Method for operating machine tool, computer program product, control unit, machine tool, simulation program product and use of control unit

Abstract

The invention relates to a method (100) for operating a machine tool (10) having a first number of machine shafts (14), each of which can be moved by means of a drive (12) and can be actuated by means of a control unit (20). The control unit (20) is designed to carry out a coordinate transformation (33) about the second number of machine shafts (14) with respect to a reference point (27) on the machine tool (10). The method (100) comprises a first step (110) in which a subprogram (30) for machining a workpiece is provided by means of the machine tool (10). In a second step (120), at least one rotational axis (13) of the crankshafts (14) is determined and the determined at least one rotational axis (13) is locked for actuation. The method (100) has a third step (130) in which control commands (35) for a plurality of the crankshafts (12), except for the at least one rotational axis (13) determined in the second step (120), are determined. In a fourth step (140), the at least one rotational axis (13) determined in the second step (120) is placed in the machining position (38) and the corresponding rotational movement (36) is determined.

Description

Technical Field

[0001] The invention relates to a method for operating a machine tool and a computer program product designed for this purpose. The invention also relates to a corresponding control unit and a machine tool having such a control unit. The invention also relates to a simulation program product and to a use of the control unit. Background Art

[0002] Patent application EP 2 216 698 A2 discloses a method for generating transformed control data for a machine tool. In this method, control data are provided which describe the intended machining of a workpiece which is clamped in a position corresponding to a desired state of the clamping situation. Furthermore, the actual state of the clamping situation is determined for the workpiece and compared with the desired state of the clamping situation. A clamping situation deviation is thereby determined and the transformed control data is calculated based on this.

[0003] Machine tools are used to produce components with increasingly complex geometries. Likewise, the number of actuable axes in machine tools is also increasing. Likewise, the demands on machine tools regarding cost efficiency in terms of acquisition and operation are increasing and there is a need to use control units that are as simple as possible. This applies in particular to complex, high-performance control units that are not available everywhere due to legal restrictions. Furthermore, compatibility between different machine tools is desirable so that subroutines can be run in a simple manner on machine tools of different structural types. The object of the present invention is to provide improvements in at least one of the aspects outlined above. Summary of the invention

[0004] The proposed object is achieved by a method for operating a machine tool according to the invention. The machine tool has a first number of machine axes, through which a tool can be moved translationally and rotationally. The machine axes thus include a translation axis and a rotation axis. The machine axes can be moved by a drive and can be actuated via a control unit. In particular, the machine axes can be moved directly by a single drive. The control unit is at least functionally assigned to the machine tool. In addition, the control unit is designed to perform a coordinate transformation around a second number of machine axes relative to a reference point on the machine tool. The method comprises a first step, in which a subroutine is provided, which is designed for machining a workpiece by means of a machine tool. The subroutine, for example, comprises a plurality of instructions for at least one drive, through which a tool can pass through a machining path directly along a workpiece surface or spaced apart from a workpiece surface. In addition, the method also comprises a second step, in which at least one rotation axis in the machine axis is determined. In the second step, the at least one rotation axis determined is locked for actuation. The locking can be designed in the form of a mechanical block, suppression of a control command to the corresponding drive and / or rejection of a control command generated by the corresponding drive. In a second step, the determined rotational axis is essentially locked in the current or set position.

[0005] Furthermore, the method comprises a third step, in which control commands are determined for a plurality of machine axes, by means of which the subroutine can be executed. The plurality of machine axes, for which the control commands are determined in the third step, do not include the at least one rotation axis determined and locked in the second step. The third step is therefore carried out excluding the rotation axis in the second step. In the third step, the control commands can be determined by means of a coordinate transformation, which corresponds to the position occupied by the machine tool in the second step. In other words, the control commands in the third step are determined as if the rotation axis determined in the second step did not exist.

