Compensating tool deviations by dynamically adjusting tool geometries

Abstract

A digital controller (4) of the machine tool receives a subprogram (7) which determines a path (8) along which a workpiece (2) should be machined in a material removal manner by means of a machining tool (3) of the machine tool. The digital controller determines control commands (Ci) for a plurality of position-controlled axes (1) of the machine tool by means of a subprogram (7) and controls the position-controlled axes (1) as a function of the determined control commands (Ci), the machining tool (3) being moved in a position-controlled manner relative to the workpiece (1) by means of the axes. The digital controller (4) determines a control command (Ci) such that the workpiece (2) is machined in a material-removing manner by the machining tool (3) along the path (8) determined by the subprogram (7). During the machining of the workpiece (2) by the machining tool (3), the digital controller receives in real time an actual value (I) characterizing a machining force (F) exerted by the workpiece (2) on the machining tool (3) during the machining of the workpiece (2) by the machining tool (3). When determining the control command (Ci), the digital controller (4) takes into account the geometric measurement (g) of the machining tool (3) and the machining force (F). The machining force (F) is taken into account as a function of the machining force (F) in such a way that the geometric measurement (g) of the machining tool (3) varies dynamically and in real time during the machining.

Description

Technical Field

[0001] The invention is based on a method for operating a machine tool.

[0002] wherein the numerical controller of the machine tool receives a subroutine which determines a path along which the workpiece is to be machined to remove material using a machining tool of the machine tool,

[0003] wherein for a plurality of position-controlled axes of a machine tool, a numerical controller determines control commands by means of a subroutine and controls the position-controlled axes according to the determined control commands, wherein a machining tool is moved relative to a workpiece in a position-controlled manner by means of the axes,

[0004] wherein the numerical controller determines control commands so that the workpiece is machined by the machining tool along a path determined by the subroutine in such a way as to remove material,

[0005] wherein the digital controller receives in real time during machining of the workpiece by the machining tool actual values ​​representative of machining forces applied by the workpiece to the machining tool during machining of the workpiece by the machining tool,

[0006] - wherein the digital controller takes into account geometrical measurements of the machining tool and machining forces when determining control commands.

[0007] The invention is also based on a control program for a numerical controller, wherein the control program includes a machine code, the processing of which by the numerical controller causes the numerical controller to execute such an operating method.

[0008] The invention is also based on a digital controller which is programmed with the aid of such a control program in such a way that the digital controller carries out such an operating method during operation.

[0009] The present invention is also based on a machine tool,

[0010] wherein the machine tool has a numerical controller and is capable of receiving a subprogram from the numerical controller, the subprogram defining a path along which the workpiece is to be machined in such a way as to remove material,

[0011] wherein the machine tool has a plurality of position-controlled axes, by means of which a machining tool of the machine tool can be moved in a position-controlled manner relative to the workpiece,

[0012] wherein the digital controller is connected to the position-controlled axis in order to preset control commands to the position-controlled axis,

[0013] wherein the machine tool has a device by which a plurality of actual values ​​characterizing the machining forces exerted on the machining tool during machining of the workpiece can be detected or determined during machining of the workpiece,

[0014] - wherein the digital controller is connected to a device for receiving actual values. Background Art

[0015] This operating method, the corresponding numerical controller, the associated machine tool and in fact also the control program are known, for example, from DE 10 2017 206 931 A1 or the corresponding US 2018 / 0 307 200A1.

[0016] Similar facts can be derived from EP 2 871 547 A1 and US 2008 / 0 105 094 A1.

[0017] In DE 10 2017 206 931 A1, a test workpiece with a known geometry is first processed synchronously in a learning cut by means of a milling cutter (processing tool of DE 10 2017 206 931 A1). In the course of the learning cut, a correlation is determined between the torque of the spindle drive for the milling cutter and the resulting deflection of the milling cutter, wherein the torque is substantially proportional to the processing force. This correlation is stored in a numerical control and can thus be taken into account synchronously when processing subsequent workpieces.

[0018] In DE 10 2017 206 931 A1, the relationship between torque and deflection is determined in the form of axis stiffness. This determination is performed individually for each axis. This is taken into account by correcting the position setpoint of the axis as a function of the respective axis stiffness and the deflection forces occurring (processing forces in DE 10 2017 206 931 A1).

