METHOD AND CONTROL APPARATUS FOR OPTIMIZED CONTROL OF A MACHINE TOOL

Abstract

A method and control apparatus for generating control data for controlling a tool on a machine tool for machining a clamped-in workpiece, the machine tool having a control apparatus and a tool for controlling the tool, comprising: generating a path program using a setpoint geometry of generated setpoint parameters, the path program describing a path having supporting points and line elements; controlling the machine tool according to the generated path program; detecting actual parameters by a feedback loop; iteratively optimizing the path program using the detected actual parameters for generating a new path program with a new path, the new path program being dynamically supplied in real time and the new path program dynamically changing and/or dynamically replacing the previous path program; providing CAM functionality for changing an order of the supporting points; and embodying both the path program and the new path program as a CNC program.

Claims

1.-13. (canceled)

14. A method for generating control data for controlling a tool on a machine tool for processing a clamped-in workpiece by way of a processing process, in particular machining, wherein the machine tool comprises a control apparatus and a tool for controlling the tool in relation to the clamped-in workpiece with a three-dimensional free tool movement, said method comprising: generating a path program on the basis of a setpoint geometry of generated setpoint parameters for controlling the machine tool, with the path program describing a path having a plurality of supporting points and line elements, with each line element connecting to one another supporting points of a pair of the supporting points; controlling the machine tool in accordance with the generated path program; detecting actual parameters of the processing process by a feedback loop; iteratively optimizing the path program on the basis of the detected actual parameters for generating a new path program with a new path, with the new path program being dynamically supplied in real time during processing by the machine tool and the new path program dynamically changing and/or dynamically replacing the previous path program and the previous path during processing; providing a CAM functionality for changing an order of the supporting points, with the CAM functionality capable of being run in real time; embodying both the path program and the new path program as a CNC program, with the CNC program of the new path program changing and/or replacing a previous CNC program of the path program during processing; and running the path program to process the clamped-in workpiece.

15. The method of claim 14, wherein following a control of the tool by the previous path program, the tool is first controlled by a transitional strategy.

16. The method of claim 14, wherein following, a control of the tool by the previous path program, the tool is first controlled by a transitional program with a transitional path, with the transitional program being generated in addition to the new path program.

17. The method of claim 14, wherein at least one further iterative optimization of the generated new path program is performed.

18. A control apparatus for generating control data for controlling a tool on a machine tool for processing a clamped-in workpiece by way of a processing process, in particular machining, wherein the machine tool comprises a control apparatus and a tool for controlling the tool in relation to the clamped-in workpiece with a three-dimensional free tool movement, the control apparatus configured to: generate a path program on the basis of a setpoint geometry of generated setpoint parameters for controlling the machine tool, with the path program describing a path having a plurality of supporting points and line elements, with each line element connecting to one another supporting points of a pair of the supporting points; control the machine tool in accordance with the generated path program; detect actual parameters of the processing process by a feedback loop; iteratively optimize the path program on the basis of the detected actual parameters for generating a new path program with a new path, with the new path program being dynamically supplied in real time during processing by the machine tool and the new path program dynamically changing and/or dynamically replacing the previous path program and the previous path during processing; provide a CAM functionality for changing an order of the supporting points, with the CAM functionality capable of being run in real time; embody both the path program and the new path program as a CNC program, with the CNC program of the new path program changing and/or replacing a previous CNC program of the path program during processing; and run the path program to process the clamped-in workpiece.

19. The control apparatus of claim 18, further comprising at least one further iterative optimization of the generated new path program.

20. The control apparatus of claim 18, wherein a dynamic new technology parameter is selected from the group consisting of tool type, processing-relevant technology variables and machine-related information, and is dynamically changeable and/or dynamically replaceable during processing.

21. The control apparatus of claim 18, wherein the new path program contains a transitional strategy.

22. The control apparatus of claim 18, wherein the transitional strategy includes a transitional program with a transitional path.

23. The control apparatus of claim 18, wherein the iterative optimization of the path program is capable of being achieved in real time by the feedback loop at defined intervals of time, with the new path program being dynamically supplied at defined intervals of time during processing by the machine tool and changing or replacing the previous path program and the previous path.

