 may be supported by a track 636 in preparation for forming multiple structural components with a single extruder 604 and dynamic die 606. Although wheels 634 and tracks 636 may be used to provide motion to trolley 608 in one embodiment, it should be appreciated that other motion mechanisms may be used to control the motion of trolley 608. For example, a conveyor, a suspension, or a track drive system may be used to control the movement of the trolley 608 for use.
The controller 612 may be configured to support a variety of structural parts such that the extrusion-molding system 600b may form different structural parts simultaneously through different presses 610a and 610 b. Because the controller 612 is capable of storing parameters that can be operated to form a variety of structural parts, the controller 612 can prepare to form two different structural parts using a single extruder 604 and dynamic die 606 by simply changing the control of the dynamic die 606 and trolleys 608a and 608b using the parameters in a common software program. It should be appreciated that additional presses 610 and trolleys 608 may be used to produce more structural parts substantially simultaneously through a single extruder 604 and dynamic die 606.
FIG. 7 is an exemplary exploded view of the dynamic die 606 depositing the extruded composite material 625 onto the lower mold 626 supported by the trolley 608. As shown, the dynamic die 606 includes a plurality of flow control elements 624a-624 i. It should be appreciated that the number of flow control elements 624 may be increased or decreased depending on the resolution (resolution) or detail of the structural features being formed. As shown, the flow control elements 624 are positioned at different heights to provide a greater or lesser volumetric flow rate of the extruded composite material 625 associated with each flow control element 624. For example, the flow control element 624a are fully closed, thereby preventing the composite material from passing through that portion of the dynamic die 606. Thus, the volumetric flow rate f associated with the closed flow control element 624aaIs zero. Flow control element 624b is opened to a height h1Thereby providing a volumetric flow rate f of the extruded composite material 625bb. Similarly, the flow control element 624c is opened to form a larger opening to allow the extruded composite material 625c to flow at a higher volumetric flow rate fcAnd output to the lower mold 626.
As indicated by the change in shading of the extruded composite material 625 associated with each flow control element 624, the flow control elements 624 may be dynamically adjusted based on the structural part formed by the lower and upper dies 626 and 632. Accordingly, based on the structural part being formed (e.g., deep drawing over a region), the flow control elements 624 can be adjusted to vary the volumetric flow rate of the extruded composite material 625 over a limited region of the lower and upper molds 626. In other words, the composite material layer 628 may vary in thickness based on the cavity 630 defined by the lower mold 626 and the upper mold 632. For example, composite layer region 628a is thinner than composite layer region 628b, and composite layer region 628b is thicker to substantially fill cavity 630a, wherein cavity 630a has a deeper draft (draft) than other locations of cavity 630 within lower mold 626. In other words, the extruded composite material layer 628 is dynamically changed based on the depth of the cavity 630 defined by the dies 626 and 632. In two-axis and three-axis control processes that can be performed on the extrusion-molding system 600a, the extruded composite layer 628 may be dynamically varied in thickness based on the volumetric flow rate of the extruded composite material 625 and the travel speed of the trolley 608.
Depending on the structural part being produced, deposition of the extruded composite material onto the lower die may be performed by controlling the amount of extruded composite material deposited in two or three axes. For two-axis control, the motion of the trolley can be controlled along the axis of motion to deposit the extruded composite material in varying amounts along the deposition axis. For three-axis control, the output of the extruder may use a dynamic die that includes flow control elements to provide different volumetric flow rates along an axis perpendicular to the axis of motion that are simultaneously deposited onto the lower die. It should be appreciated that other embodiments may provide off-axis (off-axis) or non-axis (non-axis) control to deposit the extruded composite material in specific locations on the lower die.
By providing control over the trolley and the composite material applied to the lower die, any pattern from a thick continuous layer to a thin profile of a circle or ellipse can be formed on the lower die, and any two-dimensional shape that can be described by discrete mathematics can be traced with material (trace). In addition, because there is control over the amount of composite material deposited on a given area, three-dimensional patterns can be created to provide structural components to be produced, such as with deep draw draft (deep draft) and/or hidden ribs. Once the structural part is cooled, a stripper (ejector) may be used to push the consolidated material away from the mold. The principles of the present invention may be designed so that two or more distinct parts may be produced simultaneously, thereby maximizing production efficiency through the use of a nearly continuous flow of composite material.
Incremental gains of the extrusion-forming process
With this extrusion-molding system, large long fiber reinforced plastic parts can be produced at very low tooling costs and in-line. The features of the extrusion system provide a reinforced plastic part production line that provides (i) flexibility in materials, (ii) deposition processes, (iii) low pressure, and (iv) processing efficiency. Material flexibility enables savings in both material and machine costs from in-line mixing, and further provides flexibility in material properties. The deposition process adds value to the material deposition process, allowing for more complex shapes (e.g., large draft angles and ribs), better material flow, and ease of including large inserts in the mold. The low pressure is intended to reduce the forming pressure, which will simultaneously alleviate wear on the die and the machine, and lock only minimal stresses in the structural parts. Processing efficiency provides the ability to use two or more disparate dies at once to increase the efficiency of the extrusion system, thereby reducing the number of machines required to run a production operation. Additionally, a material delivery system in accordance with the principles of the present invention may be integrated with many existing machines.
Material flexibility
The extrusion-forming process allows for the use of several different types of resins and fibers to mix the customized composite mixture. The extrusion system may utilize several resins as described above to produce parts. With conventional compression molding methods, a pre-prepared thermoplastic sheet, known as a blank (blank), is purchased from a thermoplastic sheet manufacturer to combine the resin with the fibers and desired additives. However, these blanks are expensive because they have already passed several intermediaries and are usually sold only in the form of a predetermined mixture. By using an extrusion-forming process in accordance with the principles of the present invention, these costs can be reduced by an in-line mixing process that uses raw materials to produce the structural part without the need to purchase pre-fabricated sheets. Labor and machine costs are also significantly reduced because the extrusion-molding system does not require a furnace to preheat the material and does not require an operator to move the heated sheet to the mold. Since the operator controls the mixing ratio as desired, nearly unlimited flexibility is added to the process, including the ability to change properties, for example, during molding, or to create gradual changes in color. Moreover, unlike sheet forming, the extrusion-molding system does not require the material to have melt strength, which gives the system increased flexibility. In one embodiment, the extrusion-molding system may utilize a thermosetting resin to produce the structural part. The extrusion-molding system may also utilize a variety of fiber materials, including carbon fibers, glass fibers, and other fibers as described above for reinforcement having fiber volume percentages in excess of 50% and fiber lengths of 1 to 4 inches or more that are achievable, while a high proportion of fiber length of 85% or more is maintained from the raw material to the finished part.
