Display device

Abstract

The present invention provides a display device capable of displaying a position where a large step difference that affects machining accuracy is generated on a machining track without actual machining, and capable of accurately predicting generation of a step difference of a machining track at low cost. The problem is solved by a display device that acquires time-series data of positions of driven bodies or motors of each axis of a machine tool, calculates machining tracks from the acquired time-series data of positions of driven bodies or motors of each axis, sets a reference plane with respect to heights of the machining tracks based on a result of the calculation of the machining tracks, compares heights from the reference plane of adjacent machining tracks, and displays a position where a difference in height equal to or greater than a set threshold value on the machining tracks is generated.

Description

Technical Field

[0001] This invention relates to a display device for the machining trajectory of a drive axis driven and controlled by a servo control device in a machine tool or industrial machinery, and particularly to a display device for displaying the location in the machining trajectory where a step difference is generated. Background Technology

[0002] In the machining of machine tools and industrial machinery, machining defects occur due to various reasons. One known cause is a problem arising from issues in the machining path. For example, if a step difference occurs on the machining path, the surface quality of the workpiece deteriorates, the machining accuracy decreases, and the workpiece becomes a defective product.

[0003] Therefore, in the past, in order to address problems related to machining trajectories and to identify the problems in machining trajectories, or to detect the reduction in machining accuracy from the machining trajectories, display devices that can display various characteristics of tool trajectories were designed.

[0004] Patent Document 1 describes an invention of a display device that, in a machine tool that performs machining via interpolation of a servo axis, at the reversal point where the movement direction (polarity) of the servo axis is reversed, the shape error between the shape of the tool movement command and the shape of the actual movement trajectory (machining shape) tends to increase. Therefore, the reversal point is displayed on the tool path in a manner that allows the speed of the servo axis to be monitored.

[0005] Patent Document 2 describes an invention that, in NC-controlled machining, when machining marks are produced on the workpiece, it is necessary to quickly and accurately determine the cause of the marks. Therefore, a display device is provided that can appropriately display NC data corresponding to the investigation of the cause of the marks. Specifically, for one axis selected from the three axes of XYZ (the spatial coordinates that generate the machining trajectory), such as the Z-axis, the slope of the small line segments obtained by dividing the machining trajectory is determined as positive / negative / 0. Different display characteristics, such as display color, are assigned to each slope, and the unevenness of the tool trajectory can be determined based on its changes.

[0006] Patent document 3 describes an invention of an image display device that, when a machining problem such as stripes appearing on the machining surface of a workpiece occurs during machine tool processing, determines whether the cause of the machining problem is due to a reversal of the tool's movement direction, and then visualizes the reversed part of the tool and overlays it onto an image of the workpiece.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2014-78102

[0010] Patent Document 2: Japanese Patent Application Publication No. 2004-21954

[0011] Patent Document 3: Japanese Patent Application Publication No. 2020-98523 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] As mentioned above, corresponding to the situation where problems on the machining path are listed as one of the reasons for the decrease in machining accuracy due to machining performed by machine tools, etc., a display device that displays specific conditions of the machining path has been developed based on the insight that the cause of the decrease in machining accuracy can be traced from the machining path. However, even using these display devices, it is difficult to predict the occurrence of step differences in the machining path without actual machining, that is, before actual machining is performed.

[0014] In Patent Document 1, the reversed parts of the tool can be displayed on the tool's trajectory, but the step difference in the machining trajectory may not occur in all the reversed parts of the tool. In addition, the degree of the step difference in the machining trajectory cannot be known. Therefore, it is not possible to properly and accurately predict the generation of the step difference in the machining trajectory that will adversely affect the machining accuracy.

[0015] In actual processing, Patent Document 2 identifies the generation of processing marks from the display device after actual processing, rather than predicting the step difference of the processing trajectory before actual processing. Furthermore, in order to accurately detect processing marks as minute irregularities without overlooking them, the processing trajectory needs to be divided into many tiny line segments for calculation, which presumably results in enormous computational capacity and cost.

[0016] The display device in Patent Document 3 detects whether the stripes on the processed surface after actual processing are caused by the reversal of the tool's movement trajectory by aligning the reversed part of the tool's movement trajectory with the image of the processed surface after actual processing. It does not predict the step difference of the processing trajectory before actual processing.

