Outer diameter measurement method
By measuring the non-grinding portion at two locations to calculate and apply the inclination, the method reduces measurement errors in the outer diameter of the grinding part, ensuring accurate grinding process termination.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2023-06-27
- Publication Date
- 2026-06-02
Smart Images
Figure 0007868562000001 
Figure 0007868562000002 
Figure 0007868562000003
Abstract
Description
Technical Field
[0001] This disclosure relates to an outer diameter measurement method.
Background Art
[0002] In the grinding process of a cylindrical workpiece using a numerically controlled machine tool, the grinding process is performed while measuring the outer diameter of the grinding part at any time, and when the outer diameter reaches within a predetermined dimensional tolerance, the grinding process is terminated. For example, Patent Document 1 discloses a multi-tasking machine equipped with a sizing device for measuring the outer diameter of the grinding part.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] The inventor has considered a method of measuring the outer diameter of the grinding part by a touch probe that can slide along a moving axis substantially parallel to the rotation axis of the workpiece (i.e., the central axis of the workpiece). In this method, before measuring the outer diameter of the grinding part on the workpiece, the known outer diameter of the non-grinding part on the workpiece is measured by the touch probe, and the measured value of the outer diameter of the grinding part is calibrated.
[0005] However, the central axis of the workpiece and the moving axis of the touch probe are not exactly parallel. Therefore, in the above method, there is a problem that the measurement error of the outer diameter of the grinding part increases as the measurement position of the outer diameter of the grinding part moves away from the measurement position (i.e., the calibration position) of the known outer diameter of the non-grinding part.
[0006] This disclosure has been made in view of the above problems, and provides an outer diameter measurement method capable of reducing the measurement error of the outer diameter of the grinding part by a touch probe. [Means for solving the problem]
[0007] The outer diameter measurement method according to one aspect of this disclosure is: The process involves rotating a cylindrical workpiece around its central axis while grinding it with a grinding tool, and An outer diameter measuring method comprising the steps of measuring the outer diameter of a grinding portion on a workpiece using a touch probe that is positioned opposite to the grinding tool via the workpiece and is slidable along a movement axis substantially parallel to the rotation axis of the workpiece, Prior to the step of measuring the outer diameter of the grinding portion, By measuring the known outer diameter of the non-grinding portion of the workpiece at two different locations using the touch probe, the inclination of the moving axis with respect to the rotating axis is calculated. In the step of measuring the outer diameter of the grinding portion, The calculated inclination is used to calibrate the measured value of the outer diameter of the grinding section.
[0008] In one aspect of the present disclosure, the outer diameter measurement method involves measuring the known outer diameter of the non-grinding portion of a workpiece at two different locations using a touch probe, thereby calculating the inclination of the touch probe's movement axis relative to the workpiece's rotation axis. Then, in the step of measuring the outer diameter of the grinding portion, the calculated inclination is used to calibrate the measured value of the outer diameter of the grinding portion. This configuration reduces measurement errors in the outer diameter of the grinding area using a touch probe.
[0009] The non-grinding portion includes first and second non-grinding portions provided on both axial ends of the grinding portion, and when calculating the inclination, the known outer diameters of the first and second non-grinding portions may be measured by the touch probe. With this configuration, the inclination can be calculated with high accuracy.
[0010] The grinding tool is detachably mounted on a tool mounting section that slides along a tool movement axis parallel to the rotation axis. Prior to the grinding step performed by the grinding tool, another touch probe may be attached to the tool mounting section, and the outer diameter of the non-grinding portion may be measured and known using the other touch probe. With this configuration, the outer diameter of the non-grinding portion can be measured and known with high accuracy. [Effects of the Invention]
[0011] According to this disclosure, it is possible to provide an outer diameter measurement method that can reduce measurement errors of the outer diameter of the grinding part using a touch probe. [Brief explanation of the drawing]
[0012] [Figure 1] This is a flowchart showing the outer diameter measurement method according to the first embodiment. [Figure 2] This is a schematic partial side view showing an example of a numerically controlled machine tool for illustrating the outer diameter measurement method according to the first embodiment. [Figure 3] This is a schematic partial side view showing an example of a numerically controlled machine tool for illustrating the outer diameter measurement method related to the comparative example. [Modes for carrying out the invention]
[0013] 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.