Deposition process
In accordance with the principles of the present invention, the extrusion system allows for variable lay-down of composite materials, for example, in areas where the die is to use more material due to deep draw draft (draft) or hidden ribs, thereby minimizing the forces used during forming and pressing. The application of the variable composite material results in greater accuracy, a more filled mold, and less "shot-out" than typical compression forming processes, as is understood in the art. Variable layup also allows large features to be molded on both sides of the structural part while allowing inserts or cores to be placed into the structural part. Finally, because the material is deposited onto the mold in a molten state with relatively low viscosity (as opposed to being pre-blended into a sheet and then pressed into the mold), the fibers can easily enter the ribs and cover large areas without being concentrated or oriented in an undesirable manner.
Low pressure
The thermoplastic composite deposited during extrusion-forming is much more fluid than the thermoplastic composite from the heated pre-mix sheet, making it much easier to flow the thermoplastic composite into the die. The flowability of the composite material deposited on the mold results in a significant reduction in molding pressure requirements compared to most other molding processes. The press used in the process typically operates in the range of 100 psi compared to 1,000psi for compression forming. Lower pressures translate into less wear and thus reduce mold and press maintenance. Because of the lower pressures, aluminum molds capable of withstanding 300,000 cycles can be used, which only costs $40,000 to manufacture, without steel tooling that can cost more than $200,000. Cheaper tools also mean more flexibility for future design changes. As the thermoplastic resin is repositioned and shaped on the surface of the mold at lower pressures, there is less stress on the lock-in material, resulting in better dimensional tolerances and less warping (warping).
Efficiency of processing
Since the extrusion-forming process can be used with two or more dies running at the same time, the average cycle time per part is reduced, thereby increasing throughput as the first die set can be cooled and removed while the second die is being filled and pressurized. Moreover, the extrusion-molding system utilizes a minimum of redundant components. In one embodiment, the extrusion system uses a separate press for each die, but other equipment can be combined and shared among multiple sets of dies, and modifications can be readily made in the software to accommodate the other dies. The extrusion and delivery system 600a may further be integrated into current manufacturing equipment and existing compression dies and presses may be combined.
FIG. 8A is an exemplary flow chart depicting an extrusion-forming process that may be employed to form an article or structural part using two-axis or three-axis control for depositing a composite material onto a lower mold 626. The extrusion-forming process begins at step 802. The thermoplastic material is heated to form a molten thermoplastic material at step 804 and blended with the fibers to form a composite material at step 802. At step 708, the molten composite material is conveyed through the dynamic mold to be deposited onto the lower mold 626. For a two-axis extrusion deposition process, a fixed output from the die may be used. In the two-axis process, the motion of the trolley is maintained at a constant speed. In a three-axis extrusion control process, a dynamic die 606 may be used in combination with varying the speed of the trolley or die. For both two-axis and three-axis extrusion control processes, the lower mold 626 may be moved in space and time while receiving the composite material to follow the amount of composite material required for the cavity 630 defined by the lower and upper molds 626 and 632 at step 810. In step 812, the upper mold 632 is pressed against the lower mold 626 to press the composite material into the lower and upper molds 626 and 632. The process ends at step 814.
Fig. 8B is an exemplary flow chart for producing a structural part by a three-axis controlled extrusion-forming process using the extrusion-molding system 600a of fig. 6A. The process for producing the structural part begins at step 816. At step 818, thermoplastic material is received. At step 822, the thermoplastic material is heated. In one embodiment, the thermoplastic material is heated to a molten or molten state. At step 820, a fiber having a predetermined fiber length is received. At step 822, the fibers are mixed with the heated thermoplastic material to form a composite material. The fibers may be long strands of glass or other rigid material used to form large structural parts. For example, fiber lengths of 1/2 inches (1/2 ") to 4 inches (4") or more in length may be used in the formation of the structural part.
The composite material is extruded in step 826. During the extrusion process, the auger 620 or other mechanism used to extrude the composite material is configured to substantially avoid damage to the fibers, such that the initial fiber length is substantially maintained (e.g., 85% or greater). For example, in the case of the auger 620, the thread spacing (thread spacing) is selected to be greater than the length of the fiber, thereby substantially avoiding damage to the fiber.
At step 828, the extruded composite material 625 may be dynamically output at different volumetric flow rates across the plane, thereby providing control over the deposition of the extruded composite material 625 onto the lower mold 626. At step 830, the lower mold 626 may be positionally synchronized to receive the extruded composite material 625 at different volumetric flow rates relative to the transverse plane P. In one embodiment, the position synchronization of the mold 626 is performed according to a flow control element 624 located at a height d above the trolley 608, which trolley 608 can translate at a substantially constant or adjustable rate. For example, to deposit a constant or flat extruded composite layer 628, the trolley 608 is moved at a substantially constant rate, but to increase or decrease the volume of the extruded composite layer 628, the trolley 608 may be moved at a slower or faster rate, respectively. At step 832, the extruded composite material 625 formed into the extruded composite material layer 628 is pressed into a die 626 to form a thermoplastic structural part. The formation of the structural feature ends at step 834.
Fig. 9 is an exemplary block diagram 900 of the controller 612, the controller 612 configured to communicate with a controller operating within the components of the extrusion system 600a of fig. 6A. To enable bi-directional communication, the controller 612 communicates with different controllers using digital and/or analog communication channels, as is known in the art. The controller operating within the components may be open or closed loop control software based on processor operation as is known in the art and may operate as a servo computer for the controller 612. Alternatively, these controllers may be non-processor based controllers, such as analog or digital circuits, that operate as a slave unit (slave unit) for the controller 612.
