Wire electrical discharge machine

Abstract

A wire electric discharge machine (100) has: a machining liquid control section (31) that temperature-controls a machining liquid (13), acquires a temperature difference between a first temperature at which a machining result is measured based on a temperature of the machining liquid (13) detected during machining and a second temperature at which machining is performed; a first control section that calculates a machining error between a size of the workpiece (W) after machining by a target size at the first temperature measurement based on the acquired temperature difference, a thermal expansion coefficient of the workpiece (W), and thermal expansion coefficients of an X-axis linear scale (2b) and a Y-axis linear scale (3b), corrects the target size in real time during machining by the calculated machining error, drives an X-axis table (2) having an X-axis drive section (2a) and a Y-axis table (3) having a Y-axis drive section (3a) based on an axis command value of the corrected target size; and a second control section that performs a pass / fail determination of machining performed by the corrected target size, and changes the axis command value in the case of failure.

Description

Technical Field

[0001] The present invention relates to a wire electrical discharge machine. Background Art

[0002] A wire EDM machine processes workpieces by generating an arc discharge between a wire electrode and the workpiece. In a wire EDM, applying a high voltage between the electrodes, or shortening the distance between the electrodes to increase the electric field strength, causes discharge due to dielectric breakdown, removing material from the workpiece. Wire EDM is typically performed in a liquid known as a machining fluid. Immersing the workpiece in the machining fluid suppresses temperature fluctuations and reduces machining precision defects caused by thermal expansion and contraction.

[0003] This isn't limited to wire-type EDM machines; machine tools are generally adjusted to produce good machining results in a 20°C ambient temperature. However, due to air conditioning costs and other factors, the machining environment is often not set at 20°C; only the temperature at which the machining results are measured is set at 20°C. Machining in this environment can cause problems: the difference between the machining temperature and the temperature at which the machining results are measured can cause thermal expansion and contraction in the workpiece, potentially preventing the machining results from meeting the desired dimensional tolerances.

[0004] In order to solve this problem, the following content is proposed in Patent Document 1, namely, the temperature of each axis scale for detecting the movement amount of each axis of the processing machine and the temperature of the workpiece are detected, and the difference in the expansion and contraction amount calculated from the reference temperature caused by the difference in their thermal expansion coefficients is used as the axis movement correction value to correct the error.

[0005] Patent Document 1: Japanese Patent No. 4803491 Summary of the Invention

[0006] Patent Document 1 states that in order to verify the pass / fail status of axis movement calibration, the temperature and dimensions of the workpiece must be measured on the actual machine. This requires replacing the spindle with a temperature probe or dimensional measurement probe, requiring additional time for measurement operations in addition to machining. Furthermore, if the calibration pass / fail result is not within the acceptable range, re-machining is required, resulting in reduced productivity.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a wire electric discharge machine capable of performing temperature correction and pass / fail determination of the correction in real time during machining, thereby improving productivity.

[0008] To solve the above problems and achieve the object, in the wire electric discharge machine of the present application, discharge is generated by applying a voltage between a workpiece immersed in a processing liquid in a processing tank and a wire electrode, the position of a moving shaft that relatively moves the wire electrode and the workpiece is detected by a position detector, the detected position of the moving shaft is fed back to a target value corresponding to a target dimension, the workpiece is processed, and the temperature of the position detector is synchronized with the temperature of the processing liquid. The wire electric discharge machine is characterized by having: a processing liquid control section that temperature-controls the processing liquid, acquires a temperature difference between a first temperature at which the processing result is measured based on the temperature of the processing liquid detected during processing and a second temperature at which processing is performed; a first control section that calculates a processing error between a dimension of the workpiece processed based on the target dimension at the first temperature and the target dimension based on the acquired temperature difference, a thermal expansion coefficient of the workpiece, and a thermal expansion coefficient of the position detector, corrects the target dimension in real time during processing by the calculated processing error, and drives the moving shaft by an axis command value based on the corrected target dimension; and a second control section that performs pass / fail determination of processing performed by the corrected target dimension, and changes the axis command value in the case of failure.

