Machining method, evaluation method, control device, program, and evaluation workpiece

Abstract

The machining method for producing an evaluation workpiece for evaluating thermal displacement of a machine tool is characterized by including a thermal displacement load operation step (S101) in which the machine tool is operated based on thermal displacement load information, which is information for reproducing the thermal displacement caused by the machine tool performing actual machining, and an evaluation machining step (S102) in which the machine tool is operated based on an evaluation machining path in which the amount of movement of the tool that moves in contact with the workpiece in a plane perpendicular to a first direction, which is the evaluation direction of the thermal displacement, changes depending on the reference position of the tool in the first direction.

Description

[Technical Field]

[0001] The present disclosure relates to a processing method, an evaluation method, a control device, a program, and an evaluation workpiece for evaluating thermal displacement. [Background technology]

[0002] Heat is generated during the operation of machine tools. For example, heat is generated when converting electricity into power, and heat is generated due to friction between the tool and the workpiece being machined. When this heat is transferred to the structure of the machine tool, the temperature of the structure of the machine tool rises, causing thermal expansion, which can cause the structure to deform. When the structure deforms, it can change the relative position of the tool to the workpiece, and this type of displacement is called thermal displacement. Thermal displacement is known to result in a decrease in machining accuracy. It is important to accurately evaluate thermal displacement.

[0003] Patent Document 1 discloses a technique for evaluating thermal displacement of a machine tool by machining a workpiece tilted with respect to the Y-axis direction, which is the direction of machining, without moving it in the Z-axis direction, which is perpendicular to the direction of machining, and measuring the length of the cutter mark obtained as a result of machining.The technique disclosed in Patent Document 1 makes it possible to evaluate thermal displacement without installing a displacement sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-86325 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional technology has a problem in that it may not be possible to accurately evaluate thermal displacement during actual machining. For example, the above-mentioned conventional technology does not disclose what kind of operating operation should be given to the machine tool when evaluating thermal displacement. Since thermal displacement varies depending on what kind of operating operation is performed, the above-mentioned conventional technology may have a different state of thermal displacement during evaluation and actual machining, making it difficult to accurately evaluate thermal displacement during actual machining.

[0006] The present disclosure has been made in consideration of the above, and aims to obtain a processing method that can improve the evaluation accuracy of thermal displacement during actual processing when evaluating thermal displacement without installing a displacement sensor. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the machining method according to the present disclosure is a machining method for producing an evaluation workpiece for evaluating thermal displacement of a machine tool, and includes a pre-machining surface generation step for performing flat machining using a tool with a diameter equal to or less than half the pitch distance of the ball screw of the feed axis of the machine tool, a thermal displacement load operation step for operating the machine tool based on thermal displacement load information which is information for reproducing thermal displacement caused by the machine tool performing actual machining, and a thermal displacement load operation step for operating the tool in a first direction which is the evaluation direction of the thermal displacement. Start processing By location , Wa The tool that moves in contact with the work In a plane perpendicular to the first direction and an evaluation machining step of operating the machine tool based on an evaluation machining path in which the amount of movement is changed to machine the workpiece. [Effects of the Invention]

[0008] The machining method according to the present disclosure has the effect of improving the accuracy of evaluating thermal displacement during actual machining when evaluating thermal displacement without installing a displacement sensor. [Brief explanation of the drawings]

[0009] [Figure 1] A diagram showing an example of the configuration of a processing system [Figure 2] Diagram showing an example of the configuration of a machine tool [Figure 3] FIG. 1 is a diagram illustrating an example of a functional configuration of a control device according to a first embodiment; [Figure 4] An explanatory diagram of an example of thermal displacement load operation [Figure 5] An explanatory diagram of an example of a machining path for evaluation [Figure 6] Illustrative diagram of the correlation between thermal displacement and cutter mark length [Figure 7] 4 is a flowchart illustrating the operation of the control device shown in FIG. 3. [Figure 8] FIG. 10 is a diagram illustrating an example of a functional configuration of a control device according to a second embodiment. [Figure 9] An explanatory diagram of the pitch distance of the ball screw on the feed axis of a machine tool [Figure 10] Fig. 9 is an explanatory diagram of the motion error that occurs in the feed axis of the machine tool. [Figure 11] FIG. 10 is an explanatory diagram of the effect of generating a pre-machined surface according to the second embodiment. [Figure 12] An explanatory diagram of a pre-processed surface according to a comparative example. [Figure 13] 9 is a flowchart illustrating the operation of the control device shown in FIG. 8. [Figure 14] FIG. 10 is a diagram illustrating an example of a functional configuration of a control device according to a third embodiment. [Figure 15] An explanatory diagram of an evaluation workpiece produced by the control device shown in Figure 14. [Figure 16] FIG. 15 shows an actual evaluation workpiece produced by the control device shown in FIG. 14. [Figure 17] 15 is a flowchart illustrating the operation of the control device shown in FIG. 14. [Figure 18] FIG. 1 is a diagram illustrating an example of a hardware configuration of a control device according to first to third embodiments. [Figure 19] FIG. 1 is an explanatory diagram of dedicated hardware used to realize the functions of the control device according to the first to third embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a processing method, an evaluation method, a control device, a program, and an evaluation workpiece according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1 FIG. 1 is a diagram showing an example configuration of a machining system 100. The machining system 100 has a control device 1 and a machine tool 2. The control device 1 generates motor control commands for controlling the machine tool 2 based on a machining program, and provides the generated motor control commands to the machine tool 2. The machine tool 2 machines a workpiece to produce an evaluation workpiece 3 for evaluating thermal displacement. The workpiece is an object machined by the machine tool 2, and is also called a machined object. The machining program is an EIA (Electrical and Instrumentation Automation) program such as G-code, and is created in advance by a user.

