JP2023162649A - Spherical surface grinding method and spherical surface grinding device - Google Patents

Abstract

To provide a spherical surface grinding method and a spherical surface grinding device which can grind a work-piece with high accuracy.SOLUTION: A spherical surface grinding method includes: a first step in which a shape of a grindstone is measured by a shape measuring mechanism in a state where the grindstone is not inclined with respect to a turning center shaft for turning the grindstone; a second step in which the shape of the grindstone is measured by the shape measuring mechanism in a state where the grindstone is inclined with respect to the turning center shaft; a third step in which shape data on the grindstone obtained in the first step is synthesized with shape data on the grindstone obtained in the second step to obtain estimated shape data in a state where the grindstone is inclined with respect to the turning center shaft; a fourth step in which a contact point between the grindstone and a work-piece with a desired curvature radius is calculated, on the basis of the estimated shape data; a fifth step in which an inclination angle of the grindstone with respect to the turning center shaft, which is set in actual processing, is calculated, on the basis of the contact point ; and a sixth step in which the grindstone is inclined at the inclination angle to grind the work-piece into a spherical shape.SELECTED DRAWING: Figure 5

Description

The present invention relates to a spherical surface grinding method and a spherical surface grinding device.

Patent Document 1 discloses a technique for spherically grinding a workpiece using a cup-shaped grindstone.

Patent No. 4456520

In spherical grinding of a workpiece, a grindstone is brought into contact with the workpiece while being inclined at a predetermined angle, and processing is performed by rotating both the grindstone and the workpiece. At this time, in order to achieve high-precision grinding, it is important to understand the point of contact between the grindstone and the workpiece and to appropriately set the positional relationship between the two.

However, with conventional techniques such as Patent Document 1, it is difficult to determine the exact contact point between the grindstone and the workpiece, and there is a problem that highly accurate grinding cannot be performed.

The present invention has been made in view of the above, and an object of the present invention is to provide a spherical surface grinding method and a spherical surface grinding device that can grind a workpiece with high precision.

In order to solve the above-mentioned problems and achieve the objects, the spherical surface grinding method according to the present invention provides a spherical surface grinding method according to the present invention. a first step of measuring the shape with the shape measuring mechanism; a second step of measuring the shape of the whetstone with the shape measuring mechanism in a state where the whetstone is tilted with respect to the rotation center axis; and a second step of measuring the shape of the whetstone with the shape measuring mechanism. By combining the shape data of the whetstone acquired in the first step and the shape data of the whetstone acquired in the second step, the estimated shape when the whetstone is tilted with respect to the center axis of rotation a third step of acquiring data; a fourth step of calculating a contact point between the grinding wheel and a workpiece with a desired curvature based on the estimated shape data; A fifth step of calculating the inclination angle of the grindstone with respect to the rotation center axis, which is set in processing; and a sixth step of setting the grindstone to the inclination angle and performing spherical grinding of the workpiece. .

Further, in the spherical surface grinding method according to the present invention, in the above invention, the third step includes the shape data of the grindstone acquired in the first step and the shape data of the grindstone acquired in the second step. a feature point extraction step of extracting feature points common to the above, based on the feature points, the shape data of the grindstone obtained in the first step, and the shape of the grindstone obtained in the second step; and an estimated shape data acquisition step of synthesizing the estimated shape data with the estimated shape data.

Further, in the spherical surface grinding method according to the present invention, in the above-mentioned invention, the second step changes the shape of the grindstone in a state where the grindstone is tilted at a plurality of different angles with respect to the rotation center axis. Based on the shape data of the grindstone measured by the shape measuring mechanism and measured in the first step and the shape data of the plurality of grindstones measured in the second step, the true center axis of rotation is determined. The method further includes a step of estimating a turning center axis, and the fifth step calculates the inclination angle using the true turning center axis.

In order to solve the above-mentioned problems and achieve the objects, a spherical grinding device according to the present invention includes a workpiece holding mechanism that holds a workpiece, a workpiece rotation mechanism that rotates the workpiece holding mechanism about a workpiece rotation axis, and a cup. a grindstone holding mechanism that holds a shaped grindstone; a grindstone rotation mechanism that rotates the grindstone around a grindstone rotation axis; and a grindstone rotation mechanism that rotates the grindstone rotation mechanism about a rotation center axis that is perpendicular to the grindstone rotation axis. , a shape measuring mechanism whose optical axis is an axis parallel to the work rotation axis, an NC moving mechanism that moves the shape measurement mechanism in a three-dimensional direction, and a work holding mechanism located at a position away from the grindstone rotation axis. A retraction mechanism for retracting, a shape of the grindstone in a state where the grindstone holding mechanism is not inclined with respect to the turning center axis, and a shape of the grindstone in a state where the grindstone holding mechanism is inclined with respect to the turning center axis. , a measurement control mechanism that controls the shape measurement mechanism and the NC movement mechanism, and the shape data of the grindstone acquired by the measurement control mechanism are combined, and the grindstone holding mechanism is adjusted to the rotation center axis. a data processing device that calculates an inclination angle of the grindstone holding mechanism to obtain a workpiece with a desired curvature from data on a contact point between the workpiece and the grindstone when the workpiece is tilted at a desired angle with respect to the grindstone; A processing control mechanism that controls the grindstone rotation mechanism based on the output result of the data processing device.

