Pitch correction method for numerically controlled machine tools

Abstract

To prevent a reduction in production efficiency resulting from pitch correction.SOLUTION: A pitch correction method for a numerically controlled machine tool according to an aspect of the present disclosure is a pitch correction method for a numerically controlled machine tool including a pallet on which a workpiece is mounted. The method includes: mounting a pitch master on the pallet together with the workpiece, the pitch master having an upper surface provided with holes for pitch measurement arranged in an X-axis direction and a Y-axis direction, respectively; measuring pitches of the holes arranged in the X-axis direction and the Y-axis direction in the pitch master on the pallet; calculating a ratio of the measured pitch to reference pitches of the holes in the X-axis direction and the Y-axis direction in the pitch master measured in advance at a predetermined reference temperature; and determining pitch correction values in the X-axis direction and the Y-axis direction of the workpiece, based on the calculated ratio of the measured pitch to the reference pitch, in the pitch master.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to a pitch correction method for numerically controlled machine tools.

Background Art

[0002] In numerically controlled machine tools, pitch errors due to thermal deformation (thermal expansion and thermal contraction) occur in the workpiece and the machine tool depending on the temperature during workpiece machining. If a constant temperature room that can maintain the numerically controlled machine tool and the workpiece at a constant temperature is installed, the occurrence of pitch errors itself can be suppressed, but the cost increases due to the installation of the constant temperature room. Therefore, for example, as disclosed in Patent Document 1, pitch correction is performed to reduce the influence of pitch errors due to thermal deformation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor has found the following problems regarding the pitch correction method for numerically controlled machine tools. For example, there is known a pitch correction method in which a workpiece is experimentally machined at various temperatures in advance, and pitch correction is performed using the acquired data. In such a pitch correction method, it takes time to acquire data for pitch correction, and there is a problem that production efficiency decreases.

[0005] This disclosure has been made in view of the above-described problems, and provides a pitch correction method capable of suppressing a decrease in production efficiency associated with pitch correction.

Means for Solving the Problems

[0006] The pitch correction method for a numerically controlled machine tool according to one aspect of this disclosure is A method for correcting the pitch of a numerically controlled machine tool equipped with a pallet for mounting a workpiece, The steps include: mounting a pitch master, which has holes for pitch measurement arranged in the X-axis and Y-axis directions on its upper surface, onto the pallet together with the workpiece; The steps include measuring the pitch of the holes arranged in the X-axis and Y-axis directions on the pitch master on the pallet, A step of calculating the ratio between the measured pitch and the reference pitch of the hole in the X-axis and Y-axis directions in the pitch master, which was measured in advance at a predetermined reference temperature. The method includes the step of determining pitch correction values ​​in the X-axis direction and the Y-axis direction of the workpiece based on the ratio of the measured pitch in the calculated pitch master to the reference pitch.

[0007] In a pitch correction method for a numerically controlled machine tool according to one aspect of this disclosure, the pitch of holes aligned in the X-axis and Y-axis directions in a pitch master mounted on a pallet together with the workpiece is measured, and the ratio of this pitch to a reference pitch of holes measured in advance at a predetermined reference temperature is calculated. Then, based on the ratio of the measured pitch to the reference pitch in the pitch master, pitch correction values ​​in the X-axis and Y-axis directions of the workpiece are determined. This configuration significantly reduces the time required for pitch correction and suppresses the decrease in production efficiency associated with pitch correction.

[0008] After the step of mounting the pitch master on the pallet, and before the step of measuring the pitch, coolant may be applied to the pitch master and the workpiece to bring them to the same temperature. This configuration eliminates the need to measure the temperature of the pitch master and the workpiece.

[0009] The pitch master may be constructed from the same material as the workpiece, and in the step of determining the pitch correction value of the workpiece, the calculated pitch correction value of the pitch master may be used as the pitch correction value of the workpiece.

[0010] Alternatively, the pitch master may be made of a different material from the workpiece, and in the step of determining the pitch correction value of the workpiece, the pitch correction value of the workpiece may be calculated using the thermal expansion coefficients of the pitch master and the workpiece.