[0006] In addition, the method has a fourth step, in which the rotation axis determined and locked in the second step is unlocked again and placed in a processing position. The processing position is a position in which the workpiece is processed. In the third step, the drive member of the rotation axis determined in the second step is placed in the processing position. In addition, the corresponding rotational movement is determined in the third step, by which the rotation axis reaches its processing position. The determination of the corresponding rotational movement can include measuring the rotation angle and the direction of rotation. In addition, the method includes a fifth step, in which an adapted control command group for a plurality of machine axes is determined. The adapted control command group is calculated based on the control command determined in the third step and the rotational movement determined in the fourth step. For this purpose, the control command from the fourth step can be coordinate-transformed according to the rotation axis from the fourth step. In the fifth step, the control command in the third step is basically converted to a position of the machine tool corresponding to the processing position set in the fourth step. The adapted control command group is therefore a modification of the control command from the third step after coordinate transformation. In addition, the method according to the present invention includes processing the workpiece by running the adapted control command group. By means of adapted control command sets, the drives of the multiple machine axes are actuated and the tool is moved.

[0007] The method according to the invention allows the subprograms to be transferred to different machine tools in a simple manner. By temporarily locking at least one rotational axis, the number of degrees of freedom is reduced, which allows simpler coordinate transformations around fewer machine axes. The required computational effort is thereby reduced.

[0008] In an embodiment of the claimed method, the first number of machine shafts can include three rotational axes, in particular exactly three rotational axes.

[0009] In a further embodiment of the claimed method, the first number of machine axes is greater than the second number of machine axes. The machine tool accordingly has more machine axes than can be processed by coordinate transformation. In particular, the first number can be five and the second number can be four. Alternatively, the first number can be six or seven and the second number can be five. A control unit with a reduced number of processable, i.e. coordinate-transformable machine axes is particularly cost-effective and easy to obtain. The claimed method allows the use of a simple control unit with a reduced number of coordinate-transformable machine axes to achieve substantially the same technical advantages as using a more complex control unit with more machine axes that can be coordinate-transformed.

[0010] Furthermore, in the claimed method, the reference point of the machine tool can be the tool center point. The tool center point, TCP for short, can be, for example, the tip of a milling cutter, the center point of a cutting wheel, the tip of a robot actuator or the output nozzle of a spraying device. The tool center point makes it possible to describe the sequence of subroutines in a simple manner.

[0011] In a further embodiment of the claimed method, at least one of the machine axes can be designed to move a tool or a workpiece. The moving tool can be, for example, a milling cutter. The machine axis that moves the workpiece can be, for example, a rotatable clamping part of the workpiece, for example in a lathe. The claimed method can therefore be applied to a plurality of machine tools.

[0012] In addition, the fourth and fifth steps of the claimed method can be performed for multiple rotation axes. For example, the machine tool can be locked around multiple rotation axes and a suitable coordinate transformation for the control command can be performed for each locked rotation axis in turn, individually or in combination, in order to determine an adapted control command group. The claimed method can therefore be easily transferred to complex machine tools with an increased number of machine axes, for example to a machine tool with eight machine axes. The claimed method is particularly suitable for use with robot actuators with multiple joints and multiple rotation axes. The claimed method is therefore suitable for future machine tools with increased complexity and can be used particularly for a long time.

[0013] In the claimed method, the orientation of the tool relative to the workpiece surface can be determined in the third and / or fifth step. The orientation includes in particular the angle between the spindle of the tool and at least one section of the surface of the workpiece. For tools in the form of spraying devices, the angle at which the paint is sprayed onto the workpiece surface may be process-dependent. In addition, in tools such as ball-end milling cutters, its orientation relative to the workpiece is decisive for the achievable manufacturing quality. The orientation of the workpiece, that is, the clamping direction, can be preset by the user and / or a suitable detection device for this purpose. In the claimed method, this orientation can be taken into account in at least one coordinate transformation. The presentation of the orientation of the tool is compatible with the coordinate transformation, so that the consideration of the orientation can be achieved with reduced computational effort. At least one step of the claimed method can be repeated until the desired orientation of the tool is achieved. Therefore, the claimed method can be performed automatically to a large extent. Alternatively or additionally, the surface quality of the machined workpiece is set by a suitable angular orientation of the tool relative to the workpiece surface during cutting.

