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

Description

[0001] The invention relates to a method for operating a machine tool and a computer program product designed therefor. The invention also relates to a corresponding control unit and a machine tool with such a control unit. A simulation program product and the use of a control unit are not included in the scope of protection.

[0002] Patent application EP 2 216 698 A2 discloses a method for generating transformed control data for a machine tool. This method provides control data that describe the intended machining of a workpiece clamped in a position corresponding to a target clamping situation. Furthermore, an actual clamping situation is determined for the workpiece and compared with the target clamping situation. From this, a clamping situation deviation is determined, and transformed control data is calculated based on this.

[0003] Machine tools are used to manufacture increasingly geometrically complex components. The number of operable machine axes in machine tools is also increasing. At the same time, increasing demands are being placed on machine tools with regard to cost-effectiveness in acquisition and operation, and the use of control units that are as simple as possible is required. This applies particularly to complex, high-performance control units, which are not available everywhere due to legal restrictions. Furthermore, compatibility between different machine tools is being sought so that part programs can be easily executed on different types of machine tools. The invention is based on the object of providing an improvement in at least one of the aspects outlined above.

[0004] The problem is solved by a method according to the invention for operating a machine tool. The machine tool has a first number of machine axes, by means of which a tool can be moved translationally and rotationally. The machine axes thus comprise translational axes and rotational axes. The machine axes can each be moved by a drive means and actuated via a control unit. In particular, the machine axes can each be moved directly by a single drive means. The control unit is at least functionally assigned to the machine tool. Furthermore, the control unit is designed to carry out a coordinate transformation about a second number of machine axes with respect to a reference point on the machine tool. The method comprises a first step in which a parts program is provided which is designed to machine a workpiece using the machine tool.The parts program comprises, for example, a plurality of instructions for at least one of the drive means, by means of which the tool can follow a machining path directly along a surface of the workpiece or at a distance from the surface of the workpiece. The method further comprises a second step in which at least one axis of rotation among the machine axes is determined. The determined at least one axis of rotation is blocked from actuation in the second step. The blocking can be embodied as a mechanical blocking, a suppression of control commands to the corresponding drive means and / or as a refusal to accept control commands by the corresponding drive means. The determined axis of rotation is essentially locked in a present or set position in the second step.

[0005] Furthermore, the method comprises a third step in which control commands are determined for a plurality of machine axes by means of which a part program 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 rotary axis determined and locked in the second step. The third step thus takes place while excluding the rotary axis from the second step. In the third step, the control commands can be determined via a coordinate transformation that corresponds to the position assumed by the machine tool in the second step. In other words, the control commands are determined in the third step as if the rotary axis determined in the second step did not exist.

[0006] The method further comprises a fourth step in which the rotary axis determined and locked in the second step is unlocked again and set in a machining position. The machining position is the position in which the workpiece is to be machined. The drive means of the rotary axis determined in the second step is brought into the machining position in the third step. Furthermore, in the third step, a corresponding rotary movement is determined by which the rotary axis reaches its machining position. Determining the corresponding rotary movement can include measuring an angle of rotation and a direction of rotation. Furthermore, the method comprises a fifth step in which an adapted control command set for the plurality of machine axes is determined. The adapted control command set is calculated based on the control commands determined in the third step and the rotary movement determined in the fourth step.For this purpose, a coordinate transformation of the control commands from the fourth step can be performed based on the rotation axis from the fourth step. In the fifth step, the control commands from the third step are essentially transferred to a position of the machine tool that corresponds to the machining position set in the fourth step. The adapted control command set thus represents a coordinate-transformed modification of the control commands from the third step. Furthermore, the method according to the invention comprises machining the workpiece by executing the adapted control command set. By means of the adapted control command set, the drive means of a plurality of machine axes are actuated and the tool is set in motion.

[0007] The method according to the invention allows for the simple transfer of part programs to different machine tools. By temporarily blocking at least one rotary axis, the number of degrees of freedom is reduced, allowing for simpler coordinate transformation involving fewer machine axes. This reduces the required computational effort.