[0012] The machine tool 2 is a machine that processes a workpiece, and is, for example, a machining center shown in Fig. 2. Fig. 2 is a diagram showing an example of the configuration of the machine tool 2.

[0013] The machine tool 2 is a vertical cutting machine with three orthogonal axes. The machine tool 2 has a spindle control unit 92 including a process control device that controls one of the spindles 83, an X-axis drive unit 93 including a servo control device that drives the X-axis, a Y-axis drive unit 94 including a servo control device that drives the Y-axis, and a Z-axis drive unit 95 including a servo control device that drives the Z-axis. The machine tool 2 drives a tool 76 in the X-axis and Z-axis directions, drives a workpiece 78 placed on a worktable 77 in the Y-axis direction, and rotates the tool 76 using the spindle 83, thereby machining the workpiece 78. The machine tool 2 operates under the control of the control device 1, machining the workpiece 78 into a desired shape.

[0014] The X-axis drive unit 93 has a motor 71X, a guide mechanism 72X, and a feed screw 73X. The Y-axis drive unit 94 has a motor 71Y, a guide mechanism 72Y, and a feed screw 73Y. The Z-axis drive unit 95 has a motor 71Z, a guide mechanism 72Z, and a feed screw 73Z. A rotation angle detector 80X that detects the rotation angle of the motor 71X is attached to the motor 71X. A rotation angle detector 80Y that detects the rotation angle of the motor 71Y is attached to the motor 71Y. A rotation angle detector 80Z that detects the rotation angle of the motor 71Z is attached to the motor 71Z. Hereinafter, when there is no need to distinguish between the motors 71X, 71Y, and 71Z, the common reference numeral 71 will be used and they will be simply referred to as motor 71. The motor 71X is the motor 71 provided in the X-axis drive unit 93. Similarly, when there is no need to distinguish between the guide mechanisms 72X, 72Y, and 72Z, they will simply be referred to as guide mechanisms 72, and when there is no need to distinguish between the feed screws 73X, 73Y, and 73Z, they will simply be referred to as feed screws 73.

[0015] In machine tool 2, the rotational motion of motor 71, which is an actuator, is converted into linear motion in the drive direction of each axis by feed screw 73. At this time, the rotational motion is supported by guide mechanism 72, so the axis has a degree of freedom only in the feed direction of feed screw 73. As a result, machine tool 2 achieves movement in three-dimensional space of XYZ, that is, three degrees of freedom, by combining the linear motion of each axis to achieve two degrees of freedom of movement of tool 76 in the XZ plane and one degree of freedom of movement of workpiece 78 in the Y-axis direction. Machine tool 2 rotates tool 76 using spindle 83, and machines workpiece 78 by removing material from the portion where workpiece 78 interferes with tool 76.

[0016] 3 is a diagram illustrating an example of the functional configuration of the control device 10 according to the first embodiment. The control device 10 has a thermal displacement load operation unit 11, an evaluation workpiece preparation unit 12, and an evaluation unit 13. The control device 10 controls the machine tool 2 to machine a workpiece 78 and prepare an evaluation workpiece 3 for evaluating the thermal displacement of the machine tool 2.

[0017] Here, thermal displacement will be explained. When the machine tool 2 processes the workpiece 78, heat is generated within the machine tool 2. For example, the motor 71 and servo amplifier (not shown), which serve as actuators, generate heat when converting electrical power into motive power. Furthermore, heat is generated due to material deformation and friction during processes such as cutting and polishing. Furthermore, friction generated when the feed axis is operated also generates heat. When this heat is transferred to the structure of the machine tool 2, the temperature of the structure rises, causing thermal expansion. Because the temperature of a structure does not necessarily change uniformly, thermal expansion can cause differential expansion depending on the position of the structure, resulting in deformation other than simple expansion and contraction, such as tilting, distortion, or twisting of the structure. Such deformation causes an error in the relative position between the tool 76 and the workpiece 78. This error, i.e., the amount of change in the relative position between the tool 76 and the workpiece 78 caused by thermal deformation, is called thermal displacement. It is known that thermal displacement can reduce the positioning accuracy of the machine tool 2, thereby reducing machining accuracy.

[0018] The control device 10 has a function of causing the machine tool 2 to perform an operation that causes thermal displacement, and then preparing an evaluation workpiece 3 for evaluating the thermal displacement. The control device 10 may also have a function of evaluating the thermal displacement of the machine tool 2 using the evaluation workpiece 3. In FIG. 3, the control device 10 is shown to have the function of the evaluation unit 13, but the evaluation of the thermal displacement may be performed manually, in which case the function of the evaluation unit 13 is omitted.

[0019] The thermal displacement loading unit 11 controls the machine tool 2 in accordance with a machining program for a thermal displacement loading step, causing the machine tool 2 to perform a thermal displacement loading operation in which the machine tool 2 operates in an operating pattern that causes thermal displacement in the machine tool 2. Note that, in the thermal displacement loading operation, the thermal displacement loading unit 11 may operate only the main spindle 83, only the feed axis, or both the main spindle 83 and the feed axis. In this case, the thermal displacement loading unit 11 causes the machine tool 2 to perform the thermal displacement loading operation based on the thermal displacement load information. Examples of thermal displacement loading operations include rotating the main spindle 83 at a predetermined rotation speed for a predetermined time, reciprocating the feed axis at a predetermined feed rate for a predetermined time, a combination of the above operations, or an operation according to a machining program for evaluating the machine tool 2, written in G-code, for example. Note that, to measure the amount of thermal displacement under no load, the thermal displacement loading unit 11 does not need to operate the main spindle 83 or the feed axis. When the thermal displacement loading operation is completed, the thermal displacement loading operation unit 11 outputs information indicating that the thermal displacement loading operation is completed to the evaluation workpiece preparation unit 12.