[0014] In a further embodiment of the claimed method, the tool can be constructed asymmetrically or chiral. An asymmetrical tool can be a tool with a blade such that the suitability of the tool is determined by its orientation. A chiral tool can be understood, for example, as a hand of a robot actuator, which cannot be brought into the desired orientation by a single rotational movement. The claimed method can easily take these additional details into account and therefore has a wide range of potential applications. In particular, with the claimed method, faulty controls due to coordinate transformations can be avoided, which in turn allows for reliable operation of the machine tool.

[0015] In addition, the tool can be a drill, a milling cutter, a ball-end cutter, a cutting disc, a robot actuator, a welding device, a 3D printing head, a laser, a water jet device, a plasma beam device or a spraying device. Such a machine tool is manufactured with a greater number of machine axes. At the same time, it is sought to operate the machine tool with a control unit that is as simple as possible. The claimed method allows the machining path to be passed with increased accuracy and thus the workpiece to be machined more accurately. Therefore, the claimed method is applicable to a plurality of different machine tools.

[0016] In the claimed method, when running the adapted control command group, only the machine axes (for which the control commands are determined in the third step) can be moved. The rotary axes locked in the second step can thus be locked, i.e. rigidly held, when the adapted control command group is running. In particular, when cutting a workpiece, the rotary axes locked in the second step can be held in the machining position in such a way that the lever arm length from the locked rotary axis to the tool is minimized. This can minimize vibrations of the workpiece and increase the achievable manufacturing accuracy. The achievable feed is also increased, and thus the achievable chip volume per unit time is increased. This in turn leads to an increase in the productivity of the machine tool. In addition, the accessibility of the tool is thereby improved.

[0017] Furthermore, in the claimed method, at least one rotary axis locked in the second step can be determined according to fixed or settable specifications. For example, it can be specified for the structural type of the machine tool that at least one rotary axis is locked in the second step. This is a fixed specification. Likewise, the rotary axis can be determined by a user specification, by which the rotary axis is directly selected, or according to a criterion that can be selected by the user specification. Alternatively, at least one rotary axis locked in the second step can be determined by an algorithm, which is designed to evaluate a subroutine. In particular, the algorithm can simulate the flow of an adapted control command group. Based on the simulation, a settable criterion can be determined, based on which a rotary axis is selected. For example, the expected vibration of the workpiece and / or the tool can be determined, so that in the second step a rotary axis for locking is selected, in which the minimum vibration is expected. Alternatively or additionally, the energy demand or wear at the end of the adapted control command group can also be determined. The claimed method can be executed in multiple cycles. The algorithm can be constructed as an optimization algorithm, in particular as an artificial intelligence with a simulation of the machine tool. The claimed method can thus be combined with multiple algorithms for optimizing the operation of the corresponding machine tool. This can be, for example, an optimization with respect to minimizing the energy requirement, minimizing the processing time or minimizing the wear of the tool and / or the drive element. Thus, the technical potential of the corresponding machine tool is further fully utilized.

[0018] The proposed purpose based on is also achieved by a computer program product according to the present invention, which is designed to operate a machine tool. The computer program product is suitable for processing subroutines and outputs an adapted control command group to the machine tool accordingly. The computer program product is suitable for running on a control unit, which is at least functionally assigned to the machine tool. The computer program product can be constructed as a whole, that is, for running on a single hardware platform. Alternatively, the computer program product can be constructed modularly, that is, it includes a plurality of subroutines, which run on different hardware platforms and cooperate through a data connection for communication, for example, through an Internet connection or a mobile radio connection. According to the present invention, the computer program product is designed to execute at least one of the methods described above. The computer program product according to the present invention only requires a reduced computing power for sufficiently fast operation. Therefore, the computer program product according to the present invention can be implemented on the control unit without power loss.

[0019] Likewise, the proposed objects described at the beginning are achieved by a control unit according to the invention, which is designed for operating a machine tool. The control unit is suitable for driving the drive elements for the individual axes of the machine tool. For this purpose, the control unit has a storage unit and a computing unit, which are designed for implementing a computer program product on the control unit. According to the invention, the control unit is designed for executing at least one embodiment of the above-mentioned method. Alternatively or additionally, the computer program product that can be implemented and stored on the control unit can be constructed according to one of the above-mentioned embodiments.