[0019] Compared to a process that does not take into account the machining forces, the teaching of DE 10 2017 206 931 A1 leads to significantly improved results. However, it is very computationally complex and cannot be easily applied in the case of more complex machining processes.

[0020] It is also known from US 2008 / 0 105 094 A1 to vary the actual geometry of a machining tool as a function of the machining force, for example by means of a piezoelectric element arranged in the machining tool. Summary of the invention

[0021] The object of the present invention is to create an option by means of which machining forces occurring during machining of a workpiece by a machining tool can be taken into account in a simpler manner.

[0022] This object is achieved by an operating method having the features of claim 1. Advantageous embodiments of the operating method are the subject matter of dependent claims 2 to 7.

[0023] According to the invention, an operating method of the type mentioned in the introduction is designed in such a way that the numerical controller takes the machining forces into account by dynamically and in real time changing geometrical measurements of the machining tool as a function of the machining forces during machining.

[0024] The invention is therefore based on the idea that instead of calculating a new path, it can be assumed purely computationally that the geometry of the machining tool has changed. It can be said that the numerical controller is deceived into believing that the geometry of the machining tool has changed. In reality, however, the geometry of the machining tool has not changed. However, the machining tool has been deflected by the machining forces. If the change in geometry is chosen appropriately (purely computationally), the effects of the deviation can thereby be compensated.

[0025] The process according to the invention first simplifies the learning cut. Because the learning cut must be performed for each machining tool (as in DE 10 2017 206 931 A1). However, only a single correlation of the dependence of the geometric measurement on the machining force needs to be determined. However, this correlation does not need to be determined individually for the position-controlled axes.

[0026] The subsequent operation of the machine tool is also significantly simpler (from the perspective of the numerical controller), since only the geometrical measurements of the machining tool have to be changed. The relevant influence on the control commands of the individual position-controlled axes is automatically generated based on the changed geometrical measurements of the machining tool.

[0027] The actual value characterizing the processing force can be obtained in a metered manner. Alternatively, the actual value can also be determined. Examples are explained below in conjunction with preferred embodiments.

[0028] If the machining tool is designed as a milling cutter, so that the machining of the workpiece by the machining tool is a milling operation, the operating method according to the invention works particularly simply and reliably. In this case, the geometric measurement of the machining tool is the milling cutter radius of the milling cutter, and the numerical controller only needs to change the milling cutter radius according to the machining force.

[0029] In the case of a milling cutter, the operating method according to the invention generally only works reliably if the machining of the workpiece by the milling cutter is performed synchronously. However, this can be easily ensured. The term "synchronous" has a clearly defined meaning for those skilled in the art.

[0030] During milling, the actual value characterizing the machining force can include a current value, with which the spindle drive of the rotating milling cutter of the machine tool is loaded. The current value can be acquired in a metered manner by means of a current sensor. Alternatively, the current value can also be determined. In particular, in a determined case, it can be a set current with which the spindle drive should be loaded. If necessary, the current value can be preprocessed in a variety of ways. For example, only the current that produces the torque can be used and / or the current value can be corrected for deviations. A corresponding processing method is known from DE 10 2017 206 931 A1.

[0031] The operating method according to the invention is not limited to milling. Alternatively, the machining tool can be designed as a turning tool, for example, so that the machining of the workpiece by the machining tool is turning (English: lathing). In this case, the geometric measurement of the machining tool is the length of the turning tool, and the numerical controller only needs to change the length of the turning tool according to the machining force.

[0032] During turning, the actual value characterizing the machining force can include the current value, with which the spindle drive of the rotating workpiece of the machine tool is loaded. The current value can be measured or otherwise determined by means of a current sensor. The above-mentioned embodiments for the case of a milling cutter can be applied in an analogous manner. This also applies to any necessary preprocessing of the current value.

[0033] The operating method according to the invention can also be used in other machining operations, for example in grinding with a grinding tool.

[0034] Preferably, the numerical controller first determines geometrical measurements as a function of the process forces, then determines a position setpoint value for the position-controlled axis using a subroutine and the determined geometrical measurements, and finally determines a control signal for the position-controlled axis as a function of the position setpoint value and the position actual value of the position-controlled axis. This procedure makes it possible to take the process forces into account in a particularly simple manner when determining the control signal.

[0035] The difference between the position setpoint and the position actual value is relevant for determining the control signal. Therefore, instead of taking into account the geometrical measure when determining the position setpoint, the geometrical measure can alternatively also be taken into account by correcting the actual position value or the difference between the position setpoint and the actual position value.

