METHOD AND DEVICE FOR THE AUTOMATIC DETERMINATION OF MACHINING PARAMETERS FOR A MACHINING PROCESS

Abstract

A method for automatic determination of machining parameters for a machining process includes selecting certain machining parameters from stored machining parameters on the basis of predefined conditions for machining a workpiece depending on a position along a machining path, determining limit values for the machining parameters of the machining process to be performed, specifying new machining parameters by taking these limit values into consideration, and guiding a machining head along the machining path over the workpiece with the new machining parameters which take the limit values into consideration. If the limit values are not approached or reached, the machining process is continued using the certain machining parameters as the new machining parameters. If the limit values are approached or reached, the machining process is continued using changed machining parameters as the new machining parameters in order to perform the machining process without violating the limit values.

Claims

1. A method for the automatic determination of machining parameters for a machining process in order to obtain results without quality losses and without exceeding or falling below limit values for the machining parameters, the method comprising the steps of: selecting certain machining parameters from stored machining parameters on the basis of predefined conditions for machining at least one workpiece depending on a respective position along a machining path, determining limit values for the machining parameters of the machining process to be performed, wherein the step of determining limit values comprises inputting or automatically determining the limit values for the machining parameters prior to performing the machining process or automatically determining the limit values for the machining parameters while performing the machining process, specifying new machining parameters for the machining process to be performed by taking these limit values into consideration, and guiding a machining head along the machining path over the at least one workpiece with the new machining parameters which take the limit values into consideration, wherein if the limit values for the machining parameters are not approached or reached, the machining process is continued using the certain machining parameters as the new machining parameters and if the limit values for the machining parameters are approached or reached, the machining process is continued using changed machining parameters as the new machining parameters in order to perform the machining process without violating the limit values.

2. The method according to claim 1, wherein prior to the selection of the certain machining parameters for the machining process to be performed, ideal machining parameters are determined and stored by means of test machining processes on several test workpieces along test machining paths, in each case with a certain position and arrangement of the test workpieces, and the certain machining parameters are determined at the respective position along the machining path for the machining process to be performed from the stored ideal machining parameters for the certain positions and arrangements of the test workpieces.

3. The method according to claim 2, wherein the certain machining parameters at the respective position along the machining path for the machining process to be performed depending on the current position and arrangement of the at least one workpiece are determined by means of interpolation of the stored ideal machining parameters.

4. The method according to claim 1, wherein the input or determined limit values for the machining parameters are stored.

5. The method according to claim 1, wherein in addition to the limit values for the machining parameters, alternative machining parameters are stored.

6. The method according to claim 1, wherein a warning is output and/or information is stored, respectively, in response to a certain machining parameter for the machining process to be performed approaching a limit value for the machining parameters or reaching a limit value for the machining parameters.

7. The method according to claim 1, wherein in response to approaching or reaching at least one limit value for a machining parameter as certain machining parameter for the machining process to be performed, this at least one limit value is selected for a machining parameter or approached limit value for a machining parameter or stored alternative machining parameter as new machining parameter for the machining process to be performed.

8. The method according to claim 1, wherein when selecting the certain machining parameters for the machining process to be performed, the limit values for the machining parameters are taken into consideration prior to the machining process.

9. The method according to claim 8, wherein the machining process to be performed is simulated with the certain machining parameters, and the new machining parameters are specified for the machining process to be performed.

10. The method according to claim 1, wherein the limit values for the machining parameters are taken into consideration during the machining process when selecting the certain machining parameters for the machining process to be performed, and the new machining parameters for the machining process to be performed are specified.

11. The method according to claim 10, wherein the machining process is stopped in response to the new machining parameters differing from the certain machining parameters by a predefined factor and/or by a predefined absolute value, respectively.

12. The method according to claim 11, wherein in response to the new machining parameters deviating from the certain machining parameters by the predefined factor and/or by the predefined absolute value, respectively, a warning is output and/or information is stored, respectively.