[0009] Effects of the Invention

[0010] According to the wire electric discharge machine of the present application, the following effects are obtained, that is, temperature correction and pass / fail determination of the correction can be performed in real time during processing, and productivity is improved. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a conceptual view showing a configuration example of a wire electric discharge machine according to an embodiment.

[0012] Figure 2 is a view for explaining a processing error in the wire electric discharge machine according to the embodiment.

[0013] Figure 3 is a view for explaining a calculation method of a temperature difference in the wire electric discharge machine according to the embodiment.

[0014] Figure 4 is a block diagram showing a configuration example of a control system of the wire electric discharge machine according to the embodiment.

[0015] Figure 5 is a view for explaining a method of deriving an interelectrode distance between a workpiece and a wire in the wire electric discharge machine according to the embodiment.

[0016] Figure 6 is a block diagram showing a configuration for deriving a dimension of a workpiece in the wire electric discharge machine according to the embodiment.

[0017] Figure 7 This is a block diagram showing a configuration for performing pass / fail determination of dimensions of a workpiece in a wire electric discharge machine according to an embodiment.

[0018] Figure 8 This is a block diagram showing the hardware configuration of a control system of a wire electrical discharge machine according to the embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, a wire electrical discharge machine according to an embodiment will be described in detail with reference to the drawings.

[0020] Implementation method.

[0021] Figure 1 This is a conceptual diagram illustrating an example configuration of a wire electrical discharge machine 100 according to an embodiment. The wire electrical discharge machine 100 processes a workpiece W by generating electrical discharge between a wire 1, serving as a wire electrode supported between a lower arm 14 and an upper arm 15, and the workpiece W. The wire electrical discharge machine 100 includes a support table 21, and a column 20 is mounted on the support table 21. The lower arm 14, which extends horizontally, is disposed below the column 20, and the upper arm 15, which extends horizontally, is disposed above the column 20.

[0022] A lower guide 24 is provided at the front end of the lower arm 14, and an upper guide 25 is provided at the front end of the upper arm 15. The thread 1 is held vertically by the lower guide 24 and the upper guide 25. The thread 1 is supplied by a thread feeding mechanism (not shown) and wound by a thread winding mechanism (not shown).

[0023] Machining fluid 13 is accumulated in the machining tank 10. A workpiece W is placed on a workpiece mounting table 11, and the area surrounding the workpiece W is filled with the machining fluid 13. The workpiece mounting table 11 is moved in the horizontal direction by a workpiece moving mechanism 4. The workpiece moving mechanism 4 includes: an X-axis table 2 having an X-axis drive unit 2a for moving the workpiece W in the X direction; and a Y-axis table 3 having a Y-axis drive unit 3a for moving the workpiece W in the Y direction. An X-axis linear scale 2b serving as an X-axis position detector for detecting the X-direction position of the X-axis table 2 is provided on the X-axis table 2. A Y-axis linear scale 3b serving as a Y-axis position detector for detecting the Y-direction position of the Y-axis table 3 is provided on the Y-axis table 3. In addition, the positions of the X-axis table 2 and the Y-axis table 3 may be detected by other position detectors, such as a detector for detecting the rotational speed of a ball screw.

[0024] The machining fluid control unit 31 controls the temperature of the machining fluid 13 in the machining tank 10. The power supply unit 32 applies voltage to the wire 1 and the workpiece W. Discharge occurs between the wire 1 and the workpiece W, thereby removing the workpiece W.

[0025] In the above configuration, the workpiece W is moved in the XY directions, but the wire 1 may be moved in the XY directions. That is, the wire 1 moves relative to the workpiece W in the XY directions, thereby processing the workpiece W into a desired shape.

[0026] The control unit 30 controls the driving of the machining fluid control unit 31 , the power supply unit 32 , the X-axis driving unit 2 a , and the Y-axis driving unit 3 a .

