US20030187624A1 - CNC control unit with learning ability for machining centers - Google Patents

Abstract

A CNC control unit1with learning ability solves the problem of automatic and intelligent generating of NC programs for CNC machining centers for milling, drilling and similar operations. The key module of the CNC control unit1is a neural network (NN) device7,that learns to generate the NC control programs through an NN teaching module4.Upon completion of learning process the NN device7can generate automatically, without any intervention of the operator, merely on the basis of the CAD 2D, 2,5D or 3D part models, taken from a conventional CAD/CAM system29, various new NC control programs for different parts, which have not been in the machining process before. The CNC control unit1with learning ability is suitable especially for machining centers intended for milling, including face milling (rough), contour milling (rough), final milling following the contour and in Z-plane, final contour 3D milling, contour final milling, milling in Z-plane, final contour milling on the equidistant, and milling of pockets; drilling, including normal drilling, deep drilling, and center drilling; and reaming, sinking and threading.

Description

FIELD OF THE INVENTION
• The invention relates to manufacturing technology, in particular to programming and numerical control of machining centers for milling, drilling and similar operations.[0001]
• The conventional control units for the CNC (Computer Numerical Control) machining tools, especially the control units for machining centers intended for milling, drilling and similar operations, typically contain a microcomputer, consisting of a decoder, a position memory, a function memory, an interpolation program, and a functions program. The NC program is fed to the computer either through a punched tape reading device or in a DNC (Direct Numerical Control) mode through an interface. A manual input is also foreseen, but it is limited to smaller corrections of the NC control program or to individual changes of technological parameters. The NC functions program comprising the technological data is sent to the NC machine through an adaptable interface. The NC positions program is send through a comparison unit and an amplifier unit to a step motor of the NC machine. Either the support for the part or the cutting tools of the machine can be moved following the geometric data. A position meter perceives every movement and sends a regulated position value to a position-measuring module, which forwards the data to comparison unit, where the difference between the actual and the desired position is calculated. The geometric data is obtained from the NC control program for the part and is processed in the position loop.[0002]
• A new NC control program must be supplied to the CNC control system for each part, as the control system does not remember the operations already performed and can not automatically change the program parameters, with the exception of some technological parameters, for example the cutting conditions, corrections of tool length, offset of reference or zero points.[0003]
• The use of modern CAD/CAM systems does not solve this problem. These systems just enable that a new NC control program is performed faster and more reliably. Some systems allow saving of certain processing strategies, nevertheless, the intervention of skilled NC programmer is still necessary. The programs made in this way cannot be used directly for the CNC control of the machine tool; they must be adapted in a post-processing phase. The task of this phase is to modify a generally valid file of the tool path (CLDATA) for each machine tool, i.e. for each CNC control. Every NC control program and every change must go through such post-processing phase.[0004]
• The technical problems indicated above can be solved by an NC control system with learning ability and the ability of automatic intelligent generation of NC control programs which follow the computer read engineering drawings and/or 3D CAD models of the parts to be processed.[0005]
• In the patent DE4O1 1591 (JP19890098177) an NC control unit with integrated learning function is described. The NC control unit makes a teaching NC control program that is compared with the inserted NC control program to make the resulting NC control program. The actual NC control program can be changed or supplemented by the machine operator who chooses the “teaching” way of operation and then supplements the NC control program. The solution requires the intervention of a skilled operator or a programmer.[0006]
• The patent application US2001/0000805 A1 describes a device for generating a tool path on NC machines and the pertinent NC control system. First, the device identifies the geometric feature characteristics of a CAD model, and then it chooses the most suitable tool path amongst the stored processing procedures (machining cycles, sub-programs). Only the machining procedures, which have been defined as typical processing procedures for particular sub-programs, are available for selection.[0007]
• The patent U.S. Pat. No. 6,022,132 describes a method and a device for programming the CNC machine tools on the basis of a probe built-in into the main spindle of the machine tool. The probe is moved manually following the required profile (tool path). After receiving the data the computer generates an automatic NC control program, which gives the commands for the movement to the CNC control system. This method does not include any elements of artificial intelligence.[0008]
• The patent US63 14412B1 describes an evolutional control of a driving machine in a vehicle with respect to chosen coefficients. A scheme of the control unit is constructed on the evolution principles. The system is adapted for building-in into a vehicle.[0009]
