Abstract:
A method and a device for operating a machine tool are disclosed, wherein a machining operation of the machine tool is controlled by a parts program by storing a simulated configuration of the machine tool in the parts program, determining an actual configuration of the machine tool, comparing the actual configuration with the simulated configuration of the machine tool stored in the parts program, and generating a warning message if the actual configuration is not in conformance with the simulated configuration. This prevents errors in the machining process resulting from a discrepancy between the configuration of the machine tool used in the simulation of the parts program and the configuration of the actual machine tool during the actual machining operation.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of European Patent Application, Serial No. 07021943, filed Nov. 12, 2007, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a method and a device for operating a machine tool. 
         [0003]    Nothing in the following discussion of the state of the art is to be construed as an admission of prior art. 
         [0004]    In order to reliably prevent collisions, the machining time and the freedom from errors in parts programs for manufacturing workpieces by machine tools, it has become increasingly common to simulate parts programs, which include a model of the real machine tool, prior to the actual real machining operation on the real machine tool. Only after the simulation has been carried out successfully is the parts program transferred to the real machine tool, and the machining operation is controlled using the parts program. 
         [0005]    However, the simulation can only provide additional safety with respect to the criteria of absence of collisions, machining time and freedom from errors if the configuration of the modeled machine tool in the simulation conforms to the actual configuration of the machine tool, i.e., the actual configuration of the real machine tool present at the time of the machining operation. 
         [0006]    Examples for such a configuration are:
   1. tool-equipment data, for example in form of tool dimensions, tool holder geometries and magazines used in the tool change,   2. blank data, such as the position and geometry of the blank,   3. tool clamping piece data such as the position and geometry of the clamping pieces for clamping the blank,   4. software configuration, for example in form of control software version and/or parameterizations of the control and drives.   
 
         [0011]    The confidence instilled by the “successful” simulation in the quality of the parts program tested by such means, and the demand for ever faster production times, often causes in practice further tests on the real machine tool (for example, carrying out the machining operation with a markedly reduced feed) to be eliminated. However, the actual configuration, i.e. the configuration of the machine tool actually present at the time of the pending machining operation, often does not correspond to the configuration used in the simulation (referred to below as the simulated configuration). In a worst case scenario, a “successfully” simulated parts program may therefore still cause damage to the real machine tool or costly workpiece rejects. Additionally, incorrectly calculated machining times lead to a deterioration in the ability to plan cycle times and machine movements. 
         [0012]    It would therefore be desirable and advantageous to develop an improved method and a device for operating a machine tool to obviate prior art shortcomings and to avoid, during a machining process, faults caused when the configuration of the machine tool used to simulate the parts program does not conform to the configuration of the real machine tool during the real machining operation. 
       SUMMARY OF THE INVENTION 
       [0013]    According to one aspect of the invention, in a method for operating a machine tool, a machining operation of the machine tool can be controlled by means of a parts program, wherein an actual configuration of the machine tool is determined, wherein the actual configuration is compared to a simulated configuration of the machine tool stored in the parts program, wherein a warning message is generated in the case where the actual configuration does not conform to the simulated configuration. 
         [0014]    According to another aspect of the invention, a device for operating a machine tool controls the machining operation of the machine tool by means of a parts program, wherein the device is designed such that an actual configuration of the machine tool can be determined by the device and the device can compare the actual configuration to a simulated configuration of the machine tool stored in the parts program and a warning message can be generated by the device in the case where the actual configuration does not conform to the simulated configuration. 
         [0015]    According to another advantageous feature of the present invention, the machining operation may be initiated if the actual configuration and the simulated configuration conform, whereas the machining operation may not be initiated if the actual configuration and the simulated configuration do not conform, because damage to the machine tool and/or the production of faulty workpieces, for example, can be reliably avoided by this measure. 
         [0016]    According to another advantageous feature of the present invention, the simulated configuration may be stored in encrypted form in the parts program and subsequently decrypted. This prevents the possibility of manipulating the simulated configuration stored in the parts program. 
         [0017]    According to another advantageous feature of the present invention, at least parts of the actual configuration may be determined using an image acquisition device and/or a sensor and/or a measuring device. The actual configuration can then be automatically determined. 
         [0018]    According to another advantageous feature of the present invention, the actual configuration may be available in form of data relating to the tool-equipment and/or the blanks and/or the tool clamping pieces and/or the actual configuration may be available in form of the software configuration. Such a form of the actual configuration represents a typical form of the actual configuration of a machine tool. 