[0027] The detection values ​​of the X-axis linear scale 2b and the Y-axis linear scale 3b are fed back to the control unit 30. In the wire EDM 100, the X-axis linear scale 2b and the Y-axis linear scale 3b, acting as position detectors, detect the position of the movable axis that relatively moves the wire 1 and the workpiece W. The detected position of the movable axis is fed back to the target dimension as a target value instructed by the control unit 30, and machining of the workpiece W is performed. In this case, the movable axis that relatively moves the wire 1 and the workpiece W corresponds to the X-axis table 2 and the Y-axis table 3. However, in a configuration in which the wire 1 is moved in the XY directions, the mechanism for moving the wire 1 in the XY directions corresponds to the movable axis.

[0028] Figure 2 1 is a diagram for explaining machining errors in the wire electric discharge machine 100 according to the embodiment. Figure 2 In , □ represents the size of the square. Figure 2 In the figure, the solid square represents the target size Sa of the workpiece W, the dotted square outside the solid line represents the size Sb of the workpiece W after processing in an environment of (20+ΔTa)℃, and the dotted square inside the solid line represents the size Sc of the workpiece W after processing measured at 20℃.

[0029] When machining with the wire EDM 100, if Sa is set as the target machining dimension, then if the temperature Ta1 when measuring the machining result and the temperature Ta2 during machining are consistent, no correction is required and the target dimension Sa can be directly output as the target value. In the wire EDM 100, since the workpiece W is immersed in the machining fluid 13, the temperature Ta2 during machining corresponds to the temperature of the machining fluid 13. The temperature Ta1 when measuring the machining result corresponds to the first temperature, and the temperature Ta2 during machining corresponds to the second temperature. However, the temperature Ta1 when measuring the machining result is generally 20°C. If there is a temperature difference ΔTa between the temperature Ta2 during machining and the temperature Ta1 (=20°C), the X-axis linear scale 2b and the Y-axis linear scale 3b, which serve as the reference for axis movement in the XY directions, expand due to their respective thermal expansion coefficients Ea. Therefore, when a target value corresponding to the target dimension Sa is specified, the dimension Sb of the workpiece W after machining is expressed as follows (1):

[0030] Sb=Sa+ΔTa×Ea (1)

[0031] The dimension Sc of the workpiece W after the processing is measured in an environment of temperature Ta1 (=20° C.) shrinks according to the thermal expansion coefficient Eb of the workpiece W, and is expressed by the following formula (2).

[0032] Sc=Sb-ΔTa×Eb · · · (2)

[0033] Therefore, a machining error Ha between a target dimension Sa and a dimension Sc measured in a 20° C. environment of the workpiece W after machining is expressed by the following formula (3).

[0034] Ha=Sa-Sc=ΔTa×(Eb-Ea) · · · (3)

[0035] Specifically, during machining, the temperature difference ΔTa, the thermal expansion coefficients Ea of the X-axis linear scale 2b and the Y-axis linear scale 3b, and the thermal expansion coefficient Eb of the workpiece W are detected in real time and substituted into equation (3), thereby calculating the machining error Ha in real time. Furthermore, as shown in equation (4), a correction is performed by adding the machining target dimension Sa to the machining error Ha, and the corrected target dimension Sa′ is calculated. This is then commanded in real time, thereby enabling real-time, error-free machining.

