Control method for machine tools and / or production machines

Abstract

The present invention relates to a method for controlling the rotary motion of a tool (6) in a machine tool (1) by means of a part program, wherein a retraction motion and a lateral motion to be performed by the tool (6) are specified in the part program, wherein the rotary motion (D) of the tool (6) is decelerated during the retraction motion and / or the lateral motion.

Description

Technical Field

[0001] This invention relates to a method for controlling the rotary motion of tools in machine tools and / or production machines. Background Technology

[0002] DE 10 2010 015 221 A1 relates to a control device for a machine tool, the machine tool including a feed axis drive motor, a first power consumption calculation section for calculating the power consumption of the feed axis drive motor, a second power consumption calculation section for calculating the power consumption of the calculation device to operate at a constant power, and a motor control section that determines a rated time constant related to the acceleration time and / or delay time of the feed axis drive motor based on the sum of the power consumption calculated by the first power consumption calculation section and the power consumption calculated by the second power consumption calculation section, and controls the feed axis drive motor based on the rated time constant.

[0003] DE 10 2019 103 563 A1 discloses a control device for the synchronous operation of the control spindle and feed axis of a machine tool.

[0004] The motion curves of a multi-axis system should be energetically optimized in EP 2 952 991 A1. The proposed method is as follows: a first axis and a second axis connected thereto perform corresponding first and second movements. The two movements begin together at a first time point and end together at a second time point. The time interval between the first and second time points is determined. The corresponding acceleration curves of one or both movements are optimized to have at least one continuous transition from one acceleration value to another within this time interval.

[0005] Some machine tools are particularly well-suited for thread cutting, especially in tapping centers. Crucially, the machine's productivity is closely related to the spindle's performance. Certain thermodynamic issues can reduce productivity.

[0006] Thermodynamic problems are usually solved by accelerating the spindle only at its rated current, or by operating it at or slightly above its rated current. However, this is particularly disadvantageous in terms of dynamics, as only one-third of the possible acceleration is possible. Summary of the Invention

[0007] The object of this invention is to improve spindle control, particularly in terms of thermodynamics.

[0008] This objective is achieved by claim 1, namely, a method for controlling the rotary motion of a tool by means of a part program in the case of a machine tool and / or a production machine, wherein a retracting motion and a lateral motion to be performed by the tool are specified in the part program, wherein the rotary motion of the tool decelerates during the retracting motion and / or the lateral motion, wherein the tool accelerates in a first rotational direction, wherein the tool decelerates while rotating in the first rotational direction, wherein the tool accelerates in a second rotational direction, wherein the tool decelerates while rotating in the second rotational direction, wherein the duration of the deceleration of the tool rotating in the second rotational direction is greater than the duration of the deceleration of the tool rotating in the first rotational direction.

[0009] Preferably, the spindle decelerates during the time it takes for the spindle to move to the next machining position.

[0010] The next machining location is, for example, the place where another thread should be cut.

[0011] An advantageous implementation is to decelerate the tool only during the retraction motion, so that the rotational motion is equal to zero in the case of a defined retraction plane.

[0012] This method prevents the spindle from overheating.

[0013] Advantageously, the defined retraction plane is between 5mm and 15mm, especially between 8mm and 12mm.

[0014] Other planes are also feasible, especially when obstacles need to be overcome.

[0015] Another advantageous implementation is to decelerate the tool as it decelerates during lateral movement, so that the rotational motion is zero at the end of the lateral movement.

[0016] Therefore, the available time interval for deceleration is particularly long, resulting in only a small amount of heating during deceleration.

[0017] Another advantageous implementation is to slow down the rotational motion of the tool during the retraction motion and at least partially during the lateral motion.

[0018] This implementation method is also advantageous in terms of thermodynamic issues.

[0019] The tool accelerates in a first rotational direction, while the tool decelerates in the first rotational direction. The tool accelerates in a second rotational direction, while the tool decelerates in the second rotational direction. The duration of the deceleration in the second rotational direction is greater than the duration of the deceleration in the first rotational direction.

[0020] It is explained in detail in the accompanying drawings.

[0021] Another advantageous implementation is to determine the duration required to perform the specified lateral movement by means of the lateral movement of the tool specified in the part program, wherein the force required for deceleration is determined based on the duration.

[0022] Furthermore, the solution to this objective is achieved through a control unit used to execute the method.

[0023] The solution to this objective can also be achieved through machine tools equipped with control devices.

[0024] The solution to this objective is also achieved through a computer product that includes instructions that cause the control device to execute the method when the program is implemented via a control device.

[0025] This invention is particularly advantageous because it utilizes flexible start and end conditions for the tapping process.

[0026] In most cases, the program starts and ends with all axes stopped.