[0008] In one embodiment of the claimed method, the first number of machine axes may comprise 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 higher than the second number of machine axes. The machine tool accordingly has more machine axes than can be processed by the coordinate transformation. In particular, the first number can be five and the second number four. Alternatively, the first number can be six or seven and the second number five. Control units with a reduced number of processable, i.e., coordinate-transformable, machine axes are particularly cost-effective and readily available. The claimed method makes it possible to achieve essentially the same technical advantages with a simple control unit with a reduced number of coordinate-transformable machine axes as with a more complex control unit with which more machine axes can be coordinate-transformed.

[0010] Furthermore, the reference point of the machine tool in the claimed method can be a tool reference point. The tool reference point, also called a 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 manipulator, or the dispensing nozzle of a painting device. The tool reference point makes it easy to describe the flow of the part program.

[0011] In a further embodiment of the claimed method, at least one of the machine axes can be configured to move the tool or to move the workpiece. The moved tool can be, for example, a milling cutter. The machine axis that moves the workpiece can be, for example, a rotatable clamping device for the workpiece, such as in a lathe. The claimed method is therefore transferable to a variety of machine tools.

[0012] Furthermore, the fourth and fifth steps of the claimed method can be performed for a plurality of rotary axes. For example, the machine tool can be locked about several rotary axes, and a suitable coordinate transformation for control commands can be performed successively for each of the locked rotary axes, individually or in combination, to determine an adapted control command set. The claimed method is thus readily transferable to complex machine tools with an increased number of machine axes, for example, to machine tools with eight machine axes. The claimed method is particularly suitable for use with robot manipulators with a large number of joints and rotary axes. Consequently, the claimed method is also suitable for future machine tools with increased complexity and can be used for a particularly long time.

[0013] In the claimed method, an orientation of the tool with respect to a surface of the workpiece can be determined in the third and / or fifth step. The orientation comprises, in particular, an angle between a main axis of the tool and at least a portion of the surface of the workpiece. For a tool designed as a painting device, the angle at which paint is sprayed onto the surface of the workpiece can be process-relevant. Furthermore, for tools such as a ball-end milling cutter, its orientation relative to the workpiece can determine the achievable manufacturing quality. An orientation, i.e. a clamping direction, of the workpiece can be specified for this purpose by a user and / or a suitable detection means. The orientation can be taken into account in the claimed method in at least one of the coordinate transformations.The representation of the tool's orientation is compatible with the coordinate transformations, allowing for the orientation to be taken into account with reduced computational effort. At least one of the steps of the claimed method can be performed repeatedly until a desired tool orientation is achieved. The claimed method can therefore be carried out largely automatically. Alternatively or additionally, during machining, the surface quality of the machined workpiece can be adjusted by a suitable angular position of the tool relative to the workpiece surface.

[0014] In a further embodiment of the claimed method, the tool can be asymmetrical or chiral. An asymmetrical tool can be a tool with a blade, so that the suitability of the tool is determined by its orientation. A chiral tool is understood, for example, to be the hand of a robot manipulator, which cannot be brought into a desired orientation by a single rotational movement. The claimed method is suitable for readily taking such additional information into account and thus has a broad potential range of applications. In particular, the claimed method can prevent incorrect control due to coordinate transformation, which in turn allows reliable operation of the machine tool.

[0015] Furthermore, the tool can be a drill, a milling cutter, a ball-end cutter, a cutting wheel, a robot manipulator, a welding device, a 3D printing head, a laser, a water jet device, a plasma jet device, or a painting device. Such machine tools are being manufactured with an increasing number of machine axes. At the same time, the aim is to operate them with the simplest possible control units. The claimed method allows machining paths to be followed with increased precision, thus machining workpieces more accurately. The claimed method is therefore suitable for a wide variety of different machine tools.

[0016] In the claimed method, when the adapted control command set is executed, only those machine axes can be moved for which control commands are determined in the third step. The rotary axis locked in the second step can thus be locked, i.e. held rigidly, when the adapted control command set is executed. In particular, during machining of the workpiece, the rotary axis 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 minimizes vibration of the workpiece and increases the achievable manufacturing precision. Likewise, the achievable infeed and thus the achievable chip volume per unit time are increased. This, in turn, results in increased productivity of the machine tool. Furthermore, accessibility to the tool is improved.