13. The method according to claim 1, wherein the limit values for the machining parameters are determined automatically prior to performing the machining process by virtually passing through the machining process.

14. A device for machining a workpiece by means of a machining head along a machining path with certain machining parameters, which is formed for carrying out the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be described in more detail on the basis of the enclosed drawings, in which:

[0028] FIG. 1 shows a schematic illustration of a machining device for performing a method for the automatic determination of machining parameters for a machining process according to the prior art;

[0029] FIG. 2 shows a schematic illustration of a machining device for performing a method according to the invention for the automatic determination of machining parameters for a machining process by taking limit values for the machining parameters into consideration;

[0030] FIG. 3A to 3D show test workpieces comprising test machining paths in various positions with respect to the gravity acceleration vector for the determination of ideal machining parameters;

[0031] FIG. 4 shows an exemplary embodiment of the specification of new machining parameters on the basis of a welding process in consideration of limit values of the welding speed; and

[0032] FIG. 5 shows a further exemplary embodiment of the specification of new machining parameters on the basis of a welding process by taking limit values of the angle of attack of the welding torch to the workpiece into consideration.

DETAILED DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a schematic illustration of a machining device 1 for performing a method for the automatic determination of certain machining parameters P(x) for a machining process BP according to the prior art. The machining device 1 includes a machining robot 2, to which a machining head 3, for example a welding torch 10, is fastened. During the machining process BP, the machining head 3 is guided along a machining path X over at least one workpiece W to be machined. To machine the workpiece W, certain machining parameters P(x) are selected on the basis of predetermined conditions B(x) from a plurality of possible machining parameters P(x), which are stored, for example, in a memory 5, depending on the respective position x along the machining path X, by means of which machining parameters the workpiece W is machined in order to attain a desired machining result. The respective condition B(x), which depends essentially on the respective machining task, provides the control device 4 of the machining device 1 with corresponding information, on the basis of which the certain machining parameters P(x) are selected from the stored machining parameters P(x).

[0034] The machining device 1 can be, for example, a welding device 8 for performing a joining process or coating process on a workpiece W. A welding torch 10 is thereby fastened by means of a consumable welding wire 11 to a welding robot 9, by means of which two or several workpieces W can be connected to one another, or a coating can be applied to a workpiece W. In this case, the result of the machining process BP is a weld seam 12 between two or several workpieces W, which are to be connected, or a weld bead on the surface of a workpiece W. The machining device 1 can further also be formed by means of a device for treating the surface of a workpiece W by means of a plasma torch, a varnishing device, a cutting device, and many more (not illustrated). Depending on the machining process, the result of the machining process BP differs along the machining path X.

[0035] FIG. 2 shows a schematic illustration of a machining device 1 for performing a method according to the invention for the automatic determination of new machining parameters P(x) for a machining process BP by taking limit values P.sub.G(x) for the machining parameters P(x) into consideration. According to the invention, limit values P.sub.G(x) for the machining parameters P(x), for example upper limit values P.sub.G,o(x) and lower limit values P.sub.G,u(x) are now determined during the machining process BP to be performed, and are stored, for example, in a database 6, and these stored limit values P.sub.G(x) are taken into consideration for the machining parameters P(x) when selecting the new machining parameters P(x) for the machining process BP to be performed. The limit values P.sub.G(x) for the machining parameters P(x) can be input, for example, via an input device 7, and can be stored in the database 6. The limit values P.sub.G(x) for the machining parameters P(x) can likewise be determined automatically prior to performing the machining process BP, and can preferably be stored, for example by virtually passing through the machining process BP. The limit values P.sub.G(x) for the machining parameters P(x) can furthermore also be determined automatically while performing the machining process BP and can possibly be stored. When virtually or computationally passing through the machining process BP, respectively, limit values P.sub.G(x), which are caused by clamping devices or the like, are also taken into consideration for the machining parameters P(x), for example.