[0020] Here, the thermal displacement load information will be described. The thermal displacement load information is information for reproducing the thermal displacement caused by the machine tool 2 performing actual machining. For example, the thermal displacement load information is information for operating the machine tool 2 based on the machining path of the actual machining. Note that "operating the machine tool 2 based on the machining path" refers to controlling at least one of the spindle 83 and the feed axis so that the tool 76 attached to the machine tool 2 moves relative to the workpiece according to the machining path. The thermal displacement load information may also be information for operating at least one of the spindle 83 and the feed axis of the machine tool 2 so that the average torque during the thermal displacement load operation matches the average torque during actual machining. In actual machining, a cutting force torque is applied to the spindle 83. However, if actual cutting is performed every time the thermal displacement is evaluated, the workpiece 78 is consumed each time the thermal displacement is evaluated, which is costly. Therefore, the average torque of the spindle 83 during the actual machining is measured in advance, and in the thermal displacement load operation, the spindle 83 is repeatedly accelerated and decelerated so that the average torque of the spindle 83 matches that during actual machining.

[0021] Fig. 4 is an explanatory diagram of an example of thermal displacement load operation. The upper part of Fig. 4 shows the change over time in the torque of the spindle 83 during actual machining. In the thermal displacement load operation, the average torque of the spindle 83 during actual machining and the average torque T ave The machine tool 2 is operated in an operation pattern that matches the above. Since a high torque is applied to the spindle 83 during acceleration and deceleration, by repeating acceleration and deceleration, a high torque can be generated on average even when the workpiece 78 is not being cut. This average torque T ave By making it so that it matches the average torque during actual machining, it is possible to simulate the load during actual machining and apply it to the machine tool 2, making it possible to reproduce the thermal displacement during actual machining.

[0022] Returning to the explanation of Figure 3, when information indicating that the thermal displacement loading operation has ended is output from the thermal displacement loading operation unit 11, the evaluation workpiece preparation unit 12 controls the machine tool 2 based on the machining program for the evaluation machining step, thereby operating the spindle 83 and feed axis of the machine tool 2 based on the evaluation machining path to machine the workpiece 78 and prepare the evaluation workpiece 3. Here, the evaluation machining path is a machining path in which there is a correlation between the position of the tool 76 in a first direction, which is the evaluation direction of thermal displacement, and the amount of movement of the tool 76 in a plane perpendicular to the first direction. The position of the tool 76 may be the tip point of the tool 76 or the point where the tool 76 and the workpiece 78 contact each other.

[0023] FIG. 5 is an explanatory diagram of an example of a machining path 40 for evaluation. Here, the Z direction is the first direction, which is the evaluation direction of thermal displacement, and the X direction is the second direction, which is the movement direction of the tool 76 and is perpendicular to the first direction. The tool 76 is a ball end mill. The machining path 40 has a correlation between the position of the tool 76 in the Z direction and the movement amount of the tool 76 in the XY plane. Specifically, the machining path 40 has two components: a first movement amount, which is the movement amount of the tool 76 in the Z direction, and a second movement amount, which is the movement amount of the tool 76 in the Y direction. The second movement amount is the first movement amount multiplied by a predetermined magnification. A groove is formed in a part of the workpiece 78 when the tool 76 comes into contact with the workpiece 78 and the workpiece 78 is machined. This groove is called a cutter mark 41. In the following description, depending on the state of the cutter mark 41, the cutter marks 41 may be distinguished from one another by using a number following a hyphen, such as cutter mark 41-1, 41-2, etc.

[0024] For example, if the workpiece 78 is set up so that the relative distance between the tool 76 and the workpiece 78 approaches zero at the center coordinate in the Z direction of the machining path 40, and machining is performed using the machining path 40, the tool 76 will separate from the workpiece 78 midway through the workpiece 78. As a result, the cutter mark 41 will be formed only on a portion of the workpiece 78. The length of the cutter mark 41 changes in proportion to the amount of thermal displacement occurring in the Z axis. For example, a machining path is created with a first movement amount of 0.1 mm and a second movement amount of 100 mm. In this case, the second movement amount is 1000 times the first movement amount.

[0025] FIG. 6 is an explanatory diagram of the correlation between thermal displacement and the length of the cutter mark 41. Here, the tip position of the tool 76 is defined as the position of the tool 76. When no thermal displacement occurs, the tip position of the tool 76 is aligned with the coordinate of the center of the workpiece 78 in the Z direction, and this position is defined as the reference point A0. When thermal displacement occurs, deviations occur even when the tip position of the tool 76 is intended to be aligned with the coordinate of the center of the workpiece 78 in the Z direction. The left side of FIG. 6 shows the workpiece 78 when evaluation machining is performed from reference point A1, where deviations in the negative Z direction occur due to thermal displacement. The right side of FIG. 6 shows the workpiece 78 when evaluation machining is performed from reference point A2, where thermal displacement in the positive Z direction occurs. When thermal displacement 42-1 occurs in the negative Z direction, the length m1 of the cutter mark 41-1 formed on the workpiece 78 is defined as the length m0. As shown on the left side of FIG. 6, when thermal displacement occurs in the negative Z direction, the length m1 of the cutter mark 41-1 is longer than the length m0 of the cutter mark 41 when no thermal displacement occurs. Furthermore, the length of cutter mark 41-2 when thermal displacement 42-2 occurs in the positive Z direction is defined as m2. As shown on the right side of Fig. 6, when thermal displacement occurs in the positive Z direction, the length m2 of cutter mark 41-2 becomes shorter than the length m0 of cutter mark 41 when there is no thermal displacement.