In the spherical grinding method and spherical grinding apparatus according to the present invention, data on the accurate contact point between the grinding wheel and the workpiece can be obtained by estimating the shape data of the grinding wheel when the grinding wheel is inclined with respect to the central axis of rotation. can be obtained. Thereby, the workpiece can be ground with high precision.

FIG. 1 is a diagram schematically showing the position of a grindstone during shape measurement and workpiece processing in spherical grinding of a workpiece. FIG. 2 is a diagram schematically showing how shape measurement is performed with the grindstone tilted. FIG. 3 is a front view showing an example of the configuration of a spherical surface grinding device according to an embodiment of the present invention. FIG. 4 is a side view showing an example of the configuration of a spherical surface grinding device according to an embodiment of the present invention. FIG. 5 is a flowchart showing the flow of the spherical surface grinding method according to the embodiment of the present invention. FIG. 6 shows how the shape data of the grindstone obtained in the first shape measurement step and the shape data of the grindstone obtained in the second shape measurement step are combined in the spherical surface grinding method according to the embodiment of the present invention. FIG. FIG. 7 is a diagram schematically showing the contact point between the grindstone and the workpiece before tilting. FIG. 8 is a diagram schematically showing the grindstone after tilting. FIG. 9 is a diagram schematically showing contact points between the grindstone and the workpiece after tilting. FIG. 10 is a diagram for explaining a method for estimating the true center axis of rotation in the spherical surface grinding method according to the embodiment of the present invention. FIG. 11 is a diagram for explaining a method for estimating the true center axis of rotation in the spherical surface grinding method according to the embodiment of the present invention. FIG. 12 is a diagram for explaining a method for estimating the true center axis of rotation in the spherical surface grinding method according to the embodiment of the present invention. FIG. 13 is a diagram schematically showing a case where there is no undulation in the turning orbit of the grindstone around the turning center axis. FIG. 14 is a diagram schematically showing a case where the whirling orbit of the grindstone around the center axis of whirlpool has undulations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a spherical surface grinding method and a spherical surface grinding apparatus according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and the components in the following embodiments include those that can be easily replaced by those skilled in the art, or those that are substantially the same.

In spherical grinding of a glass lens or the like, the workpiece is processed by rotating the workpiece to be processed and a cup-shaped grindstone that is in line contact with the workpiece. At that time, the curvature of the workpiece to be machined can be changed by changing the inclination of the grinding wheel. However, if the workpiece is continuously processed, the shape of the grinding wheel changes due to wear, so the inclination of the grinding wheel can be changed while checking the workpiece finish. I had to adjust.

Therefore, conventionally, a shape measuring mechanism whose optical axis is parallel to the rotation axis of the workpiece (hereinafter referred to as "workpiece rotation axis") is used to measure the shape of the grindstone every time the workpiece is processed. The point of contact between the grinding wheel and the workpiece was determined and the amount of movement of the workpiece, such as the angle of inclination of the grinding wheel and the depth of cut, was adjusted.

When measuring the shape of a grindstone, the shape measurement mechanism 22 measures from above the grindstone 14, as shown in section A in FIG. 1, for example. On the other hand, when processing the workpiece W, the grindstone 14 is used while being inclined with respect to the center axis of rotation Ac, as shown in section B in the figure. Therefore, for example, due to limits of equipment accuracy, an error may occur between the theoretical (simulation) center axis of rotation Ac and the actual center axis of rotation (true center axis of rotation) Ac. As a result, the contact point between the grindstone and the workpiece measured by the shape measuring mechanism 22 differs from the actual contact point.

Therefore, it is conceivable to measure the shape of the grindstone 14 using the shape measuring mechanism 22, for example, with the grindstone 14 tilted at the angle at which the workpiece W is actually processed (see B in FIG. 1). However, when the whetstone 14 is tilted in this way, as shown in FIG. 2, for example, it is possible to measure only the shape of one end of the cup-shaped whetstone 14 (on the left side in the figure), and the shape of the other end cannot be measured. It may not be possible to measure the shape of the part. Therefore, it becomes unclear where the measured shape of the grindstone 14 is located from the center of the grindstone, and it becomes impossible to grasp the absolute position of the grindstone 14 in the coordinate system of the entire apparatus. In other words, when machining is performed by tilting the grindstone 14, the shape and position of the entire machining area cannot be grasped.

In this way, when measuring the shape of a grinding wheel from above, there is an error in the expected position of the grinding wheel when it is tilted at a predetermined angle. When trying to measure it, the shape and position of the entire grinding wheel become unknown. As a result, in either case, a problem arises in that it is not possible to determine the point of contact when the grindstone is tilted at a predetermined angle.

Therefore, in the spherical surface grinding method and spherical surface grinding device according to the present invention, such problems are solved and data on the accurate contact point of the grinding wheel is obtained in the grinding state (tilted state) of the grinding wheel. Achieves high precision grinding.