[0020] Furthermore, the above objects are achieved by a machine tool according to the invention. The machine tool comprises a plurality of machine axes and a control unit, each of which can be actuated by a drive member. The control unit is designed to control, i.e. actuate, the drive member according to an adapted control command set. According to the invention, the control unit is constructed according to one of the above-described embodiments.

[0021] The described purpose is also achieved by a simulation program product according to the present invention, which is suitable for simulating the operating characteristics of a control unit of a machine tool. A simulation program product should be understood as a computer program product for simulation. With the help of the simulation program product, the operating characteristics of at least the control unit can be simulated. In addition, the movement of the tool of the machine tool can also belong to the operating characteristics of the simulation. According to the present invention, the operating characteristics of the simulation include at least one passing through the processing path by the tool of the machine tool. The processing path to be passed is thus determined by an adapted control command group, and a control command group can be generated by means of a control unit to be simulated. The adapted control command group is determined according to the embodiment of the method. For this purpose, the simulation program product can be constructed as a so-called digital twin of a control unit and / or a machine tool, such as described in the public text US2017 / 286572A1. The disclosure of US2017 / 0286572 A1 is included in the present application by reference. Different adapted control command groups can be tested and verified by the simulation program product. The adapted control command group can be quickly determined and can be directly evaluated for the simulation program product by the method. The simulation program product according to the invention can thus also be executed quickly, so that a plurality of adapted control command groups can be evaluated by simulation in a time-saving manner. The simulation program product can thus be easily executed while the machine tool is in operation. The simulation program product can be designed to evaluate and select the simulated adapted control command group according to settable criteria. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is explained in more detail below with the aid of embodiments in the drawings. The features of the embodiments described in the drawings can be combined with the features described above. Shown in detail here:

[0023] Figure 1 A schematic diagram showing a first embodiment of the claimed method. DETAILED DESCRIPTION

[0024] A first embodiment of the claimed method 100 is Figure 1 . The method 100 is used to operate a machine tool 10 having a plurality of machine axes 14 around which or along which a tool 15 can be moved. The tool 15 is designed as a milling cutter 17 and is suitable for cutting a workpiece 25, not shown in detail. The tip of the milling cutter 17 forms a reference point 27 on the machine tool 10, the so-called tool center point, TCP for short. The machine tool 10 is therefore a milling machine. The workpiece 25 can be clamped in a clamping part 18 of the machine tool 10. The clamping part 18 is designed to be rotatable around an axis of rotation 13. Each machine axis 14 is at least functionally coupled to a drive element 12, not shown in detail, so that the corresponding machine axis 14 can be actuated. In Figure 1The machine tool 10 shown in the drawing comprises three translation axes 16 and three rotation axes 13, by means of which a tool 15 can be guided and / or aligned along a machining path. The drive element 12 is at least functionally coupled to a control unit 20, which is designed to actuate the drive element 12. The control unit 20 comprises a computing unit 22 and a storage unit 24, which are designed to implement a computer program product 50, with which the claimed method 100 is performed.

[0025] The method 100 comprises a first step 110, in which a subprogram 30 is provided, which comprises a plurality of subprogram commands 32, by which a machining path of a tool 15 relative to a workpiece 25 is determined. The subprogram 30 is therefore independent of the machine tool 10 used. The subprogram 30 is further processed in the claimed method 100 to machine the workpiece 25. In addition, the method 100 comprises a second step 120, in which one of the rotation axes 13 of the machine axis 12 of the machine tool 10 is determined and then locked. By locking, the determined rotation axis 13 is held in a locked position 34. This is achieved by mechanical locking, by suppressing control commands to the corresponding drive 12, and / or by the corresponding drive 12 refusing to receive control commands that cause movement. The rotation axis 13 locked in the locked position 34 is selected via a user input on the input unit 21 or via an algorithm 23, which is designed to evaluate the subprogram 30. In particular, the algorithm 23 is designed to determine which of the rotation axes 13 is most suitable for the second step 120.