[0036] Sa′=Sa+Ha · · · (4)

[0037] Figure 3This is a diagram for explaining a method for calculating the temperature difference ΔTa in the wire electric discharge machine 100 according to the embodiment. The machining fluid control unit 31 controls the temperature of the machining fluid 13 returned from the machining tank 10 and supplies the machining fluid 13, thereby controlling the machining fluid 13 to a constant temperature. In addition, the machining fluid control unit 31 derives the temperature difference ΔTa based on the temperature of the machining fluid 13 detected during machining. Figure 3 As shown, the control unit 30 outputs a temperature command value of 20°C + Tb to the machining fluid control unit 31. Based on the temperature command value 20°C + Tb, the machining fluid control unit 31 controls the temperature of the machining fluid 13 supplied to the machining tank 10. Consequently, the machining fluid 13 supplied from the machining fluid control unit 31 to the machining tank 10 is controlled to 20°C + Tc. The machining fluid 13 in the machining tank 10 is cooled and heated by the supplied machining fluid 13 before returning to the machining fluid control unit 31. The temperature of the machining fluid 13 returning from the machining tank 10 to the machining fluid control unit 31 is 20°C + Td.

[0038] In the in-line EDM 100, the workpiece W is immersed in the machining fluid 13, whose temperature is controlled by the machining fluid control unit 31. The temperature of the workpiece W is synchronized with the temperature of the machining fluid 13. The temperature of the machining fluid 13 during machining is synchronized with the temperature of the machining fluid 13 returned from the machining tank 10 to the machining fluid control unit 31, which is 20°C + Td. Therefore, the temperature difference ΔTa is considered to be the same as the temperature Td obtained by subtracting 20°C from the temperature of the machining fluid 13 returned from the machining tank 10 to the machining fluid control unit 31, which is 20°C + Td. Therefore, the temperature difference ΔTa can be derived by the machining fluid control unit 31 by detecting the temperature of the machining fluid 13 returned from the machining tank 10 to the machining fluid control unit 31, which is 20°C + Td, and subtracting 20°C from the detected temperature. As described above, the machining fluid control unit 31 detects the temperature of the machining fluid 13 returned from the machining tank 10 during machining, and based on the detected temperature, obtains in real time the temperature difference ΔTa between the first temperature Ta1 when the machining result is measured and the second temperature Ta2 when machining.

[0039] The temperature command value 20°C + Tb output from the control unit 30 to the machining fluid control unit 31 is set to be equal to, for example, the outside air temperature Te. As the temperature command value 20°C + Tb, a temperature that is changed by a constant temperature from the outside air temperature Te can be used.

[0040] In the in-line EDM 100, the temperatures of the X-axis linear scales 2b and Y-axis linear scales 3b are synchronized with the temperature of the machining fluid 13. Specifically, in the in-line EDM 100, the temperatures of the machining fluid 13, the temperature of the workpiece W, and the temperatures of the X-axis linear scales 2b and Y-axis linear scales 3b are synchronized. For example, by flowing the machining fluid 13 through the module on which the X-axis linear scales 2b and Y-axis linear scales 3b are mounted, the temperatures of the X-axis linear scales 2b and Y-axis linear scales 3b are synchronized with the temperature command value 20°C + Tb of the machining fluid 13. Furthermore, if the temperature command value 20°C + Tb output from the control unit 30 to the machining fluid control unit 31 is set to be equal to the outside air temperature Te, it is assumed that the temperatures of the X-axis linear scales 2b and Y-axis linear scales 3b are equal to the outside air temperature Te, thereby synchronizing the temperatures of the X-axis linear scales 2b and Y-axis linear scales 3b with the temperature of the machining fluid 13.

[0041] Furthermore, in the wire EDM 100, during machining, the voltage Va supplied from the power supply unit 32 to the workpiece W and the wire 1, as well as the discharge distance Sh over which discharge can occur between the workpiece W and the wire 1, need to be varied depending on the material of the workpiece W. Therefore, material-specific control parameters, including the voltage Va and discharge distance Sh, are determined based on the material of the workpiece W. Therefore, by adding the material-specific value of the thermal expansion coefficient Eb of the workpiece W to the material-specific control parameters, the thermal expansion coefficient Eb of the workpiece W can be determined during machining.

[0042] Furthermore, the thermal expansion coefficient Ea of the X-axis linear scale 2b and the Y-axis linear scale 3b is constant regardless of the material of the workpiece W. Therefore, if it is set as a control parameter independent of the material, the thermal expansion coefficient Eb can be obtained during machining.