[0026] For example, let's say the length m0 of the cutter mark 41 is 50 mm. In this example, let's assume that a displacement of 0.01 mm occurs in the positive Z direction, which is the evaluation direction of the thermal displacement. In the example on the right of Figure 6, let's assume that the thermal displacement 42-2 is 0.01 mm. In this case, the relative positions of the workpiece 78 and the tool 76 move apart throughout the entire machining path 40-2, so the length m2 of the cutter mark 41-2 is 10 mm shorter than the length m0 of the cutter mark 41. In the example of Figure 6, the length m0 - m2 = 10 mm. In this way, the displacement in the Z direction and the length of the cutter mark 41 are the same as the ratio between the second movement amount and the first movement amount. Therefore, by using the machining path 40, minute displacements occurring in the Z direction can be magnified and detected.

[0027] Returning to the explanation of Figure 3, the evaluation unit 13 evaluates thermal displacement using the evaluation workpiece 3 produced by the evaluation workpiece producing unit 12. For example, the evaluation unit 13 may include a camera that photographs the surface of the evaluation workpiece 3 on which the cutter mark 41 is formed. The evaluation workpiece 3 is photographed with the camera while an object of known length, such as a jig or ruler, is placed on the evaluation workpiece 3, and the length of the cutter mark 41 can be identified by comparing the cutter mark 41 with the object of known length in the photographed image.

[0028] Here, the control device 10 evaluates the thermal displacement in the evaluation unit 13, but the user may manually measure the length of the cutter mark 41 using a measuring instrument such as a ruler to evaluate the thermal displacement.

[0029] Figure 7 is a flowchart for explaining the operation of control device 10 shown in Figure 3. First, thermal displacement loading operation unit 11 executes a thermal displacement loading operation step (step S101). The thermal displacement loading operation step is a step for operating spindle 83 and feed axes of machine tool 2 based on thermal displacement load information, which is information for reproducing thermal displacement caused by machine tool 2 performing actual machining.

[0030] Following the thermal displacement load operation step, the evaluation workpiece preparation unit 12 executes an evaluation machining step (step S102). The evaluation machining step is a step in which the evaluation workpiece 3 is prepared by operating the machine tool 2 based on the evaluation machining path to machine the workpiece 78. The evaluation machining path is a machining path in which the movement amount of the tool 76, which moves in contact with the workpiece 78 in a plane perpendicular to the first direction, which is the evaluation direction of thermal displacement (the Z direction in the above example), changes depending on the reference position of the tool 76 in the first direction. In the example shown in FIG. 5, the evaluation machining path 40 has two components: a first movement amount in the Z direction and a second movement amount in the X direction. The second movement amount is the first movement amount multiplied by a predetermined magnification.

[0031] Following the evaluation processing step, the evaluation unit 13 executes an evaluation step in which the thermal displacement of the machine tool 2 is evaluated using the evaluation workpiece 3 (step S103). In the evaluation step, the thermal displacement of the machine tool 2 is evaluated using the evaluation workpiece 3 produced in the evaluation processing step of step S102. The evaluation result is, for example, the amount of thermal displacement. As described above, the evaluation step may be performed manually by the user.

[0032] As described above, according to the first embodiment, a machining method for producing an evaluation workpiece 3 for evaluating thermal displacement of a machine tool 2 can be provided, the machining method including: a thermal displacement load operation step for operating the machine tool 2 based on thermal displacement load information, which is information for reproducing thermal displacement caused by the machine tool 2 performing actual machining; and an evaluation machining step for operating the machine tool 2 based on an evaluation machining path in which the amount of movement of the tool 76, which moves in contact with the workpiece 78 in a plane perpendicular to a first direction, changes depending on the reference position of the tool 76 in the first direction, which is the evaluation direction of the thermal displacement. Note that the first direction corresponds to the Z direction in the above embodiment. In this way, the thermal displacement load information is used in the thermal displacement load operation step, making it possible to reproduce thermal displacement that is closer to the thermal displacement actually occurring during actual machining, thereby improving the evaluation accuracy of thermal displacement during actual machining without installing a displacement sensor. Furthermore, in the evaluation machining step, the machine tool 2 is operated to machine the workpiece 78 based on an evaluation machining path in which the amount of movement of the tool 76, which contacts and moves with the workpiece 78 in a plane perpendicular to the first direction, changes depending on the reference position of the tool 76 in the first direction, which is the evaluation direction of thermal displacement. This makes it possible to obtain an evaluation workpiece having cutter marks, which are grooves whose length varies depending on thermal displacement. Therefore, a user can evaluate thermal displacement by, for example, measuring the length of the cutter marks machined on the evaluation workpiece, thereby enabling evaluation of thermal displacement without installing a sensor. The cutter mark length may be measured manually, or the control device 10 may have a function for measuring the cutter mark length. If the control device 10 has a function for measuring the cutter mark length, for example, the control device 10 can measure the cutter mark length by analyzing images captured of the machined surface of the evaluation workpiece.