[0027] However, a particular advantage is that the tapping process begins very quickly. Preferably, the spindle and the participating feed axis are synchronized with the programmed speed and / or spindle rotation at a user-defined coordinate (e.g., 1 mm before the thread).

[0028] Specifically, "rapid end" is described as the user-specified spindle speed (e.g., 6000 rpm) when exiting the thread (e.g., 1 mm after the thread).

[0029] A further example of a reasonable specification of start and / or end conditions is that, although—as is the case now—the program starts and ends with all axes stopped, the end point is set to the retraction plane. Subsequently, the spindle does not need to decelerate to a position directly behind the bore (e.g., 1 mm), but only on the defined retraction plane (e.g., 10 mm).

[0030] From a thermodynamic perspective, it has significant advantages.

[0031] It is advantageous to use the motion curve that minimizes loss.

[0032] If the above-mentioned starting and / or ending conditions are specified, it is advantageous to calculate and output motion curves in a manner with minimal losses in the numerical control (NC) system. Users can seamlessly switch between generating time-optimized curves and using curves with minimal losses to reduce losses.

[0033] Preferably, the method for parameterizing the motion that minimizes loss includes the following steps: Preferably, the user determines the maximum feasible acceleration. Using a factor, the user can then explicitly set a trade-off between reducing loss and positioning time. Attached Figure Description

[0034] The present invention will now be described and illustrated in detail with reference to the embodiments shown in the accompanying drawings.

[0035] This is shown here: Figure 1 A typical thread cutting cycle using a machine tool is shown. Figure 2 An improved thread cutting cycle is shown. Figure 3 Feasible solutions for reducing thermodynamic load are shown. Figure 4 This demonstrates the application of the least-loss localization method to sources Figure 2 The tapping process, Figure 5 A feasible scheme for positioning with minimal loss at slightly increased maximum acceleration values ​​is shown. Figure 6 Feasible solutions for energy conservation are shown. Figure 7 The machine tool was shown. Figure 8 The method is shown, and Figure 9 The simulation program product is shown. Detailed Implementation

[0036] Figure 1 A typical thread cutting cycle using a machine tool is shown.

[0037] In this diagram, tapping ZA is performed first for 550 ms, followed by moving to the next drill hole ZB for 490 ms. Time t is given in seconds (s) in the diagram. ZB in this diagram is characterized by movement and stopping.

[0038] The attached diagram shows the machine's speed curve during a tapping operation. During thread drilling, the spindle interpolates along the Z-axis. After thread drilling / tapping, the spindle stops, and the Y and Z axes move to the next hole. The tapping operation restarts.

[0039] The spindle accelerates to, for example, 100 revolutions per second (or: revolutions per second; rev / s), i.e., 6000 revolutions per minute (see spindle speed SS and extension curve 31 for this), decelerates, changes direction, accelerates in another direction, decelerates again, and stops. A short pause, for example, defined by precise stopping, can be achieved between acceleration in the first direction and acceleration in the second direction, in this case, for example, 42 ms.

[0040] To perform the tapping operation quickly, current is applied to the spindle at maximum acceleration; however, the spindle is not designed to withstand this current for extended periods. The tapping is paused afterward, and then accelerated again.

[0041] Thermodynamics is a very large load. If such a cycle continues for too long, for example, 1 minute, the spindle will overheat. For example, the machine tool may stop working due to spindle overheating, sometimes for several minutes. Optionally or additionally, it may be necessary to reduce the spindle acceleration.

[0042] In addition, the figure shows curve 32, which represents the velocity YS in mm / s along the Y-axis, and curve 33, which represents the velocity ZS in mm / s along the Z-axis.

[0043] Figure 2 An improved thread cutting cycle is shown.

[0044] The graph schematically illustrates the spindle speed development as curve 35. The spindle speed SS in the attached figure is a maximum of 6000 rpm (revolutions per minute) or -6000 rpm in the other direction of rotation.

[0045] The current supplied to the spindle during constant acceleration is also given in amperes (A).

[0046] and Figure 1 Unlike other methods, the spindle rotates at -6000 rpm after tapping and takes time to decelerate before reaching the next hole. In ZBrush, the spindle can recover within 490 ms.

[0047] Therefore, the effective current in the entire cycle is reduced to approximately 46 A (previously approximately 56 A), which corresponds to a saving of approximately 18%. The heat load is reduced proportionally to the square of the effective current (in this case, approximately 32%).

[0048] The tapping process, in which the spindle stops before and after thread cutting, is problematic in terms of thermodynamic load.

[0049] When avoiding spindle deceleration during retraction from the cutting thread, such as Figure 2 As shown, the heat load is reduced.

[0050] Figure 3An alternative feasible approach for reducing thermodynamic load is shown.

[0051] Figure 3 The mathematical relationships are shown.

