Determination system

Abstract

The main causes of poor machining surface and shape error are determined in a short time by comparing the machining surface shape calculated based on the actual position of the motor with the machining surface shape obtained by actually measuring the machining surface of the workpiece after machining. The determination system comprises: a motor position acquisition unit, which acquires the actual position of the motor for driving the drive shaft of the machine tool; a mechanical information acquisition unit, which acquires mechanical information including the drive shaft structure of the machine tool, the tool shape and the shape of the unmachined workpiece; a motor position machining surface calculation unit, which calculates the shape of the machining surface of the machined workpiece based on the actual position of the motor and the mechanical information; an actual machining surface acquisition unit, which acquires the shape of the machining surface of the workpiece after actual machining; and a machining surface analysis unit, which compares the first correlation, which is the correlation between the shape of the machining surface calculated by the motor position machining surface calculation unit and the shape of the machining surface acquired by the actual machining surface acquisition unit.

Description

Technical Field

[0001] The present invention relates to a determination system for determining the main causes of machining surface defects, shape errors, etc. Background Art

[0002] As is known to all, the accuracy of position control of motors driving the drive shafts of machine tools has a great influence on machining results. Therefore, various techniques are known for determining the main causes of surface defects and shape errors of workpieces machined using machine tools (for example, see Patent Documents 1 to 3).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 6366875

[0006] Patent Document 2: Japanese Patent No. 5197640

[0007] Patent Document 3: Japanese Patent Application Publication No. 2017-30066 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] However, there is no technology that directly compares the machined surface shape calculated based on the actual motor position with the machined surface shape actually measured after machining, and it currently takes a long time to identify the main causes of machined surface defects and shape errors.

[0010] Therefore, it is desirable to provide a technology that can compare a machined surface shape calculated based on an actual motor position with a machined surface shape actually measured after machining of a workpiece, thereby determining the main causes of machined surface defects, shape errors, etc. in a short time.

[0011] Solutions for solving problems

[0012] One embodiment of the present disclosure is a determination system comprising: a motor position acquisition unit, which acquires the actual position of a motor for driving a drive shaft of a machine tool; a mechanical information acquisition unit, which acquires mechanical information including the drive shaft structure of the machine tool, the shape of a tool, and the shape of an unprocessed workpiece; a motor position processing surface calculation unit, which calculates the shape of a processing surface of a processed workpiece based on the actual position of the motor and the mechanical information; an actual processing surface acquisition unit, which acquires the shape of the processing surface of the workpiece after actual processing; and a processing surface analysis unit, which compares a first correlation, which is a correlation between the shape of the processing surface calculated by the motor position processing surface calculation unit and the shape of the processing surface acquired by the actual processing surface acquisition unit.

[0013] Effects of the Invention

[0014] According to the present disclosure, the correlation between the machined surface shape calculated based on the actual motor position and the machined surface shape actually measured after machining can be directly compared to determine the main causes of machined surface defects, shape errors, etc. in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a functional block diagram showing the structure of the determination system according to the present embodiment.

[0016] Figure 2 It is a diagram for explaining a method of calculating a reference surface in each of the shapes A to D according to the present embodiment.

[0017] Figure 3 This is a diagram for explaining how shapes A to D according to the present embodiment are expressed in the same coordinate system.

[0018] Figure 4 This is a diagram for explaining a method of analyzing major causes of machined surface defects and shape errors according to the present embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings.

[0020] Figure 1 1 is a functional block diagram showing the structure of the determination system 100 according to the present embodiment. Figure 1 As shown, the determination system 100 includes a program generation unit 1 , a numerical controller 2 , a servo control device 3 , a motor 4 , a machine tool 5 , and a determination unit 6 .

[0021] The program generation unit 1 generates a machining program based on the shape data of the workpiece before and after machining (unmachined workpiece and machined workpiece), the mechanical information described later, etc. The shape data may include three-dimensional CAD (Computer Aided Design) data, etc. The machining program may include a machining program produced by CAM (Computer Aided Manufacturing).