• The patent EP0726509A1 describes an interactive programming system for CNC machine tools. It allows the operator to choose interactively between different control programs and procedures, which are then automatically composed into an NC control program. The solution requires the intervention of an operator or a programmer.[0010]
• The patent JP2001034155 describes a learning method and a device made for this purpose. A special man-machine interface is built-in into the control unit of the machine to enable a conversation with the user and the learning process.[0011]
• The patent JP 11242510 describes a device and a method for generating the NC control programs. A special device saves the data about the part, pertinent coordinates, junction's characteristics and the time necessary for assembling the individual electronic components. The solution enables a reduction of time needed for preparing the NC control programs and a reduction of mistakes arising at preparing the programs.[0012]
• In all the solutions presented above manual intervention of a skilled operator or a programmer is necessary for preparing the NC control program for CNC machine tools. The systems cannot create the NC control programs for the parts, which are not saved in the database, and cannot choose and use the machining strategies automatically.[0013]
DETAILED DESCRIPTION OF THE INVENTION
• The object of the invention is to provide an improved programming and numerical control for machining centers intended for milling, drilling and similar operations which has the learning ability and the ability of automatic intelligent generation of NC control programs. The said object of the invention is achieved by means of a neural network (NN), which learns to generate NC control programs through a teaching module. Consequently, the NC control programs can be generated automatically without any intervention of the operator, merely on the basis of the 2D, 2,5D or 3D computer models of the parts to be processed.[0014]
• The objects, advantages and features of the invention will be presented in detail by means of drawings in the following figures:[0015]
• FIG. 1—shows a block diagram of a CNC unit with learning ability for machining centers according to present invention,[0016]
• FIG. 2—shows a schematic layout of a neural network device, FIG. 3—shows a flow chart of learning and generating the neural network, FIG. 4—shows a schematic layout of the neural network.[0017]
• The learning process and the automatic intelligent generation of the[0018]NC control programs28 take place in a neural network (NN), built-in in aspecial NN device7, which receives the learning instructions from the NNteaching module4. The NNteaching module4 is not a constituent part of theCNC unit1 and works independently. Upon completion of learning process theNN device7 can generate automatically, merely on the basis of theCAD part model5, coming from conventional CAD/CAM system29, and without any intervention by the operator, various newNC control programs28 for different parts, which have not been in the machining process before.
• The[0019]NC control programs28 are fed from theNN device7 to a modifiedmicrocomputer2, which includesinternal interface9 for transmission ofNC control programs28 to aposition memory11 and to afunction memory12. To thefunction memory12, themanual commands6 from themanual input module8 can be fed as well, to wit through thedecoding module10. Thecommands6 are mostly of technological nature, i.e. feed rate, revolution speed, switch on/off of cooling liquid etc.
• The teaching data for the[0020]NN device7 come from aspecial teaching module4, which is not a constituent part of theCNC control unit1. The task of theteaching module4 is to teach the neural network in theNN device7 the principles and the technology of NC programming for all the machining operations on CNC machining centers, above all for milling, drilling and similar operations.
• In general, different neural network systems and different software products, also software developed for commercial purposes, can be applied. However, if special criteria have to be considered and met in machining processes, e.g. costs, time, quality of cutting, tool life, high speed cutting etc., the neural networks developed especially for specific purposes should be used.[0021]
• The schematic diagram of the[0022]NN device7 according to the invention is shown in FIG. 3. The NNdevice7 consists of amodule25 designed to recognize geometric and technological features fromCAD part model5 and to generate the features basedCAD part model26. TheCAD part model26 is fed to theNN milling module27, which has before that, namely in the learning phase, been instructed by the NNteaching module4 to generate the specificNC control program28 for specific machining operation, e.g. for milling or drilling or similar operation.
• In the learning phase, the[0023]N7N device7 is connected to theteaching module4 designed for instructing the neural network (NN). Theteaching module4 takes the data from conventional, commercially available CAD/CAM system for programming the NC/CNC machine tools. By means of a conventional CAD/CAM system29, theteaching NC programs36 are prepared for different parts, defined inengineering drawings module35, and are sent to theteaching module4. In thedecision module38, subsequent to thetesting module37, the decision is taken on the success of teaching. In case that the decision is NO, thepath39 is active and the repetition of the teaching process takes place. If on the other hand theNN device7 has learned enough, thepath40 is active and the generated neural network is sent to theNN device7.
• The functioning principle of the[0024]NN device7 is shown on FIG. 4. The neural network built-in in theNN device7 consists of three layers: theinput layer43, the hiddenlayer44 and theoutput layer45. On theinput layer43, the X-Y-Z sets42 of coordinate points appear, representing the coordinate point values obtained from the modifiedCAD model26 for individual machining operations types41. The coordinate point values are determined according to special procedure. Through the intermediate hiddenlayer44 the input coordinates are transposed intooutput layer45 in a form of a set of coordinate points X₁, Y₁,Z₁46, representing the position values of the tool path for individual machining operations.