The feeder 614 may include a speed and temperature controller 902, and the speed and temperature controller 902 may be operable to control the speed and temperature of the feeder 614 for mixing the composite material M1 and the fibrous material M2. The feeder speed and temperature controller 902 may be formed of a single or multiple controllers to control the motor and heater. The controller 612 may be operable to specify or command the speed or rate and temperature of the feeder 614, while the speed and temperature controller 802 of the feeder 614 may be operable to execute the commands received by the controller 812. For example, based on the amount of composite material being extruded through the dynamic die 606, the controller 612 may increase the rate at which the materials M1 and M2 are fed into the extruder 606.
The controller 612 is further in communication with a heater controller 904. The controller 612 may transmit control data to the heater controller 904 based on feedback data received from the heater controller 904. For example, if the temperature of heater controller 904 decreases during a feeding operation, controller 612 may issue a command to heater controller 904 via control data 1018 to increase the temperature of heater 618. Alternatively, the heater controller 904 may adjust the temperature to the temperature given by the controller 612 using a feedback adjustment loop as is known in the art and simply report the temperature to the controller 612 for monitoring purposes.
The controller 612 is further in communication with an extruder speed and temperature controller 906, the extruder speed and temperature controller 906 providing control of the speed of the auger 620 and the temperature of the extruder 604. The extruder speed and temperature controller 906 is operable to control a plurality of heaters within a zone of the extruder 604 and communicate the temperature of each heater to the controller 612. It should be appreciated that the extruder speed and temperature controller 906 may be comprised of multiple controllers.
The controller 612 is further in communication with a dynamic mode controller 908, the dynamic mode controller 908 controlling a flow control element 624 of the dynamic mode 606. The dynamic mode controller 908 may be operable to control each flow control element 624, either collectively or individually. Alternatively, each flow control element 624 may be controlled individually by a separate controller. Accordingly, the controller 612 may operate in an open-loop manner to issue instructions to the dynamic mode controller 908 to set a position for each flow control element 624. For example, a stepper motor may be used in an open loop manner. The actual position of each flow control element 624 may be communicated back to the controller 612 via feedback data 1022 for use by the controller 612 in controlling the position of the flow control element 624.
The controller 612 is further in communication with a trolley controller 910, the trolley controller 910 being connected to the trolley 608 and operable to control the position of the trolley 608 and the temperature of the lower mold 626. The controller 612 may provide control signals 1018 to the trolley controller 910, wherein the trolley controller 910 operates as a servo that drives the trolley 608 to a position given by the controller 612, wherein the controller 612 positions the lower mold 626 accordingly with the extruded composite material 625 being deposited onto the lower mold 626. Although the extruded composite material layer 628 deposited onto the lower mold 626 is molten at the time of deposition, the previously deposited extruded composite material layer 628 tends to cool at the time of the subsequent extruded composite material 625 being deposited. Accordingly, the controller 612 may transmit control data 1018 to the trolley controller 910 to maintain the temperature of the extruded composite layer 628, or at a substantially constant temperature based on the deposition time of the extruded composite material 625, and/or based on other factors, such as the molten state temperature requirements of the thermoplastic material M1. Feedback data 1022 may provide the current temperature and position and velocity status of the trolley 608, as well as the temperature of the lower mold 626, so that the controller 612 may perform management and monitoring functions.
The controller 612 is further in communication with a heating/cooling controller 912, the heating/cooling controller 912 being operable to control the temperature of the heater and/or cooler for the extrusion-molding system 600 a. Heating/cooling controller 912 may receive control data 1018 from controller 612, and controller 612 may command heating/cooling controller 912 to operate at a specific or variable temperature based on several factors, such as thermoplastic material M1, ambient temperature, characteristics of the structural part being produced, production rate, and the like. The heating/cooling controller 912 may control system-level heaters and coolers, or component-level heaters and coolers. The feedback data 1022 may provide the current temperature and status of the heater and cooler so that the controller 612 may perform management and monitoring functions.
The controller 612 is further in communication with a press controller 914, the press controller 914 being operable to control press operation and temperature of the upper die 632. The press controller 914 may be a standard controller provided by the manufacturer of the press 610 with the press 610. Similarly, the press controller 914 may include a temperature controller that controls the temperature of the upper die 932. Alternatively, the temperature controller may not be associated with the press controller 914 provided by the manufacturer of the press 910. The feedback data 612 may provide the current position and force of the press, as well as the temperature of the upper die 632, so that the controller 612 may perform management and monitoring functions.
The controller 612 is further in communication with a drawing (extraction) tool controller 916, the drawing tool controller 916 being operable to control a drawing operation on the molded structural component. In response to the controller 612 receiving notification from the press controller 914 that the press 610 has completed a pressing operation, the controller 612 may issue a control signal 1018 to the extraction tool controller 916 to initiate an extraction operation of the molded structural component. Accordingly, feedback data 1022 may be used to indicate the current operation of the pattern drawing tool. If the feedback data 1022 indicates that the extraction tool has difficulty extracting the molded structural component, the operator of the extrusion-molding system 600a may be notified that a problem has occurred with the extraction tool, the lower or upper molds 626 and 632, the press 610, the heaters or coolers of the upper or lower molds 626 and 632, or other components or functions of the extrusion-molding system 600 a.
It should be appreciated that while the controller 612 may be configured as a master controller for each component of the extrusion-molding system 600a, the controller 612 may be configured to manage the components in the form of a more distributed controller. In other words, the controller of the component may operate as a more intelligent controller that calculates operational and control parameters using the parameters of the structural part being produced, and less as a servo device that is commanded by the controller 612 to perform a function. It should be further appreciated that the controller 612 may be programmed to accommodate different mechanical configurations of the extrusion-molding system 600 a. For example, if the extrusion-molding system 600a is configured such that the output of the extruder 606 translates or moves relative to a stationary lower mold 626, which may or may not be coupled to the trolley 608, the controller 612 may be programmed to control the motion of the output of the extruder 606 rather than the motion of the trolley 608.
Fig. 10 is an exemplary block diagram of the controller 612 of fig. 6A. The controller 612 includes a processor 1002 connected to a memory 1004 and a user interface 1006. The user interface 1006 may be a touch screen, an electronic display device and keyboard, a pen-controlled interface, or any other user interface known in the art. The processor 1002 is further coupled to input/output (I/O) units and a storage unit 1010 that stores information in databases or files 1012a-1012n (collectively 1012). The database 1012 may be used to store control parameters for controlling the extrusion-molding system 600a, such as data associated with the lower and upper molds 626 and 632. Additionally, the database 1012 may also be used to store data fed back from the extrusion system 600a during operation of the extrusion system 600 a.