[0036] Preferably, the numerical controller determines the correction value for the geometrical measurement as a function of the process forces, and the geometrical measurement is determined by adding a basic geometrical variable, which is independent of the process forces and is known to the numerical controller, to the correction value.

[0037] This object is also achieved by a control program having the features of claim 9. According to the invention, the processing of the control program by the digital controller causes the digital controller to carry out the operating method according to the invention.

[0038] This object is further achieved by a digital controller having the features of claim 10. According to the invention, the digital controller is programmed with a control program according to the invention, so that the digital controller carries out the operating method according to the invention.

[0039] This object is further achieved by a machine tool having the features of claim 11. According to the invention, in a machine tool of the type mentioned at the outset, the numerical controller is designed as a numerical controller according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above characteristics, features and advantages of the present invention and the methods for achieving them will become clearer and easier to understand with reference to the following description of exemplary embodiments in conjunction with the accompanying drawings. Here, it is shown in a schematic diagram:

[0041] Figure 1 A first embodiment of a machine tool is shown,

[0042] Figure 2 A second embodiment of the machine tool is shown,

[0043] Figure 3 Showing the flow chart,

[0044] Figure 4 The curve showing the machining force,

[0045] Figure 5 The corresponding curves showing the geometric measurements,

[0046] Figure 6 Shows the deviation of the processing tool,

[0047] Figure 7 Another curve showing the processing force, and

[0048] Figure 8 The corresponding curves of the geometrical measurements are shown. DETAILED DESCRIPTION

[0049] according to Figure 1 and Figure 2 The machine tool has n position-controlled axes 1. The number n of position-controlled axes 1 can be determined as required. The minimum number n is 1. However, the number n of position-controlled axes 1 is usually greater than 1. The workpiece 2 is held (clamped) in the machine tool. The workpiece 2 is to be machined in the machine tool by means of a machining tool 3 of the machine tool in a material-removing manner.

[0050] The machine tool also has a numerical controller 4. The numerical controller 4 is connected to the position-controlled axis 1. The connection of the numerical controller 4 to the position-controlled axis 1 is used, on the one hand, to transmit control signals Ci (i=1, 2, ..., n) to the position-controlled axis 1. On the other hand, the connection of the numerical controller 4 to the position-controlled axis 1 is used to receive actual position values ​​xi (i=1, 2, ..., n) from the position-controlled axis 1 respectively. As a result, the position-controlled axis 1 is thus controlled by the numerical controller 4. Due to the corresponding control of the position-controlled axis 1, the machining tool 3 is moved relative to the workpiece 2 in a position-controlled manner by the numerical controller 4.

[0051] The digital controller 4 is programmed with a control program 5 (system program). The control program 5 includes a machine code 6 which can be processed by the digital controller 4. The processing of the machine code 6 by the digital controller 4 causes the digital controller 4 to execute the following operations in conjunction with Figure 3 The operating method is explained in more detail.

[0052] according to Figure 3 In step S1, the digital controller 4 receives the subroutine 7 (utility program). Figure 1 , a subroutine 7 determines a path 8 along which the workpiece 2 is machined by means of a machining tool 3 in a material-removing manner.

[0053] In step S2, the basic geometrical dimension g0 of the machining tool 3 is known by the numerical controller 4. Figure 1 In the case of an embodiment of a machine tool of , in which the machining tool 3 is designed as a milling cutter and the machining of the workpiece 2 by the machining tool 3 is therefore milling, the basic geometrical dimension g0 is the initial milling cutter radius r0 of the milling cutter. During milling, the number n of position-controlled axes 1 is usually 3 or more. Figure 2 In the case of an embodiment of a machine tool, in which the machining tool 3 is designed as a turning tool and the machining of the workpiece 2 by the machining tool 3 is therefore turning, the basic geometrical dimension g0 is the initial turning tool length 10 of the turning tool. During turning, the number n of position-controlled axes 1 is usually 2 or more.

[0054] Step S1 and step S2 must only be executed if there are changes in this respect, for example, if the subprogram 7 is changed or the processing tool 3 is replaced. In contrast, step S3 and the steps S4 to S10 following step S3 bring about the control required for processing the workpiece 2 by the processing tool 3 with respect to the position-controlled axis 1. Steps S3 to S10 are repeatedly and cyclically executed by the numerical controller 4 with a position control cycle T. The position control cycle T is usually less than 1 ms, for example, 125 μs or 250 μs. The values ​​are given purely by way of example.