[0033] In the above embodiment, the tool 76 moves straight in the X direction, and therefore the "amount of movement of the tool 76 that moves in contact with the workpiece 78 in a plane perpendicular to the first direction" is the amount of movement in the second direction. In the first embodiment, the tool 76 moves straight so that the cutter mark 41 is a straight line, but the cutter mark 41 is not limited to a straight line and may be a curved line.

[0034] In this machining method, the thermal displacement load information may be information for operating the main spindle 83 so that the average torque of the main spindle 83 in the thermal displacement load operation step matches the average torque of the main spindle 83 in actual machining. Alternatively, the thermal displacement load information may be information for operating the feed axis so that the average torque of the feed axis in the thermal displacement load operation step matches the average torque of the feed axis in actual machining. Specifically, the thermal displacement load information may be the average torque of the main spindle 83 when operating the main spindle 83 in actual machining, or the average torque of the feed axis when operating the feed axis in a machining pass in actual machining. Here, the average torque is the temporal average value of torque measured over a predetermined period of time. For example, if the thermal displacement load operation is an operation of moving the main spindle 83, the thermal displacement load information may include the average torque of the main spindle 83 in actual machining. If the thermal displacement load operation is an operation of moving the feed axis, the thermal displacement load information may include the average torque of the feed axis when operating the feed axis in a machining pass in actual machining.

[0035] In the thermal displacement load operation step, the machining torque actually generated by machining the workpiece 78 with the tool 76 may be simulated. As another method, since high torque is generated when the spindle 83 is accelerated and decelerated, the machining torque can also be simulated by repeating acceleration and deceleration of the spindle 83. This method of repeating acceleration and deceleration can produce a high torque on average even when the workpiece 78 is not being cut. Similarly, for the feed axis, the torque when the tool 76 machines the workpiece 78 may be used to calculate the average torque, or the torque when the feed axis is accelerated and decelerated may be used to calculate the average torque.

[0036] In the machining method according to the first embodiment, the evaluation machining path has two components: a first movement amount in a first direction and a second movement amount in a second direction perpendicular to the first direction, and the second movement amount is the first movement amount multiplied by a predetermined magnification. In the above embodiment, the first direction corresponds to the Z direction, and the second direction corresponds to the X direction.

[0037] According to the first embodiment, it is possible to provide an evaluation workpiece 3 that is produced by carrying out the above processing method.

[0038] Moreover, according to the first embodiment, it is possible to provide a control device 10 that executes the above-mentioned machining method. The control device 10 is a device that controls a machine tool 2, and is characterized by including: a thermal displacement load operating unit 11 that operates the machine tool 2 based on thermal displacement load information, which is information for reproducing thermal displacement caused by the machine tool 2 performing actual machining; and an evaluation workpiece preparing unit 12 that prepares an evaluation workpiece 3 for evaluating thermal displacement of the machine tool 2 by operating the machine tool 2 to machine a workpiece 78 based on an evaluation machining path in which the amount of movement of the tool 76 that moves in contact with the workpiece 78 in a plane perpendicular to a first direction, which is an evaluation direction of thermal displacement, changes depending on the reference position of the tool 76 in the first direction.

[0039] Furthermore, according to embodiment 1, a program can be provided that causes the machine tool 2 to produce an evaluation workpiece 3 for evaluating thermal displacement by executing a thermal displacement load operation step in which the machine tool 2 operates based on thermal displacement load information, which is information for reproducing the thermal displacement that occurs when the machine tool 2 performs actual machining, and an evaluation machining step in which the machine tool 2 operates based on an evaluation machining path in which the amount of movement of the tool 76 that comes into contact with the workpiece 78 and moves in a plane perpendicular to the first direction changes depending on the reference position of the tool 76 in the first direction, which is the evaluation direction of the thermal displacement.

[0040] Embodiment 2 8 is a diagram showing an example of the functional configuration of a control device 10A according to the second embodiment. The control device 10A has a thermal displacement load operation unit 11, an evaluation workpiece preparation unit 12, an evaluation unit 13, and a pre-machining surface generation unit 14. The control device 10A has the pre-machining surface generation unit 14 in addition to the configuration of the control device 10 according to the first embodiment. Below, detailed description of the parts that are the same as those of the control device 10 will be omitted, and the parts that are different from the control device 10 will be mainly described.

[0041] Before the thermal displacement loading operation unit 11 executes the thermal displacement loading operation step, the pre-machining surface generation unit 14 executes the pre-machining surface generation step by controlling the machine tool 2 based on the machining program for the pre-machining surface generation step, thereby generating the pre-machining surface of the evaluation workpiece 3. The pre-machining surface is the surface to be machined when evaluation machining is performed in the evaluation machining step. In the second embodiment, a surface onto which the motion error occurring in the machine tool 2 is transferred is generated as the pre-machining surface, making it possible to evaluate the thermal displacement and the motion error separately.

[0042] Examples of motion errors that occur in the machine tool 2 include errors in parallelism in the feed axis direction caused by the accuracy of assembly of a single feed axis, errors in the squareness of two feed axes caused by the accuracy of assembly of the feed axes, parallelism errors caused by the feed axis bending due to its own weight, and pitch errors that occur repeatedly with the pitch period of the ball screw that drives the feed axis.These errors are strongly dependent on the position of the feed axis, and are characterized by the fact that the errors are reproducible when the feed axis is positioned in the same position.