[0017] Currently, evaluating the step difference in the machining trajectory requires the visual assessment of the actual processed workpiece by the person in charge of the manufacturing process. This evaluation lacks reliability due to the inherent biases of each supervisor, and also leads to problems such as reduced workpiece yield and increased costs. The accuracy of the evaluation and cost reduction become particularly critical during machine startup.

[0018] The objective of this disclosure is to provide a display device that can display the location of a large step difference that affects machining accuracy on the machining trajectory without actual machining, and can accurately predict the occurrence of step differences in the machining trajectory at low cost.

[0019] Methods for solving problems

[0020] To address the aforementioned issues, the present disclosure discloses a display device for displaying the machining trajectory of a servo control device that controls the motors driving the axes of machine tools and industrial machinery. This display device includes: a data acquisition unit that acquires timing data of the position of the driven body or motor of each axis; a trajectory calculation unit that calculates the machining trajectory based on the timing data of the position of the driven body or motor of each axis acquired by the data acquisition unit; a trajectory comparison unit that, based on the calculation results of the trajectory calculation unit, sets a reference plane for the height of the machining trajectory and compares the height of adjacent machining trajectories from the reference plane; and a display unit that displays on the machining trajectory the location where a height difference between adjacent machining trajectories exceeds a set threshold.

[0021] Invention Effects

[0022] According to the display device disclosed herein, it is possible to provide a display device that can display the location of large step differences affecting machining accuracy on the machining trajectory, and can accurately predict the occurrence of step differences in the machining trajectory at low cost. Furthermore, quantitative evaluation can be performed, and in particular, improvements in the efficiency of the evaluation process during machine startup can be expected. Attached Figure Description

[0023] Figure 1 This is a block diagram showing the structure of the display device of this disclosure;

[0024] Figure 2 This diagram illustrates the step difference at the reversal point of the machining trajectory.

[0025] Figure 3 This is the first diagram showing the steps involved in determining the step difference.

[0026] Figure 4 The second diagram illustrates the steps involved in determining the step difference.

[0027] Figure 5 The third diagram illustrates the steps involved in determining the step difference.

[0028] Figure 6 The fourth diagram shows the steps involved in determining the step difference.

[0029] Figure 7 This is the fifth diagram, which shows the steps involved in determining the step difference.

[0030] Figure 8 This is a diagram showing an example of a workpiece being processed by a machine tool.

[0031] Figure 9 This diagram illustrates an example of displaying the workpiece using a display device.

[0032] Figure 10 This is a diagram showing an example of a part that exhibits a step difference compared to other workpieces.

[0033] Figure 11 This is a flowchart illustrating the display method of this disclosure. Detailed Implementation

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0035] Figure 1 This is a block diagram showing the structure of a display device according to an embodiment of the present disclosure. For example... Figure 1 As shown, the display device 20 of this disclosure obtains (receives) data from the servo control device 10 that controls the drive of the machine tool or industrial machinery, performs the data processing required for display, and displays the results of its data processing.

[0036] The servo control device 10 comprises a control unit (CPU) 11, such as a microcomputer, a storage unit 12 containing memory components such as ROM and RAM, and a transmission / reception unit 13 that transmits and receives signals to and sends data required for display on the display device 20. Signals (data) are exchanged between the control unit (CPU) 11, the storage unit 12, and the transmission / reception unit 13.

[0037] The display device 20 includes: a data acquisition unit 21, which is a transmission and reception unit that transmits and receives signals with the servo control unit 10, and acquires data required for display from the servo control unit; a storage unit 22, which has memory components such as ROM and RAM; a data processing unit 23, which is composed of a microcomputer or the like, and performs data processing required for display; and a display unit 24, which displays the results processed by the data processing unit 23. Signals (data) are exchanged between the data acquisition unit 21, the storage unit 22, the data processing unit 23, and the display unit 24.

[0038] The data processing unit 23 includes a trajectory calculation unit 231 and a trajectory comparison unit 232. The data acquired by the data acquisition unit 21 of the display device 20 is sent to the data processing unit 23. In the data processing unit 23, as will be described in detail later, the trajectory calculation unit 231 calculates the machining trajectory, and the trajectory comparison unit 232 compares the heights of adjacent machining trajectories to determine whether there is a step difference. The results are then sent to the display unit 24 for display.

