The invention relates to 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 by generating a path program on the basis of a setpoint geometry of generated setpoint parameters for controlling the machine tool, wherein the path program describes at least one path, wherein the path consists of a plurality of supporting points and line elements and each line element connects a pair of the supporting points to one another, and the control of the machine tool is effected in accordance with the generated path program. The invention also relates to a further control apparatus.
In the following, a line element is to be understood as, for example, a straight line, a circle element or a higher-level geometric element (for example a spline) or a combination thereof.
During the processing of a workpiece (e.g. in tool making and die making) path programs based on CNC (computer numerical control) are as a rule used for controlling the machine in question, particularly if it is a milling machine. Nowadays, path programs (also called parts programs) are mainly generated by CAD/CAM/PP systems. The body or object to be produced is initially designed with a CAD (computer aided design) program and then transformed by a CAM (computer aided manufacturing) program into a machine-independent code (describes the processing process). A post-processor (PP) transforms the machine-independent code into a machine-dependent code, the so-called CNC-based path program, that can be used for controlling the particular concrete machine. The processing here is divided into various steps, e.g. rough machining, first-finishing and finishing.
In the finishing process, for example, the surfaces to be processed or produced are broken down into essentially equidistantly running path programs that describe the surface contour of the workpiece, which are then, for example in a machining process, milled by a milling machine. Such a path program is a path that consists of supporting points, pairs of which are connected by line elements (hereafter also called linear sets).
A section of such a program, or its graphical visualization, is reproduced in
The path program that originated in the CAD/CAM/PP system is normally installed on a machine with an NC control unit and then run by a machine operator on the machine using the NC control unit. Here, the NC control unit treats each milling path section individually with a certain future time and distance horizon (look-ahead) and evaluates variations.
The path program, which may have been written in a CNC programming language, is created in advance and is not further modified at the time of processing by the CNC control unit. The processing technology, the tools, the technology parameters such as rotational speed of spindles, the machine functions, the path curve to be milled and the orientation and associated feed rate are defined in the path program in advance. As a rule, the values defined in the path program are not scrutinized by the CNC control unit. The path program itself is created before processing in a CAM system or other programming system and is then sent to the CNC control unit for processing.
This procedure does not permit autonomous modification of the path geometry or of the associated technology parameters at the time the CNC program is run by the CNC control unit, except through manual intervention by an operator. As a result, a potential optimum as regards minimal processing time, or full utilization of the tool and machining potentials such as tool life, machining performance or dynamics, is not achievable.
Moreover, the same processing problem is solved differently by different programmers and worked through differently on different machine types. Even in the case of identical machine characteristics, i.e. the same machine type, differing productivity as regards processing time, quality and costs is achieved in different production plants due to differing programming knowledge and strategies.
EP 2 216.698 A2 relates to a method and an apparatus for generating transformed control data for controlling a tool on a machine tool for processing a workpiece clamped into a clamping-in means of the machine tool by way of machining, with the process step of defining control data that specifies which first tool path, with which first tool orientation, is to be followed by the tool of the machine tool in order to process the clamped-in workpiece if the workpiece is clamped into the clamping-in means in accordance with a desired status of a clamping-in situation that represents a desired status of a clamping-in situation of the workpiece clamped into the clamping-in means, wherein the further process steps of determining an actual status of a clamping-in situation that represents an actual actual status of the clamping-in situation of the workpiece clamped into the clamping-in means, determining a variation in the clamping-in situation between the actual status of the clamping-in situation and the desired status of the clamping-in situation, which represents a variation between the actual status of the clamping-in situation and the desired status of the clamping-in situation, and generating transformed control data by undertaking a transformation of at least a part, depending on the determined variation in the clamping-in situation, of the defined control data, wherein the transformed control data indicates which second tool path, with which second tool orientation, is to be followed by the tool of the machine tool in order to process the clamped-in workpiece, with the determined variation of the clamping-in situation, if the workpiece is clamped into the clamping-in means in accordance with the actual status of the determined clamping-in situation.
The object of the invention is to provide a method and a control apparatus that have improved processing time and full utilization of tool and machine potentials in relation to the prior art.