[0036] In addition to the limit values P.sub.G(x) for the machining parameters P(x), alternative machining parameters P.sub.a(x) can be stored in the database 6 or in a memory at an arbitrary storage location, which parameters are specified and used as new machining parameters P(x) for the machining process BP in the event a limit value P.sub.G(x) for a machining parameter P(x) is approached or reached. The limit values P.sub.G(x) are thus taken into consideration in the case of the specified new machining parameters P(x). If determined limit values P.sub.G(x) for the machining parameters P(x) are not reached or approached, the machining process BP is performed by means of the certain machining parameters P(x), which are selected on the basis of the condition B(x), as new machining parameters (P(x)) (see FIG. 1).

[0037] If the limit values P.sub.G(x) are reached or approached, the machining process BP is performed by means of new machining parameters P(x), which adhere to the limit values P.sub.G(x). The new machining parameters (P(x)) differ from the certain machining parameters (P(x)) in this case. The new machining parameters (P(x) are to be understood to be more suitable or optimal by adhering to the limit values P.sub.G(x), at least with regard to the machining quality, which is to be attained, during the machining process.

[0038] FIG. 3A to 3D show test workpieces 14 comprising test weld seams 13 in various positions with respect to the gravity acceleration vector g for the determination of ideal welding parameters P.sub.i(x). According to FIG. 3A, for example the ideal welding parameters P.sub.i(x) of an overlap seam are detected and stored first in a first position, here in flat position. For this purpose, an expert determines the ideal welding parameters P.sub.i(x) according to the welding task while performing a test welding process. If the welding task is fulfilled satisfactorily, and if an improvement cannot be expected with regard to the result of the welding task by changing the set values, the set values are stored as ideal welding parameters P.sub.i(x) for an overlap seam in the flat position. FIG. 3B shows the flat test workpieces 14 in a further position, the overhead position, FIG. 3C and FIG. 3D show the positions of the test workpieces 14 comprising a test welding path 13, which is tilted by 45 and horizontally arranged, for which the ideal welding parameters P.sub.i(x) are also determined and stored. In the case of the straight test welding paths 13 illustrated here, the direction of the tangential vector t is equal to the direction of the test welding path 13. Ideal welding parameters P.sub.i(x) for different alignments of the test welding path 13 with respect to the gravity acceleration vector g are furthermore detected.

[0039] FIG. 4 shows an exemplary embodiment of the specification of new welding parameters as new machining parameters P(x) by taking limit values P.sub.G(x) of the welding speed v.sub.s during the welding of a workpiece W into consideration. The welding torch 10 is first guided with a welding speed v.sub.s along the distance A of the machining path in the form of a vertical-down weld, thus a vertical welding path. In the rounding in the region B of the machining path Z, only a lower welding speed V.sub.s can be performed, i.e. the welding speed V.sub.s has an upper limit value V.sub.s,G,o, which is selected as new target value for the welding speed. Other welding parameters, such as the welding current, the feed speed of the welding wire, etc., are correspondingly adapted in the region B of the machining path X. A reduced welding speed V.sub.s as new machining parameter P(x) is thus specified in the region B for the welding process to be performed. As soon as the region C, a horizontally running transverse seam, of the machining path X was reached, the welding process can be continued at a higher welding speed V.sub.s and the other corresponding welding parameters again.

[0040] Lastly, FIG. 5 shows an exemplary embodiment of the specification of suitable welding parameters by taking limit values of the angle of attack da of the welding torch 10 to the workpiece W into consideration. Due to geometric conditions of the workpiece W or of the workpieces W, the adherence of the usually certain angle of attack A of the welding torch 10 to the workpiece is not possible. A limit value thus exists for the angle of attack .sub.A,G of the welding torch 10, which is used as new angle of attack A of the welding torch 10 for performing the welding process, so that a touching of the welding torch 10 on the workpiece W is securely prevented.

[0041] The present invention provides for an automatic determination of new machining parameters by taking limit values for machining parameters into consideration, which can be input or determined prior to or during the machining process.