24. The control apparatus of claim 18, further comprising a database configured to store at least the path program and the new path program.

25. The control apparatus of claim 25, wherein the database is configured to save technology parameters, new technology parameters, and the detected actual parameters of the path program.

26. The control apparatus of claim 18, wherein the new path program is supplied to the control apparatus manually or automatically.

Description

[0035] Further features, characteristics and advantages of the present invention can be found in the following description with reference to the attached schematic figures:

[0036] FIG. 1: is a pictorial representation of an NC path program in accordance with the prior art,

[0037] FIG. 2: shows a processing process of a workpiece by a tool in accordance with the prior art,

[0038] FIG. 3: shows dynamic program and path generation for CNC controlled machine tools according to the invention,

[0039] FIG. 4: is a schematic representation of an example of processing order according to the invention,

[0040] FIG. 5: shows, as a first example, rough machining (trimming) with a cutting depth predefined by the programmer in accordance with the prior art,

[0041] FIG. 6: shows the corresponding rough machining (trimming) with dynamically optimized cutting depth according to the invention,

[0042] FIG. 7: shows, as a second example, face milling with a tool diameter predefined by the programmer in accordance with the prior art,

[0043] FIG. 8: shows the corresponding face milling with optimized tool diameter according to the invention,

[0044] FIG. 9: shows, as a third example, face milling with lateral positioning predefined by the programmer in accordance with the prior art,

[0045] FIG. 10: shows the corresponding face milling with dynamically optimized lateral positioning according to the invention.

[0046] Although the invention has been illustrated and described in detail by the preferred exemplary embodiment, the invention is not limited by the disclosed examples. Those skilled in the art can derive variations from them without departing from the scope of protection of the invention as defined by the claims below.

[0047] FIG. 1 is a pictorial representation of a path program in accordance with the prior art and has already been described.

[0048] FIG. 2 is a schematic representation of a processing process of a workpiece by a tool in accordance with the prior art, i.e. the currently customary order in the CAD-CAM-CNC process chain. Nowadays CNC machine tools are controlled via the path program, for example in accordance with DIN 66025.

[0049] In such workpiece processing apparatus the positioning and movement of a tool employed in the processing of workpieces is controlled relative to a workpiece by means of a numerical control device (CNC control unit 5).

[0050] Here, the CNC path program 6 is created in advance at a programming station 7 and is not further modified by the CNC control unit 5 at the time of processing.

[0051] In addition, on the basis of CAD data 4, the processing is broken down by the programmer into individual processing elements 8 and the individual processing elements 8 are assigned, the technology parameters 9. The path program 6 is then created by the CAM system.

[0052] The programming station 7 can be embodied as part of the control unit 5.

[0053] It is also possible to define entire processing features such as, for example, pockets, via standardized interfaces. Here too, however, the CNC programs created are not further modified in the CNC control unit at the time of processing, except in a few exceptional cases. Modification of the data in the path program 6 is currently only known to a limited extent. The CNC control unit 5 is divided into a non cyclical part 5a and a cyclical part 5b. The non-cyclical part 5a comprises 10, geometry preparation, and 11, speed control, including look-ahead, as well as the generation of transformed control data by undertaking a transformation of control data depending on the determined variation in the clamping-in situation, or machine kinematics. The cyclical part 5b here primarily comprises interpolation and, if applicable, positioning control 50.

[0054] Modification of the technology parameters during runtime, both in the cyclical part 5b and the part 5a, is currently only known to a limited extent. This includes reduction of the programmed path speed, either as a result of the limited dynamic possibilities of the machine axes of the machine tool (reduction in speed) or by the operator, modification of the feed rate by adaptive control 12 depending on the spindle output, modification of the spindle speed in order to avoid chattering, by overlaying a wobble signal and a interfering signal, or permanent modification of the spindle speed.

[0055] In addition, in the prior art the technology parameter feed rate and the operating speed of the machine tool are calculated by sensors 13 in the case of the machine tool 14, sensors 15 in the case of the spindle 16 and by sensors 20 in the processing process 19, or in the controller 17 of the drive 18, and sent for process analysis, e.g. to the adaptive control 12. The adaptive control 12 can therefore only influence speed and feed rate. Also, it can only bring the technology parameters into the CNC control unit 5 cyclically. No further parameters are influenced.

