Pitch correction method for numerically controlled machine tool

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] The present disclosure relates to a pitch compensation method for a numerically controlled machine tool. [Background technology]

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

[0003] [Patent Document 1] JP 2006-116654 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventor has found the following problem regarding the pitch correction method for a numerically controlled machine tool. For example, a pitch correction method is known 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, which reduces production efficiency.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and provides a pitch correction method that can suppress a decrease in production efficiency due to pitch correction. [Means for solving the problem]

[0006] A pitch correction method for a numerically controlled machine tool according to one aspect of the present disclosure includes: A pitch correction method for a numerically controlled machine tool having a pallet on which a workpiece is mounted, comprising the steps of: A step of mounting a pitch master having pitch measurement holes arranged in the X-axis direction and the Y-axis direction on an upper surface thereof on the pallet together with the workpiece; measuring the pitch of the holes aligned in the X-axis direction and the Y-axis direction in the pitch master on the pallet; calculating a ratio between the measured pitch and a reference pitch of the holes in the X-axis direction and the Y-axis direction in the pitch master previously measured at a predetermined reference temperature; and determining pitch correction values ​​in the X-axis and Y-axis directions of the work based on the calculated ratio between the measured pitch in the pitch master and the reference pitch.

[0007] In a pitch correction method for a numerically controlled machine tool according to one embodiment of the present disclosure, the pitches of holes aligned in the X-axis and Y-axis directions in a pitch master mounted on a pallet together with a workpiece are measured, and a ratio to a reference pitch of holes previously measured at a predetermined reference temperature is calculated. Then, based on the ratio between the measured pitch and the reference pitch in the pitch master, pitch correction values ​​in the X-axis and Y-axis directions of the workpiece are determined. With this configuration, the time required for pitch correction can be significantly reduced, and the decrease in production efficiency due to pitch correction can be suppressed.

[0008] After the step of mounting the pitch master on the pallet and before the step of measuring the pitch, the pitch master and the workpiece may be sprayed with coolant to bring the pitch master and the workpiece to the same temperature. With this configuration, it is possible to omit measuring the temperature of the pitch master and the workpiece.

[0009] The pitch master may be made of 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 set as the pitch correction value of the workpiece.

[0010] Alternatively, the pitch master may be made of a material different from that of 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 coefficient of the pitch master and the workpiece.

[0011] A convex portion protruding downward may be provided at the center of the bottom surface of the cylindrical pitch master, and the holes provided in the pitch master may be through holes extending from the top surface to the bottom surface at the peripheral portion of the pitch master, and in the step of mounting the pitch master on the pallet, the pitch master may be fixed to the pallet so that only the convex portion contacts the top surface of the pallet, and a gap may be provided between the bottom end of the hole and the top surface of the pallet. This configuration makes it easier for the pitch master to thermally deform in the X-axis and Y-axis directions, and also makes it possible to suppress clogging of the holes due to cutting powder from the workpiece. Effect of the Invention

[0012] According to the present disclosure, it is possible to provide a pitch correction method capable of suppressing a decrease in production efficiency due to pitch correction. [Brief description of the drawings]

[0013] [Figure 1] 4 is a flowchart showing a pitch correction method for the numerically controlled machine tool according to the first embodiment. [Diagram 2] FIG. 2 is a plan view of the Pitch Master mounted on a pallet together with the workpiece. [Diagram 3] FIG. 2 is a plan view of the pitch master. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIGS. 2 and 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings are appropriately simplified for clarity of explanation.

[0015] <First embodiment> A pitch correction method for a numerically controlled machine tool according to a first embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a flowchart showing the pitch correction method for a 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 IV-IV cutting line in Figs. 2 and 3.

[0016] Needless to say, the right-handed XYZ coordinate system shown in Figures 2 to 4 is for the sake of convenience in explaining the positional relationship of the components. Usually, the positive direction of the Z axis is vertically upward, and the XY plane is a horizontal plane, which is common among the drawings.

[0017] The pitch correction method for a numerically controlled machine tool according to this embodiment performs pitch correction of a feed system in a numerically controlled machine tool (not shown). The numerically controlled machine tool is equipped with 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 a numerically controlled machine tool according to this 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 placed on the pallet 20 together with the workpieces to be machined (step ST1). Fig. 2 shows an example of a state in which the workpieces W1 to W6 and the pitch master 10 are fixed on the pallet 20 equipped in a machine tool. In the example shown in Fig. 2, the cylindrical pitch master 10 is fixed to 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. The fixing location of the pitch master 10, the shape, number and fixing location of the workpieces are appropriately set and are not limited in any way. The pitch master 10 is not limited to a cylindrical shape, and may be, for example, a rectangular column shape.