[0022] The numerical control device 2 distributes the command position of the motor to the command position acquisition unit 11 described later based on the machining program. Specifically, the numerical control device 2 generates a position command for the motor 4 based on the machining program generated by the program generation unit 1. The position specified by the position command refers to the command position of the motor 4 (hereinafter, also referred to as the "command position"). In addition, the numerical control device 2 distributes the command position to the servo control device 3. As a control for distributing commands, CNC (Computerized Numerical Control) can be listed. In addition, the numerical control device 2 stores mechanical information including the drive shaft structure, tool shape, and unprocessed workpiece shape of the machine tool 5 described later in a rewritable memory such as an EEPROM.

[0023] The servo control device 3 controls the drive current of the motor 4 based on the position command (command position) from the numerical control device 2 and the position feedback detected by the encoder provided in the motor 4 .

[0024] The motor 4 is provided in the machine tool 5. The motor 4 includes a movable part in the machine tool 5, and a motor for driving, for example, a feed axis of a tool and a feed axis of a workpiece. The motor 4 is provided with an encoder (not shown) for detecting the rotational position (rotational angle) of the motor 4. The rotational position detected by the encoder refers to the actual position of the motor 4 and is used as position feedback. Here, there is a corresponding relationship between the rotational position of the motor 4 and the position of the movable part of the machine tool 5, so the rotational position detected by the encoder, i.e., the position feedback, indicates the position of the tool and the position of the workpiece.

[0025] The machine tool 5 is a machine that performs cutting processing on the surface of a workpiece (processing object) using a tool such as a ball end mill. Each drive shaft of the machine tool 5 is driven by a motor 4 .

[0026] Next, the determination unit 6 according to the present embodiment will be described in detail. The determination unit 6 according to the present embodiment is composed of, for example, a computer or other computing device including a CPU, ROM, RAM, etc. Figure 1 , an example is shown in which the determination unit 6 is configured by a computer or the like independent of the numerical control device 2 , but the determination unit 6 may be configured integrally with the numerical control device 2 .

[0027] like Figure 1 As shown, the determination unit 6 involved in this embodiment includes a position information acquisition unit 10, a mechanical information acquisition unit 12, a command processing surface calculation unit 13, a motor position processing surface calculation unit 22, an actual processing surface acquisition unit 24, a program processing surface calculation unit 26 and a processing surface analysis unit 50.

[0028] The position information acquisition unit 10 includes: a command position acquisition unit 11 that acquires the command position of the motor 4 for driving each drive axis of the machine tool 5; and a motor position acquisition unit 21 that acquires the actual position (hereinafter also referred to as "actual position") of the motor 4 for driving each drive axis of the machine tool 5. Specifically, the command position of the motor 4 is acquired from the numerical control device 2. In addition, the actual position of the motor 4 is acquired from the servo control device 3.

[0029] The mechanical information acquisition unit 12 acquires mechanical information including the drive shaft structure, tool shape, and unprocessed workpiece shape of the machine tool 5. Specifically, the mechanical information is acquired from the program generation unit 1 or the numerical control device 2. Alternatively, the mechanical information can be acquired by directly inputting and setting the mechanical information by the user.

[0030] The commanded machined surface calculation unit 13 calculates the shape of the machined surface of the workpiece after the machined process based on the commanded position acquired by the commanded position acquisition unit 11 and the mechanical information acquired by the mechanical information acquisition unit 12 .

[0031] Specifically, the commanded machined surface calculation unit 13 calculates the tool path based on the commanded position and the position information of each drive axis of the machine tool 5, and simulates the shape of the three-dimensional machined surface based on the tool shape and the shape of the unmachined workpiece. The commanded machined surface calculation unit 13 obtains the machined surface shape of the machined workpiece based on the result of the simulation.