[0052] Figure 3 The factor K = 3 / 2 is shown, along with the acceleration +A in the positive direction and -A in the negative direction.

[0053] A further significant reduction in heat load can be achieved by using the acceleration curve with minimal loss. The acceleration is not constant at that point, but decreases linearly to zero in stages over time.

[0054] Figure 3 The appropriate curve is shown. Here, the initial acceleration is chosen to be approximately 50% greater than the normal (constant) acceleration. This ensures that the distance traveled in the same amount of time is the same. Consequently, the thermodynamic load is reduced by approximately 25%.

[0055] For the positioning with the least loss, a suitable acceleration curve a(t) and the velocity curve v(t) derived therefrom are shown.

[0056] The standard acceleration curve is labeled 200, while the curve with the least energy consumption or the least loss is shown as 201.

[0057] The integrals under velocity curves 203 and 204 are at least substantially the same, preferably exactly the same, meaning the shaft covers the required distance in the same amount of time. However, the area under the square of acceleration is reduced by about 25%. The current heat loss is at least substantially proportional to i² (especially when only ohmic losses are considered, i.e., eddy current losses are ignored, and resistance changes with temperature are not taken into account).

[0058] Thermodynamic losses are reduced by approximately 25%. The maximum velocity V at curve 203 is... klass The maximum velocity V at curve 204 is greater than Emin .

[0059] according to Figure 3 The formula also shows the typical thermodynamic load FL klass and the load FL with the least loss of thermodynamics Emin The relationship.

[0060] Applications Figure 2 The tapping example in the text leads to the conclusion. Figure 4 The curve shown.

[0061] Figure 4 This demonstrates the application of the least-loss localization method to sources Figure 2 The tapping process. Curve 36 rotates at a maximum of 4500 rpm or -4500 rpm in the diagram.

[0062] The effective current drops to approximately 37.2A.

[0063] If a smaller maximum current is available, then it is advantageous to match the maximum acceleration value accordingly. Preferably, a factor of 1.5 is applied for the curve (and trigonometric curve) with minimal loss, thereby achieving a saving of approximately 25%. Therefore, this factor can be selected between 1.0 (the conventional curve) and 1.5 (minimum energy consumption or minimum energy expenditure or minimum loss).

[0064] When the maximum acceleration is only about 3% higher than the base value in motion with minimal loss, the loss has already been reduced by nearly 15%. A 7.5% increase in acceleration already allows for a loss reduction of nearly 20%.

[0065] It is advantageous if the tool operates according to the motion curve that minimizes loss.

[0066] Preferably, as shown in the figure, the motion curve is at least partially parabolic in shape.

[0067] Figure 5 The potential for energy saving is shown, in which curve 505 is compared with the conventional rectangular curve 504, the triangular curve 506 which saves about 25% energy, and the mentioned acceleration a increases of 3% (see point 5A) and 7.5% (see point 5B).

[0068] In addition, the figure shows the standard curve 501, as well as the curve with the lowest energy 502 (approximately 3% more acceleration) and the curve with the lowest energy 503 (approximately 7.5% more acceleration).

[0069] Advantageously, this method can be adapted to any conventional acceleration value.

[0070] The curve with the least loss can also be determined while adhering to the impact limits.

[0071] In principle, the time before the tapping process can also be used for a smooth spindle start-up. This procedure is similar to the slowing down or deceleration of the spindle at the end of the process, as already described.

[0072] Here, feasible solutions for energy conservation are also presented, and these preferably depend on the available time. For illustration, while... Figure 6 The diagram shows the speed variation process for the standard curve of this program.

[0073] Curve 37 illustrates the spindle's acceleration of 100 and deceleration of 110.

[0074] like Figure 6As shown, it is also advantageous to use a method for controlling the rotary motion of a tool in a machine tool by means of a part program, wherein the feed motion and lateral motion to be performed by the tool are specified in the part program, wherein the tool accelerates during the feed motion and / or lateral motion.

[0075] At least partially preferably, the process is accelerated during the journey to the processing position.

[0076] This allows rotation to be achieved without putting stress on the spindle.

[0077] Figure 7 The machine tool and / or production machine 1 and the control system 2 are shown.

[0078] They form system 3.

[0079] The machine tool and / or production machine 1 in this figure includes a spindle 5 on which a fixed tool 6 (particularly suitable for thread cutting) is fastened. Machine 1 is suitable for performing this method.

[0080] The spindle rotation (and therefore the tool rotation) is marked with D in the diagram.

[0081] Advantageously, the tool tip or interference point of tool 6 is described as tool center point 61 (abbreviated as TCP). Tool center point 61 is located at the tool tip in the figure.

[0082] In the figure, workpiece 8 is present on worktable 7. Advantageously, tool 6 is used to process workpiece 8.