         [0019]    According to another advantageous feature of the present invention, the parts program may be generated by simulating the machining operation using a simulated configuration of the machine tool and a parts program in which the simulated configuration has not yet been stored, and by subsequently storing the simulated configuration in that parts program. A parts program in which the simulated configuration is stored can thereby be generated in a simple fashion. 
         [0020]    According to another advantageous feature of the present invention, the simulated configuration may be stored in an encrypted form because this prevents later manipulation of the simulated configuration in the parts program. 
         [0021]    According to another advantageous feature of the present invention, the machining operation may be initiated by the device if the actual configuration and the simulated configuration conform, whereas the machining operation may not be initiated by the device if the actual configuration and the simulated configuration do not conform, because damage to the machine tool and/or the production of faulty workpieces, for example, can be reliably prevented with this measure. 
         [0022]    According to another advantageous feature of the present invention, the simulated configuration may be stored in the parts program in an encrypted form and that it can be decrypted by the device. This prevents the possibility of manipulating the simulated configuration stored in the parts program. 
         [0023]    According to another advantageous feature of the present invention, at least parts of the actual configuration may be determined by the device using an image acquisition device and/or a sensor and/or a measuring device. The actual configuration can thereby be automatically determined. 
         [0024]    According to another advantageous feature of the present invention, the actual configuration may be available in form of data relating to the tool-equipment and/or the blanks and/or the tool clamping pieces and/or the actual configuration is available in form of the software configuration. Such a form of the actual configuration represents a typical form of the actual configuration of a machine tool. 
         [0025]    Furthermore, the device may advantageously be designed such that the parts program is generated by the device by simulating the machining operation, using a simulated configuration of the machine tool and a parts program in which the simulated configuration has not yet been stored, wherein the simulated configuration is subsequently stored in the parts program in which the simulated configuration has not yet been stored. A parts program in which the simulated configuration is stored can then be generated in a simple fashion. 
         [0026]    According to another advantageous feature of the present invention, the simulated configuration may be stored in the parts program in an encrypted form because this prevents later manipulation of the simulated configuration in the parts program. 
         [0027]    Advantageously, a machine tool may be designed which includes the device according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0028]    Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
           [0029]      FIG. 1  shows a device according to the invention for operating a machine tool; 
           [0030]      FIG. 2  shows a method according to the invention for operating a machine tool; and 
           [0031]      FIG. 3  shows a parts program according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0032]    Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
         [0033]    Turning now to the drawing, and in particular to  FIG. 1 , there is shown in a schematic illustration the device according to the invention in form of a block diagram. It is customary to initiate the manufacturing process of a workpiece to be produced by modeling the workpiece using a CAD (Computer-Aided Design) system  1 . The geometry-related data of the workpiece determined as such using the CAD system  1  is transferred as an input variable to a CAM (Computer-Aided Manufacturing) system  3 , as indicated by arrow  2 . Using the CAM system  3 , the milling paths (in the case of an exemplary milling operation) are determined from the geometry-related data of the workpiece to be produced and the later configuration of the machine tool, as well as from the geometry-related data of a blank which forms the starting part for the later machining operation by the machine tool, wherein these milling paths have to be traversed by the machine axes of the machine tool to manufacture the workpiece to be produced from the blank. In this way, the movements of the machine axes required to manufacture the workpiece are determined by the CAM system  3  and are made available as input variables for a so-called postprocessor  5 , as indicated in  FIG. 1  by arrow  4 . 
         [0034]    The postprocessor  5 , which is present in form of a program being executed on a computer, generates from the movements of the machine axes determined by the CAM system and the later configuration of the machine tool a parts program, in particular an NC parts program, by means of which the control device of the machine tool later controls the machining operation of the machine tool, in order to manufacture the workpiece from the blank. 
         [0035]    The parts program is generally present in form of a file containing commands generally written in DIN code which are arranged line after line in ASCII code. Such command (e.g. G3 X115 Y113.3 I-43 J25.52) may, for example, involve moving a tool (e.g. a milling cutter) along segment of a circle to a target position in order to, for example, mill a recess into the blank. The individual commands of the parts program are later read by the control device  9  of the machine tool. The control device  9  calculates the intended position values Xsoll n  for each drive n of the drive system  10  of the machine tool according to the commands of the parts program. 
         [0036]    However, for safety reasons, it is customary in commercial applications to transfer the parts program, after it has been generated by the postprocessor  5 , to a simulation unit  7  which can for be, example, in form of a simulation program running on a computer, as indicated by arrow  6 . The simulation unit  7 , which includes a model of the machine tool which is more or less true in detail, simulates the later real machining operation, wherein the parts program generated by the postprocessor  5  is checked as to whether, for example, collisions of machine elements amongst themselves or with the blank occur during the machining operation, and/or whether the intended machining times and machining precision are met. If the simulation is completed successfully, i.e., if the machining operation runs without errors and has the desired outcome, then the parts program tested in this manner is transmitted to the control device  9 , indicated in  FIG. 1  by arrow  8 , and the real machining operation of the machine tool can be initiated. 