[0032] The motor position machined surface calculation unit 22 calculates the shape of the machined surface of the workpiece after the machined process based on the actual position acquired by the motor position acquisition unit 21 and the mechanical information acquired by the mechanical information acquisition unit 12 .

[0033] Specifically, the motor position processing surface calculation unit 22 calculates the tool path based on the actual position and the position information of each drive axis of the machine tool 5, and simulates the shape of the three-dimensional processing surface based on the tool shape and the shape of the unprocessed workpiece. The motor position processing surface calculation unit 22 obtains the processing surface shape of the processed workpiece based on the result of the simulation.

[0034] The actual machined surface acquisition unit 24 measures and acquires the machined surface shape of the workpiece after actual machining based on the machining program generated by the program generation unit 1. As a measuring device, any device that can measure the machined surface shape can be used. For example, the machined surface shape of the workpiece after machining can be acquired based on the measurement results measured using a conventionally known surface roughness meter or the like.

[0035] The program machined surface calculation unit 26 calculates the shape of the machined surface of the workpiece based on the machining program. In this embodiment, the program machined surface calculation unit 26 calculates the shape of the machined surface of the workpiece after machining based on the position of the motor in the machining program and the mechanical information acquired by the mechanical information acquisition unit 12.

[0036] More specifically, the program machined surface calculation unit 26 calculates the tool path based on the position of the motor in the machining program and the position information of each drive axis of the machine tool 5, and simulates the shape of the three-dimensional machined surface based on the tool shape and the shape of the unmachined workpiece. The program machined surface calculation unit 26 obtains the machined surface shape of the machined workpiece based on the result of the simulation.

[0037] The machining surface analysis unit 50 analyzes the third correlation, the second correlation and the first correlation, thereby analyzing the main causes of machining surface defects, shape errors, etc., wherein the third correlation is the correlation between the shape of the machining surface calculated by the program machining surface calculation unit 26 (hereinafter also referred to as "shape A") and the shape of the machining surface calculated by the command machining surface calculation unit 13 (hereinafter also referred to as "shape B"), the second correlation is the correlation between the shape of the machining surface calculated by the command machining surface calculation unit 13 (shape B) and the shape of the machining surface calculated by the motor position machining surface calculation unit 22 (hereinafter also referred to as "shape C"), and the first correlation is the correlation between the shape of the machining surface calculated by the motor position machining surface calculation unit 22 (shape C) and the shape of the machining surface acquired by the actual machining surface acquisition unit 24 (hereinafter also referred to as "shape D").

[0038] In order to easily compare the correlation between the shapes A to D, the processed surface analysis unit 50 preferably expresses the shapes A to D in the same coordinate system. Figure 2 and Figure 3 An example of a method of expressing the shapes A to D in the same coordinate system will be described. Figure 2 It is a diagram for explaining the calculation method of the reference surface in each of the shapes A to D. Figure 3 This is a diagram for explaining how the shapes A to D are expressed in the same coordinate system.

[0039] In order to express each shape A to D in the same coordinate system, it is necessary to calculate the reference plane of each machined surface shape. Therefore, the method of calculating the equation of the reference plane based on the point group on the machined surface as the object is described. First, when the point on the machined surface is defined as Pn (Xn, Yn, Zn) and the reference plane is defined as d = aX + bY + cZ, the distance ln from the point Pn on the machined surface to the reference plane d is expressed by the following formula (1).

[0040] [Number 1]

[0041] ln=|aXn+bYn+cZn-d| / sqrt(a 2 +b 2 +c 2 )…Formula (1)

[0042] The plane that minimizes the sum L of the squares of the distances from each processing point is set as the reference plane. That is, a, b, c, and d that minimize L represented by the following formula (2) are determined.

[0043] [Number 2]

[0044] L=∑ln 2 …Formula (2)

[0045] Specifically, a matrix A is defined as in the following equation (3), and the reference plane is calculated by performing singular value decomposition (SVD) on the matrix A.