[0055] In step S3, the numerical controller 4 receives from the position-controlled axis 1 its corresponding actual position value xi. In step S4, the numerical controller 4 receives a plurality of actual values ​​I from a device 9 of the machine tool. The numerical controller 4 communicates with the device 9 (see at least for this purpose) Figure 1 and Figure 2 ) connection. Independent of the number and type of the actual value I, the actual value I is determined such that it characterizes the machining force F which is applied by the workpiece 2 to the machining tool 3 during the machining of the workpiece 2 by the machining tool 3. Since step S4 is incorporated into the loop processing of steps S3 to S10, the actual value I is received during the machining of the workpiece 2 by the machining tool 3 and in real time. The actual value I is acquired by the device 9 in a metered manner or is determined by it in an arithmetically manner. The arithmetically determined value can be based on a specified and / or metered acquired value.

[0056] The actual value I can include, in particular, a current value (setpoint value or actual value) for a spindle drive 10 of a machine tool (see Figure 1 and Figure 2 ) Load current value. Figure 1 In the case of the embodiment of the machine tool of , in which the machining tool 3 is designed as a milling cutter, the milling cutter is rotated by means of the spindle drive 10. Figure 2 In the case of an embodiment of a machine tool in which the machining tool 3 is designed as a turning tool, the workpiece 2 is rotated by means of a spindle drive 10 .

[0057] In step S5, the numerical controller 4 determines the machining force F according to the actual value I. In step S6, the numerical controller 4 changes the geometrical measurement g of the machining tool 3 according to the machining force F. Since step S6 is incorporated into the sequence of steps S3 to S10, this change occurs dynamically and in real time during the machining of the workpiece 2 by the machining tool 3. For example, in step S6, the numerical controller 4 can first determine the correction value δg and then determine the geometrical measurement g by adding the basic geometrical dimension g0 to the correction value δg. Figure 1 In the case of the embodiment of the machine tool (the processing tool 3 is designed as a milling cutter), therefore, the milling cutter radius of the milling cutter changes. Figure 2 In the case of the embodiment of the machine tool of FIG. 5 , in which the machining tool 3 is designed as a turning tool, the turning tool length of the turning tool varies inversely. Figure 4 and Figure 5 Purely by way of example, for a simple case (machining tool 3 designed as a milling cutter, travel movement in the X direction, orientation of the milling cutter from the base parallel to the Z direction) the curves of machining force F and geometrical measure g, here the effective milling cutter radius, are shown. Figure 6 The deflection of the machining tool 3 caused by the machining force F is also shown schematically and in a considerably enlarged manner.

[0058] References below Figures 4 to 6 The process of the invention is explained in detail. Here, the explanation is given in conjunction with the exemplary embodiment of the machining tool 3 as a milling cutter. If the machining tool 3 is designed differently, this explanation can also be applied (in a correspondingly adapted manner).

[0059] The milling cutter has a certain geometrical measurement g0, for example, in the case of a milling cutter, a radius r0. Figure 5 If the machining tool 3 is to be machined along the line marked with K in FIG. 1 and the machining tool 3 is to be infinitely rigid, the axis of rotation of the machining tool 3 must be exactly at a spacing r0 from the line K. Therefore, in step S2, the basic geometrical dimension g0 of the machining tool 3 is made known to the numerical controller 4 so that the numerical controller 4 can take the basic geometrical dimension g0 (in the case of a milling cutter, the radius r0) into account accordingly. This procedure is standard in every numerical controller 4.

[0060] However, according to Figure 6 , the processing tool 3 deviates due to the processing force F. The radius r0 of the milling cutter or, in general, the geometrical measurement g0 of the processing tool 3 generally does not change. However, if no further measures are taken, milling would be performed along the line K' instead of the line K, for example. In order to reach the line K, the spacing of the rotation axes of the processing tool 3 must therefore be reduced. According to the invention, this is achieved in the following way: (again: purely computationally within the numerical controller 4) the milling cutter radius or, in general, the geometrical measurement g of the processing tool 3 is adjusted accordingly dynamically as a function of the processing force F. In this way, the deviation can be compensated purely computationally. Therefore, it can be said that the numerical controller 4 is deceived: that is, the "wrong milling cutter radius" changes dynamically (or the wrong geometrical measurement g changes dynamically in general), so that the precise deviation caused by the processing force F is compensated. However, the processing tool 3 itself does not change.