[0043] Figure 4 This is a block diagram showing a configuration example of a control system of the wire discharge machine 100 according to the embodiment. The control system of the wire discharge machine 100 includes a control unit 30, a machining fluid control unit 31, a control parameter storage unit 33, a material-based control parameter determination unit 34, a machining error detection unit 35, a target size output unit 36, and an axis command value control unit 37. The control unit 30, the control parameter storage unit 33, the material-based control parameter determination unit 34, the machining error detection unit 35, the target size output unit 36, and the axis command value control unit 37 correspond to the first control unit. Figure 4 In FIG. 1 , a part of the X-axis driving unit 2 a and the Y-axis driving unit 3 a are omitted and are shown as driving units 2 a and 3 a .

[0044] The control unit 30 controls the components of the wire electric discharge machine 100 based on the NC program. The NC program includes a target dimension Sa of machining the workpiece W and a material of the workpiece W.

[0045] The control parameter storage section 33 stores control parameters that are independent of the material. Among the control parameters stored in the control parameter storage section 33, there are thermal expansion coefficients Eaof the X-axis linear scale 2b and the Y-axis linear scale 3b.

[0046] The material-specific control parameter decision section 34 stores, for each material of the workpiece W, material-specific control parameters including the voltage Va supplied to the workpiece W, the discharge distance Sh, and the thermal expansion coefficient Eb of the workpiece W.

[0047] If the processing is started, the control section 30 outputs a control parameter output instruction to the control parameter storage section 33, outputs the material information of the workpiece W to the material-specific control parameter decision section 34, and outputs a target temperature instruction Tb to the processing liquid control section 31. In addition, the control section 30 outputs the target size Sa of the workpiece W to the target size output section 36.

[0048] The control parameter storage section 33 outputs the thermal expansion coefficients Eaof the X-axis linear scale 2b and the Y-axis linear scale 3b to the processing error detection section 35. The material-specific control parameter decision section 34 outputs the thermal expansion coefficient Eb of the workpiece W corresponding to the material included in the input material information to the processing error detection section 35. In addition, the material-specific control parameter decision section 34 outputs the discharge distance Sh corresponding to the material included in the input material information to the axis command value control section 37. In addition, the material-specific control parameter decision section 34 outputs the voltage Va corresponding to the material included in the input material information to the power supply section 32. The processing liquid control section 31 controls so that the temperature of the processing liquid 13 supplied to the processing tank 10 becomes 20°C + Tb in accordance with the input target temperature instruction Tb. In addition, the processing liquid control section 31 detects the temperature 20°C + Td of the processing liquid 13 returned from the processing tank 10 to the processing liquid control section 31 as described in the foregoing, calculates the temperature Td obtained by subtracting 20°C from the detected temperature 20°C + Td, and outputs the temperature Td to the processing error detection section 35 as the aforementioned temperature difference ΔTa. Figure 3

[0049] The processing error detection section 35 calculates the processing error Ha using the input thermal expansion coefficients Ea, Eb and the temperature difference ΔTa and the aforementioned formula (3). The processing error detection section 35 outputs the calculated processing error Ha to the target size output section 36. The target size output section 36 calculates the corrected target size Sa' using the input target size Sa and the processing error Ha and the aforementioned formula (4).

[0050] ​The target size output section 36 outputs the calculated corrected target size Sa' to the axis command value control section 37. The axis command value control section 37 decides the axis command value Sg required to process the target size Sa' based on the target size Sa' and the discharge distance Sh. The target size output section 36 outputs the axis command value Sg to the X-axis drive section 2a and the Y-axis drive section 3a, and drives and controls the X-axis table 2 and the Y-axis table 3.