[0043] FIG. 9 is an explanatory diagram of the pitch distance P of the ball screw of the feed axis of machine tool 2. The pitch distance P of feed screw 73Y, which is a ball screw, is a value corresponding to the distance traveled in the feed direction per rotation. In machine tool 2 (not shown in FIG. 9) having feed screw 73X that drives in the X-axis direction and feed screw 73Y that drives in the Y-axis direction as shown in FIG. 9, when the feed axis is driven by feed screw 73Y, which is a ball screw, an error occurs in a direction different from the Y direction, which is the feed direction, in this case the Z direction, due to the influence of the whirling of feed screw 73Y. This error is called a motion error, and occurs repeatedly at a period equal to the pitch distance P of the ball screw.

[0044] FIG. 10 is an explanatory diagram of a motion error that occurs in a feed axis of a machine tool 2 having the configuration shown in FIG. 9. In machine tool 2 having the configuration shown in FIG. 9, when the feed axis is driven by a feed screw 73Y, which is a ball screw, a motion error with a period of pitch distance P occurs repeatedly in the Z direction, as shown in FIG. 10. Motion errors related to parallelism and perpendicularity occur almost identically even at positions that differ by a few millimeters. In contrast, pitch error is an error that fluctuates periodically within one period of the ball screw. If the position differs by half the error period, i.e., by more than half the pitch distance P, the amount of pitch error that occurs will differ significantly and will not be reproduced. Because the pitch of a ball screw is generally several millimeters to several tens of millimeters, a position difference of a few millimeters can result in a large difference in motion error.

[0045] For this reason, when generating the pre-machined surface by flattening, a tool 76 with a diameter sufficiently smaller than the pitch distance P of the ball screw is used, so that the pitch error is reflected in the pre-machined surface. The tool 76 used for this machining is, for example, a square end mill, and it is sufficient that the diameter is at least half the pitch distance P or less.

[0046] FIG. 11 is an explanatory diagram of the effect of generating a pre-machined surface according to the second embodiment. As described above, in the second embodiment, the pre-machined surface is generated by flattening before the thermal displacement load operation. Here, the feed direction is the Y direction, and the pre-machined surface is generated with the Z-direction motion error transferred. Here, the diameter Φ of the tool 76, e.g., a square end mill, is smaller than half the pitch distance P of the ball screw driving the Y axis. As a result, the pitch error, which is the Z-direction motion error, is reflected in the pre-machined surface. In other words, although the pre-machined surface is flattened, there is a difference in the Z-direction position due to the motion error. The height of the pre-machined workpiece 78 varies in the Z direction depending on the motion error corresponding to the Y-direction position. In the evaluation machining step, by using the pre-machined workpiece 78, the distance between the tool 76 and the surface of the workpiece 78 is constant during evaluation machining in the absence of thermal displacement, as shown in the lower diagram of FIG. 11. In this way, by creating the pre-machined surface of the evaluation workpiece 3 using a machining path that is roughly the same as the evaluation machining step, the motion error when generating the pre-machined surface is made the same as the motion error during evaluation machining, and only the effects of thermal displacement during evaluation machining appear as cutter marks 41.

[0047] FIG. 12 is an explanatory diagram of a pre-machined surface according to a comparative example. FIG. 12 is a comparative example of the example shown in FIG. 11, in which the pre-machined surface is generated using a tool whose diameter Φ is greater than half the pitch distance P. In this case, the motion error in the Z direction while driving the feed screw 73Y is not transferred to the surface of the workpiece 78, and the pre-machined surface is flat. In this case, as shown in the lower diagram of FIG. 12, during evaluation machining, the relative position between the tool 76 and the workpiece 78 changes depending on the position in the Y direction, and the cutter mark 41 formed on the workpiece 78 after evaluation machining reflects not only the influence of thermal displacement but also the influence of motion error.

[0048] Fig. 13 is a flowchart for explaining the operation of the control device 10A shown in Fig. 8. The pre-machined surface generating unit 14 of the control device 10A executes a pre-machined surface generating step (step S201). In the pre-machined surface generating step, a workpiece 78 is subjected to flattening processing using a tool 76 having a diameter Φ equal to or less than half the pitch distance P of the ball screw that drives the feed axis. The subsequent steps S101 to S103 are the same as those in the first embodiment, and therefore detailed description thereof will be omitted.

[0049] As described above, according to the second embodiment, it is possible to provide a machining method that further includes, in the machining method described in the first embodiment, a pre-machining surface generation step in which, prior to the thermal displacement load operation step, flattening is performed using a tool with a diameter Φ that is equal to or less than half the pitch distance P of the ball screw of the feed axis.

[0050] In the machining method according to the second embodiment, the influence of the motion error of the machine tool 2 can be eliminated and only the influence of the thermal displacement can be extracted, thereby making it possible to evaluate the thermal displacement occurring during actual machining with even greater accuracy.

[0051] Embodiment 3 14 is a diagram showing an example of the functional configuration of a control device 10B according to the third embodiment. The control device 10B has a thermal displacement loading operation unit 11, an evaluation workpiece preparation unit 12B, an evaluation unit 13B, and a pre-machining surface generation unit 14. The thermal displacement loading operation unit 11 is the same as in the first and second embodiments, and the pre-machining surface generation unit 14 is the same as in the second embodiment, so detailed explanations will be omitted.

[0052] Fig. 15 is an explanatory diagram of the evaluation workpiece 3 produced by the control device 10B shown in Fig. 14. The evaluation workpiece producing unit 12B operates the spindle 83 and the feed axis according to the evaluation machining path to form one cutter mark 41, and then controls the tool 76 to move in the pick direction relative to the workpiece 78, thereby forming multiple cutter marks 41 on the workpiece 78.