[0039] Next, the step difference generated in the machining trajectory will be explained. Two main reasons are listed as the primary causes of this step difference. The first is due to the reversal of the machining tool, and the second is that the instruction trajectory generated by the machining program has a step difference. Even in the case where the machining program is the cause of the second main reason, there are situations where it is necessary to set a step difference, and even if it causes a decrease in machining accuracy, it must be addressed separately.

[0040] The first major cause of step difference is the reversal of the machining tool. In machine tool machining, when the machining tool maintains a constant tilt relative to the machining surface and travels at a constant speed, no step difference occurs in the machining trajectory. However, at the point of tool reversal, the tool's tilt relative to the machining surface and its travel speed change drastically. Considering the delay in servo response to these drastic changes, overshoot / undershoot occurs through the acceleration / deceleration time constants and feedforward / speed feedforward settings, resulting in a step difference in the machining trajectory.

[0041] Reference Figure 2 The step difference caused by the reversal of the processing trajectory is explained. Figure 2 In this process, machining is performed on the surface of the workpiece 31 according to the sequence of the first path 41, the second path 42, and the third path 43 of the machining trajectory 40. The boxes at the left ends of these machining trajectories indicate the vicinity of the location where the machining tool is reversed, that is, the vicinity of the location where the machining trajectory is reversed. In the IV-IV section at this location, a height difference, or step difference, is generated between the machining trajectories as shown in the enlarged view below.

[0042] Next, according to Figures 3 to 7 The method for determining whether a step difference occurs at the reversal point of the machining trajectory in this disclosure is explained. First, as... Figure 3 As shown, the position where the travel direction of the machining tool 50 is reversed in the machining trajectory 40 is detected. Figure 3 The part enclosed by the ellipse is the reverse part 4. In addition, the method for detecting the reverse part 4 of the machining trajectory 40 is known (Patent Document 1, etc.).

[0043] Next, as Figure 4 As shown, measurement points are selected on the machining trajectory 40 before and after the detected reversal part 4. Then, the formula for the average plane is derived from the measurement points. This plane is used as the reference plane 60. The number of average planes is appropriately determined based on the length of the detected reversal part 4, the width of the machining trajectory, the inclination, etc. Furthermore, as... Figure 5 As shown, the direction perpendicular to the reference plane 60 is defined as the height direction.

[0044] Next, as Figure 6As indicated by the middle arrow, determine the adjacent paths on machining trajectory 40. Then, as... Figure 7 As shown, the height of each measurement point relative to the reference plane 60 is calculated and compared with the height of adjacent paths. If the maximum value of this height difference is above the set threshold, it is determined that a step difference has occurred.

[0045] Furthermore, as a method for determining the step difference based on the height difference, as described above, it can also be determined based on the distance between the measurement point (machining point) on the adjacent machining trajectory 40 and the reference plane 60, or it can be determined based on the absolute value of the dot product of the vectors of the adjacent machining trajectories 40. This is because it can be said that the greater the height difference between the adjacent machining trajectories 40 at the reversal part 4, the more different their inclinations will be.

[0046] Next, refer to Figures 8 to 10 Specific display examples in the display section 24 of the display device 20 of this disclosure will be described. Figure 8 This indicates an example of the workpiece 32 of the machine tool disclosed herein, and... Figure 9 The text indicates that the processing trajectory of the tool on the workpiece 32 is displayed on the display screen 24-10 of the display unit 24 of the display device 20. Figure 8 The workpiece 32 shown is an impeller used in pumps, etc., which has a fairly complex surface shape, such as Figure 9 As shown, the machining tool is observed to follow a complex trajectory.

[0047] Figure 9 The display screen 24-10 consists of a large screen on the right and three smaller screens divided vertically on the left. The large screen on the right is a 3D screen 24-11 that provides a three-dimensional view of the machining trajectory of the workpiece 32. Since only the machining trajectory on the surface of the workpiece 32 is extracted and displayed, the machining trajectory on the back side hidden in the actual workpiece 32 can also be observed, and the entire machining trajectory is displayed in 3D space.