[0014] (First Embodiment) The outer diameter measurement method according to the first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a flowchart of the outer diameter measurement method according to the first embodiment. Figure 2 is a schematic partial side view showing an example of a numerically controlled machine tool for illustrating the outer diameter measurement method according to the first embodiment. Figure 3 is a schematic partial side view showing an example of a numerically controlled machine tool for illustrating an outer diameter measurement method according to a comparative example.
[0015] Of course, the right-handed XYZ coordinates shown in FIGS. 2 and 3 are for convenience in explaining the positional relationship of the components. In FIGS. 2 and 3, the Z axis coincides with the rotation axis of the workpiece 10, and the X-axis direction is the direction in which the workpiece 10 is ground by the grinding tool 22 in the radial direction of the workpiece 10.
[0016] As shown in FIG. 2, in the outer diameter measurement method according to the present embodiment, the outer diameter of the grinding portion 13 of the columnar workpiece 10 ground by the grinding tool 22 is measured by the touch probe TP. In this specification, the columnar shape includes a cylindrical shape.
[0017] As shown in FIG. 1, first, the known outer diameters φ1 and φ2 of two different non-grinding portions 11 and 12 of the workpiece 10 shown in FIG. 2 are measured by the touch probe TP. Then, the inclination of the moving axis of the touch probe TP with respect to the rotation axis of the workpiece 10 is calculated (step ST1).
[0018] Here, as shown in FIG. 2, the touch probe TP is disposed opposite to the grinding tool 22 through the workpiece 10 and can slide along a moving axis substantially parallel to the rotation axis of the workpiece 10. However, as shown in FIG. 2, the moving axis of the touch probe TP is not exactly parallel to the rotation axis of the workpiece 10.
[0019] The touch probe TP is mounted on, for example, the lower tool rest of a machining center. That is, the moving axis of the touch probe TP shown in FIG. 2 is, for example, the moving axis of the lower tool rest. Also, in FIG. 2, the inclination of the moving axis of the touch probe TP with respect to the rotation axis of the workpiece 10 is exaggeratedly drawn.
[0020] The operation of the touch probe TP in step ST1 will be described in more detail. In the example shown in Figure 2, first, at calibration position 1 (Z-axis coordinate z1), the touch probe TP moves in the X-axis direction and contacts the workpiece 10, measuring the known outer diameter φ1 of the non-grinding portion (first non-grinding portion) 11 of the workpiece 10. As shown in Figure 2, if the X-coordinate measured by the touch probe TP at calibration position 1 (Z-axis coordinate z1) is x1, then the calibration value c1 = φ1 / 2 - x1 at calibration position 1 (Z-axis coordinate z1) is obtained.
[0021] Next, the touch probe TP moves along its axis to calibration position 2 (Z-axis coordinate z2). Then, the touch probe TP moves in the X-axis direction and contacts the workpiece 10, measuring the known outer diameter φ2 of the non-grinding portion (second non-grinding portion) 12 of the workpiece 10. As shown in Figure 2, if the X-coordinate measured by the touch probe TP at calibration position 2 (Z-axis coordinate z2) is x2, then the calibration value c2 = φ2 / 2 - x2 at calibration position 2 (Z-axis coordinate z2) is obtained.