[0061] In step S7, the numerical controller 4 determines the position setpoint xi* (i=1, 2, ..., n) of the position-controlled axis 1. The position setpoint xi* is determined using the subroutine and the geometric measurement g, as determined in step S6. The position setpoint xi* is determined (assuming that the position-controlled axis 1 is controlled accordingly) so that the workpiece 2 is machined by the machining tool 3 along the path 8 determined by the subroutine 7 in a material-removing manner.

[0062] In step S8, the numerical controller 4 determines a control signal Ci for the position-controlled axis 1 according to the position set value xi* and the actual position value xi of the position-controlled axis 1. The control signal Ci can be, for example, a speed set value or a current set value or a combination of these set values. In step S9, the numerical controller 4 controls the position-controlled axis 1 according to the determined control signal Ci. As a result, the machining tool 3 is correspondingly moved relative to the workpiece 2 in a position-controlled manner.

[0063] In step S10, the numerical controller 4 checks whether the subroutine 7 has been completely processed. If this is not the case, the numerical controller 4 returns to step S3, wherein in step S7 the position setpoint xi* is always re-determined according to the progress of the processing of the subroutine 7. Otherwise, the process ends. Figure 3 The processing method.

[0064] In order to be able to carry out the dynamic variation according to the invention of the geometrical measurement g, the numerical controller 4 must know the corresponding correlation with the processing force F. This correlation can, for example, be determined once in advance and then stored in the numerical controller 4. However, other procedures are also possible. In the simplest case, there is a purely linear correlation, so that the correction value δg is proportional to the processing force F. However, other correlations are also possible.

[0065] In summary, therefore, the present invention relates to the following facts:

[0066] The numerical controller 4 of the machine tool receives a subroutine 7 which determines a path 8 along which a workpiece 2 is to be machined in a material-removing manner by means of a machining tool 3 of the machine tool. For a plurality of position-controlled axes 1 of the machine tool, by means of which the machining tool 3 is moved in a position-controlled manner relative to the workpiece 1, the numerical controller 4 determines control commands Ci by means of the subroutine 7 and controls the position-controlled axes 1 in accordance with the determined control commands Ci. The numerical controller 4 determines the control commands Ci so that the workpiece 2 is machined in a material-removing manner by the machining tool 3 along the path 8 determined by the subroutine 7. The numerical controller 4 receives in real time during machining of the workpiece 2 by the machining tool 3 an actual value I characterizing a machining force F exerted by the workpiece 2 on the machining tool 3 during machining of the workpiece 2 by the machining tool 3. When determining the control commands Ci, the numerical controller 4 takes into account the geometrical measurement g of the machining tool 3 and the machining force F. The machining force F is taken into account in that the geometrical measurement g of the machining tool 3 is varied dynamically and in real time as a function of the machining force F during machining.

[0067] The invention has many advantages. In particular, the operating method can be easily applied when machining free-form contours. This is because the machining forces F acting on the individual regulated axes 1 do not need to be recalculated. Nor is there any need to interpret the direction of the forces for each position-controlled axis 1. This can be done significantly more simply due to the correction of the geometric measurement g. Figure 7 and Figure 8 Purely by way of example, for a Figure 4 and Figure 5The diagram shows the machining force F and the geometrical measure g, here the effective milling cutter radius, for the case of (the machining tool 3 is a milling cutter, which is oriented parallel to the Z direction from the base) a free contour (the milling cutter moves in the X direction and in the Y direction). The operating method according to the invention can also be used in other machining technologies, for example in grinding.

[0068] Although the present invention has been illustrated and described in detail by preferred exemplary embodiments, the present invention is not limited to the disclosed examples and variations thereof can be derived therefrom by those skilled in the art without departing from the scope of protection of the present invention.