[0017] Furthermore, in the claimed method, the at least one axis of rotation that is locked in the second step can be determined based on a fixed or adjustable specification. For example, for a type of machine tool, it is possible to specify which at least one axis of rotation is to be locked in the second step. This represents a fixed specification. Likewise, the axis of rotation can be determined via a user specification by which the axis of rotation is selected directly, or can be selected based on a criterion that can be specified by the user. Alternatively, the at least one axis of rotation that is locked in the second step can be determined using an algorithm that is designed to evaluate the part program. Among other things, the algorithm can simulate the sequence of the adapted control command set. Based on the simulation, an adjustable criterion can be determined on the basis of which the axis of rotation is selected.For example, an expected vibration of the workpiece and / or the tool can be determined so that the rotational axis for locking is selected in the second step, where the lowest vibrations are expected. Alternatively or additionally, an energy requirement or wear during execution of the adapted control command set can also be determined. The claimed method can be carried out in multiple passes. The algorithm can be designed as an optimization algorithm, in particular as artificial intelligence with a simulation of the machine tool. The claimed method can thus be combined with a variety of algorithms for optimizing the operation of the respective machine tool. These can be optimizations with regard to minimized energy consumption, minimal machining time, or minimized wear of the tool and / or drive means, for example.The technical potential of the corresponding machine tool is thus further exploited.

[0018] The underlying problem is also solved by a computer program product according to the invention, which is designed to operate a machine tool. The computer program product is suitable for processing a parts program and, correspondingly, outputting an adapted set of control commands to the machine tool. The computer program product is suitable for running on a control unit that is at least functionally assigned to the machine tool. The computer program product can be monolithic, i.e., for running on a single hardware platform. Alternatively, the computer program product can be modular, i.e., comprise a plurality of parts programs that run on different hardware platforms and interact via a communicative data connection, for example, via an internet connection or a mobile phone connection.According to the invention, the computer program product is designed to perform at least one of the methods described above. The computer program product according to the invention requires only reduced computing power for a sufficiently fast execution. Consequently, the computer program product according to the invention can be executed on the control unit essentially without any loss of performance.

[0019] The object outlined above is also achieved by a control unit according to the invention, which is designed to operate a machine tool. The control unit is suitable for controlling drive means for each machine axis of the machine tool. For this purpose, the control unit has a memory unit and a computing unit, which are designed to execute a computer program product on the control unit. According to the invention, the control unit is designed to carry out at least one embodiment of the method described above. Alternatively or additionally, the computer program product, which is stored executably on the control unit, can be designed according to one of the embodiments presented above.

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

[0021] A simulation program product suitable for simulating the operating behavior of a control unit of a machine tool is not included in the scope of protection. A simulation program product is understood here to be a computer program product aimed at simulation. By means of the simulation program product, the operating behavior of at least the control unit can be simulated. In addition, a movement of a tool of the machine tool can also be part of the simulated operating behavior. According to the invention, the simulated operating behavior comprises at least one traversal of a machining path by the tool of the machine tool. The machining path to be traversed is thus determined by an adapted control command set that can be generated by the control unit to be simulated. The adapted control command set is determined according to one embodiment of the outlined method.For this purpose, the simulation program product can be designed, for example, as a so-called digital twin of the control unit and / or the machine tool, as described, for example, in the document US 2017 / 286572 A1. The simulation program product can be used to test and validate different adapted control command sets. Using the described method, the adapted control command sets can be quickly determined and immediately evaluated for the simulation program product. This also allows the simulation program product to be implemented quickly, so that a large number of adapted control command sets can be evaluated via simulation in a time-saving manner. The simulation program product can therefore easily be implemented alongside the operation of the machine tool. The simulation program product can be designed to evaluate and select simulated adapted control command sets according to an adjustable criterion.

[0022] The invention is explained in more detail below using an embodiment in a figure. It shows in detail: FIG 1 a schematic representation of a first embodiment of the claimed method.

[0023] A first embodiment of the claimed method 100 is shown in FIG 1 shown schematically. The method 100 serves to operate a machine tool 10 having a plurality of machine axes 14 around or along which a tool 15 is movable. The tool 15 is designed as a milling cutter 17 and is suitable for machining a workpiece 25 (not shown in detail). The tip of the milling cutter 17 forms a reference point 27 on the machine tool 10, namely the so-called tool center point, or TCP for short. The machine tool 10 is accordingly a milling machine.