[0048] The left side is divided into three smaller screens, arranged from top to bottom as follows: XY plane view 24-12, XZ plane view 24-13, and YZ plane view 24-14. At the front of the XZ plane view 24-13, there is a grid for measuring the length of an object on the surface.

[0049] Figure 10 This shows an example of a problematic object (e.g., a part causing a step difference in the machining trajectory) displayed on screen 24-10. Figure 10 In the explicit examples, for ease of understanding, an example is shown where the workpiece 32 exhibits a simple shape (conical). For example... Figure 10 As shown, the problematic area is represented by a curve in the 3D view on the right side of screen 24-10, and the corresponding areas are also displayed in the 2D XY plane view 24-12 and the 2D YZ plane view 24-14. Based on these displays, the user can quickly and accurately identify the problematic area.

[0050] Next, use Figure 11 The flowchart illustrates a method for displaying the step difference generated at the reversal point of the machining trajectory in the display device of this disclosure. For example... Figure 11 As shown, the display device first obtains the timing data of the position of the driven axis or motor of each axis of the machine tool or industrial machinery from the servo control device of the machine tool or industrial machinery (step St1), and calculates the machining trajectory of the tool based on the obtained timing data of the position of the driven axis or motor of each axis of the machine tool or industrial machinery (step St2).

[0051] Next, based on the calculated machining trajectory, the reverse portion of the machining trajectory is detected using a known method (step St3), and a reference plane is set at one of the detected reverse portions (step St4). As described above, when detecting and displaying the step difference of the machining trajectory with the reverse portion as the object, measurement points (machining points) on the machining trajectory are selected before and after the reverse portion of the machining trajectory, and an average plane is calculated based on these machining points, and this plane is defined as the reference plane.

[0052] Next, adjacent machining paths are selected at the reversed part of the object, and their heights are compared among the adjacent machining paths (step St5). Specifically, starting from the reference plane set in step St4, the direction perpendicular to the reference plane is taken as the height direction, and the height difference between adjacent machining paths is calculated. In addition, as described above, as a method for calculating (determining) the height difference, there is a method based on the maximum distance from the machining point on each adjacent machining path to the reference plane.

[0053] Next, the height difference calculated in step St5 is compared with a set threshold to determine whether the height difference is above the threshold (step St6). The threshold is set based on factors such as the required smoothness accuracy of the processed surface. If the determination in step St6 is "yes," that is, if the height difference is above the threshold, the process proceeds to step St7; if the determination in step St6 is "no," that is, if the height difference is below the threshold, the process proceeds to step St8.

[0054] If, in step St6, the height difference at the reversal point of adjacent machining trajectories exceeds a threshold, in step St7, it is determined that a step difference has occurred, and the reversal point of the adjacent machining trajectory is highlighted on the 3D screen of the stereoscopic view of the display device. Furthermore, in embodiments of this disclosure, as described above, it is also displayed on the 2D screens of the corresponding XY plane view, XZ plane view, and YZ plane view.

[0055] After step St7, proceed to step St8 to determine whether the comparison of the height difference of all adjacent machining trajectories at the reversed position of the machining trajectory to be targeted has been completed. If the determination in step St8 is "yes," that is, if the comparison of the height difference of all adjacent machining trajectories at the reversed position of the machining trajectory to be targeted has been completed, proceed to step St9. If the determination in step St8 is "no," that is, if the comparison of the height difference of all adjacent machining trajectories at the reversed position of the machining trajectory to be targeted has not been completed, return to step St5. Then, repeat the loop from step St5 to step St8 until the determination in step St8 is "yes."

[0056] In step St9, an evaluation is performed on the reversal points of all detected machining trajectories to determine whether a step difference has occurred. If a step difference has occurred, it indicates whether all such processes have been completed. If the determination in step St9 is "yes," meaning the evaluation on the reversal points of all detected machining trajectories has determined whether a step difference has occurred, and the completion of all such processes is indicated, the objective of this disclosure is achieved, and the process ends. If the determination in step St9 is "no," meaning the evaluation on the reversal points of all detected machining trajectories has determined whether a step difference has occurred, and the completion of all such processes is indicated, it returns to step St4. The cycle from step St4 to step St9 is then repeated until the determination in step St9 is "yes."