Claims

1. A method for operating a machine tool, -in, The numerical controller (4) of the machine tool receives a subprogram (7) which defines a path (8) along which the workpiece (2) is to be machined by means of a machining tool (3) of the machine tool in a material-removing manner, - wherein, for a plurality of position-controlled axes (1) of the machine tool, by means of which the machining tool (3) is moved relative to the workpiece (1) in a position-controlled manner, the numerical controller (4) determines control commands (Ci) using the subroutine (7) and controls the position-controlled axes (1) according to the determined control commands (Ci), - wherein the numerical controller (4) determines the control command (Ci) so as to cause the machining tool (3) to machine the workpiece (2) along the path (8) determined by the subroutine (7) in a manner that removes material, - wherein, during the processing of the workpiece (2) by the processing tool (3), the digital controller (4) receives in real time an actual value (I), wherein the actual value represents a processing force (F) applied by the workpiece (2) to the processing tool (3) during the processing of the workpiece (2) by the processing tool (3), - wherein the numerical controller (4) takes into account the geometrical measurements (g) of the machining tool (3) and the machining forces (F) when determining the control commands (Ci), characterized in that The numerical controller (4) takes the machining forces (F) into account by the numerical controller dynamically and in real time changing the geometrical measurement (g) of the machining tool (3) according to the machining forces (F) during the machining.

2. The operating method according to claim 1, characterized in that: The machining tool (3) is designed as a milling cutter, so that machining of the workpiece (2) by the machining tool (3) is a milling operation, and the geometric measurement (g) of the machining tool (3) is the milling cutter radius of the milling cutter.

3. The operating method according to claim 2, characterized in that: The actual value (I) characterizing the machining force (F) comprises a current value which is applied to a spindle drive (10) of the machine tool which rotates the milling cutter.

4. The operating method according to claim 1, characterized in that: The machining tool (3) is designed as a turning tool, so that machining of the workpiece (2) by the machining tool (3) is a turning operation, and so that the geometrical measurement (g) of the machining tool (3) is the length of the turning tool.

5. The operating method according to claim 4, characterized in that: The actual value (I) characterizing the machining force (F) comprises a current value which is applied to a spindle drive (10) of the machine tool which rotates the workpiece (2).

6. The operating method according to any one of claims 1 to 5, characterized in that: The numerical controller (4) determines the geometrical measurement (g) based on the machining force (F), determines the position set value (xi*) for the position-controlled axis (1) using the subroutine (7) and the determined geometrical measurement (g), and determines the control signal (Ci) for the position-controlled axis (1) based on the position set value (xi*) and the actual position value (xi) of the position-controlled axis (1).

7. The operating method according to any one of claims 1 to 5, characterized in that: The numerical controller (4) determines the geometrical measurement (g) as a function of the machining force (F), determines a position setpoint value (xi*) for the position-controlled axis (1) using the subroutine (7), and determines the control signal (Ci) for the position-controlled axis (1) as a function of the difference between the position setpoint value (xi*) and the actual position value (xi) determined for the position-controlled axis (1), and the numerical controller (4) takes the geometrical measurement (g) into account when determining the actual position value (xi) determined or the difference determined.

8. The operating method according to claim 6 or 7, characterized in that: The numerical controller (4) determines a correction value (δg) for the geometrical measurement (g) as a function of the machining force (F) and determines the geometrical measurement (g) by adding a basic geometrical dimension (g0) known to the numerical controller (4) and independent of the machining force (F) and the correction value (δg).

9. A control program for a digital controller (4), wherein: The control program comprises a machine code (6), the processing of which by the numerical controller (4) causes the numerical controller (4) to execute an operating method according to any one of the preceding claims. 10 . A digital controller, which is programmed with the aid of a control program ( 5 ) according to claim 6 , such that during operation the digital controller executes an operating method according to any one of claims 1 to 8 .

11. A machine tool, -in, The machine tool has a numerical controller (4) from which a subprogram (7) can be received, the subprogram defining a path (8) along which the workpiece (2) is to be machined in a material-removing manner, wherein the machine tool has a plurality of position-controlled axes (1), by means of which a machining tool (3) of the machine tool can be moved in a position-controlled manner relative to the workpiece (2), - wherein the digital controller (4) is connected to the position-controlled axis (1) to set a control command (Ci) for the position-controlled axis (1), - wherein the machine tool has a device (9) by which a plurality of actual values ​​(I) can be acquired or determined during the machining of the workpiece (2) by the machining tool (3), the actual values ​​characterizing machining forces (F) exerted by the workpiece (2) on the machining tool (3) during the machining of the workpiece (2) by the machining tool (3), - wherein the digital controller (4) is connected to the device (9) to receive the actual value (I), It is characterized in that The digital controller (4) is designed as a digital controller according to claim 10.

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