[0026] Furthermore, the claimed method 100 comprises a third step 130, in which a control command 35 is determined based on the subroutine 30. In order to determine the control command 35, a coordinate transformation 33 is applied to the subroutine 30. The control unit 20 is designed to perform a coordinate transformation 33 around a number of machine axes 14, which is less than the number of machine axes 14 of the machine tool 10. Three translation axes 14 and two rotation axes 13 of the machine tool 10 are taken into account during the coordinate transformation 33. The control unit 20 is therefore suitable for performing a coordinate transformation 33 around five machine axes 33 simultaneously. The machine axes 14 taken into account, i.e. the three translation axes 14 and the two rotation axes 13, belong to a machine axis group 39. The consideration of the machine axis group 39 is indicated by an arrow 37. The rotation axes 13 determined and locked in the second step 120 are excluded from the coordinate transformation 33. Exclusion of the locked rotation axes 13 Figure 1 The problem is characterized by a wire break in the crankshaft assembly 39 .

[0027] The claimed method 100 further comprises a fourth step 140, in which the rotational axis 13 determined and locked in the second step 120 is unlocked, i.e. released for movement. The tool 15 is moved around the corresponding rotational axis 13 and brought into the processing position 38. During the fourth step 140, the rotational movement 36 is also captured, with which the rotational axis 13 is brought from the locking position 34 into the processing position 38. For this purpose, the direction of the rotational movement 36 and the associated rotation angle are numerically captured. This is followed by a fifth step 150, in which the coordinate transformation 33 is applied to the control command 35 determined in the third step 130. The coordinate transformation 33 in the fifth step 150 is carried out in a manner that does not include the rotational axis 13 determined and locked in the second step 120. The coordinate transformation 33 in the fifth step 150 takes into account the rotational movement 36 captured in the fourth step 140, i.e. its numerical direction and rotation angle. An adapted control command set 40 is generated by the coordinate transformation 33 performed in the fifth step 150, the control command set comprising a plurality of adapted control commands 42. The adapted control commands 42 are each associated with a drive element 12 of the machine tool and are suitable for causing an actuation of the corresponding drive element 12. By means of the coordinate transformation 33 performed in the fifth step 150, the control command 35 provided in the third step 130 is adapted to the machining position 38 occupied by the rotary axis 13, which was determined in the second step 120 during the execution of the adapted control command set 40.

[0028] The method 100 also takes into account the orientation 19 of the tool 15. If the first determined adapted control command group 40 leads to an orientation 19 of the tool 15 in which the desired machining of the workpiece 25 is not possible or at least impractical, the method 100 is repeated in a second step 120 with the selection of a different rotation axis 13. The orientation 19 of the tool 15 can be taken into account in this way by the algorithm 23. The algorithm 23 can also be designed to determine the expected energy demand and / or expected wear of the machine tool 10, in particular the drive 12 and / or the tool 15. For this purpose, the algorithm 23 can be designed as an optimization algorithm, in particular as an artificial intelligence. After one or more cycles of the method 100, the determined control command group 40 is output to the machine tool 10 in order to machine the workpiece 25.

[0029] In addition, the operating characteristics of the control unit 20 of the machine tool 10 are represented by a simulation program product 60, which is not shown in detail. The simulation program product 60 is designed as a digital twin, in which the mechanical characteristics of the machine tool 10 can also be represented. The mechanical characteristics of the machine tool 10 include, but are not limited to, the vibration characteristics of the machine tool 10 around at least its rotation axis 13. The adaptive control command group 40 determined in the cycle of the method 100 can be tested by the simulation program product 60. In particular, it can be calculated from this that what degree of vibration is expected on the machine tool 10 and what degree of influence the vibration has on the expected manufacturing accuracy. The adaptive control command group 40 determined by the claimed method 100 can be evaluated in a simple manner by the simulation program product 60, so that a larger number of adaptive control command groups 40 can be quickly tested. The simulation program product 60 is suitable for making the method 100 be carried out in multiple cycles in order to obtain higher manufacturing accuracy. To this end, the simulation program product 60 includes a digital representation of the control unit 20 and the machine tool 10, in particular a digital representation of the associated drive 12.