• By means of the neural network the following machining operations can be carried out: face milling (rough), contour milling (rough), final milling after the contour and in Z-plain, final contour 3D milling, contour final milling, milling on Z-plain, final contour milling on equidistant, milling of pockets, normal drilling, deep drilling, centering, reaming and threading.[0025]
• The[0026]CNC control unit1 according to the invention can function in either of the following two modes:
• 1. Programming mode, i.e. the mode of intelligent and completely automated processing of a CAD part model into a specific NC control program.[0027]
• 2. Learning mode, in which a learned NC programming system based on the principle of a neural network is entered through the[0028]teaching module4 into theNN device7.
• The principle of generation of the NC control program is shown in FIG. 4. In the programming mode, the[0029]CNC control unit1 gets the data package of theCAD part model5 from the conventional, commercially available CAD/CAM system29 intended for programming the CNC machines. The model is then transmitted to theNN device7, which identifies and classifies the individual geometric andtechnological features25 of the CAD part model. Based on these characteristic features a newCAD part model26 is built, which is transmitted to theN7N milling module27, where on the basis of learned intelligent procedures the most suitable machining operations and cutting parameters (cutting speed, feed-rate and the depth of cutting) with respect to chosen conditions (machining time, surface quality, machining costs) are defined.
• The output of the[0030]NN milling module27 is theNC control program28 for the processed part, which includes the geometric data about the mode of cutting tool path (linear G01 or circular G02/G03 interpolation), the coordinates of the cutting tool path (e.g. milling cutter), the technological data (revolution speed, feed-rate, depth of cutting) and auxiliary data (coordinates of reference, zero and starting points, direction of rotation of the main spindle M02/M03, change of cutting tools M06, etc.).
• The data is then transmitted to[0031]internal interface9, which splits the data in the NC control program into tool path data (coordinates of movement in axis X, Y, Z and/or rotation A, B, C around coordinate axis X, Y, Z) saved inposition memory11 and into functions data (M, S, T) saved infunction memory12.
• The NC functions[0032]program14, which contains the technological data, is transmitted throughadaptable interface18 to theNC machine3. The NC position program is then sent through thecomparison unit15 and theamplifier unit17 to thestep motors19 of theNC machine3. Either the machine tool slide32 or the cutting tools31 can be moved in accordance withgeometric data24. Theposition meter20 perceives the movement and sends aregulated value22 into the position-measuringmodule16, which transmits the data tocomparison unit15, where the difference between the actual and the programmed position is calculated.
• The geometric data are obtained from the[0033]NC control program28 for each part and are treated in theposition regulation circle23.
• In the learning mode, the learned NC programming system based on the principle of a neural network is fed to the[0034]NN device7 through theteaching module4, which conducts the teaching of theNN device7. The functioning of the NN module is schematically shown in FIG. 3.
• The origin for the teaching process is the engineering drawing[0035]35 of a prismatic part, suitable for processing on machining centers, designed for milling, drilling and similar operations. First, theteaching NC program36 is generated by the conventional CAD/CAM system29 and sent to theNN teaching module4. Then, testing37 of the obtained NC program is performed. In thedecision module38, the decision is brought on whether the NC control program is suitable and whether the neural network in theNN teaching module4 has learned enough. In the beginning the statement NO39 is valid and the teaching process is repeated using the engineering drawing35 of another part. In such a way the series of teaching cycles is performed until thetesting37 shows, that the decisional condition in theIF module38 is fulfilled, i.e. that thestate40 is accomplished. Here, the teaching process of the NN module ends and the learned neural network is transmitted into theNN device7.
• The[0036]CNC control unit1 can learn how to generate the NC control programs for the following machining procedures:
• 2.1—milling[0037]
• 2.1.1—face milling (rough)[0038]
• 2.1.2—contour milling (rough)[0039]
• 2.1.3—final milling following the contour in Z-plane[0040]
• 2.1.4—final contour 3D milling[0041]
• 2.1.5—contour final milling[0042]
• 2.1.6—milling on Z-plane[0043]
• 2.1.7—final contour milling on equidistant[0044]
• 2.1.8—milling of pockets[0045]
• 2.2—drilling[0046]
• 2.2.1—normal drilling[0047]
• 2.2.2—deep drilling[0048]
• 2.2.3—centering[0049]
• 2.3—reaming,[0050]
• 2.3—sinking[0051]
• 2.4—threading[0052]
• The[0053]NN device7 can be built-in into any CNC control unit for milling machines as shown in FIG. 1. The standard parallel data transmission is used. In case that it is not possible to reprogram theinternal interface9, the NN device must be connected to existing DNC interface, which is a constituent part of every CNC control. TheNN teaching module4 is connected to theNN device7 by means of a standard serial interface. TheCAD part model6 is sent to theNN device7 through a standard communication interface.
• For teaching of the[0054]NN device7 through theteaching module4, different commercially available CAD/CAM programming systems29 can be used, for example Unigraphics Solution, I-Deas, Catia, HyperMill etc.