[0011] A protrusion projecting downwards is provided at the center of the lower surface of the cylindrical pitch master, and the holes provided in the pitch master are all through holes extending from the top surface to the bottom surface at the periphery of the pitch master. In the step of mounting the pitch master on the pallet, the pitch master may be fixed to the pallet such that only the protrusion contacts the top surface of the pallet, and a gap may be provided between the lower end of the hole and the top surface of the pallet. This configuration makes the pitch master more susceptible to thermal deformation in the X-axis and Y-axis directions, and suppresses clogging of the holes by cutting chips from the workpiece. [Effects of the Invention]

[0012] According to this disclosure, a pitch correction method can be provided that can suppress the decrease in production efficiency associated with pitch correction. [Brief explanation of the drawing]

[0013] [Figure 1] This is a flowchart showing a pitch correction method for a numerically controlled machine tool according to the first embodiment. [Figure 2] This is a plan view of the pitch master mounted on the pallet along with the workpiece. [Figure 3] This is a plan view of the pitch master. [Figure 4] Figures 2 and 3 show cross-sectional views taken along the IV-IV line. [Modes for carrying out the invention]

[0014] The following describes specific embodiments to which the present invention is applied, with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0015] <First Embodiment> Referring to FIGS. 1 to 4, a pitch correction method for a numerically controlled machine tool according to the first embodiment will be described. FIG. 1 is a flowchart showing the pitch correction method for the numerically controlled machine tool according to the first embodiment. FIG. 2 is a plan view of a pitch master mounted on a pallet together with a workpiece. FIG. 3 is a plan view of the pitch master. FIG. 4 is a cross-sectional view taken along the cutting line IV-IV in FIGS. 并びに 3.

[0016] Of course, the right-handed XYZ coordinates shown in FIGS. 2 to 4 are for convenience in explaining the positional relationship of the components. Usually, the positive Z-axis direction is vertically upward, the XY plane is a horizontal plane, and is common among the drawings.

[0017] The pitch correction method for the numerically controlled machine tool according to the present embodiment performs pitch correction of the feed system in a numerically controlled machine tool not shown. The numerically controlled machine tool includes a feed system that feeds each table in the X-axis direction and the Y-axis direction. That is, using the pitch correction method for the numerically controlled machine tool according to the present embodiment, pitch correction is performed for the pitch in the X-axis direction (X pitch) and the pitch in the Y-axis direction (Y pitch) of the numerically controlled machine tool.

[0018] First, as shown in FIG. 1, the pitch master 10 is mounted on the pallet 20 together with the workpiece which is the object to be machined (step ST1). FIG. 2 shows an example of a state where the workpieces W1 to W6 and the pitch master 10 are fixed on the pallet 20 provided in the machine tool. In the example shown in FIG. 2, a columnar pitch master 10 is fixed at the center of the disk-shaped pallet 20. Then, six workpieces W1 to W6 are evenly arranged and fixed on the pallet 20 so as to surround the pitch master 10. Note that the fixing position of the pitch master 10, the shape, number, and fixing position of the workpieces are set as appropriate and are not limited in any way. Further, the pitch master 10 is not limited to a columnar shape, and may be, for example, a prismatic shape or the like.

[0019] Here, referring to FIGS. 3 and 4, the configuration of the pitch master 10 will be described. The pitch master 10 is a calibration standard for pitch correction. As shown in FIG. 3, on the upper surface of the cylindrical pitch master 10, a pair of holes Hx1 and Hx2 for pitch measurement are provided side by side in the X-axis direction, and a pair of holes Hy1 and Hy2 for pitch measurement are provided side by side in the Y-axis direction. As shown in FIG. 3, the center distance between the holes Hx1 and Hx2 provided side by side in the X-axis direction is the X pitch Px, and the center distance between the holes Hy1 and Hy2 provided side by side in the Y-axis direction is the Y pitch Py.

[0020] Here, as shown in FIG. 4, the holes Hx1, Hx2 and the holes Hy1, Hy2 are all through holes extending from the upper surface to the lower surface at the peripheral part of the pitch master 10. Since they are through holes, clogging of the holes Hx1, Hx2 and the holes Hy1, Hy2 by the cutting powder of the workpieces W1 to W6 can be suppressed. However, the holes Hx1, Hx2 and the holes Hy1, Hy2 do not have to be through holes.

[0021] Also, as shown in FIGS. 3 and 4, a center hole Hc for fastening is provided at the center of the pitch master 10, and the pitch master 10 is fixed to the pallet 20 by a bolt BT inserted through the center hole Hc. Although FIG. 3 is a plan view, for easy understanding, the bolt BT is shown in dot form.