[0083] The accompanying drawings illustrate optional devices for detecting the actual position value of TCP 61, such as encoders or grating rulers. The arrangement of the devices for detecting the actual position value 10 is shown in the figure only as an example.

[0084] The actual velocity and / or actual acceleration of TCP 61 can optionally be detected by sensor 11 in the figure. Sensor 11 is arranged at or near the tool center point 61 in the figure. Sensor 11 can also be arranged near the device used for detection 10. Sensor 11 can also be arranged on or near the workpiece 8 processed by the machine tool and / or production machine 1.

[0085] The control system 2, specifically configured as a digital control system, has a computer program product 21 in the figure. The computer program product 21 includes instructions that, when the control unit 2 executes the program, cause the control unit to perform the method.

[0086] Advantageously, the computer program product 21 is stored in the control system.

[0087] Figure 8 The method is shown.

[0088] In method step S1, specify the retraction and lateral movements to be performed by the tool.

[0089] Preferably, the target rotational speed of the tool is also specified.

[0090] In method step S2, the tool accelerates in the first rotational direction.

[0091] In method step S3, the tool rotating in the first rotational direction decelerates. The rotational motion of the tool decelerates during the retraction motion and / or lateral motion.

[0092] In method step S4, the tool accelerates in the second rotational direction.

[0093] In method step S5, the tool rotating in the second rotational direction decelerates. The rotational motion of the tool decelerates during the retraction motion and / or lateral motion.

[0094] The duration of deceleration of a tool rotating in the second rotational direction is greater than the duration of deceleration of a tool rotating in the first rotational direction.

[0095] Furthermore, advantageously, see Figure 9 The simulation program product 1000 is also implemented as a digital twin of the machine tool and / or production machine 1, which includes instructions that cause the computer or simulation unit to implement the method when the computer 1100 or simulation unit executes the program.

[0096] This allows for the simulation of the tapping process and the estimation of thermal load when necessary.

[0097] Therefore, this method can be well implemented digitally.

[0098] The simulation program product can be configured externally on a separate computer or on control unit 2.

Claims

1. A method for rotary motion (D) using a part program control tool (6) in the presence of a machine tool and / or production machine (1), wherein, The part program specifies the retraction and lateral movements to be performed by the tool (6), wherein the rotational movement (D) of the tool (6) decelerates during the retraction and / or lateral movements, wherein the tool (6) accelerates in a first rotational direction, wherein the tool (6) decelerates while rotating in the first rotational direction, wherein the tool (6) accelerates in a second rotational direction, wherein the tool (6) decelerates while rotating in the second rotational direction, and wherein the duration of the deceleration of the tool rotating in the second rotational direction is greater than the duration of the deceleration of the tool rotating in the first rotational direction.

2. The method according to claim 1, wherein, When the tool (6) decelerates only during the retraction motion, the tool (6) is decelerated so that the rotational motion is equal to zero in the case of the defined retraction plane.

3. The method according to claim 2, wherein, The defined retraction plane is between 5mm and 15mm, particularly between 8mm and 12mm.

4. The method according to any one of the preceding claims, wherein, When the tool (6) decelerates during the lateral movement, the tool (6) is decelerated so that the rotational motion is equal to zero at the end of the lateral movement.

5. The method according to any one of the preceding claims, wherein, The rotational motion (D) of the tool (6) is slowed down during the retraction motion and at least partially during the lateral motion.

6. The method according to any one of the preceding claims, wherein, The duration required to perform the specified lateral movement is determined by means of the lateral movement of the tool (6) specified in the part program, wherein the force required for deceleration is determined based on the duration.

7. The method according to any one of the preceding claims, wherein, The spindle is decelerated during the time it takes for the spindle to move to the next machining position.

8. The method according to any one of the preceding claims, wherein, Specify the target rotational speed.

9. The method according to any one of the preceding claims, wherein, The tool (6) is operated according to the motion curve that minimizes loss.

10. The method according to claim 9, wherein, The motion curve is at least partially parabolic in shape.

11. The method according to any one of the preceding claims, wherein, The part program specifies the feed motion and additional lateral motion to be performed by the tool (6), wherein the tool (6) accelerates during the feed motion and / or the additional lateral motion.

12. A control device for performing the method according to any one of claims 1 to 11.

13. A machine tool and / or production machine (1) including the control device according to claim 12.

14. A computer program product (21) comprising instructions that, when the program is implemented by a control device (2), cause the control device to perform the method according to any one of claims 1 to 11.

15. A simulation program product (1000) implemented as a digital twin of a machine tool and / or production machine (1) according to claim 13, the simulation program product comprising instructions that, when the program is implemented by a computer (1100) or simulation unit, cause the computer or simulation unit to perform the method according to any one of claims 1 to 11.

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