The processor 1002 is operable to execute software 1014 used to control the various components of the extrusion-molding system 600a and to manage the database 1012. In controlling the extrusion-molding system 600a, the software 1014 communicates with the extrusion-molding system 600a via the I/O unit 1008 and the control bus 1016. The control data 1018 is communicated to the extrusion-molding system 600a via data packets and/or analog control signals over the control bus 1016. It should be appreciated that the control bus 1016 may be comprised of multiple control buses, whereby each control bus is associated with a different component of the extrusion-molding system 600 a. It should further be appreciated that the control bus 1016 may operate utilizing either a serial or parallel protocol.
During operation, the feedback bus 1020, which may be a single bus structure or a multi-bus structure, may be operated to feed back data 1022 from the extrusion-molding system 600 a. The feedback data 1022 may be sensory data such as temperature, position, velocity, level, pressure, or any other sensory information measured by the extrusion-molding system 600 a. Accordingly, the I/O unit 1008 is operable to receive feedback data 1022 from the extrusion-molding system 600a and communicate the feedback data 1022 to the processor 1002 for use by the software 1014. The software 1014 may store the feedback data in the database 1012 and utilize the feedback data 1022 to control the components of the extrusion-molding system 600 a. For example, in the case of a heater temperature fed back to the controller 612 by the heater controller 904, if the temperature of the heater 618 becomes too low, the controller 612 may issue a command to the heater 618 via the control data 1018 to increase the temperature of the heater 618. The controller 612 or component (e.g., heater) may include an automated control system as is known in the art for performing control and adjustment of the component.
During operation, the controller 612 may store control parameters for producing one or more structural parts with the extrusion-molding system 600 a. For example, data associated with parameters of the molds 626 and 632, such as dimensions of the cavities 630, may be stored in the database 1012. By storing multiple sets of parameters for different structural parts, the extrusion-molding system 600a may be used to form these structural parts substantially simultaneously. The processor 1002 may execute the software 1014 with different sets of parameters in parallel to form the structural part substantially simultaneously. That is, when one structural part is pressed, another structural part may be formed by the dynamic die 606 by applying the extruded composite material 625 to the lower die 626.
Fig. 11 is an exemplary block diagram of software 1014, the software 1014 being executed by the processor 1002. The system manager 1100 is operable to manage various aspects of the controller 612. The system manager 1100 interfaces with an operator interface 1102, a system driver 1104, and a database manager 1106.
The operator interface 1102 is used to provide an interface for an operator of the extrusion-molding system 600a to manually control the extrusion-molding system 600a or to create a program and/or profile (profile) for producing a structural part. The operator interface 1102 is in communication with a program selector 1108, which, when preprogrammed, allows the operator to select a program for producing the structural part. For example, the program established to produce the pallet (pallet) may be selected by the operator via the operator interface 1102 to control the extrusion-molding system 600a to produce the pallet as defined by the pallet designer in accordance with the lower and upper molds 626 and 632. In one embodiment, the program selector 1108 selects only a general purpose program (generic program) that controls the extrusion-molding system 600a to produce a particular structural part by utilizing a particular set of parameters for controlling the component accordingly. The program selector 1108 may be in communication with a parameter selector/editor 1110 that allows the operator to select a particular set of parameters to form a particular structural part and/or edit the parameters to change the process for forming the structural part. The parameter selector/editor 1110 may interface with the database manager 1106 to select a particular set of parameters from among a number of different parameter data files that may be used by the controller 612 to drive the components of the extrusion-molding system 600a to form different structural parts. For example, the data manager 1106 may access parameter sets for production trays, I-beams, backplanes (backplanes), and the like. It should be appreciated that each component of the extrusion-molding system 600a may be controlled by a common drive, and that the parameters selected to produce the structural part may change the behavior of each component of the extrusion-molding system 600a accordingly.
As is understood in the art, the system driver 1104 may be used to integrate components of the extrusion-molding system 600 a. For example, separate system drivers 1104 may be used to control the feeder 614, heater 618, extruder 604, dynamic die 606, trolley 608, and press 610. The system driver 1104 may be customized by an operator of the extrusion-molding system 600a or may be a general purpose driver provided by a particular component, such as the manufacturer of the extruder 610. During operation of extrusion-molding system 600a to produce a structural part, system driver 1104 may drive components of extrusion-molding system 600a using parameters selected to produce the structural part.
In controlling the components of the extrusion-molding system 600a, the database 1012 and the status alert feedback manager 1114 are used to provide feedback control for each component of the extrusion-molding system 600 a. For example, the heater 618 may feed back the actual temperature through a temperature sensor (not shown). Based on the measured temperature of the heater 618, the system driver 1104, which is used to control the heater 618, may increase or decrease the temperature of the heater 618 based on the actual temperature measurement. Accordingly, other sensors may be used to feedback the temperature, pressure, velocity, weight, position, etc. of each component and/or composite within extrusion-molding system 600 a. In the event of a fatal failure of a component, an alarm signal may be fed back to the controller 612 and detected by the status alarm feedback manager 1114. If the alarm signal is deemed to be a catastrophic failure, the system driver 1104 may shut down one or more components of the extrusion-molding system 600a to prevent damage to hardware or personal injury to an operator. In response to such an alert, the system manager 1100 may trigger the operator interface 1102 to display the fault and provide notification of corrective action or other content.
FIG. 12 is an exemplary schematic illustration of the flow control elements 624a-624f and the lower mold 626, which is cut into a grid 1202. The grid spacing is defined by flow control elements 624 along the y-axis (identified as spacings 1-5) and by spacings a-e along the x-axis. It should be appreciated that by utilizing more flow control elements 624 along the y-axis and defining smaller spacing along the x-axis, a higher grid resolution (resolution) may be achieved. Depending on the particular structural part being formed, a higher or lower resolution may be required, and parameters established by an operator to define the higher or lower resolution may be stored in the controller 612 by the database manager 1106 for use in producing the structural part.