[0056] To summarize, in the prior art, influence is therefore only exerted on two technology parameters, namely feed rate and speed. Once programmed, the pre-programmed path is not departed from. Extensive optimization in accordance with the present invention is therefore not possible. As a result, a potential optimum as regards minimal processing time and full utilization of the tool and machining potentials such as machining performance or dynamics, is not achievable.

[0057] In FIG. 3 the present invention shows a way of dynamizing this established procedure, with the aim of significantly reducing processing time and increasing productivity. The aim is to achieve the same productivity in identical machines and identical tools, irrespective of the programmer's know-how.

[0058] The dynamization of CNC processing according to the invention is achieved by exerting influence on more parameters than just the parameter feed rate or speed. According to the invention, it has been found that integral optimization of processing is only possible if integral adaptation, both of technology parameters and the course of the path during the processing process, is enabled, i.e. in particular, deviation from the programmed path and orientation during runtime are permitted. Only through deviation from the programmed path and orientation during runtime are optimal utilization of the tool's potential and its machining features possible.

[0059] Initiallyas in the prior arta target part described by CAD data 4 (FIG. 2) is broken down into processing elements 8 (FIG. 2) at a programming station 7 (FIG. 2) and assigned to this technology parameter, and in the CAM system 9 (FIG. 2) a CNC path program 6 is generated and sent to the CNC control unit 5. The actual parameters 24 are detected via the sensors 20, 15, 13 (FIG. 2) during the processing process 19, in the Spindle 16 and in the machine tool 14, as well as in the controller 17 (FIG. 2) in the drive 18. It is possible here for the actual parameters 24 also to comprise the status variables 23.

[0060] According to the invention, a feedback loop 21 is now provided that comprised of sensors 20, 15, 13 and the controller 17 for measuring status variables 23, and the actual parameters 24 for influencing the current path program 6 (FIG. 2) and for dynamically calculating a new path.

[0061] To this end, a process analysis 25 is then conducted in the feedback loop 21 and, as a result of this, a new path program_new 26 with corresponding updated technology parameters_new 27 is generated. The current path program 6 is then changed into and/or replaced by a path program_new 26 and a new optimized path_new and the current technology parameters 9 (FIG. 2) are changed into or replaced by new technology parameters_new. The new technology parameters_new 27 and the new path program_new 26 are then calculated with the aid of a CAM function that is executable in real time. It is also possible, in advance, to generate a transitional strategy 29, with a transitional program and transitional parameters, which then converts the old path program into the path program_new 26. In this way, a dynamic transition from the current path program 6 (current processing) (FIG. 2) to the new path program_new 26 (new processing) can be assured. The path program_new 26 and the new technology parameters_new 27 then become the current path program 6. These are replaced in the CNC control unit 5 (FIG. 2), both in the cyclical part 5a (FIG. 2) and in the non-cyclical part 5b (FIG. 2) in real time, i.e. during processing, and result in the measurement of new current status variables 23 and actual parameters 24. The CAM system that can be executed in real time can react immediately to identified optimization potential and during processing provide the CNC control unit 5 (FIG. 2) with an optimized CNC path program, or with an optimized path course. The details of the calculation steps and of the underlying data can be saved in a database 37.

[0062] The invention thus enables dynamic influencing of technology parameters, and hence of path and orientation, during a processing process.

[0063] The technology parameters for optimization can be divided into tool type, processing-relevant technology parameters and machine-related information. Examples of tool types are tool diameter and tool length, as well as, for example, number of cogs. Examples of processing-relevant technology parameters that can be used are cutting speed, feed rate/cog, and both lateral positioning and positioning of the tool in relation to depth. Examples of machine-related information are maximum possible spindle output, maximum possible spindle torque and maximum possible axis dynamics, as well as maximum possible feed rate.