[0051] As described above, in the wire electric discharge machine 100, the processing error Ha is calculated based on the thermal expansion coefficients Ea, Eb and the temperature difference ΔTa, the target size Sa' corrected in such a manner as to cancel the processing error Ha is decided, and the X-axis table 2 and the Y-axis table 3 are driven by the axis command value Sg decided in accordance with the target size Sa' and the discharge distance Sh, whereby a processing result without error is obtained at the temperature Tal at which the processing result is measured.

[0052] Next, a structure for determining whether or not the processing result obtained by the correction of the target size is acceptable will be described. Figure 5 is a diagram for explaining a method for deriving the discharge distance Hc between the workpiece W and the wire 1, i.e., the interelectrode distance, in the wire electric discharge machine 100 according to the embodiment. Figure 6 is a block diagram showing a structure for deriving the size Se of the workpiece W in the wire electric discharge machine 100 according to the embodiment. Figure 7 is a block diagram showing a structure for determining whether or not the size of the workpiece W is acceptable in the wire electric discharge machine 100 according to the embodiment. In Figure 6 , Figure 7 In FIGS. 10 to 12, a part of the X-axis table 2 and the Y-axis table 3 is omitted and illustrated as the table 2, 3, and a part of the X-axis linear scale 2b and the Y-axis linear scale 3b is omitted and illustrated as the scale 2b, 3b. In addition, in FIGS. 10 to 12, a part of the X-axis drive section 2a and the Y-axis drive section 3a is omitted and illustrated as the drive section 2a, 3a. Figure 7 In FIGS. 10 to 12, a part of the X-axis table 2 and the Y-axis table 3 is omitted and illustrated as the table 2, 3, and a part of the X-axis linear scale 2b and the Y-axis linear scale 3b is omitted and illustrated as the scale 2b, 3b. In addition, in FIGS. 10 to 12, a part of the X-axis drive section 2a and the Y-axis drive section 3a is omitted and illustrated as the drive section 2a, 3a. Figure 7 The workpiece size calculation section 41, the target size temperature conversion section 42, the size comparison section 43, and the axis command value control section 37 shown in FIG. 9 correspond to the second control section.

[0053] As described above, in the wire electric discharge machine 100, the processing error Ha is calculated based on the thermal expansion coefficients Ea, Eb and the temperature difference ΔTa, the target size Sa' corrected in such a manner as to cancel the processing error Ha is decided, and the X-axis table 2 and the Y-axis table 3 are driven by the axis command value Sg decided in accordance with the target size Sa' and the discharge distance Sh, whereby a processing result without error is obtained at the temperature Tal at which the processing result is measured. Figure 5As shown in FIG. 1 , in order to determine the size Se of the workpiece W, the inter-electrode distance Hc between the workpiece W and the wire 1 is detected based on the waveform of the discharge voltage generated between the workpiece W and the wire 1. Specifically, the distance calculation unit 40 calculates the resistance R between the workpiece W and the wire 1 using the voltage drop V caused by the discharge current during discharge and the discharge current value A, as shown in the following equation (5).

[0054] R=V / A · · · (5)

[0055] Furthermore, since the space between the workpiece W and the wire 1 is filled with the machining fluid 13 having a known resistivity ρ, the inter-electrode distance Hc can be obtained by the following equation (6).

[0056] Hc=R / ρ (6)

[0057] exist Figure 5 , it is shown that the inter-electrode distance Hc is obtained when the voltage V is decreased, and that a closer inter-electrode distance Hc′ is obtained when the voltage V′ is decreased even further.

[0058] like Figure 6 As shown, the workpiece size calculation unit 41 calculates the size Se of the workpiece W by subtracting the inter-pole distance Hc from the current axis position Sd as shown in the following formula (7), based on the inter-pole distance Hc calculated by the distance calculation unit 40 and the current axis position Sd measured by the X-axis linear scale 2b and the Y-axis linear scale 3b.