[0022] Therefore, as can be easily understood from Figure 2, the inclination α of the movement axis of the touch probe TP with respect to the rotation axis of the workpiece 10, calculated in step ST1, can be expressed by the following equation (1) using the Z-axis coordinates z1, z2 and calibration values c1, c2 at calibration positions 1 and 2. α = (c² - c¹) / (z² - z¹) ... (1)
[0023] Furthermore, the inclination α can be calculated even if calibration is performed at two different locations on either the non-grinding sections 11 and 12 shown in Figure 2. However, as shown in Figure 2, the inclination α can be calculated with high accuracy by performing calibration at both the non-grinding sections 11 and 12, which are provided on both axial ends of the grinding section 13. Furthermore, step ST1 must be performed before step ST3 (described later), but it may be performed after step ST2 (described later).
[0024] Returning to Figure 1, we will continue the explanation of the outer diameter measurement method. Next, as shown in Figure 1, the workpiece 10 is rotated around its central axis (i.e., around the Z-axis) while being ground with the grinding tool 22 (step ST2).
[0025] In the example shown in Figure 2, the grinding tool 22 is detachably mounted on a tool mounting section 21 that slides along a tool movement axis parallel to the rotation axis of the workpiece 10. The grinding tool 22 presses the grinding section 13 of the workpiece 10 in the positive X-axis direction, rotates around a tool rotation axis parallel to the X-axis, and slides in the Z-axis direction along the tool movement axis. The grinding tool 22 is, for example, a grinding wheel.
[0026] Furthermore, for example, if the length of the grinding section 13 in the Z-axis direction is smaller than the diameter of the grinding tool 22, the grinding tool 22 does not need to slide in the Z-axis direction. In other words, it is not essential that the grinding tool 22 is slidable in the Z-axis direction. Also, the axis of rotation of the grinding tool 22 does not have to be parallel to the X-axis; for example, it may be parallel to the Z-axis.
[0027] Next, as shown in Figure 1, the outer diameter φ3 of the grinding portion 13 on the workpiece 10 is measured using the touch probe TP, and the measured value of the outer diameter φ3 of the grinding portion 13 is calibrated using the tilt α of the movement axis of the touch probe TP calculated in step ST1 (step ST3).
[0028] Specifically, as shown in Figure 2, the touch probe TP moves along the movement axis to the measurement position (Z-axis coordinate z3). Then, the touch probe TP moves in the X-axis direction to measure the unknown outer diameter φ3 of the grinding portion 13 on the workpiece 10. Here, as shown in Figure 2, the calibration value c3 at the measurement position (Z-axis coordinate z3) can be calculated using the slope α obtained from equation (1) by the following equation (2). c3 = c1 + α × (z3 - z1) ... (2)
[0029] Therefore, if the X coordinate measured by the touch probe TP at the measurement position (Z-axis coordinate z3) is x3, then x3+c3 calibrated using the calibration value c3 is equal to half of the outer diameter φ3 of the grinding section 13 (i.e., the radius φ3 / 2 of the grinding section 13). Thus, the outer diameter φ3 of the grinding section 13 can be calculated by the following equation (3), which calibrates the measured X coordinate x3 using the calibration value c3 obtained from equation (2). φ3 = (x3 + c3) × 2 ···(3)
[0030] Finally, as shown in Figure 1, it is determined whether the outer diameter φ3 of the ground portion 13 obtained in step ST3 is within a predetermined dimensional tolerance (step ST4). If the outer diameter φ3 of the ground portion 13 is within the dimensional tolerance (YES in step ST4), the grinding process is terminated. On the other hand, if the outer diameter φ3 of the ground portion 13 is not within the dimensional tolerance (NO in step ST4), the process of grinding the ground portion 13 in step ST2 and measuring the outer diameter φ3 of the ground portion 13 in step ST3 is repeated.
[0031] Here, we will explain the outer diameter measurement method related to the comparative example shown in Figure 3. In the comparative example shown in Figure 3, the outer diameter measurement method is assumed to be perfectly parallel to the rotation axis of the workpiece 10, and calibration is performed only at calibration position 1 (Z-axis coordinate z1). In the comparative example shown in Figure 3, as in Figure 2, the calibration value c1 = φ1 / 2 - x1 at the Z-axis coordinate z1 is the same.