[0022] Here, as shown in FIG. 4, the pitch master 10 has a cylindrical convex part 11 protruding downward at the center of the lower surface, and the pitch master 10 is fixed to the pallet 20 so that only the convex part 11 contacts the upper surface of the pallet 20. That is, since only the central part of the pitch master 10 is constrained by the pallet 20, the pitch master 1 is likely to thermally deform in the horizontal direction (X-axis direction and Y-axis direction). In addition, since a gap is formed between the lower ends of the holes Hx1, Hx2 and the holes Hy1, Hy2 and the upper surface of the pallet 20, clogging of the holes Hx1, Hx2 and the holes Hy1, Hy2 by the cutting powder of the workpieces W1 to W6 can be further suppressed.

[0023] Returning to FIG. 1, the description of the pitch correction method will be continued. Next, as shown in Figure 1, the pitch of holes Hx1 and Hx2 aligned in the X-axis direction (X pitch Px) and the pitch of holes Hy1 and Hy2 aligned in the Y-axis direction (Y pitch Py) on the pitch master 10 on the pallet 20 are measured (step ST2). Specifically, as shown in Figure 4, the probe of the touch probe TP is inserted into holes Hx1, Hx2 and holes Hy1 and Hy2, and the X pitch Px and Y pitch Py shown in Figure 3 are measured by measuring the center position of each hole. Here, the touch probe TP is structurally capable of accurately detecting the center positions of holes Hx1, Hx2 and holes Hy1 and Hy2.

[0024] Next, as shown in Figure 1, the ratio of the X pitch Px and Y pitch Py measured in step ST2 to the reference X pitch Pxr and reference Y pitch Pyr measured in advance at a predetermined reference temperature (e.g., 20°C) is calculated (step ST3). The calculated ratios Px / Pxr and Py / Pyr are the pitch correction values ​​for the X pitch and Y pitch in the pitch master 10 due to temperature changes, respectively.

[0025] Finally, as shown in Figure 1, the pitch correction values ​​for the X pitch and Y pitch in the workpiece are determined based on the calculated pitch correction values ​​of the pitch master 10 (step ST4).

[0026] Specifically, the pitch correction values ​​Cx and Cy for the X pitch and Y pitch in the workpiece can be expressed by the following equations (1) and (2), respectively, using the pitch correction values ​​Px / Pxr and Py / Pyr in the pitch master 10. Cx=Px / Pxr×{1+β(Tw-Tr)} / {1+α(Tm-Tr)}···(1) Cy=Py / Pyr×{1+β(Tw-Tr)} / {1+α(Tm-Tr)}···(2) Here, Tm is the temperature of the pitch master 10, Tw is the temperature of the workpiece, Tr is the reference temperature, and α and β are the thermal expansion coefficients of the pitch master 10 and the workpiece, respectively.

[0027] In equations (1) and (2), for example, Tr = 20°C. In that case, the pitch correction values ​​Cx and Cy in the workpiece can be expressed by the following equations (3) and (4), respectively. Thus, the pitch correction values ​​Cx and Cy in the workpiece can be calculated using the pitch correction values ​​Px / Pxr and Py / Pyr in the pitch master 10, as well as the thermal expansion coefficients α and β of the pitch master 10 and the workpiece. Cx=Px / Pxr×{1+β(Tw-20)} / {1+α(Tm-20)}···(3) Cy=Py / Pyr×{1+β(Tw-20)} / {1+α(Tm-20)}···(4)

[0028] The temperature Tm of the pitch master 10 and the temperature Tw of the workpiece are measured, for example, after step ST1 and before step ST2. Alternatively, after step ST1 and before step ST2, coolant may be applied to the pitch master 10 and the workpiece for a predetermined time to bring the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece to the same temperature as the coolant temperature Tc. In other words, the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece may be made to the same temperature.

[0029] In that case, since Tm=Tw=Tc holds in equations (3) and (4), the pitch correction values ​​Cx and Cy in the workpiece can be expressed by the following equations (5) and (6). Cx=Px / Pxr×{1+β(Tc-20)} / {1+α(Tc-20)}···(5) Cy=Py / Pyr×{1+β(Tc-20)} / {1+α(Tc-20)}···(6) This configuration eliminates the need for separate measurements of the pitch master temperature Tm and the workpiece temperature Tw. In other words, measuring the coolant temperature Tc can substitute for measuring the pitch master temperature Tm and the workpiece temperature Tw.