[0046] [Number 3]

[0047]

[0048] The vector v corresponding to the smallest singular value σ is the normal vector of the reference plane to be determined. Therefore, if v=(a, b, c) is determined, the reference plane d can be calculated by the following equation (4).

[0049] [Number 4]

[0050] d=l / n∑(aXn+bYn+cZn)…Equation (4)

[0051] The above describes a method of calculating a reference surface from the coordinate values ​​of a point group, but the method is not limited thereto. For example, an ideal processing surface may be set externally and used as the reference surface.

[0052] Next, after the reference plane is calculated as described above, a new coordinate system (X axis and Y axis) is determined on the calculated reference plane. In addition, a function representing the concave-convex information z at the point (x, y) projected from the processing point on the reference plane is defined as the following equation (5).

[0053] [Number 5]

[0054] z=f(x,y)…Formula (5)

[0055] In this way, the function representing the concave-convex information about the shape A can be defined as z=f A (x, y),

[0056] The function representing the concave-convex information related to the shape B can be defined as z=f B (x, y),

[0057] The function representing the concave-convex information related to the shape C can be defined as z=f C (x, y),

[0058] The function representing the concave-convex information related to the shape D can be defined as z=f D(x, y).

[0059] The processed surface analysis unit 50 can calculate the function (z=f A (x, y)) is the same as the function (z = f B (x, y)) to compare the correlation between shape A and shape B (third correlation). The same is true for the correlation between shape B and shape C (second correlation) and the correlation between shape C and shape D (first correlation).

[0060] The processed surface analysis unit 50 calculates the correlation of the concave-convex information of the processed surface using a general method for calculating the correlation of images. As a general method for calculating the correlation between two images A(x, y) and B(x, y), there is a method using the following equations (6) to (8). Equation (6) is a method called SAD (Sum of Absolute Difference), equation (7) is a method called SSD (Sum of Squared Difference), and equation (8) is a method called NCC (Normalized Cross-Correlation).

[0061] [Number 6]

[0062]

[0063] [Number 7]

[0064]

[0065] [Number 8]

[0066]

[0067] Next, use Figure 4 A method of analyzing the main causes of machined surface defects, shape errors, etc. in the machined surface analysis unit 50 will be described. Figure 4 This is a diagram for explaining a method of analyzing factors of machined surface defects, shape errors, and the like according to the present embodiment.

[0068] like Figure 4 As shown, shape A is the shape of the machining surface calculated based on the machining program, shape B is the shape of the machining surface calculated based on the command position, shape C is the shape of the machining surface calculated based on the actual position, and shape D is the shape of the machining surface of the workpiece after actual machining.

[0069] When a machined surface defect or shape error is confirmed on the machined workpiece, the machined surface analysis unit 50 compares the correlation between the shape C and the shape D. Furthermore, when it is determined that there is no correlation, the machined surface analysis unit 50 determines that the main cause (problem location) of the machined surface defect or shape error is other (tool, etc.). The reason for this is that, for example, the actual position (actual position of the motor 4) and the tool shape between the machined surfaces have an influence and it is determined that there is no correlation.

[0070] When it is determined that there is a correlation between shape C and shape D, the machined surface analysis unit 50 compares the correlation between shape B and shape C. When it is determined that there is no correlation, the machined surface analysis unit 50 determines that the main cause of the machined surface defect and shape error is the servo control device 3 that controls the motor 4. The reason for this is that it is considered that there is no correlation because the command position and the actual position deviate.

[0071] When it is determined that there is a correlation between shape B and shape C, the machined surface analysis unit 50 compares the correlation between shape A and shape B. Furthermore, when it is determined that there is no correlation, the machined surface analysis unit 50 determines that the main cause of the machined surface defect and shape error is the numerical controller 2 that assigns the command position of the motor 4. The reason for this is that it is considered that there is no correlation because the position of the motor in the machining program deviates from the command position of the motor 4 assigned by the numerical controller 2.