The object in relation to the method is achieved by providing 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 by:
The object in relation to the apparatus is achieved by providing 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 by generating a path program on the basis of a setpoint geometry of generated setpoint parameters for controlling the machine tool, wherein the path program describes at least one path, wherein the path consists of a plurality of supporting points and line elements and each line element connects a pair of the supporting points to one another, and the subsequent control of the machine tool is provided in accordance with the generated path program, wherein a feedback loop for detecting actual parameters of the processing process is provided, and wherein iterative optimization of the path program is provided on the basis of the detected actual parameters for generating a new path program_new with a new path_new which are supplied during processing by the machine tool and which dynamically change or dynamically replace the previous path program and the previous path during processing.
According to the invention, iterative optimization of the path program on the basis of the detected actual parameters is now possible during the processing process due to the change in the technology parameters. It is possible here for the actual parameters also to comprise the status variables. 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, lateral positioning and positioning in relation to depth. Examples of machine-related information are maximum permitted spindle output, maximum permitted spindle torque and maximum permitted axis dynamics, as well as maximum permitted feed rate. Technology parameters can also include the order of processing with different tools. Changing the technology parameters creates clearly established peripheral conditions for the generation of the new path program_new, which has a new path, or path and orientation.
The invention enables economically optimal utilization of the tool's potential and its machining features.
The present invention shows a way of dynamizing established procedure, i.e. working through an NC program generated in advance, with the aim of significantly reducing processing time and increasing cost-effectiveness. According to the invention, in order dynamically to influence technology parameters and thus also path and orientation during a processing process, a feedback loop from the processing process, for the measurement of actual parameters, is provided for the dynamic calculation of a new path.
The invention enables the same productivity to be achieved in identical machines and identical tools, irrespective of the programmer's know-how.
The dynamization of CNC processing according to the invention is achieved by exerting influence on more parameters than just the parameter “feed rate”.
According to the invention, 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 possible, i.e. in particular, deviation from, for example, a programmed path and orientation during runtime are permitted. Only in this way are optimal utilization of the tool's potential and its machining features possible.
The invention thus enables control-integrated dynamic optimization of processing by taking account of the specific machining features (“process analysis”) and technology possibilities.
Further advantages can be seen in reduced programming complexity and reduced processing time, or increased productivity, all charged tools being taken into account and, for example, automatic optimization of technology. The machine can also be programmed as a self-learning machine.
Further advantageous measures, which can be combined with one another as desired to achieve further advantages, are listed in the subclaims.
Preferably, at least one further iterative optimization of the generated path program_new and the path_new is possible. This means that the path program and the path itself can be continuously iteratively optimized.
Preferably, CAM functionality is provided for changing the order of the supporting points. It must be possible to execute the CAM function in real time, i.e. be able to react to identified optimization potential immediately and be able, during processing, to provide the CNC control unit with an optimized CNC program, or with an optimized path course.
In another preferred embodiment both the path program and the path program_new are embodied as a CNC program, with the CNC program of the path program_new changing and/or replacing the previous CNC program of the path program during processing. However, other machine languages are also possible.
Preferably, the path program_new contains a transitional strategy, in particular a transitional program with a transitional path. In this way an improved, dynamic transition from the old program to the new program can be achieved.
In an exemplary embodiment, iterative optimization of the path program is achieved in real time on the basis of the detected actual parameters for generating a new path program_new with a new path_new, which are dynamically supplied in real time during processing by the machine tool, and which change and/or replace the previous path program.
In an exemplary embodiment a database is provided that stores at least the path program and the path program_new. In a preferred embodiment, both the technology parameters/technology parameters_new and the detected actual parameters of the path program are also saved, as is the path program_new. In this way it is, possible to recycle the history and use it for subsequent workpieces.
As a result, empirical values can be generated that can be employed later for a self-learning machine or better, error-free processing.
Preferably, the path program_new can be supplied to the control apparatus either manually or automatically. This can be predefined by the programmer.
Further features, characteristics and advantages of the present invention can be found in the following description with reference to the attached schematic figures:
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.
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).
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.
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.
The programming station 7 can be embodied as part of the control unit 5.
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.
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.
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.
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.
In
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.
Initially—as in the prior art—a target part described by CAD data 4 (
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 (
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 (
The invention thus enables dynamic influencing of technology parameters, and hence of path and orientation, during a processing process.
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.
The invention is schematically depicted below by way of the example of the following steps (
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.
Number | Date | Country | Kind |
---|---|---|---|
15187409.6 | Sep 2015 | EP | regional |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2016/070564 | 9/1/2016 | WO | 00 |