[0030] Furthermore, if the pitch master 10 is constructed from the same material as the workpiece, the thermal expansion coefficient α = β holds true in equations (5) and (6). Therefore, the pitch correction values ​​Cx and Cy in the workpiece can be expressed by the following equations (7) and (8). Cx = Px / Pxr ... (7) Cy = Py / Pyr···(8) In other words, the pitch correction values ​​Px / Pxr and Py / Pyr calculated in step ST3 for the pitch master 10 become the pitch correction values ​​Cx and Cy for the workpiece. In this case, the measurement of the coolant temperature Tc in equations (5) and (6) can also be omitted.

[0031] As described above, in the pitch correction method for the numerically controlled machine tool according to this embodiment, the pitches Px and Py of holes aligned in the X-axis and Y-axis directions in the pitch master 10 mounted on the pallet 20 together with the workpiece are measured. The ratio Px / Pxr and Py / Pyr of the measured hole pitches Px and Py to the reference holes Pxr and Pyr measured in advance at a predetermined reference temperature is calculated as the pitch correction value in the pitch master 10. Then, based on the pitch correction value Px / Pxr and Py / Pyr of the pitch master, the pitch correction values ​​Cx and Cy in the workpiece are determined. This configuration significantly reduces the time required for pitch correction, thereby suppressing a decline in production efficiency.

[0032] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. Furthermore, the present invention may be implemented by combining the above embodiments or examples thereof as appropriate. [Explanation of Symbols]

[0033] 10 Pitch Master 11 Convex part 20 pallets BT Bolt Hc Center Hole Hx1, Hx2, Hy1, Hy2 holes TP Touch Probe W1~W6 Work

Claims

1. A method for correcting the pitch of a numerically controlled machine tool equipped with a pallet for mounting a workpiece, The steps include mounting a cylindrical pitch master, which has holes for pitch measurement arranged in the X-axis and Y-axis directions on its upper surface, in the center of the upper surface of the pallet parallel to the XY plane, and mounting workpieces around the pitch master on the upper surface of the pallet, The steps include measuring the X-pitch Px, which is the pitch of the holes arranged in the X-axis direction on the pitch master on the pallet, and the Y-pitch Py, which is the pitch of the holes arranged in the Y-axis direction. A step of calculating the ratios Px / Pxr and Py / Pyr, respectively, between the measured X pitch Px and Y pitch Py and the reference X pitch Pxr and reference Y pitch Pyr of the hole in the X-axis direction and Y-axis direction in the pitch master, which were measured in advance at a predetermined reference temperature. The system includes the step of determining pitch correction values ​​Cx and Cy in the X-axis and Y-axis directions of the workpiece, respectively, based on the calculated ratios Px / Pxr and Py / Pyr. A method for correcting the pitch of a numerically controlled machine tool.

2. After the step of mounting the pitch master on the pallet, and before the step of measuring the pitch, Coolant is applied to the pitch master and the workpiece to bring them to the same temperature. A method for correcting the pitch of a numerically controlled machine tool as described in claim 1.

3. The pitch master is constructed from the same material as the workpiece. In the step of determining the pitch correction values ​​Cx and Cy of the workpiece, The calculated ratios Px / Pxr and Py / Pyr are defined as the pitch correction values ​​Cx and Cy of the workpiece, respectively. A pitch correction method for a numerically controlled machine tool as described in claim 2.

4. The pitch master is constructed from a material different from the workpiece. In the step of determining the pitch correction values ​​Cx and Cy of the workpiece, Using the pitch master and the thermal expansion coefficient of the workpiece, the pitch correction values ​​Cx and Cy of the workpiece are calculated. A pitch correction method for a numerically controlled machine tool according to claim 1 or 2.

5. A protrusion is provided in the center of the lower surface of the pitch master, which protrudes downward. The holes provided in the pitch master are all through holes extending from the top surface to the bottom surface at the periphery of the pitch master. In the step of mounting the pitch master on the pallet, The pitch master is fixed to the pallet such that only the protrusions contact the upper surface of the pallet, and a gap is provided between the lower end of the hole and the upper surface of the pallet. A pitch correction method for a numerically controlled machine tool according to claim 1 or 2.

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