Tables 2-10 are exemplary data tables used to control the components of the extrusion-molding system 600 a. In particular, the tables provide control data 1018 for controlling the components and feedback data 1022 received by the controller 612 from the components. Table 2 provides control over the feeder 614, which feeder 614 is used to feed the thermoplastic composite M1, the fibrous material M2, and any other materials (e.g., pigments) that form the structural part. As shown, the control data 1018 includes the rate at which each feeder 614 delivers material to the extrusion-molding system 600a, and the feedback data 1022 includes the level of material currently within each feeder 614. During operation of the extrusion-molding system 600a, the rate of material delivered from the feeder 614 is controlled and the level of material in the feeder 614 is measured, and in response to the material in the feeder 614 reaching a minimum amount, the operator may be notified of the level of material so that the operator may dispense additional material to the feeder 614.
TABLE 2
Table 3 is an exemplary table providing temperature control for heaters within extruder 604. Where extruder 604 is defined to have 7 temperature zones 1-n, the temperature of each zone can be set by extruder temperature control, which is defined to be set to heat or cool, on or off, and/or a specific temperature (not shown). Feedback data 1022 may include the actual temperature of each zone of extruder 604. Accordingly, a temperature sensor is integrated into each zone of the extruder 604, and the sensed temperature is fed back to the controller 612 for feedback control via a feedback bus 1020.
TABLE 3
Table 4 is an exemplary table providing speed control of a motor (not shown) driving a propeller 620 operating within the extruder 604. Control data 1018 includes speed control settings for the drive motor. The actual speed and load of the motor is fed back to the system driver 1104 via feedback data 1022, and the system driver 1104 is used to control the speed of the auger 620 of the extruder 604 via control data 1018.
TABLE 4
Table 5 defines the temperature control of the heaters within the dynamic die 606. The control data 1018 may be defined by regions 1-n within the dynamic model 606. Similar to the temperature control of the extruder 604, the heater 618 may include heating and cooling controls and/or switch settings for controlling and/or adjusting the temperature of different zones within the dynamic die 606. Accordingly, the feedback data 1022 may include the actual temperature of each region within the dynamic model 606 to control it.
TABLE 5
Table 6 is an exemplary table for controlling the flow control element 624 of the dynamic die 606. As shown, the control data includes the flow control elements 1-n and the position of each flow control element 624, where the position of the flow control element 624 ranges from 1-m. It should be appreciated that the flow control element 624 may have an almost infinite number of positions. However, for practical purposes, the position of the flow control element is typically set to have some predetermined position, such as every quarter inch ranging from zero to six inches, for example. In controlling the position of the flow control element 624, a stepper motor or other type of motor may be used. Accordingly, the feedback data 1022 for the flow control element 624 includes the current position of the flow control element 624, such that any positional deviation from the control data 1018 conveyed by the controller 612 to the dynamic die 606 can be corrected by the feedback loop via the feedback data 1022, as is understood in the art.
TABLE 6
Table 7 is an exemplary table providing temperature control of the lower mold 626. It should be appreciated that a similar table may be used to control the temperature of the upper die 632. As shown, the lower mold 626 may be divided into zones 1-n where heaters and/or coolers may be applied to each zone to heat and cool the lower mold 626 as commanded by the control data 1018. Accordingly, the feedback data 1022 may provide an actual temperature for the lower mold 626 so that feedback control may be performed by the controller 612 to regulate the temperature of the lower mold 626. For example, as the extruded composite material 625 is applied to the lower mold 626, the temperature of the lower mold 626 may be adjusted over all of these areas, such that the temperature of the extruded composite material layer 628 may be adjusted based on time and other factors as the composite material is deposited onto the lower mold 626 until the structural part is removed from the molds 626 and 632.
TABLE 7
Table 8 is an exemplary table that provides exemplary control parameters for controlling the trolley 608. As shown, control data 1018 includes position, speed, and elevation control for the trolley 608. It should be appreciated that additional control data 1018 may be included to control the movement of the trolley 608. For example, acceleration, rotation, or angular position, or other dynamic control data may be used to move or synchronize the trolley 608 to properly adjust the lower mold 626 with respect to the application of the extruded composite material 625 being deposited or deposited onto the lower mold 626. Feedback data 1022 for trolley 608 may include the actual position and current velocity of trolley 608. The lift control data may be used to engage and disengage the wheels 634 of the trolley 608 during deposition of the extruded composite material 625 into the lower mold 626 and pressing of the extruded composite material layer 628 into the molds 626 and 632 by the press 610, respectively. The actual position of the elevation may be fed back to ensure that the press 610 is not activated until the wheels 634 are disengaged by the elevation mechanism (e.g., air tubes).
TABLE 8
Table 9 is an exemplary table that provides control of the press 610. Control data 1018 may include lock control data and cycle squeeze time. The feedback data 1022 may include the position of the trolley 608 within the press 610 as well as the position of the press platen (toten). Other control and feedback parameters may be additionally included to control the press. For example, temperature control of the upper die 632, force of the press 610, and the like may also be included.
TABLE 9
Table 10 provides an exemplary table for controlling a drawing tool (not shown) used to draw an already formed structural part from the dies 626 and 632 during the forming of the structural part, after the pressing process and optionally the cooling process is completed. Control data 1018 may include the starting drawing cycle and feedback data 1022 may include the position of a single drawing (extraction) tool. It should be appreciated that multiple drawing tools or elements of a drawing tool may be used, and other sensory feedback data may be sensed and fed back to the controller 612.
Watch 10
FIG. 13 is a top view of the flow control elements 624a-624i, with the flow control elements 624a-624i aligned to deposit composite material on the lower mold 626 of FIG. 6A. As shown, the flow control elements 624 are disposed along the y-axis, which provides three-axis control of the deposition of the extruded composite material 625 onto the lower mold 626. Accordingly, x-axis control of the deposited extruded composite material 625 may be provided by controlling the movement of the trolley 608 at different speeds under the flow control element 624, y-axis control of the deposited extruded composite material 625 may be provided by adjusting the flow control element 624, and z-axis control of the deposited extruded composite material 625 may result from controlling the deposition of the extruded composite material 625 along the x-axis and y-axis.