[0064] The invention is schematically depicted below by way of the example of the following steps (FIG. 4): [0065] Step 30: Input of CAD data of an unfinished part and the CAD data of the finished part (target part), as well as input of tolerance data and, where applicable, identification of features, [0066] Step 31: Creation of a processing list with the aid of the input CAD data in the CAM system, in particular, creation of a path program. It should be noted here that in the first step it is not yet necessary for said creation to be automated. As a rule, the first step takes place during the process planning on the CAD-CAM system, [0067] Step 32: Working through the NC path program and detecting status variables 23 and actual parameters 24 (FIG. 3), analyzing the status variables 23 and actual parameters 24 (FIG. 3), calculating alternative processing scenarios and evaluating and deciding whether optimization of processing is possible, in order to increase productivity. If the decision is in favor of optimized processing it can also include suggestions for the subsequent loading of tools, [0068] Step 33: For optimized processing: generating a new path program_new 26 (FIG. 3) and a new path_new (FIG. 3), as well as a transitional strategy 29 (FIG. 3), with the aid of the new technology parameters_new 27 (FIG. 3), [0069] Step 34: Automatic or, if applicable, manual changing of the old path program 6 (FIG. 2) and the old technology parameters 9 (FIG. 2) by dynamically loading the new path program_new 26 (FIG. 3), as well as a transitional strategy 29 (FIG. 3) and the new technology parameters_new 27, into the CNC control unit 5 (e.g. changing the machining strategy and thus changing the path program 6), e.g. possibility of manually replacing or subsequently loading tools by changing the path program 6/and thus changing the technology parameters during processing, including the transitional strategy 29 (FIG. 3), from the current path program 6/from current technology parameters 9 to the new path program_new 26/new technology parameters_new 27 or, for example, from old z positioning to new z positioning, is made possible by a new tool, [0070] Step 37: Saving the details of the calculation steps and the underlying data in a database (FIG. 3), [0071] Step 35: Optional repetition of the process from Step 32 onwards, in order to check for further optimization potential. Discontinuing optimization if no significant improvement is found, [0072] Step 36: Completion of processing with the current path program and current technology parameters and saving in the database 37.

[0073] That means that both the new calculation and the subsequent new calculations of the path program, as well as of the technology parameters, are supplied to the CNC control unit in real time. The findings (materials, tool, operation, production strategy, technology parameters, etc.) are saved in a database 37.

[0074] FIG. 5, 6 show the prior art in comparison with the invention, by way of the example of the rough machining of an open pocket, with rough machining denoting the removal of material having a large chip volume. Rough machining in accordance with the prior art can be seen in FIG. 5. Here, the tool 42 always removes a hard programmed, unchangeable amount 41 from the material over a distance 43. FIG. 6 shows rough machining according to the invention. In this case, an amount 41 is also removed first. At point 44a, however, the optimization of this amount by means of the feedback loop 21 according to the invention (FIG. 3) begins. The changed path with the newly found amount 50 is supplied to the CNC control unit (FIG. 3) as path program_new 26, as a result of which the old NC path program, including a transitional path, which continues to the point 44b, is replaced dynamically. This results in reduced processing time. This can involve replacing the tool with, for example, a new tool 45.

[0075] FIG. 7, 8 show the prior art during stone milling processing in comparison with the invention, by way of the example of an exchangeable tool. FIG. 7 shows the processing in accordance with the prior art of a workpiece by a tool with the diameter 46. The diameter 46 has been predefined by the programmer and cannot be changed during the whole path 47. By contrast, FIG. 8 shows a tool, with a new diameter 48 and a newly calculated path 49, that has been changed by means of the feedback loop 21 (FIG. 3). The change of tool effected here results in a shorter processing time being achieved.

[0076] FIG. 9, 10 also show stone milling, in the comparison between a milling path 51 and a new milling path 52. In FIG. 9 the possibility of intervention, the feed rate, the cutting depth and the feed rate/cog have been predefined by the programmer, in accordance with the prior art. FIG. 10 shows the milling path dynamically influenced by means of the feedback loop 21 according to the invention (FIG. 3). Here, the superpositioning a.sub.c of the tool (lateral positioning) has been optimized. As a result the cutting parameters have been changed.