[0024] The workpiece 25 can be clamped in a clamping device 18 of the machine tool 10. The clamping device 18 is designed to be rotatable about a rotational axis 13. Each of the machine axes 14 is at least functionally coupled to a drive means 12 (not shown in detail), so that the respective machine axis 14 can be actuated. FIG 1 The machine tool 10 shown comprises three translational axes 16 and three rotational axes 13, by means of which the tool 15 can be guided and / or aligned along a machining path. The drive means 12 are at least functionally coupled to a control unit 20, which is designed to actuate the drive means 12. The control unit 20 comprises a computing unit 22 and a memory unit 24, which are designed to execute a computer program product 50 with which the claimed method 100 is carried out.

[0025] The method 100 comprises a first step 110 in which a part program 30 is provided, which comprises a plurality of part program commands 32, by which a machining path of the tool 15 relative to the workpiece 25 is determined. The part program 30 is therefore independent of the machine tool 10 used. The part program 30 is further processed in the claimed method 100 in order to machine the workpiece 25. The method 100 further comprises a second step 120 in which one of the rotational axes 13 among the machine axes 12 of the machine tool 10 is determined, which is then locked. By locking, the determined rotational axis 13 remains in a locked position 34. This is achieved by mechanical blocking, in that control commands to the corresponding drive means 12 are suppressed, and / or the corresponding drive means 12 refuses to accept control commands that lead to a movement.The rotational axis 13 locked in the locking position 34 is selected by a user input on an input unit 21 or via an algorithm 23 designed to evaluate the part program 30. In particular, the algorithm 23 is designed to determine which of the rotational axes 13 is most suitable for the second step 120.

[0026] Furthermore, a third step 130 belongs to the claimed method 100, in which control commands 35 are determined based on the part program 30. To determine the control commands 35, a coordinate transformation 33 is applied to the part program 30. The control unit 20 is configured to perform a coordinate transformation 33 around a number of machine axes 14 that is fewer than the number of machine axes 14 that the machine tool 10 has. During the coordinate transformation 33, the three translational axes 14 and two rotary axes 13 of the machine tool 10 are taken into account. The control unit 20 is accordingly suitable for performing a coordinate transformation 33 around five machine axes 33 at once. The machine axes 14 taken into account, i.e., the three translational axes 14 and the two rotary axes 13, belong to a machine axis set 39.The consideration of the machine axis set 39 is represented by the arrow 37. The rotation axis 13 determined and locked in the second step 120 is excluded from the coordinate transformation 33. The exclusion of the locked rotation axis 13 is shown in . FIG 1 symbolized by the broken lines in machine axis set 39.

[0027] The claimed method 100 also includes 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 about the corresponding rotational axis 13 and brought into a machining position 38. During the fourth step 140, the rotational movement 36 with which the rotational axis 13 is moved from the locked position 34 to the machining position 38 is also recorded. For this purpose, a direction of the rotational movement 36 and an associated angle of rotation are recorded in terms of magnitude. This is followed by a fifth step 150, in which a coordinate transformation 33 is applied to the control commands 35 determined in the third step 130. The coordinate transformation 33 in the fifth step 150 occurs exclusively around 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 detected in the fourth step 140, i.e., its direction and its absolute value of the angle of rotation. The coordinate transformation 33 performed in the fifth step 150 generates an adapted control command set 40 comprising a plurality of adapted control commands 42. The adapted control commands 42 are each directed to a drive means 12 of the machine tool and are suitable for triggering actuation of the respective drive means 12. By means of the coordinate transformation 33 performed in the fifth step 150, the control commands 35 provided in the third step 130 are adapted to the machining position 38 that the rotational axis 13 determined in the second step 120 assumes when the adapted control command set 40 is executed.

[0028] In method 100, an orientation 19 of the tool 15 is also taken into account. The method 100 is executed again in the second step 120, selecting a different axis of rotation 13, if an initially determined, adapted control command set 40 leads to an orientation 19 of the tool 15 in which the desired machining of the workpiece 25 is impossible or at least impractical. Such consideration of the orientation 19 of the tool 15 can be carried out by the algorithm 23. The algorithm 23 can also be designed to determine an expected energy requirement and / or an expected wear of the machine tool 10, in particular of a drive means 12 and / or the tool 15. For this purpose, the algorithm 23 can be designed as an optimization algorithm, in particular as artificial intelligence.The control command set 40, which is determined after one or more passes of the method 100, is output to the machine tool 10 in order to machine the workpiece 25.