[0072] On the contrary, when it is determined that there is a correlation between shape A and shape B, the machined surface analysis unit 50 determines that the main cause of the machined surface defect and shape error is the program generation unit 1 that generated the machining program. This is because it is considered that the main cause of the machined surface defect and shape error is not the numerical controller 2, the servo control device 3, the motor 4, and the machine tool 5.

[0073] As described above, the determination system 100 involved in the present embodiment comprises: a motor position acquisition unit 21, which acquires the actual position of the motor 4 for driving the drive shaft of the machine tool 5; a mechanical information acquisition unit 12, which acquires mechanical information including the drive shaft structure of the machine tool 5, the tool shape and the shape of the unprocessed workpiece; a motor position processing surface calculation unit 22, which calculates the shape of the processing surface of the processed workpiece based on the actual position of the motor 4 and the mechanical information; an actual processing surface acquisition unit 24, which acquires the shape of the processing surface of the workpiece after actual processing; and a processing surface analysis unit 50, which compares the correlation between the shape of the processing surface calculated by the motor position processing surface calculation unit 22 and the shape of the processing surface acquired by the actual processing surface acquisition unit 24, i.e., a first correlation.

[0074] Thus, the machined surface analysis unit 50 can directly compare the correlation between the shape of the machined surface (shape C) calculated by the motor position machined surface calculation unit 22 and the shape of the machined surface (shape D) acquired by the actual machined surface acquisition unit 24. Therefore, it is possible to mechanically determine in a short time whether the main cause of a defective machined surface, shape error, etc. is the tool shape, etc. In other words, it is possible to directly compare the correlation between the machined surface shape (shape C) calculated based on the actual motor position and the machined surface shape (shape D) obtained by actually measuring the machined surface of the workpiece after machining, so as to determine in a short time the main cause of a defective machined surface, shape error, etc.

[0075] In addition, the determination system 100 involved in the present embodiment also includes: an instruction position acquisition unit 11, which acquires the instruction position of the motor 4 for driving the driving shaft of the machine tool 5; and an instruction processing surface calculation unit 13, which calculates the shape of the processing surface of the workpiece after processing based on the instruction position and mechanical information, and the processing surface analysis unit 50 analyzes the second correlation and the first correlation, and the second correlation is the correlation between the shape of the processing surface calculated by the instruction processing surface calculation unit 13 and the shape of the processing surface calculated by the motor position processing surface calculation unit 22.

[0076] Thus, the machined surface analysis unit 50 can compare the correlation (first correlation) between the shape C and the shape D, and can also compare the correlation (second correlation) between the shape of the machined surface calculated by the command machined surface calculation unit 13 (shape B) and the shape of the machined surface calculated by the motor position machined surface calculation unit 22 (shape C). Therefore, it is possible to mechanically determine in a short time whether the main cause of machined surface defects, shape errors, etc. is the tool shape or the servo control device.

[0077] In addition, the determination system 100 involved in the present embodiment also includes: a program generation unit 1, which generates a machining program for a workpiece; and a program machining surface calculation unit 26, which calculates the shape of the machining surface of the workpiece based on the machining program, and a machining surface analysis unit 50 analyzes a third correlation, a second correlation, and a first correlation, wherein the third correlation is a correlation between the shape of the machining surface calculated by the program machining surface calculation unit 26 and the shape of the machining surface calculated by the instruction machining surface calculation unit 13.

[0078] Thus, the machined surface analysis unit 50 can compare the correlation (third correlation) between the shape (shape A) of the machined surface calculated by the program machined surface calculation unit 26 and the shape (shape B) of the machined surface calculated by the command machined surface calculation unit 13, in addition to comparing the correlation (first correlation) between the shape C and the shape D and the correlation (second correlation) between the shape B and the shape C. Therefore, it is possible to mechanically determine in a short time whether the main cause of the machined surface defect, shape error, etc. is the tool shape, the servo control device, the numerical control device, or the program generation unit.