Control over the deposition of the extruded composite material 625 along the x, y, and z axes can be performed using a variety of techniques, including: (1) the volumetric flow rate of the composite material from the extruder 604 is controlled by the rotational speed of the impeller 620; (2) controlling the rate of movement of the trolley 608 in a single axis; (3) controlling an output orifice of the extruder 604, wherein the extruder 604 has a single flow control element 624 or a plurality of flow control elements 624 operating in unison; (4) individually controlling the plurality of flow control elements 624; and (5) control the movement of the trolley 608 in multiple axes. Each of these techniques assumes that the other variables remain constant. For example, technique (1) assumes that the output orifice of the extruder 604 is fixed and the trolley 608 moves at a constant rate below the output orifice. Technique (2) assumes that the volumetric flow rate of the composite material from the extruder 604 is constant and the output orifice of the extruder 604 is fixed. However, it should be appreciated that these techniques may be combined to provide additional control over the placement of the extruded composite material 625 on the lower mold 626 as discussed with reference to FIG. 6A, where techniques (1), (2), and (4) are combined. Technique (5) includes providing not only x-axis and y-axis control of the lower mold 626, but also z-axis control and rotational control about any number of axes. By providing such control over the lower mold 626 using technique (5), a variety of structural parts may be formed that may not otherwise be possible. In summary, the overall computer control of the various elements of the inventive process plays a key role in coordinating the extrusion process and the production of the desired part, as well as the overall operability of the process.
Finally, using the moving output orifice from the extruder 604, the extruded composite material 625 may be deposited onto the stationary or moving lower mold 626 without controlling the movement of the lower mold 626. For example, an output aperture that moves along a rail or other mechanical mechanism may be controlled to deposit the composite material at a particular location on the lower mold 626. An analogous mechanism to such a mechanism is a laser inkjet printer.
Referring again to FIG. 13, the flow control element 624 is shown relative to the lower mold 626 as the lower mold 626 passes under the dynamic mold 606, and the numbers on the right correspond in inches to the position of the trolley 608 as it passes under the dynamic mold 606. The lower mold 626 begins 10 inches into the trolley 608 because the lower mold 626 is smaller than the trolley 608. Tables 11-12 are exemplary tables providing parameters for speed and die control of the flow control element 624. These parameters may be used to produce a pallet using the extrusion-molding system 600 a.
TABLE 11
TABLE 12
Tables 11 and 12 provide positional synchronization between the flow control element 624 and the movement of the trolley 608. By coordinating the movement between the two components (i.e., the dynamic die 606 and the trolley 608), the extruded composite material 625 may be deposited at a location along the lower mold 626 as dictated by the volume of the cavity 630 defined by the lower and upper molds 626 and 632. In other words, the extruded composite material 625 is deposited onto the lower mold 626 to form the extruded composite material layer 628, the extruded composite material layer 628 having sufficient thickness to fill the cavity 630 defined by the lower mold 626 and the upper mold 632, thereby providing the ability to form deep draw draft and hidden ribs in certain locations of the structural part.
Fig. 14 is an exemplary perspective top view of a corner of a tray 1400 produced by the extrusion-molding system 600a shown in fig. 6A. As shown, the draft angle or depth d1 of the base 1402 of the tray 1400 is shallower than the depth d2 of the foot 1404 of the tray 1400. By controlling the deposition of the extruded composite material 625 on the lower die 626 using the principles described herein, large structural parts featuring deeper draw draft d2 in specific areas of the structural part, such as the feet 1404, may be formed with the reinforcement material M2 (e.g., long strands of fiber).
Fig. 15A and 15B are exemplary perspective bottom and top views, respectively, of a platform 1500 having hidden ribs 1502a-1502e (collectively 1502). As shown, the hidden ribs 1502 vary in height, but have a defined volume in one or more regions. Thus, less extruded composite material 625 is deposited on areas without the hidden ribs 1502 by depositing more extruded composite material 625 on areas with hidden ribs 1502. Because the platform 1500 is formed as a single molded composite structure using the extrusion-molding system 600a, the platform 1500 has fewer defects in the structure than a platform constructed from multiple parts.
Embedding technique (Insertion Techniques)
In addition to forming structural parts from composite materials in which fibers are blended to provide strength in forming large parts, some structural parts are further structurally improved by having other components, such as attachments, fasteners and/or reinforcements, embedded or inserted in certain areas. For example, structural parts to provide interconnectivity may use metal parts extending from composite materials to provide a strong and reliable interconnection. One such structural component is a portion of a floor covering 1600 for a rink, as shown in figure 16A. The floor covering 1600 includes a thermoplastic material 1602 and a fastener 1604, wherein the thermoplastic material 1602 may be formed from a thermoplastic material M1 and a fiber M2, and the fastener 1604 may be formed from a metal.
In forming the ground-covering layer 1600, the fasteners 1604 are positioned or configured within the lower mold 608 such that the extruded composite material layer 628 forms a bonding layer 1606 with the fasteners 1604 to maintain its position. To further secure the fastener 1604 to the floor covering 1600, holes (not shown) may be included in the fastener 1604 to allow the extruded composite layer 628 to fill the holes. During the forming process, an actuator (activator) may be configured within the lower die 626 to maintain the position of the fastener 1604 during the extrusion-forming process and to be released by the controller 612 while the extruded composite material layer 628 is still in molten form. It should be appreciated that the fastener 1604 may alternatively be disposed within the upper die 632.
Fig. 16B is an exemplary portion of a back board 1610 that is often used by caregivers. The backplane 1610 is formed from a composite material 1612 and includes an insert 1614 encapsulated within the composite material 1612. The insert 1614 may be a carbon fiber tube, such that the bottom plate 1610 may be reinforced, lightweight, and x-ray transparent. During encapsulation of the insert, the lower mold 626 may hold the insert 1614 in place with an actuator or simple pins while extruding the composite material layer 628 to form the bonding layer 1616 with the insert 1614. Again, while the extruded composite layer 628 is in a molten state, the actuators and/or pins may be loosened, thereby allowing the extruded composite layer 628 to fill any space left by the actuators or pins. It should be appreciated that the insert 1614 may be substantially any material based on the particular application or structural part being formed.