[0057] Thus, through the examples, the situation where a step difference in the machining trajectory occurs at the reversal point of the machining trajectory has been explained. This is because it is known that a step difference is prone to occur at the reversal point of the machining trajectory. In addition, the step difference generated at the reversal point of the machining trajectory affects the machining accuracy, such as the smoothness of the surface of the workpiece, and the identification of the generation of this step difference is very important.

[0058] However, as mentioned above, among the main causes of step differences in machining paths, besides those caused by the reversal of the machining path, cases can also be listed where step differences occur when the instruction path generated according to the machining program has a step difference, and thus occur stably. There are also cases where step differences need to be generated in the program, and cases where the exact location where the step difference occurs needs to be known.

[0059] The method for evaluating and displaying step differences arising from step differences in the instruction trajectory generated according to the machining program is the same as the method for evaluating and displaying step differences arising from the reversal of the machining trajectory. Furthermore, in this case, the reference plane is set by calculating the average plane based on the nearby measurement points (machining points) after the approximate position has been determined according to the machining program.

[0060] The display device according to the present invention can display the location of step differences that affect machining accuracy on the machining trajectory, and can accurately predict the occurrence of step differences in the machining trajectory at low cost. Furthermore, quantitative evaluation can be performed, and in particular, improvements in the efficiency of the evaluation process during machine startup can be expected.

[0061] In addition, the present invention can not only deal with the step difference at the reversal part of the machining trajectory, but also deal with the case where the instruction trajectory generated according to the machining program has a step difference. Therefore, it can also deal with the case of stable generation of step difference, and its application range is also wider.

[0062] The above describes the implementation of the present invention, but the present invention is not limited to such implementation in any way, and can of course be implemented in various ways without departing from the spirit of the present invention.

[0063] Explanation of reference numerals in the attached figures

[0064] 10 servo control devices

[0065] 11. Control Unit (CPU)

[0066] 12 storage units

[0067] 13 Transmitting and Receiving Units

[0068] 20 display devices

[0069] 21 Data Acquisition Unit (Transmitting and Receiving Unit)

[0070] 22 Storage Department

[0071] 23 Data Processing Department

[0072] 231 Trajectory Calculation Department

[0073] 232 Trajectory Comparison Section

[0074] 24 Display Unit

[0075] 24-10 display screen

[0076] 24-11 3D views

[0077] 24-12XY planar view 2D image

[0078] 2D view of the 24-13XZ plan view

[0079] 2D view of the 24-14YZ plan view

[0080] 31. Workpieces

[0081] 32 Workpiece (Impeller)

[0082] 4. Reversal points of the machining trajectory

[0083] 40 processing trajectories

[0084] 41. The first path of the processing trajectory

[0085] 42. The second path of the processing trajectory

[0086] 43. The third path of the processing trajectory

[0087] 50 tools

[0088] 60 reference plane.

Claims

1. A display device of a machining track of a servo control device that controls a motor driving a shaft of a machine tool or an industrial machine, characterized by comprising: a data acquisition section that acquires time-series data of a position of a driven body or a motor of each shaft; a track calculation section that calculates a machining track based on the time-series data of the position of the driven body or the motor of each shaft acquired by the data acquisition section; a track comparison section that, based on a result of calculation by the track calculation section, selects a machining point as a measurement point on a machining track at a position where a step difference is determined to exist in the machining track based on a machining program, and defines a plane averaged based on the machining point as a reference plane, thereby setting a reference plane with respect to a height of the machining track, and compares heights of adjacent machining tracks from the reference plane; and a display section that displays a position where a difference in height of the adjacent machining tracks equal to or greater than a set threshold value occurs on the machining track.

2. The display device according to claim 1, characterized in that the display section emphasizes display of the position where the difference in height of the adjacent machining tracks equal to or greater than the set threshold value occurs on a 3-dimensional display.

3. The display device according to claim 1 or 2, characterized in that the track comparison section determines the difference in height equal to or greater than the set threshold value based on a distance of the machining point on the adjacent machining track from the reference plane. ​ ​ ​ ​ ​ ​ ​ ​

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