[0079] In addition, the present invention is not limited to the above-mentioned embodiment, and modifications and improvements within the scope that can achieve the object of the present invention are included in the present invention.

[0080] For example, an example is described in which the command processing surface calculation unit 13, the motor position processing surface calculation unit 22, and the program processing surface calculation unit 26 obtain mechanical information from the mechanical information acquisition unit 12. However, the command processing surface calculation unit 13, the motor position processing surface calculation unit 22, and the program processing surface calculation unit 26 can also obtain mechanical information from the program generation unit 1 or the numerical control device 2. In this case, the program generation unit 1 or the numerical control device 2 also functions as a mechanical information acquisition unit. In addition, the mechanical information can also be directly input into the command processing surface calculation unit 13, the motor position processing surface calculation unit 22, or the program processing surface calculation unit 26 by the user. In this case, the command processing surface calculation unit 13, the motor position processing surface calculation unit 22, or the program processing surface calculation unit 26 also functions as a mechanical information acquisition unit.

[0081] In addition, the example in which the machined surface analysis unit 50 compares the correlation between the shape A and the shape B, the correlation between the shape B and the shape C, and the correlation between the shape C and the shape D has been described, but the invention is not limited thereto. In addition to these correlations, the machined surface analysis unit 50 may also compare the correlation between the shape A and the shape C, the correlation between the shape A and the shape D, and the correlation between the shape B and the shape D.

[0082] Description of Reference Numerals

[0083] 1: Program generation unit; 2: Numerical control device; 3: Servo control device; 4: Motor; 5: Machine tool; 6: Judgment unit; 10: Position information acquisition unit; 11: Command position acquisition unit; 12: Mechanical information acquisition unit; 13: Command processing surface calculation unit; 21: Motor position acquisition unit; 22: Motor position processing surface calculation unit; 24: Actual processing surface acquisition unit; 26: Program processing surface calculation unit; 50: Processing surface analysis unit; 100: Judgment system.

Claims

1. A determination system comprising: a motor position acquisition unit for acquiring an actual position of a motor for driving a drive shaft of a machine tool; a mechanical information acquisition unit, which acquires mechanical information including a drive shaft structure of the machine tool, a tool shape, and a shape of an unmachined workpiece; a motor position processing surface calculation unit, which calculates the shape of the processing surface of the processed workpiece based on the actual position of the motor and the mechanical information; An actual machined surface acquisition unit, which acquires the shape of the machined surface of the workpiece after actual machining; a command position acquisition unit that acquires a command position of a motor for driving a drive shaft of the machine tool; a commanded machined surface calculation unit that calculates a shape of a machined surface of a machined workpiece based on the commanded position and the machine information; and The machined surface analysis unit determines the problem location when a machined surface defect or shape error is confirmed on the workpiece after actual machining. Among them, the processing surface analysis unit compares the correlation between the shape of the processing surface calculated by the motor position processing surface calculation unit and the shape of the processing surface acquired by the actual processing surface acquisition unit, i.e., the first correlation. When the first correlation is determined to be a correlation, the correlation between the shape of the processing surface calculated by the instruction processing surface calculation unit and the shape of the processing surface calculated by the motor position processing surface calculation unit, i.e., the second correlation, is compared to determine the problem location.

2. The determination system according to claim 1, further comprising: a program generating unit that generates a machining program for a workpiece; and a program machined surface calculation unit that calculates the shape of a machined surface of a workpiece based on the machining program, When the first correlation is determined to be a correlation and the second correlation is determined to be a correlation, the processing surface analysis unit compares the correlation between the shape of the processing surface calculated by the program processing surface calculation unit and the shape of the processing surface calculated by the instruction processing surface calculation unit, i.e., the third correlation, to determine the problem location.

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