FIG. 17 is an exemplary flow chart 1700 describing the operation of inserting or embedding an insert, such as a fastener, support, or other element, into a structural part using the extrusion-molding system 600a of FIG. 6A. The insertion process begins at step 1702. At step 1704, an insert is constructed within the lower mold 626 or the upper mold 632. At step 1706, the molten extruded composite material 625 is deposited on the lower mold 626. At step 1708, an extruded composite material is formed around at least a portion of the insert to secure the insert within the structural part being formed. In one embodiment, the insert is encapsulated or completely embedded within the extruded composite material 625 (see, e.g., fig. 16B). Alternatively, only a portion of the insert is inserted into the extruded composite material 625 such that a portion extends from the structural part.
At step 1710, if any supports are used to provide inserts within the lower mold 626 or upper mold 632, the supports are removed. These supports, which may be simple mechanical pins controlled by an actuator or other mechanism capable of supporting the insert during deposition of the extruded composite material 625 onto the lower mold 626, are removed before the extruded composite material layer 628 is hardened in step 1712. During extrusion, vacuum processing, or other operations to form the structural part, the extruded composite layer 628 may be hardened by natural or forced cooling. By removing the supports prior to curing of extruded composite layer 628, the gaps created by the supports may be filled so as to not leave marks or defects of supports within the structural member. At step 1714, the structural part with the insert at least partially embedded therein is removed from the molds 626 and 632. The embedding process ends at step 1716.
In another embodiment of the invention, the insert is encapsulated by the process of the claimed invention. With the claimed extrusion-molding system, inserts, such as fasteners, supports, or other elements, may be encapsulated with extruded thermoplastic material in a manner similar to the process described in FIG. 17. In other embodiments of the present invention, multiple layers of material of varying thickness may be deposited one on top of the other using the claimed extrusion-molding system. In particular, a first layer of thermoplastic material is extruded into the lower die, and then a second layer of the same or different thermoplastic material is layered over the first layer. In certain embodiments of the present invention, the insert may be placed on top of the first extruded layer prior to, or without, layering the first extruded layer with the second extruded layer. This form of "layering" is advantageous for forming structures having multiple layers of thermoplastic material and different layers of embedding material of the same or different composition.
The present invention advantageously allows for molding of articles having three-dimensional features with solid protrusions (rased). A non-limiting list of these prominent features include blind ribs, posts, mounting posts, and tabs (tabs).
These articles may optionally have internal reinforcing inserts to provide additional stability and strength. Examples of reinforcing inserts are tubes, rods and mesh (mesh), although any kind of internal support structure may be used to provide the reinforcing effect. These reinforcing inserts may have any type of geometry or structure. For example, the cross-sectional profile of the reinforcing insert may be circular, hemispherical, star-shaped or square, without any limitation. The reinforcing inserts may also be formed of any kind of material, such as carbon, metal, composite, plastic or organic substances such as wood.
Large articles, such as articles longer than 0.5 feet in at least one of the z, y, and z planes, can be obtained with the present invention. In particular embodiments, large items having dimensions longer than 1 foot, 2 feet, and 3 feet may be obtained. These large items may also be heavy and may weigh more than 10 pounds (lbs). In particular embodiments, articles weighing greater than 20 pounds or 25 pounds may be prepared.
Additional embodiments of the present invention will be apparent from the examples provided below.
Example 1
In one embodiment of the invention, a single helix, diameter 4, is used1/2"extruder (equipped with six heating zones and a standard PET screw) polypropylene resin (COP3541) from General Polymers was mixed with 1/2" long fiber glass fibers (740DS) from Johns-Manville. The resin/glass mixture consisted of 70% polypropylene and 30% glass. The extruder zones were electrically heated and controlled at the following temperatures: region 1@ 350F; region 2@ 375F; region 3@ 400F; region 4@ 450F; area 5@ 475F; area 6@505F. A coupling agent (polysulfide rubber adhesive) was added to the glass resin mixture at a level of 2% to enhance bonding of the glass fibers to the resin matrix.
The heated mixture is delivered through an unobstructed delivery tube to a heated, horizontally mounted sheet extrusion die having a plurality of die openings with independently controlled die openings capable of varying the thickness of the polymer melt extruded through each die opening. The molten mixture was maintained at 505 ° F throughout the extrusion process in a die with a die. The molten resin/glass extrudate is gravity deposited onto a horizontally movable and heated mold half of a mating mold. The deposition of the molten mixture is controlled by a combination of opening and closing of the die orifice on a horizontally mounted sheet die in combination with controlled movement of the horizontally mounted matched die halves. During the extrusion process, opening and closing of the die orifice on the die and movement of the matched die halves are accomplished using computer programs and electrical controls to coordinate the precise width, length and depth of the molten material deposited at each point on the surface of the movable die. In so doing, the resulting molten material deposited into the mold represents a molten "near net shape" layup of the desired final molded product.
Upon completion of the "near net shape" fused deposition of the resin/glass mixture, the filled matched mold halves are mechanically transferred to a compression press with a trolley system for final consolidation of the molded part. Since the mold-filled half represents a "near net shape" of the final molded part, the final compression molding step using the other half of the matched mold can be accomplished at very low pressures (< 2000psi) with minimal movement of the molten resin/glass mixture. Accordingly, the rectangular matched-mold female mold section with an internal cavity measuring 12 "wide, 24" long, 1/4 "deep was filled with the molten polypropylene/glass mixture described above in a" near net shape "application. The filled female mold sections of the molds were mechanically transferred to a 300 ton White pneumatic compression molding press equipped with an 8 'x 9' platen (plate) and air bag (air bag loader). In the final molding step, the male mold half of the matched mold is pressed onto the filled female mold half of the matched mold. The mold was held until it cooled below 200F. The resulting molded sheet measured approximately 12 ". times.24". times. 1/4 ". The molded part exhibited the following characteristics:
tensile strength (10)3) Tensile modulus (10)6) Flexural strength (10)3)
Axial direction 6.630.7112.53
Transverse direction 6.730.6711.56
Note that: each is an average of a number (5) of measurements made on a number (3) of independent plates.
Thus, molded panels exhibit mechanical properties in the machine and transverse directions within 20% of each other and are therefore nearly anisotropic.
The resin was burned off the molded panel and the residual glass fibers were analyzed, revealing an average fiber length of 0.43 "in the molded panel versus an input length of 0.5". This represents that 85% of the original fiber length remains in the final molded product.