[0029] Furthermore, the operating behavior of the control unit 20 of the machine tool 10 is simulated using a simulation program product 60 (not shown in detail). The simulation program product 60 is designed as a digital twin, in which the mechanical behavior of the machine tool 10 can also be simulated. The mechanical behavior of the machine tool 10 includes, among other things, a vibration behavior of the machine tool 10 about at least its rotational axes 13. The simulation program product 60 can be used to test an adapted control command set 40 determined in one pass of the method 100. In particular, this makes it possible to calculate the extent to which vibrations can be expected on the machine tool 10 and the extent to which this will affect the expected manufacturing accuracy.The adapted control command sets 40 determined using the claimed method 100 can be easily evaluated by the simulation program product 60, allowing an increased number of adapted control command sets 40 to be quickly tested. The simulation program product 60 is suitable for running the method 100 in multiple passes to achieve increased manufacturing precision. For this purpose, the simulation program product 60 comprises a digital image of the control unit 20 and the machine tool 10, in particular the associated drive means 12.

Claims

1. Method (100) for operating a machine tool (10) having a first number of machine axes (14), each of which can be moved by means of a drive means (12) and can be actuated via a control unit (20) which is designed to perform a coordinates transformation (33) around a second number of machine axes (12) relative to a reference point (27) on the machine tool (10), comprising the step: a) providing a parts program (30) for the machining of a workpiece (25) by means of the machine tool (10); characterised by the steps: b) determining at least one axis of rotation (13) from among the machine axes (12) and blocking the at least one axis of rotation (13) determined for actuations; c) determining control commands (35) for a plurality of machine axes (12) excluding the at least one axis of rotation (13) determined in step b); d) setting the at least one axis of rotation (13) determined in step b) into a machining position (38) and determining a corresponding rotational movement (36); e) determining an adapted set of control commands (40) for the plurality of machine axes (12) on the basis of the control commands (35) determined in step c) and the rotational movement (36) determined in step d); wherein the workpiece (15) is machined by means of executing the adapted set of control commands (40).

2. Method (100) according to claim 1, characterised in that the first number of machine axes (14) comprises at least three axes of rotation (13).

3. Method (100) according to claim 1 or 2, characterised in that the first number of machine axes (12) is greater than the second number of machine axes (12).

4. Method (100) according to one of claims 1 to 3, characterised in that the reference point (27) of the machine tool (10) is a tool centre point.

5. Method (100) according to one of claims 1 to 4, characterised in that at least one of the machine axes (12) is designed to move a tool (15) or is designed to move the workpiece (25).

6. Method (100) according to one of claims 1 to 5, characterised in that steps d) and e) are performed for a plurality of axes of rotation (13).

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

8. Method (100) according to one of claims 1 to 7, characterised in that the tool (15) has an asymmetric or chiral design.

9. Method (100) according to one of claims 1 to 8, characterised in that the tool (15) is a drill, a milling cutter (17), a spherical cutter, a turning tool, a cutting disk, a robot manipulator, a welding device, a 3D print head, a laser, a water jet device, a plasma beam device, or a painting device.

10. Method (100) according to one of claims 1 to 9, characterised in that when executing the adapted set of control commands (40), only those machine axes (12) for which control commands (35) were determined in step c) are moved.

11. Method (100) according to one of claims 1 to 10, characterised in that the at least one axis of rotation (13) is determined in step b) with reference to a fixed or settable specification (21) or on the basis of an algorithm (23) which is designed to evaluate the parts program (30).

12. Computer program product (50) for operating a machine tool (10), being designed to process parts programs (30) and to output an adapted set of control commands (40) to the machine tool (10), characterised in that the computer program product (50) is designed to perform a method (100) according to one of claims 1 to 11.

13. Control unit (20) for operating a machine tool (10), being designed to activate drive means (12) for machine axes (14) of the machine tool (10) and being designed to execute a computer program product (50) by means of a memory unit (24) and a computing unit (22), characterised in that the control unit (20) is designed to perform a method (100) according to one of claims 1 to 11 and / or is provided with a computer program product (50) according to claim 12.

14. Machine tool (10) comprising a plurality of machine axes (14), each of which can be actuated via at least one drive means (12), and a control unit (20) which is designed to activate the drive means (12), characterised in that the control unit (20) is designed according to claim 13.