Claims

1. A method (100) for operating a machine tool (10), the machine tool having a first number of machine axes (14), each of which can be moved by means of a drive (12) and can be actuated via a control unit (20), the control unit being designed to carry out a coordinate transformation (33) about a second number of machine axes (12) relative to a reference point (27) on the machine tool (10), the method comprising the steps of: a) providing a subprogram (30) for machining a workpiece (25) by means of the machine tool (10); b) determining at least one rotation axis (13) of the machine shaft (12) and locking the determined at least one rotation axis (13) for actuation; c) determining control commands (35) for a plurality of machine axes (12) in addition to the at least one rotation axis (13) determined in step b); d) placing the at least one rotational axis (13) determined in step b) into a processing position (38) and determining a corresponding rotational movement (36); e) determining an adapted control command set (40) for a plurality of said machine shafts (12) based on said control commands (35) determined in step c) and said rotational movement (36) determined in step d); in, The workpiece (15) is machined by means of executing the adapted control command set (40).

2. The method (100) according to claim 1, characterized in that: The first number of shafts (14) includes at least three rotating shafts (13).

3. The method (100) according to claim 1 or 2, characterized in that: The first number of the crankshafts (12) is greater than the second number of the crankshafts (12).

4. The method (100) according to any one of claims 1 to 3, characterized in that: The reference point (27) of the machine tool (10) is a tool center point.

5. The method (100) according to any one of claims 1 to 4, characterized in that: At least one of the machine axes (12) is designed to move a tool (15) or to move the workpiece (25).

6. The method (100) according to any one of claims 1 to 5, characterized in that Step d) and step e) are performed for a plurality of rotation axes (13).

7. The method (100) according to any one of claims 1 to 6, characterized in that In step c) and / or step e), an orientation (19) of the tool (15) relative to the surface of the workpiece (25) is determined.

8. The method (100) according to any one of claims 1 to 7, characterized in that The tool (15) is designed to be asymmetric or chiral.

9. The method (100) according to any one of claims 1 to 8, characterized in that The tool (15) is a drill, a milling cutter (17), a ball-end cutter, a turning tool, a cutting disc, a robot actuator, a welding device, a 3D printing head, a laser, a water jet device, a plasma beam device or a spray device.

10. The method (100) according to any one of claims 1 to 9, characterized in that: When the adapted control command set (40) is executed, only the machine shaft (12) for which the control command (35) determined in step c) is directed is moved.

11. The method (100) according to any one of claims 1 to 10, characterized in that In step b), the at least one rotational axis (13) is determined with the aid of fixed or adjustable specifications (21) or on the basis of an algorithm (23) which is designed to evaluate the subprogram (30).

12. A computer program product (50) for operating a machine tool (10), the computer program product being designed for processing a subroutine (30) and for outputting an adapted control command set (40) to the machine tool (10), characterized in that: The computer program product (50) is designed to carry out the method (100) according to any one of claims 1 to 11.

13. A control unit (20) for operating a machine tool (10), the control unit being designed to control a drive element (12) for a machine axis (14) of the machine tool (10), and the control unit being designed to execute a computer program product (50) by means of a storage unit (24) and a computing unit (22), characterized in that: The control unit (20) is designed to carry out the method (100) according to any one of claims 1 to 11 and / or the control unit is equipped with a computer program product (50) according to claim 12.

14. A machine tool (10) comprising a plurality of machine axes (14), each of which can be actuated via at least one drive element (12), and a control unit (20), wherein the control unit is designed to drive the drive element (12), characterized in that: The control unit (20) is designed according to claim 13.

15. A simulation program product (60) for simulating the operating characteristics of a control unit (20) of a machine tool (10), on which an adapted control command set (40) is executed, characterized in that: The simulated operating behavior includes traversing a machining path according to the adapted control command set (40), wherein the adapted control command set (40) is determined by a method (100) according to any one of claims 1 to 11.

16. Use of a control unit (20) for operating a machine tool (10) on which a workpiece (25) can be machined based on a subroutine (30), characterized in that: The machine tool (10) has at least five actuable machine axes (12) and the control unit (20) is designed to perform a coordinate transformation (33) around a maximum of four actuable machine axes (12), or the machine tool (10) has at least six actuable machine axes (12) and the control unit (20) is designed to perform a coordinate transformation (33) around a maximum of five actuable machine axes (12).

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