[0059] Se=Sd-Hc · · · (7)

[0060] In addition, if Figure 7 As shown, the target size temperature conversion unit 42 obtains the converted target size Sb′ obtained by converting the corrected target size Sa′ into the temperature Ta2 during machining based on the corrected target size Sa′ calculated by the target size output unit 36, the thermal expansion coefficient Ea of the X-axis linear scale 2b and the Y-axis linear scale 3b stored in the control parameter storage unit 33, and the temperature difference ΔTa calculated by the machining fluid control unit 31, as shown in the following formula (8).

[0061] Sb′=Sa′+ΔTa×Ea · · · (8)

[0062] In addition, Figure 7 In the workpiece size calculation unit 41, as shown in FIG. Figure 6 As described above, the dimension Se of the workpiece W is calculated based on the inter-electrode distance Hc obtained by the distance calculation unit 40 and the current axis position Sd measured by the X-axis linear scale 2b and the Y-axis linear scale 3b.

[0063] The dimension comparison unit 43 compares the dimension Se of the workpiece W calculated by the workpiece dimension calculation unit 41 with the temperature-corrected target dimension Sb′ calculated by the target dimension temperature conversion unit 42, and determines whether the machining result obtained through target dimension correction is acceptable. The dimension comparison unit 43 determines whether the difference between the dimension Se of the workpiece W and the temperature-corrected target dimension Sb′ is within an acceptable range, and outputs the determination result to the axis command value control unit 37.

[0064] If the determination result is within the allowable range, the axis command value control unit 37 determines that the machining error Ha calculated using equation (3) is acceptable, and correction is terminated. However, if the determination result is not within the allowable range, the axis command value control unit 37 changes the current axis command value Sg, thereby changing the axis position Sd, and controls the difference between the size Se of the workpiece W and the target size Sb′ after temperature correction to within the allowable range. In other words, if the size Se of the workpiece W is larger than the target size Sb′, the axis command value is changed to Sg′, thereby setting the axis position to an axis position Sd′ closer to the workpiece W, and controlling the size of the workpiece W to a smaller size Se′. If the size Se of the workpiece W is smaller than the target size Sb′, the axis command value is changed to Sg″, thereby setting the axis position to an axis position Sd″ farther away from the workpiece W, and controlling the size of the workpiece W to a larger size Se″. By repeating this control until the determination result converges within the allowable range, machining can be performed without machining errors.

[0065] As described above, according to the embodiment, the machining fluid control unit 31 derives the temperature difference ΔTa based on the temperature of the machining fluid 13 during machining, calculates the machining error Ha based on the thermal expansion coefficients Ea and Eb and the temperature difference ΔTa, and determines the target dimension Sa' corrected to offset the machining error Ha. The X-axis table 2 and the Y-axis table 3 are driven based on the axis command value Sg determined based on the determined target dimension Sa'. This allows for error-free machining results to be obtained in real time at the temperature Ta1 at which the machining results are measured. Consequently, temperature correction is performed in real time during machining, improving machining productivity. Furthermore, the dimension Se of the workpiece W calculated by the workpiece dimension calculation unit 41 and the temperature-corrected target dimension Sb' calculated by the target dimension temperature conversion unit 42 are compared to determine the pass / fail status of the machining results obtained through target dimension correction. This allows for real-time determination of whether temperature correction of axis movement has been performed correctly. Consequently, temperature correction and correction pass / fail determination can be performed in real time during machining, improving productivity. Furthermore, when the pass / fail determination is negative, the current axis position Sd is changed, and therefore a processed workpiece free from processing errors can be efficiently produced.

[0066] Here, the Figure 4 The control unit 30, control parameter storage unit 33, material classification control parameter determination unit 34, machining error detection unit 35, target size output unit 36 ​​and axis command value control unit 37 are shown. Figure 7 The hardware configuration of the control system including the distance calculation unit 40, the workpiece size calculation unit 41, the target size temperature conversion unit 42 and the size comparison unit 43 will be described. Figure 8 It is a block diagram showing the hardware configuration of a control system of the wire electrical discharge machine 100 according to the embodiment.

[0067] The control system of the wire EDM 100 can be controlled by including Figure 8 The hardware structure 406 includes a computing device 404 and a storage device 405. The computing device 404 is, for example, a CPU (Central Processing Unit), a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). The storage device 405 is, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory).

[0068] The structures shown in the above embodiments represent part of the contents of the present invention and can be combined with other well-known technologies. Without departing from the scope of the present invention, appropriate combinations, or partial omissions and changes of the structures can be made.

[0069] Description of the label

[0070] 1 line, 2 X-axis worktable, 2a X-axis drive unit, 2b X-axis linear scale, 3 Y-axis worktable, 3a Y-axis drive unit, 3b Y-axis linear scale, 4 workpiece moving mechanism, 10 machining tank, 11 workpiece mounting table, 13 machining fluid, 14 lower arm, 15 upper arm, 20 column, 21 support table, 24 lower guide unit, 25 upper guide unit, 30 control unit, 31 machining fluid control unit, 32 power supply unit, 33 control parameter storage unit, 34 material classification control parameter determination unit, 35 machining error detection unit, 36 target size output unit, 37 axis command value control unit, 40 distance calculation unit, 41 workpiece size calculation unit, 42 target size temperature conversion unit, 43 size comparison unit, 100 wire electric discharge machine, 404 computing device, 405 storage device, 406 hardware structure.

Claims

1. A wire electrical discharge machine that generates discharge by applying a voltage between a workpiece immersed in a machining fluid in a machining tank and a wire electrode, detects the position of a moving axis that relatively moves the wire electrode and the workpiece using a position detector, feeds back the detected position of the moving axis to a target value corresponding to a target dimension, and machines the workpiece, wherein the temperature of the position detector is synchronized with the temperature of the machining fluid. The wire electric discharge machine is characterized by: a machining fluid control unit that controls the temperature of the machining fluid and obtains a temperature difference between a first temperature, which is a temperature at the time of measuring a machining result based on the temperature of the machining fluid detected during machining, and a second temperature, which is a temperature during machining; a first control unit that calculates a machining error between a dimension of the workpiece machined to the target dimension measured at the first temperature and the target dimension based on the acquired temperature difference, the thermal expansion coefficient of the workpiece, and the thermal expansion coefficient of the position detector, corrects the target dimension in real time during machining using the calculated machining error, and drives the movable axis using an axis command value based on the corrected target dimension; and The second control unit determines whether the machining performed to the corrected target size is acceptable or not, and changes the axis command value if the determination is negative.

2. The wire electric discharge machine according to claim 1, wherein The axis command value is determined based on the corrected target size and a discharge distance set according to the workpiece.

3. The wire electric discharge machine according to claim 1, wherein The machining fluid control unit supplies the machining fluid after temperature control to a machining tank, detects the temperature of the machining fluid returned from the machining tank during machining, and acquires the temperature difference based on the detected temperature.

4. The wire electric discharge machine according to claim 1, wherein The machining fluid is passed through the module where the position detector is installed.

5. The wire electric discharge machine according to any one of claims 1 to 4, characterized in that The second control unit includes: a distance calculating unit for calculating an inter-electrode distance, that is, a distance between the workpiece and the wire electrode; a workpiece size calculation unit that calculates the size of the workpiece after processing at the second temperature based on the current position of the movable axis and the inter-electrode distance detected by the position detector; a target size temperature conversion unit for calculating the converted target size obtained by converting the corrected target size to the second temperature using the temperature difference and a thermal expansion coefficient of the position detector; as well as A size comparison unit calculates a size difference between the size of the workpiece calculated by the workpiece size calculation unit and the converted target size, and changes the axis command value until the size difference enters the allowable range if the size difference does not enter the allowable range.

6. The wire electric discharge machine according to claim 5, wherein The inter-electrode distance is obtained based on a drop voltage of a voltage applied to the workpiece and the wire electrode during discharge.

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