[0032] On the other hand, in the comparative example shown in Figure 3, the tilt of the movement axis of the touch probe TP is not taken into consideration, so the calibration value c3 = c1 at the measurement position (Z-axis coordinate z3). Therefore, as shown in Figure 3, even if the measured value of the outer diameter φ3 of the grinding section 13 is calibrated, a measurement error occurs due to the tilt of the movement axis of the touch probe TP. Here, as shown in Figure 3, the further the measurement position (Z-axis coordinate z3) of the outer diameter φ3 of the grinding section 13 is from the measurement position of the known outer diameter φ1 of the non-grinding section 11, i.e., calibration position 1 (Z-axis coordinate z1), the larger the measurement error of the outer diameter φ3 of the grinding section 13 becomes.
[0033] In contrast, the outer diameter measurement method according to this embodiment, shown in Figure 2, measures the known outer diameters φ1 and φ2 of two different non-grinding sections 11 and 12 on the workpiece 10 using a touch probe TP, and calculates the inclination α of the touch probe TP's movement axis with respect to the rotation axis of the workpiece 10. Then, when measuring the outer diameter φ3 of the grinding section 13, the calculated inclination α of the touch probe TP's movement axis is used to calibrate the measured value of the outer diameter φ3 of the grinding section 13. Therefore, the measurement error of the outer diameter φ3 of the grinding section 13 that occurs in the comparative example shown in Figure 3 can be reduced.
[0034] In Figures 1 and 2, prior to step ST1 (and step ST2), another touch probe (not shown) may be attached to the tool mounting section 21, and the outer diameters φ1 and φ2 of the non-grinding sections 11 and 12 may be measured and known using this other touch probe. For example, the tool mounting section 21 is movable in the Y-axis direction, and the other touch probe attached to the tool mounting section 21 can directly measure the outer diameters φ1 and φ2 by contacting the non-grinding sections 11 and 12 from both sides in the Y-axis direction. With this configuration, the outer diameters φ1 and φ2 can be measured with high accuracy. Here, the tool exchange between the other touch probe and the grinding tool 22 on the tool mounting section 21 is performed, for example, by an automatic tool changer (ATC).
[0035] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its intent. [Explanation of Symbols]
[0036] 10 Work 11, 12 Non-grinding parts 13 Grinding section 21 Tool mounting section 22 Grinding Tools TP Touch Probe
Claims
1. A method for measuring the outer diameter in a numerically controlled machine tool equipped with a computer, The steps include grinding a cylindrical workpiece by rotating it around its central axis and sliding a grinding tool parallel to the axis of rotation, The system includes the step of measuring the outer diameter of the grinding portion on the workpiece using a touch probe that is positioned opposite the grinding tool via the workpiece and is slidable along a movable axis substantially parallel to the rotation axis. Prior to the step of measuring the outer diameter of the grinding portion, By measuring the known outer diameter of the non-grinding portion of the workpiece at two different locations using the touch probe, the computer calculates the inclination of the moving axis with respect to the rotating axis. In the step of measuring the outer diameter of the grinding portion, The computer uses the calculated inclination to calibrate the measured value of the outer diameter of the grinding section. How to measure outer diameter.
2. The non-grinding portion includes first and second non-grinding portions provided on both axial ends of the grinding portion, When calculating the aforementioned inclination, the known outer diameters of the first and second non-grinding portions are measured using the touch probe. The method for measuring the outer diameter according to claim 1.
3. The grinding tool is detachably mounted on a tool mounting section that slides along a tool movement axis parallel to the rotation axis. Prior to the step of grinding with the aforementioned grinding tool, Another touch probe is attached to the tool mounting portion, and the outer diameter of the non-grinding portion is measured and made known using the other touch probe. The method for measuring the outer diameter according to claim 1 or 2.