Claims (6)

1. A CNC control unit1 for machining centers for milling, drilling and similar operations with learning ability and the ability of automatic intelligent generation of NC control programs28, comprising a neural network (NN) device7, a modified microcomputer2, a comparison unit15, a position measuring unit16 and an amplifier17, the improvement comprising the NN device7 that takes instructions from the NN teaching module4, which is not a constituent part of the CNC control unit1 and operates independently taking as a basis for its operation the data package received from a conventional CAD&CAM system, in order to operate as intelligent programming module after the teaching process is completed and to automatically generate adequate NC control program28 for a given part to be processed in the machining center; the said NC control program28 being fed to the modified micro computer2 including an internal interface9 with its first output connected to the position memory11 and its second output connected to the function memory12, which accepts also the manual input commands6 fed through the manual input module8 and the decoding unit10; the modified microcomputer2 further includes a function program module14, with its input connected to the function memory12 and its output connected to the adaptable interface system18, and an interpolation program module13 with its input connected to the position memory11 and its output connected to the comparison unit15 which has its other input connected to the output of the position measuring module16, to which the position data22 are fed from a position meter20, while the output of the comparison unit15 is connected to an amplifier17 which feds the geometric data24 to the step motor19.

2. The CNC control unit1 for machining centers defined inclaim 1, wherein in the mode of intelligent and automated processing of a CAD part model5 into a specific NC control program28 the data package of the CAD part model5 is fed to the N7N device7, which first identifies and classifies the individual geometric and technological features25 of the CAD part model5 and then builds a new CAD part model26, which is transmitted to the NN milling module27, supplying on its output the NC control program28 for the processed part, the said NC control program28 being fed to the internal interface9, which splits the data in the NC control program28 into a position package saved in the position memory11 and into function data saved in the function memory12, wherein the NC function program14, containing the technological data, is transmitted through adaptable interface18 to the NC machine3, while the NC position program, generated in the interpolation program module13, is sent over the comparison unit15 and the amplifier unit17 to the step motors19 of the NC machine3 resulting in a suitable movement either of the parts support32 or of the tools31 in accordance with geometric data24, wherein the position meter20 perceives the movement and sends a regulated size22 into the position measuring module16, which transmits the data to comparison unit15, where the difference between the actual and the programmed position is calculated, while the geometric data are obtained from the NC control program for each part and are treated in the position regulation circle23.

3. The CNC control unit1 defined inclaim 1, that can automatically generate the NC control programs by means of the instructed neural network contained in the NN module4 using the engineering drawings35 of parts, wherein in the learning phase the NN device7 is connected to the teaching module4 which takes the teaching NC programs36 for different parts defined in engineering drawings module35 from the conventional CAD/CAM system29, and wherein the decision on the success of teaching is taken in the decision module38, subsequent to the testing module37, so that in case the decision is NO, the path39 is active and the repetition of the teaching process takes place, while on the other hand the NN device7 has learned enough, the path40 is active and the generated neural network is sent to the NN device7.

4. The NN device7 defined in claims1,2, and3, wherein the said NN device7 is realized in a microprocessor technique and contains an identification module25 that recognizes the geometrical and technological features of different CAD part models5, a generating module26 that produces new feature based CAD models of parts, an NN milling module27, and an automatically generated NC control program28 for a given part.

5. The CNC control unit1 defined inclaim 1 wherein the NN milling module27 enables intelligent, automatic generating of NC control programs that enable the following machining operations to be executed on prismatic parts: milling, including face milling (rough), contour milling (rough), final milling following the contour and in Z-plane, final contour 3D milling, contour final milling, milling in Z-plane, final contour milling on the equidistant, and milling of pockets; drilling, including normal drilling, deep drilling, and center drilling; and reaming, sinking and threading.

6. The procedure of teaching in the CNC control unit1 defined in claims1,2,3 and5, the improvement comprising a process of generation of NC control programs in a conventional CAD/CAM system29 based on engineering drawings of parts, the said NC control programs serving as teaching NC programs36 in the NN module4 that instructs the NN device7, wherein the decision on the success of teaching is taken in the decision module38, subsequent to the testing module37, so that in case the decision is NO, the path39 is active and the repetition of the teaching process takes place, while in case that the NN device7 has learned enough, the path40 is active and the generated neural network is sent to the NN device7

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