         [0037]    However, in practice, errors nevertheless occur frequently in the machining operation which damages machine elements of the machine tool or results in an inadequate quality of the workpiece, for example with respect to manufacturing precision. The reason for this is often found in the fact that the configuration of the machine tool used by the simulation unit  7  during the simulation (referred to as simulated configuration below) does not conform to the later occurring actual configuration of the real machine tool. For example, the simulation can be carried out using a simulated configuration of the machine tool which assumes that a drill with a diameter of 8 mm is present at a particular location of the tool holder of the tool changer, whereas in actuality a drill with a cross section  10  is later present at that particular location in the real machine tool. 
         [0038]    At this point, the method according to the invention sets in. According to the invention, the simulated configuration, i.e., the configuration of the machine tool used in the simulation, is stored in the parts program by the simulation unit  7  in the parts program which was generated by the postprocessor  5 . The simulation unit  7  thereby generates a parts program in which the machining operation is simulated, using a simulated configuration of a machine tool and a parts program in which the simulated configuration is not yet stored, and in which the simulated configuration is subsequently stored in the parts program. The parts program  24  generated in this manner is illustrated in  FIG. 3 . In this manner, the parts program  24  consists of the commands  25  of the parts program from the postprocessor  5  and of the simulated configuration  18 . The parts program  24  is generally available as a file which comprises the commands  25  and the simulated configuration  18 . In this case, the simulated configuration  18  is stored in the parts program by, for example, saving the simulated configuration  18  to the file. 
         [0039]    According to the invention, the control device  9  of the machine tool determines the actual configuration of the machine tool before initiating the machining operation of the machine tool, for example by using an image acquisition device  11  built into the machine tool, a sensor  12  and/or a measuring device  13  integrated into the machine tool. Using the image acquisition device  11 , which can for example be in form of a camera, the present position of tool clamping pieces (tool clamping piece data) and the position of the blank (blank data) can be detected, for example. The sensor  12  can for example detect the equipment of tools in the tool changer. The measuring device  13  can for example detect the dimensions of the blank. After the actual configuration of the machine tool was determined in an automated fashion in this manner, the actual configuration is compared to the simulated configuration  18  of the machine tool stored in the parts program, whereupon a warning message W is generated if the actual configuration and the simulated configuration do not conform and this warning message is transmitted to an operating unit  14  for example; this operating unit  14  displays the warning message for the operator. The machining operation is only initiated by the control device  9  if the actual configuration and the simulated configuration conform. Within the scope of the exemplary embodiment, the simulated configuration is stored by the simulation unit  7  in an encrypted form in the parts program  24 , and the control device  9  decrypts the simulated configuration  18  stored in the parts program before it compares the actual configuration with the simulated configuration. This can reliably prevent later manipulation of the simulated configuration stored in the parts program. 
         [0040]    Furthermore, the actual configuration, determined in an automated fashion, is advantageously transferred to the CAM system  3  and/or the postprocessor  5  and/or the simulation unit  7 , as indicated by arrows  16 . Determining and/or adapting the configuration of the machine tool used in the CAM system, postprocessor and during the simulation manually can thus be eliminated. 
         [0041]    The device for operating a machine tool can in the simplest case merely be designed as a control device  9  for controlling the machine tool, without the simulation unit  7 . 
         [0042]    However, the device for operating a machine tool can also be designed as a system which includes the control device  9  and a structurally separate computer, installed in an office for example, on which the simulation unit  7  is run in form of a simulation program. However, the device for operating the machine tool may also be available in form of the control device  9 , and the simulation unit  7 , implemented for example as a program, may be run on the control device  9  and thus is an integral component of the control device  9 . 
         [0043]    The control device  9  can be designed, for example, as a numerically controlled control (NC control). 
         [0044]      FIG. 2  illustrates once more the method according to the invention schematically in form of a flow chart. The parts program  19 , which at this point in time does not include a simulated configuration, is tested in a simulation  17  by taking into account the simulated configuration  18 , and a parts program  24  is generated in which the simulated configuration  18  is stored. Subsequently, the actual configuration  26  of the machine tool is determined  20 , and the actual configuration  26  is subsequently compared  21  with the simulated configuration. If the actual configuration does not conform to the simulated configuration, a warning message is generated  22 . If the actual configuration conforms to the simulated configuration, the machining operation is initiated  23 . 
         [0045]    While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0046]    What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: