Reference displacement amount correction device and numerical control device

Abstract

Provided are a reference displacement amount correction device and a numerical control device that are capable of converting an output voltage of a gap sensor into a distance with high accuracy, while reducing processing time. A reference displacement amount correction device according to the present invention is provided with: a data storage unit that stores an output voltage of a gap amount measurement unit, corresponding to a gap amount that is a distance from a workpiece surface; a correlation table generation unit that generates in advance a correlation table between output voltages and gap amounts stored in the data storage unit; an approximate expression calculation unit that calculates in advance an approximate expression indicating the relationship between the output voltages and the gap amounts stored in the data storage unit; an acquisition unit that acquires a reference displacement amount indicating a reference for a displacement amount that is a distance from a reference position set in the vicinity of the workpiece surface; a reference output voltage calculation unit that calculates a reference output voltage indicating an output voltage corresponding to the reference displacement amount on the basis of the correlation table; a calculational displacement amount calculation unit that calculates a calculational displacement amount indicating a displacement amount corresponding to the reference output voltage on the basis of the approximate expression; and a setting unit that sets the calculational displacement amount as a new reference displacement amount.

Description

Reference Displacement Correction Device and Numerical Control Device

[0001] The present disclosure relates to a reference displacement correction device and a numerical control device.

[0002] In a conventional laser processing device, the distance between the processing head and the surface of the processing object (referred to as the gap amount) is measured by a gap sensor or the like, and laser processing is performed while maintaining a constant gap amount. The voltage corresponding to the gap amount output from the gap sensor is input to a numerical control device or the like, and the gap amount is detected by the numerical control device.

[0003] For example, a technique has been proposed in which a numerical control device samples and stores the output voltage of a gap sensor, and detects the gap amount based on the stored sampling data (see, for example, Patent Document 1). In this technique, the numerical control device samples and stores the output voltage of the gap sensor at regular intervals.

[0004] Japanese Patent Application Laid-Open No. 1-78691

[0005] In a numerical control device, the output voltage of the gap sensor is converted into a distance. As a method for converting the output voltage of the gap sensor into a distance, for example, there are a table method and an approximation formula method.

[0006] In the table method, the numerical control device measures the output voltage of the gap sensor at each distance in advance and stores it as a table. The numerical control device converts the output voltage of the gap sensor into a distance based on the table.

[0007] In the approximation formula method, the numerical control device measures the output voltage of the gap sensor at each distance in advance, calculates an approximation formula, and stores the approximation formula. The numerical control device converts the output voltage of the gap sensor into a distance based on the approximation formula.

[0008] In the table method, the output voltage of the gap sensor can be converted into a distance with high accuracy. However, in the table method, the processing time for searching the table increases in proportion to the number of measurement points, so the processing time when converting the output voltage of the gap sensor into a distance may increase.

[0009] In the approximation method, the distance can be converted simply by substituting the gap sensor's output voltage into an approximation formula, thus reducing the processing time when converting the gap sensor's output voltage to distance. However, the approximation method may introduce errors when converting the gap sensor's output voltage to distance due to approximation errors.

[0010] Therefore, in numerical control devices, there is a need for a technology that can convert the output voltage of a gap sensor into distance with high accuracy while suppressing processing time.

[0011] One aspect of the present disclosure is a reference displacement correction device comprising: a data storage unit that stores the output voltage of a gap amount measuring unit corresponding to a gap amount which is the distance from the work surface; a correlation table generation unit that generates a correlation table in advance between the output voltage stored in the data storage unit and the gap amount; an approximation formula calculation unit that calculates an approximation formula in advance that shows the relationship between the output voltage stored in the data storage unit and the gap amount; an acquisition unit that acquires a reference displacement amount which is the distance from a reference position set near the work surface that indicates a reference for the displacement amount; a reference output voltage calculation unit that calculates a reference output voltage which indicates the output voltage corresponding to the reference displacement amount based on the correlation table; a calculated displacement amount calculation unit that calculates a calculated displacement amount which indicates the displacement amount corresponding to the reference output voltage based on the approximation formula; and a setting unit that sets the calculated displacement amount as a new reference displacement amount.

[0012] One aspect of the present disclosure is a numerical control device comprising: a reference displacement amount correction device described above; a displacement amount calculation unit for calculating the displacement amount; a gap control unit for controlling the gap amount so that the displacement amount calculated by the displacement amount calculation unit becomes the calculated displacement amount; and an axis control unit for controlling the drive axis of a machining head based on the gap amount controlled by the gap control unit.

[0013] This figure shows the configuration of a numerical control device according to one embodiment of the present disclosure. This figure illustrates the switching of the measurement interval in the numerical control device according to this embodiment. This figure shows an example of a correlation table according to this embodiment. This graph shows an example of the relationship between the output voltage of the gap sensor according to this embodiment and distance. This graph shows an example of an approximation formula according to this embodiment. This flowchart shows an example of a method for correcting the reference displacement of the reference displacement correction device according to this embodiment. This graph shows an example of the relationship between the output voltage of the gap sensor according to this embodiment and distance.

[0014] Hereinafter, one embodiment of this disclosure will be described in detail with reference to the drawings.

[0015] A numerical control device 1 according to one embodiment of this disclosure detects the gap amount, which is the distance between the processing head 2 of the laser processing apparatus and the workpiece surface. Specifically, the numerical control device 1 according to this embodiment detects the gap amount based on a voltage corresponding to the gap amount output from a gap sensor (not shown) provided on the processing head 2. Laser processing in this embodiment is performed while maintaining a constant gap amount based on the detected gap amount.

[0016] The gap measurement unit 21 of the machining head 2 acquires the output voltage of a gap sensor (not shown) attached to the tip of the machining head 2, for example. The acquired output voltage is transmitted to the data storage unit 11 and the displacement calculation unit 31, which will be described later.

[0017] Any gap sensor that can provide an output voltage or current can be used; for example, a capacitive gap sensor is used. This gap sensor moves together with the machining head 2 and outputs a voltage corresponding to the gap between the tip of the machining head 2 and the workpiece surface.

[0018] A laser oscillator (not shown) is connected to the processing head 2. The laser oscillator generates laser light and supplies it to the processing head 2 via an optical path. The beam-shaped laser light emitted from the processing head 2 processes the workpiece. The numerical control device 1 according to this embodiment controls a drive shaft (not shown) to move the processing head 2 in the horizontal direction (X-axis and Y-axis direction) and the vertical direction (Z-axis direction) relative to the workpiece.

[0019] Figure 1 shows the configuration of a numerical control device 1 according to one embodiment of the present disclosure. As shown in Figure 1, the numerical control device 1 comprises a reference displacement amount correction device 10, a displacement amount calculation unit 31, a gap control unit 32, and an axis control unit 33. The reference displacement amount correction device 10 comprises a data storage unit 11, a correlation table generation unit 12, an approximation formula calculation unit 13, an acquisition unit 14, a reference output voltage calculation unit 15, a calculated displacement amount calculation unit 16, and a setting unit 17. The numerical control device 1 may be configured by a computer having, for example, a CPU, memory, etc.

[0020] The numerical control device 1 and the reference displacement amount correction device 10 can be composed of one or more control units and memory units. Here, the control unit is a processor such as a CPU (Central Processing Unit), and it realizes various functions by executing programs stored in the memory unit. The memory unit consists of a ROM (Read Only Memory) that stores the OS (Operating System) and application programs, a RAM (Random Access Memory), and a storage device such as a hard disk drive or SSD (Solid State Drive) that stores various other information.

[0021] The data storage unit 11 stores the output voltage of the gap amount measuring unit 21, which corresponds to the gap amount, which is the distance from the workpiece surface. In this embodiment, the data storage unit 11 is provided within the numerical control device 1, and embedded software such as a numerical control device has limitations in storage capacity. Therefore, the data storage unit 11 can only store the output voltage of the gap amount measuring unit 21 for a limited amount of data.

[0022] More specifically, the data storage unit 11 stores multiple sampling data for correlation table generation generated by the correlation table generation unit 12 (described later) and for approximation formula calculation calculated by the approximation formula calculation unit 13. Specifically, the data storage unit 11 associates sampling data of the gap amount and output voltage when the machining head 2 and gap sensor are raised in stages from the workpiece surface, and stores this as sampling data for correlation table generation and approximation formula calculation.

[0023] The correlation table generation unit 12 pre-generates a correlation table between the output voltage and the gap amount stored in the data storage unit 11. Specifically, it pre-generates a correlation table between the output voltage and the gap amount based on the sampling data for correlation table generation stored in the data storage unit 11. Linear approximation is performed between each sampling data point, and the resulting approximation line is used in the calculation of the reference output voltage in the reference output voltage calculation unit 15, which will be described later.

[0024] The approximation formula calculation unit 13 pre-calculates an approximation formula. The approximation formula shows the relationship between the output voltage and the gap amount stored in the data storage unit 11. Specifically, based on the sampling data for calculating the approximation formula stored in the data storage unit 11 described above, an approximation formula showing the relationship between the output voltage and the gap amount is pre-calculated. Generally, capacitive sensors are often used as gap sensors, in which case the approximation formula is preferably a -1st degree equation. However, generally, with capacitive gap sensors, the output voltage of the gap sensor is often adjusted via a regulator before being input to the numerical control device, rather than directly inputting the output voltage of the gap sensor to the numerical control device. In this case, the approximation formula is preferably a polynomial approximation. For example, the approximation formula is preferably a polynomial of degree 1 to 3. When the approximation formula is a polynomial approximation, even when the output voltage of the gap sensor is adjusted via a regulator before being input to the numerical control device 1, the output voltage of the gap sensor can be converted to distance with high accuracy using the polynomial approximation formula.

[0025] The acquisition unit 14 acquires a reference displacement amount. The reference displacement amount indicates the basis for the displacement amount. The displacement amount is the distance from the reference position, which is set near the workpiece surface. The reference displacement amount is set, for example, by the user. The reference displacement amount indicates, for example, the target gap amount.

[0026] The reference output voltage calculation unit 15 calculates the reference output voltage based on the correlation table. The reference output voltage indicates the output voltage corresponding to the reference displacement. The reference output voltage calculation unit 15 calculates the reference output voltage only when the reference displacement is set. In other words, the reference output voltage calculation unit 15 does not calculate the reference output voltage during gap amount control. Therefore, the processing load on the reference displacement correction device 10 can be reduced during gap amount control (laser processing).

[0027] The displacement calculation unit 16 calculates the displacement amount based on an approximation formula. The calculated displacement amount indicates the displacement amount corresponding to the reference output voltage. Specifically, the displacement calculation unit 16 calculates the displacement amount by substituting the reference output voltage into the approximation formula. The calculated displacement amount corresponds to the value obtained by converting the reference displacement amount acquired by the acquisition unit 14 into a reference displacement amount for the approximation formula.

[0028] The setting unit 17 sets the calculated displacement amount as the new reference displacement amount. In other words, the setting unit 17 sets the reference displacement amount (calculated displacement amount) converted for the approximation formula as the new reference displacement amount.

[0029] The displacement calculation unit 31 calculates the displacement, which is the distance from a reference position set near the workpiece surface, based on the output voltage newly measured by the gap measurement unit 21 and the approximation formula previously calculated by the approximation formula calculation unit 13. Specifically, the displacement calculation unit 31 calculates the displacement, which is the distance from a reference position set near the workpiece surface, by determining the gap by substituting the output voltage newly measured by the gap measurement unit 21 into the approximation formula calculated by the approximation formula calculation unit 13. Since the displacement calculation unit 31 determines the gap using an approximation formula, the processing time can be shortened compared to when the gap is determined using a correlation table.

[0030] The gap control unit 32 controls the gap amount so that the displacement amount calculated by the displacement amount calculation unit 31 becomes the calculated displacement amount. That is, the gap control unit 32 controls the gap amount so that the gap amount between the machining head 2 and the workpiece surface is constant. Because the gap control unit 32 controls the gap amount so that the displacement amount calculated by the displacement amount calculation unit 31 becomes the calculated displacement amount converted for the approximation formula, it is possible to reduce the error between the reference position and the actual distance between the workpiece and the machining head caused by the approximation error that occurs when using the approximation formula. As a result, the output voltage of the gap sensor can be converted to distance with high accuracy.

[0031] The shaft control unit 33 controls the drive shaft of the machining head 2 based on the gap amount controlled by the gap control unit 32. This allows the machining head 2 to move while maintaining a constant gap amount, enabling laser machining.

[0032] Figure 2 is a diagram illustrating the switching of the measurement interval in the numerical control device 1 according to this embodiment. More specifically, Figure 2 shows an example of measuring the relationship between the output voltage and the gap amount while switching the measurement interval when generating a correlation table in the correlation table generation unit 12 and when calculating an approximation formula in the approximation formula calculation unit 13.

[0033] In the example shown in Figure 2, first, the output voltage of the gap sensor is measured when the machining head 2 is positioned at the reference point. Next, the output voltage of the gap sensor is measured when the machining head 2 is raised by a distance X1, and then the output voltage of the gap sensor is measured again when the machining head 2 is raised by another distance X1. That is, the output voltage of the gap sensor is measured at measurement intervals X1. In this embodiment, the distance X1 is 0.3 mm.

[0034] Next, the output voltage of the gap sensor is measured when the machining head 2 is raised by a distance X2. That is, the measurement interval is switched from X1 to X2 and the output voltage of the gap sensor is measured. In this embodiment, the distance X2 is 0.4 mm.

[0035] Next, the output voltage of the gap sensor is measured when the machining head 2 is raised by a distance X3, and then the output voltage of the gap sensor is measured again when the machining head 2 is raised by another distance X3. That is, the measurement interval is switched from X2 to X3, and the output voltage of the gap sensor is measured at each measurement interval of X3. In this embodiment, the distance X3 is 1.0 mm.

[0036] Thus, it is preferable for the gap amount measuring unit 21 to measure the gap amount such that the measurement interval at positions closer to the workpiece surface is smaller than the measurement interval at positions further from the workpiece surface. This allows for high detection accuracy to be obtained by measuring the output voltage at short measurement intervals at machining positions near the workpiece surface where high detection accuracy of the gap amount is required, while at the same time, it is possible to expand the detectable distance of the numerical control device 1 by measuring the output voltage at long measurement intervals at positions further away from the workpiece surface where high detection accuracy of the gap amount is not required.

[0037] Figure 3 shows an example of a correlation table TB1 according to this embodiment. The correlation table generation unit 12 generates the correlation table TB1 based on sampling data measured by switching the measurement interval. As shown in Figure 3, the distance interval of the correlation table is not constant.

[0038] Figure 4 is a graph L1 showing an example of the relationship between the output voltage of the gap sensor according to this embodiment and the distance. As shown in Figure 4, the correlation table generation unit 12 performs linear approximation between each sampling data. The obtained approximation line is used in the calculation of the reference output voltage by the reference output voltage calculation unit 15.

[0039] Figure 5 is a graph L2 showing an example of an approximation formula according to this embodiment. As shown in Figure 5, the approximation formula calculation unit 13 generates an approximation formula based on sampling data measured by switching the measurement interval.

[0040] Referring to Figures 6 and 7, the method for correcting the reference displacement amount of the reference displacement amount correction device 10 according to this embodiment will be described. Figure 6 is a flowchart showing an example of the method for correcting the reference displacement amount of the reference displacement amount correction device 10 according to this embodiment. The correction of the reference displacement amount is performed by executing steps S102 to S114 shown in Figure 6.

[0041] Figure 7 is a graph showing an example of the relationship between the output voltage of the gap sensor and distance according to this embodiment. In Figure 7, graph L1 is a graph showing the relationship between the output voltage of the gap sensor and distance based on the correlation table TB1 generated by the correlation table generation unit 12. Graph L2 is a graph showing the approximation formula calculated by the approximation formula calculation unit 13. Note that in Figure 7, the error of graph L2 relative to graph L1 is shown to be large for ease of understanding. In other words, the approximation error of graph L2 relative to graph L1 is shown to be large. The actual approximation error is, for example, 0.1 mm or less.

[0042] As shown in Figure 6, in step S102, the acquisition unit 14 acquires the reference displacement amount. Here, the reference displacement amount is 1.0 mm. The process proceeds to step S104.

[0043] In step S104, the reference output voltage calculation unit 15 calculates the reference output voltage. Specifically, as shown in Figure 7, the reference output voltage calculation unit 15 calculates the reference output voltage V1 corresponding to the reference displacement amount d1 based on the correlation table TB1 (see Figure 3). Here, the reference output voltage V1 is -2V. Here, the reference displacement amount d1 was the same value as the measurement point at the time of sampling, but if the reference displacement amount d1 is different from the measurement point at the time of sampling, the reference output voltage calculation unit 15 calculates the reference output voltage V1 based on an approximate straight line between the measurement points. The process proceeds to step S106.

[0044] In step S106, the calculated displacement calculation unit 16 calculates a calculated displacement indicating the displacement corresponding to the reference output voltage V1 based on an approximate expression. Specifically, as shown in FIG. 7, the calculated displacement calculation unit 16 calculates the calculated displacement d2 by substituting the reference output voltage V1 into the approximate expression. Here, the calculated displacement d2 is 1.6 mm. The process proceeds to step S108.

[0045] In step S108, the setting unit 17 sets the calculated displacement d2 as a new reference displacement. Specifically, the setting unit 17 corrects the reference displacement from 1.0 mm to 1.6 mm. The process proceeds to step S110.

[0046] In step S110, the displacement calculation unit 31 calculates the displacement. Specifically, the displacement calculation unit 31 calculates the displacement by substituting the output voltage of the gap sensor into the approximate expression. The process proceeds to step S112.

[0047] In step S112, the gap control unit 32 controls the gap amount so that the displacement calculated by the displacement calculation unit 31 becomes the calculated displacement d2. Here, the gap amount is controlled so that the displacement calculated by the displacement calculation unit 31 becomes 1.6 mm. The process proceeds to step S114.

[0048] In step S114, the axis control unit 33 controls the drive axis of the machining head 2 based on the gap amount controlled by the gap control unit 32. The process ends.

[0049] As described above with reference to Figures 1 to 7, the reference displacement amount correction device 10 according to this embodiment comprises a data storage unit 11, a correlation table generation unit 12, an approximation formula calculation unit 13, an acquisition unit 14, a reference output voltage calculation unit 15, a calculated displacement amount calculation unit 16, and a setting unit 17. The reference output voltage calculation unit 15 calculates a reference output voltage V1 that indicates the output voltage corresponding to the reference displacement amount d1 based on the correlation table TB1. The calculated displacement amount calculation unit 16 calculates a calculated displacement amount d2 that indicates the displacement amount corresponding to the reference output voltage V1 based on the approximation formula. The setting unit 17 sets the calculated displacement amount d2 as the new reference displacement amount. Therefore, the reference displacement amount is set after correcting the reference displacement amount to a value (calculated displacement amount) suitable for the approximation formula. Consequently, the error between the reference position and the actual distance between the workpiece and the machining head caused by the approximation error that occurs when using the approximation formula can be reduced. As a result, when converting the output voltage of the gap sensor to distance, the conversion can be performed with high accuracy while suppressing the processing time.

[0050] Furthermore, in the reference displacement amount correction device 10 according to this embodiment, it is preferable that the approximation formula is a polynomial approximation. When the approximation formula is a polynomial approximation, even if the output voltage of the gap sensor is adjusted via a regulator and input to the numerical control device 1, the output voltage of the gap sensor can be converted to distance with high accuracy using the approximation formula which is a polynomial approximation.

[0051] Furthermore, in the reference displacement correction device 10 according to this embodiment, the distance interval of the correlation table is not constant. Therefore, high detection accuracy can be obtained by measuring the output voltage at short measurement intervals at machining positions near the workpiece surface where high detection accuracy of the gap amount is required, while the detectable distance of the numerical control device 1 can be expanded by measuring the output voltage at long measurement intervals at positions away from the workpiece surface where high detection accuracy of the gap amount is not required.

[0052] Furthermore, the numerical control device according to this embodiment includes a reference displacement amount correction device 10, a displacement amount calculation unit 31, a gap control unit 32, and an axis control unit 33. The gap control unit controls the gap amount so that the displacement amount calculated by the displacement amount calculation unit 31 becomes the calculated displacement amount. As a result, laser processing can be performed by moving the processing head 2 while suppressing the processing time when converting the output voltage of the gap sensor to distance and maintaining a constant gap amount with high accuracy.

[0053] In the reference displacement correction device 10 according to the embodiment described with reference to Figures 1 to 7, the intervals between measurement points in the correlation table were interpolated using linear approximation, but this disclosure is not limited to this. For example, the intervals between measurement points in the correlation table may be interpolated using curve interpolation. Generally, the relationship between the output voltage of a gap sensor and distance often exhibits a curve. Therefore, interpolating the intervals between measurement points in the correlation table using curve interpolation can further improve conversion accuracy compared to interpolation using linear (e.g., straight lines).

[0054] In the reference displacement amount correction device 10 described with reference to Figures 1 to 7, the approximation formula was a polynomial approximation, but this disclosure is not limited thereto. For example, the approximation formula may be a monomial.

[0055] In the reference displacement amount correction device 10 according to the embodiment described with reference to Figures 1 to 7, the distance interval of the correlation table was not constant, but this disclosure is not limited thereto. For example, the distance interval of the correlation table may be constant.

[0056] In the reference displacement amount correction device 10 according to the embodiment described with reference to Figures 1 to 7, the approximation formula calculation unit 13 used the same sample data as the measurement points used when generating the correlation table when calculating the approximation formula, but this disclosure is not limited to this. For example, the approximation formula calculation unit 13 may use sample data different from the measurement points used when generating the correlation table when calculating the approximation formula.

[0057] The above-described adjustment support device and adjustment support method can be implemented by hardware, software, or a combination thereof. Here, implementation by software means that it is implemented by a computer loading and executing a program.

[0058] Programs can be stored and supplied to a computer using various types of non-transitor computer-readable media. Non-transitor computer-readable media include various types of tangible storage media. Examples of non-transitor computer-readable media include magnetic recording media (e.g., hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, and RAMs (random access memory)).

[0059] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above.

[0060] With respect to the above embodiments and modified examples, the following additional notes are disclosed. (Addendum 1) A reference displacement correction device comprising: a data storage unit (11) that stores the output voltage of a gap amount measuring unit corresponding to the gap amount, which is the distance from the work surface; a correlation table generation unit (12) that generates a correlation table in advance between the output voltage and the gap amount stored in the data storage unit (11); an approximation formula calculation unit (13) that calculates an approximation formula in advance that shows the relationship between the output voltage and the gap amount stored in the data storage unit (11); an acquisition unit (14) that acquires a reference displacement amount that indicates a reference for the displacement amount, which is the distance from a reference position set near the work surface; a reference output voltage calculation unit (15) that calculates a reference output voltage that indicates the output voltage corresponding to the reference displacement amount based on the correlation table; a calculated displacement amount calculation unit (16) that calculates a calculated displacement amount that indicates the displacement amount corresponding to the reference output voltage based on the approximation formula; and a setting unit (17) that sets the calculated displacement amount as a new reference displacement amount.

[0061] (Note 2) The above approximation formula is a polynomial approximation, as described in Note 1, for the reference displacement amount correction device.

[0062] (Note 3) The reference displacement amount correction device described in Note 1 or Note 2, wherein the distance interval of the correlation table is not constant.

[0063] (Note 4) A reference displacement correction device according to any one of Notes 1 to 3, wherein the intervals between measurement points in the correlation table are interpolated by curve interpolation.

[0064] (Note 5) A numerical control device comprising: a reference displacement amount correction device (10) described in any one of Notes 1 to 4; a displacement amount calculation unit (31) that calculates the displacement amount; a gap control unit (32) that controls the gap amount so that the displacement amount calculated by the displacement amount calculation unit (31) becomes the calculated displacement amount; and an axis control unit (33) that controls the drive axis of the machining head based on the gap amount controlled by the gap control unit.

[0065] 1 Numerical control device 2 Machining head 10 Reference displacement amount correction device 11 Data storage unit 12 Correlation table generation unit 13 Approximation formula calculation unit 14 Acquisition unit 15 Reference output voltage calculation unit 16 Calculated displacement amount calculation unit 17 Setting unit 21 Gap amount measurement unit 31 Displacement amount calculation unit 32 Gap control unit 33 Axis control unit

Claims

1. A reference displacement correction device comprising: a data storage unit that stores the output voltage of a gap amount measuring unit corresponding to the gap amount, which is the distance from the work surface; a correlation table generation unit that pre-generates a correlation table between the output voltage and the gap amount stored in the data storage unit; an approximation formula calculation unit that pre-calculates an approximation formula showing the relationship between the output voltage and the gap amount stored in the data storage unit; an acquisition unit that acquires a reference displacement amount that indicates a reference for the displacement amount, which is the distance from a reference position set near the work surface; a reference output voltage calculation unit that calculates a reference output voltage that indicates the output voltage corresponding to the reference displacement amount based on the correlation table; a calculated displacement amount calculation unit that calculates a calculated displacement amount that indicates the displacement amount corresponding to the reference output voltage based on the approximation formula; and a setting unit that sets the calculated displacement amount as a new reference displacement amount.

2. The reference displacement amount correction device according to claim 1, wherein the approximation formula is a polynomial approximation.

3. The reference displacement amount correction device according to claim 1 or claim 2, wherein the distance interval of the correlation table is not constant.

4. The reference displacement correction device according to any one of claims 1 to 3, wherein the intervals between measurement points in the correlation table are interpolated by curve interpolation.

5. A numerical control device comprising: a reference displacement amount correction device according to any one of claims 1 to 4; a displacement amount calculation unit for calculating the displacement amount; a gap control unit for controlling the gap amount so that the displacement amount calculated by the displacement amount calculation unit becomes the calculated displacement amount; and an axis control unit for controlling the drive axis of a machining head based on the gap amount controlled by the gap control unit.

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