[0053] FIG. 16 is a diagram showing an actual evaluation workpiece 3 produced by the control device 10B shown in FIG. 14. On the XY plane, multiple cutter marks 41 extending in the X direction are formed, aligned in the Y direction. Furthermore, tool marks remain on the pre-machined surface during formation. In the example shown in FIG. 16, when forming the pre-machined surface, machining is performed while moving the tool 76 in the X direction. However, for example, after forming the pre-machined surface while moving the tool 76 in the Y direction, evaluation machining may be performed while moving the tool 76 in the X direction. In this case, the cutter marks 41 are formed as grooves extending in a direction perpendicular to the lines of the tool marks when forming the pre-machined surface.

[0054] The evaluation unit 13B uses an evaluation workpiece 3 on which a plurality of cutter marks 41 are formed to evaluate the change in thermal displacement over time based on the lengths of the plurality of cutter marks 41. The method for evaluating each thermal displacement is the same as that of the evaluation unit 13.

[0055] 17 is a flowchart for explaining the operation of the control device 10B shown in FIG. The pre-machined surface generating step of step S201, the thermal displacement loading operation step of step S101, and the evaluation machining step of step S102 are the same as those in the second embodiment. After the evaluation machining step of step S102, the evaluation workpiece preparing unit 12B executes a pick direction moving step of moving the tool 76 in the pick direction relative to the workpiece 78 by a predetermined movement amount (step S301). After the pick direction moving step of step S301, the evaluation workpiece preparing unit 12B determines whether the processing of steps S101 to S301 has been repeated a predetermined number of times (step S302).

[0056] If the predetermined number of times has not been reached (step S302: No), the evaluation workpiece preparation unit 12B notifies the thermal displacement loading operation unit 11 to repeat the execution of the thermal displacement loading operation step, and the process is repeated from step S101. If the predetermined number of times has been reached (step S302: Yes), the evaluation workpiece preparation unit 12B notifies the evaluation unit 13B that the preparation of the evaluation workpiece 3 has been completed, and the evaluation unit 13B executes the evaluation step (step S303). The evaluation step of step S303 is a step in which the process of the evaluation step of step S103 is executed for multiple cutter marks 41 to evaluate changes in thermal displacement over time. As a result, the control device 10B can cause the machine tool 2 to repeatedly execute the thermal displacement loading operation step and the evaluation machining step two or more times, and each time the evaluation machining step is completed, execute a pick direction movement step in which the feed axis is moved in the Y direction, which is a third direction orthogonal to both the Z direction and the X direction.

[0057] As described above, according to the third embodiment, a machining method can be provided in which the thermal displacement load operation step and the evaluation machining step are repeated two or more times, and each time the evaluation machining step is completed, a pick direction movement step is further included in which the feed axis is moved in a third direction perpendicular to both the first direction and the second direction, which is the direction of travel of the tool 76.

[0058] Furthermore, according to the third embodiment, an evaluation method can be provided that includes an evaluation step that evaluates the change over time in thermal displacement caused by the thermal displacement load operation step based on the length of a plurality of cutter marks 41 formed on the workpiece 78 by contact between the tool 76 and the workpiece 78 when the above-mentioned machining method is performed.

[0059] Next, the hardware configuration of the control devices 10, 10A, and 10B according to the first to third embodiments will be described. The functions of each unit of the control devices 10, 10A, and 10B are realized using a processing circuit. The processing circuit may be realized by dedicated hardware or may be realized using a CPU (Central Processing Unit). Fig. 18 is a diagram showing an example of the hardware configuration of the control devices 10, 10A, and 10B according to the first to third embodiments.

[0060] The functions of the control devices 10, 10A, and 10B are realized by a computer system such as that shown in Fig. 18. The functions of the control devices 10, 10A, and 10B may be realized by one computer system or by multiple computer systems.

[0061] The computer system shown in FIG. 18 includes a control unit 101, an input unit 102, a storage unit 103, a display unit 104, a communication unit 105, and an output unit 106, which are connected via a system bus 107.

[0062] In FIG. 18, the control unit 101 is, for example, a CPU. The control unit 101 executes a machining program that describes each process performed by the control devices 10, 10A, and 10B of this embodiment. The input unit 102 is composed of, for example, a keyboard, a mouse, and the like, and is used by a user of the computer system to input various information. The memory unit 103 includes various memories such as RAM (Random Access Memory) and ROM (Read Only Memory) and a storage device such as a hard disk, and stores programs to be executed by the control unit 101, necessary data obtained during processing, and the like. The memory unit 103 is also used as a temporary storage area for programs. The display unit 104 is composed of, for example, an LCD (Liquid Crystal Display) and the like, and displays various screens to the user of the computer system. The communication unit 105 is, for example, a communication circuit that performs communication processing. The communication unit 105 may be composed of multiple communication circuits corresponding to multiple communication methods. The output unit 106 is an output interface that outputs data to external devices such as a printer or external storage device.

[0063] Note that Figure 18 is just an example, and the configuration of the computer system is not limited to the example of Figure 18. For example, the computer system may not include the output unit 106. Furthermore, when the functions of the control devices 10, 10A, and 10B are realized by multiple computer systems, not all of these computer systems may be the computer systems shown in Figure 18. For example, some computer systems may not include at least one of the display unit 104, output unit 106, and input unit 102 shown in Figure 18.

[0064] The functions of the control devices 10, 10A, and 10B may be realized using a cloud system. In a cloud system, the hardware of the computer system and devices such as servers for each function can be separated as desired. For example, one computer system may have the functions of multiple devices, or multiple computer systems may have the functions of one device.