Example 2
A pre-mixed ABS (acrylonitrile/butadiene/styrene) resin containing 30% by weight 1/2 "long glass fibers from LNP was extruded using the following extruder zones and die temperatures with reference to example 1: region 1@ 375F; region 2@ 400F; region 3@ 425F; area 4@ 475F; region 5@ 515F; region 6@ 515F; mold temperature @ 515F. Using the same mold as in example 1, a sample panel of approximately 12 "x 24" x 1/4 "was prepared, which exhibited the following characteristics:
tensile and bending resistant
Strength (10)3) Modulus (10)6) Strength (10)3) Modulus (10)6)
Axial direction 7.020.9512.960.71
Transverse direction 7.530.7710.960.60
Note that: each is an average of a number (3) of measurements.
The molded panels exhibit mechanical properties within 20% of each other in the machine and transverse directions, and thus, the mechanical properties approach anisotropy.
Burning off the resin from the molded panel and analyzing the residual glass fibers revealed that the average fiber length within the molded panel was 0.30 "or 60% of the initial fiber length.
Example 3
According to example 1, a blend of polypropylene and 1/2 "long fiber glass fibers (88% resin/12% glass fibers by weight) was processed using a wood match die to produce a rigid, solid ribbed antenna cover (radome cover) having dimensions of 12 'length by 8' width by 1" thickness and weighing 120 pounds.
Example 4
According to example 1, a blend of polypropylene and 1/2 "long fiberglass fibers (70% resin/30% fiberglass by weight) was processed with solid aluminum matched metal molds to produce a 7" high by 4 "wide by 8" long beam with solid diagonal reinforcing ribs weighing 22 pounds.
Example 5
According to example 1, a blend of Nylon 6 and 1/2 "long glass fibers (70% resin/30% glass fibers by weight) from General Polymers was processed using an extruder zone and a die temperature above at least 100C of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" panel.
Example 6
According to example 1, a mixture of Polyetheretherketone (PEEK) and 1 "long carbon fibers (70% resin/30% carbon fibers by weight) was processed using an extruder zone and a die temperature above at least 100C of the glass transition temperature of the resin to produce a 12' x 24" x 1/4 "panel.
Example 7
According to example 1, a mixture of Polyetheretherketone (PEEK) and 1/2 "Kevlar fibres (70% resin/30% Kevlar fibres by weight) was processed using an extruder zone and a die temperature above at least 100C of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" sheet.
Example 8
A blend of polypropylene and 3 "long fiber glass fibers (80% resin/20% glass fibers by weight) was processed according to example 1 to produce a 12" x 24 "x 1/4" panel.
Example 9
According to example 1, a blend of polypropylene and 1/2 "long fiber glass fibers (45% resin/55% glass fibers by weight) was processed to produce a 12" x 24 "x 1/4" panel.
Example 10
According to example 1, a blend of polypropylene and 1/2' long fiberglass fibers (80% resin/20% fiberglass by weight) was processed to produce two halves of a material handling tray that were subsequently combined to produce a material handling tray having dimensions of 48 "long by 40" wide by 6 "high by 63 pounds.
Example 11
According to example 1, a mixture of polypropylene and 1/2 "long fiberglass fibers (70% resin/30% fiberglass by weight) was processed to produce a support beam comprising 1" square i.d. steel tubing inserted along its length and having dimensions of 20' length by 12 "height by 6" width by 180 pounds. The steel tube is inserted into the mold during the mold filling step of the molten resin/glass and prior to the final compression forming of the beam.
Example 12
According to example 1, a mixture of polyethylene and 1 "long wood/cellulose dry fiber (80% resin/20% wood fiber) was processed using an extruder zone and a die temperature above at least 100 ℃ of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" board.
Example 13
According to example 1, a mixture of SMA (styrene/maleic anhydride) resin and 1/2 "long fiber glass fibers (82% resin/18% glass fibers by weight) was processed using an extruder zone and a die temperature above at least 100 ℃ of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" panel.
Example 14
According to example 1, a blend of PPS (polyphenylene sulfide) and 1/2 "long fiber glass fibers (70% resin/30% glass fibers by weight) was processed using an extruder zone and a die temperature above at least 100C of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" board.
Example 15
According to example 1, a blend of PC (polycarbonate) and 1/2 "long fiber glass fibers (80% resin/20% glass fibers by weight) was processed using an extruder block and a die temperature above at least 100C of the glass transition temperature of the resin to produce a 12" x 24 "x 1/4" panel.
The forming process performed in accordance with the present invention is performed at substantially lower compression pressures than typical forming processes used in the industry. These low pressures advantageously allow the use of non-metallic molds, such as wood molds, which are generally not capable of withstanding the high pressures used in the industry.
Any type of fibrous material may be used in the present invention. For example, the fibrous material may be glass fibers, fiberglass, carbon fibers, synthetic fibers, metal fibers, natural fibers, cellulose or wood.
Any thermoplastic resin may be used to prepare the articles according to the present invention. Examples of suitable thermoplastic resins are polyolefins, polyhaloolefins, polyaromatics, poly (alkenyl arenes), polystyrenes, acrylonitrile/butadiene/styrene resins, polyamides, nylons, polycarboxylic acids, polyamines, polyethers, polyacetals, polysulfones, poly (organosulfides), poly (organooxides), polyesters, polycarbonates, polyimides, polyurethanes, polyetheretherketone resins, styrene/maleic anhydride resins and mixtures thereof.
The thermoplastic resin may be a single polymer or a mixture of two or more polymers. In particular embodiments, the thermoplastic resin may comprise a homopolymer, copolymer, random copolymer, alternating copolymer, block copolymer, graft copolymer, liquid crystal polymer, or a mixture of such polymers.
The thermoplastic resin may be a virgin resin, a recycled resin, or a mixture of virgin and recycled resins in any proportion. The thermoplastic resin may optionally include a coupling agent that enhances bonding of the fibrous material to the resin.
Articles such as trays, beams, doors, radomes, structural products such as wall panels and modular parts, pipes, columns and pilings can be successfully prepared according to the claimed invention.
The foregoing description is of preferred embodiments for implementing the invention, and the scope of the invention should not be limited by this description. The scope of the invention is defined by the following claims.