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

[0020] 4, the holes Hx1, Hx2 and the holes Hy1, Hy2 are all through holes that reach the bottom surface from the top surface at the periphery of the pitch master 10. Because they are through holes, clogging of the holes Hx1, Hx2 and the holes Hy1, Hy2 due to 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] 3 and 4, a center hole Hc for fastening is provided in the center of the pitch master 10, and the pitch master 10 is fixed to the pallet 20 by a bolt BT inserted into the center hole Hc. Although Fig. 3 is a plan view, the bolt BT is shown as a dot to make it easier to understand.

[0022] 4, the pitch master 10 has a cylindrical protrusion 11 protruding downward from the center of its lower surface, and the pitch master 10 is fixed to the pallet 20 so that only the protrusion 11 comes into contact with the upper surface of the pallet 20. In other words, since only the center of the pitch master 10 is constrained by the pallet 20, the pitch master 10 is prone to thermal deformation in the horizontal direction (X-axis direction and Y-axis direction). In addition, since gaps are 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 due to cutting powder from the workpieces W1 to W6 can be further suppressed.

[0023] Returning to FIG. 1, the pitch correction method will be further described. Next, as shown in Fig. 1, the pitch (X-pitch Px) of holes Hx1, Hx2 aligned in the X-axis direction and the pitch (Y-pitch Py) of holes Hy1, Hy2 aligned in the Y-axis direction in the pitch master 10 on the pallet 20 are measured (step ST2). Specifically, as shown in Fig. 4, the probes of the touch probe TP are inserted into the holes Hx1, Hx2 and holes Hy1, Hy2, and the central positions of each hole are measured, thereby measuring the X-pitch Px and Y-pitch Py shown in Fig. 3. Here, the touch probe TP is structurally capable of detecting the central positions of the holes Hx1, Hx2 and holes Hy1, Hy2 with high accuracy.

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

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

[0026] Specifically, the pitch correction values ​​Cx and Cy of the X pitch and Y pitch of the workpiece can be expressed by the following formulas (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 formulas (1) and (2), for example, Tr=20° C. In that case, the pitch correction values ​​Cx and Cy of the workpiece can be expressed by the following formulas (3) and (4), respectively. In this way, the pitch correction values ​​Cx and Cy of the workpiece can be calculated using the thermal expansion coefficients α and β of the pitch master 10 and the workpiece in addition to the pitch correction values ​​Px / Pxr and Py / Pyr of the pitch master 10. 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 make the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece the same as the temperature Tc of the coolant. In other words, the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece may be made the same temperature.

[0029] In this 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), respectively. Cx=Px / Pxr×{1+β(Tc-20)} / {1+α(Tc-20)}···(5) Cy=Py / Pyr×{1+β(Tc-20)} / {1+α(Tc-20)}···(6) With this configuration, it is possible to omit separate measurements of the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece. In other words, the measurement of the temperature Tc of the coolant can be used as a substitute for the measurement of the temperature Tm of the pitch master 10 and the temperature Tw of the workpiece.

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

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

[0032] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention. In addition, the present invention may be implemented by appropriately combining the above-described embodiment and examples thereof. [Explanation of symbols]

[0033] 10 Pitch Master 11 Convex 20 palettes BT Bolt Hc center hole Hx1, Hx2, Hy1, Hy2 holes TP touch probe W1~W6 Work

Claims

1. A pitch correction method for a numerically controlled machine tool having a pallet on which a workpiece is mounted, comprising the steps of: a step of mounting a pitch master having pitch measurement holes arranged in the X-axis direction and the Y-axis direction on an upper surface thereof on the pallet together with the workpiece; measuring the pitch of the holes aligned in the X-axis direction and the Y-axis direction in the pitch master on the pallet; calculating a ratio between the measured pitch and a reference pitch of the holes in the X-axis direction and the Y-axis direction in the pitch master previously measured 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 between the measured pitch in the pitch master and the reference pitch. A method for pitch compensation in 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, Applying coolant to the pitch master and the workpiece to make the pitch master and the workpiece have the same temperature; 2. The pitch correction method for a numerically controlled machine tool according to claim 1.

3. The pitch master is made of the same material as the workpiece, In the step of determining a pitch correction value of the workpiece, The calculated pitch correction value of the pitch master is set as the pitch correction value of the work.

3. The pitch correction method for a numerically controlled machine tool according to claim 2.

4. The pitch master is made of a material different from that of the workpiece, In the step of determining a pitch correction value of the workpiece, Calculating a pitch correction value of the workpiece using the pitch master and the thermal expansion coefficient of the workpiece; 3. The pitch correction method for a numerically controlled machine tool according to claim 1 or 2.

5. A convex portion protruding downward is provided at the center of the lower surface of the cylindrical pitch master, The holes provided in the pitch master are all through holes extending from the upper surface to the lower surface at the peripheral portion of the pitch master, In the step of mounting the pitch master on the pallet, The pitch master is fixed to the pallet so that only the protrusion is in contact with 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.

3. The pitch correction method for a numerically controlled machine tool according to claim 1 or 2.

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