[0065] When the functions of the control devices 10, 10A, and 10B are realized using dedicated hardware, these are realized using a processing circuit 90 shown in Fig. 19. Fig. 19 is an explanatory diagram of dedicated hardware used to realize the functions of the control devices 10, 10A, and 10B according to the first to third embodiments. The processing circuit 90 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0066] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0067] For example, in the above description, the bottom and top surfaces of the workpiece 78 are assumed to be parallel planes, and an evaluation machining path having components in the X and Z directions is used as shown in FIG. 5. However, this is not a limitation. For example, the above technology can also be applied to machining using a workpiece whose bottom surface is a plane parallel to the XY plane and whose surface is inclined relative to the XY plane, and a machining path that moves straight in the X or Y direction. In either case, the tool 76 separates from the workpiece 78 during the machining path, and cutter marks 41 of different lengths can be formed depending on the reference position in the Z direction. [Explanation of symbols]

[0068] 1,10,10A,10B Control device, 2 Machine tool, 3 Evaluation workpiece, 11 Thermal displacement load operation unit, 12,12B Evaluation workpiece preparation unit, 13,13B Evaluation unit, 14 Pre-machining surface generation unit, 40,40-2 Machining path, 41,41-1,41-2 Cutter mark, 42-1,42-2 Thermal displacement, 71,71X,71Y,71Z Motor, 72,72X,72Y,72Z Guide mechanism, 73,73X,73Y,73Z Feed screw, 76 Tool, 77 Work table, 78 Workpiece, 80X,80Y,80Z Rotation angle detector, 83 Spindle, 90 Processing circuit, 92 Spindle control unit, 93 X-axis drive unit, 94 Y-axis drive unit, 95 Z-axis drive unit, 100 Machining system, 101 Control unit, 102 input unit, 103 memory unit, 104 display unit, 105 communication unit, 106 output unit, 107 system bus, A0, A1, A2 reference points, m0, m1, m2 length, P pitch distance, T ave average torque, Φ diameter.

Claims

1. A processing method for producing an evaluation workpiece for evaluating thermal displacement of a machine tool, comprising: a pre-machining surface generating step of performing flattening processing using a tool having a diameter equal to or less than half the pitch distance of the ball screw of the feed axis of the machine tool; a thermal displacement load operation step of operating the machine tool based on thermal displacement load information, which is information for reproducing thermal displacement caused by the machine tool performing actual machining; an evaluation machining step of operating the machine tool to machine the workpiece based on an evaluation machining path in which the amount of movement of the tool in a plane perpendicular to a first direction that is an evaluation direction of thermal displacement changes depending on the machining start position of the tool in the first direction that is an evaluation direction of thermal displacement; A processing method comprising:

2. The thermal displacement load information is information for operating the machine tool so that the average torque in the thermal displacement load operation step coincides with the average torque in the actual machining. The processing method according to claim 1 .

3. The thermal displacement load information is information for operating the machine tool based on the machining path of the actual machining. The processing method according to claim 1 .

4. the evaluation machining path has two types of components: a first movement amount in the first direction and a second movement amount in a second direction perpendicular to the first direction; The second movement amount is a movement amount obtained by multiplying the first movement amount by a predetermined magnification.

4. The processing method according to claim 1, wherein the processing method comprises:

5. The thermal displacement loading step and the evaluation processing step are repeated two or more times, a pick direction moving step of moving a feed axis of the machine tool in a third direction perpendicular to both the first direction and a second direction that is a traveling direction of the tool, every time the evaluation machining step is completed; Also includes 4. The processing method according to claim 1, wherein the processing method comprises:

6. an evaluation step of evaluating the thermal displacement caused by the thermal displacement loading operation step based on a length of a cutter mark formed on the workpiece by contacting the tool with the workpiece while executing the machining method according to any one of claims 1 to 3; Contains An evaluation method characterized by:

7. an evaluation step of evaluating a change over time in the thermal displacement caused by the thermal displacement loading operation step based on lengths of a plurality of cutter marks formed on the workpiece by contacting the tool with the workpiece while performing the machining method according to claim 5; Contains An evaluation method characterized by:

8. A control device for controlling a machine tool, a pre-machining surface generating unit that performs flattening processing using a tool having a diameter equal to or less than half the pitch distance of the ball screw of the feed axis of the machine tool; a thermal displacement load operating unit that operates the machine tool based on thermal displacement load information, which is information for reproducing thermal displacement that occurs when the machine tool performs actual machining; an evaluation workpiece preparation unit that prepares an evaluation workpiece for evaluating the thermal displacement of the machine tool by operating the machine tool to machine the workpiece based on an evaluation machining path in which the amount of movement of the tool that moves in contact with the workpiece in a plane perpendicular to the first direction changes depending on the machining start position of the tool in a first direction that is the evaluation direction of the thermal displacement; Equipped with A control device characterized by:

9. a pre-machining surface generation step for performing flattening processing using a tool having a diameter equal to or less than half the pitch distance of a ball screw of a feed axis of the machine tool; a thermal displacement load operation step of operating the machine tool based on thermal displacement load information, which is information for reproducing thermal displacement caused by the machine tool performing actual machining; an evaluation machining step of operating the machine tool to machine the workpiece based on an evaluation machining path in which the amount of movement of the tool in a plane perpendicular to a first direction that is an evaluation direction of thermal displacement changes depending on the machining start position of the tool in the first direction that is an evaluation direction of thermal displacement; a program for causing the machine tool to produce an evaluation workpiece for evaluating the thermal displacement by executing the program;

10. A workpiece for evaluation, which is produced by carrying out the processing method according to any one of claims 1 to 3.

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