(Spherical grinding device)
A spherical surface grinding device according to an embodiment of the present invention will be described with reference to FIGS. 3 and 4. The spherical surface grinding device is for spherically grinding the workpiece W. The spherical grinding device can perform both concave and convex machining on the workpiece W. In this embodiment, the description will be given mainly assuming a case where convex surface processing is performed.

FIG. 3 is a front view of the spherical grinding device 1 according to the embodiment, and FIG. 4 is a side view of the spherical grinding device 1. The spherical grinding device 1 includes a workpiece holding mechanism 11, a workpiece rotation mechanism 12, a retraction mechanism 13, a grindstone (first grindstone) 14, a grindstone holding mechanism 15, a grindstone rotation mechanism 16, and a grindstone rotation mechanism 17. , a grindstone (second grindstone) 18, a grindstone holding mechanism 19, a grindstone rotation mechanism 20, a grindstone rotation mechanism 21, a shape measurement mechanism 22, an NC movement mechanism 23, a measurement control mechanism 24, and a data processing device. 25, a processing control mechanism 26, and a reference surface 27.

The workpiece holding mechanism 11 is a mechanism for holding a workpiece W to be processed. The workpiece W may be, for example, a glass lens with a diameter of about 1 to 3 mm. The work rotation mechanism 12 is a mechanism for rotating the work holding mechanism 11 around the work rotation axis Aw. The retraction mechanism 13 is a mechanism for retracting the workpiece holding mechanism 11 to a position away from the rotation axes of the grindstones 14 and 18 (hereinafter referred to as "grindstone rotation axes") At1 and At2. This evacuation mechanism 13 can move the workpiece holding mechanism 11 in three-dimensional directions (X-axis direction, Y-axis direction, and Z-axis direction).

The grindstone 14 is a tool for grinding the workpiece W. This grindstone 14 is a cup-shaped grindstone, and is used for rough grinding, for example. The grindstone holding mechanism 15 is a mechanism for holding the grindstone 14. The grindstone rotation mechanism 16 is a mechanism for rotating the grindstone 14 held by the grindstone holding mechanism 15 around the grindstone rotation axis At1. The grindstone rotation mechanism 17 is a mechanism for rotating (swinging) the grindstone rotation mechanism 16 around a rotation center axis Ac that is perpendicular to the grindstone rotation axis At1.

The grindstone 18 is a tool for grinding the workpiece W. This grindstone 18 is a cup-shaped grindstone, and is used, for example, in precision grinding. The grindstone holding mechanism 19 is a mechanism for holding the grindstone 18. The grindstone rotation mechanism 20 is a mechanism for rotating the grindstone 18 held by the grindstone holding mechanism 19 around the grindstone rotation axis At2. The grindstone rotation mechanism 21 is a mechanism for rotating the grindstone rotation mechanism 20 around a rotation center axis Ac that is perpendicular to the grindstone rotation axis At2.

The shape measuring mechanism 22 is a mechanism for measuring the shapes of the grindstones 14 and 18. Examples of the shape measuring mechanism 22 include a laser displacement meter and the like. Further, the shape measuring mechanism 22 has an optical axis Ao that is parallel to the work rotation axis Aw. The NC moving mechanism 23 is a mechanism for moving the shape measuring mechanism 22 in three-dimensional directions (X-axis direction, Y-axis direction, and Z-axis direction).

The measurement control mechanism 24 determines the shape of the grindstones 14, 18 in a state where the grindstone holding mechanisms 15, 19 are not tilted with respect to the rotation center axis Ac (before tilting), and the shape of the grindstone holding mechanisms 15, 19 with respect to the rotation center axis Ac. This is a mechanism that controls the shape measuring mechanism 22 and the NC moving mechanism 23 in order to measure the shapes of the grindstones 14 and 18 in the tilted state (after tilting).

The data processing device 25 synthesizes the shape data of the grindstones 14 and 18 acquired by the measurement control mechanism 24, and calculates the contact between the workpiece W and the grindstones 14 and 18 when the grindstone holding mechanisms 15 and 19 are tilted at a desired angle. This is a mechanism for calculating the inclination angle of the grindstone holding mechanisms 15 and 19 to obtain a workpiece W having a desired curvature from point data. This data processing device 25 is realized, for example, by a general-purpose information processing device such as a personal computer or a workstation.

The processing control mechanism 26 is a mechanism for controlling the grindstone turning mechanisms 17 and 21 based on the output results of the data processing device 25. The reference surface 27 is a surface for taking a reference for the measured values of the shape measuring mechanism 22. In addition, in FIG. 3, the symbol O indicates the equipment origin of the spherical grinding device 1, the symbol St1 indicates the reference point of the grinding wheel 14 (grinding wheel reference), and the symbol St2 indicates the reference point of the grinding wheel 18 (grinding wheel reference). .

(Spherical grinding method)
A spherical surface grinding method according to an embodiment of the present invention will be described with reference to FIGS. 5 to 14. As shown in FIG. 5, the spherical surface grinding method according to the embodiment includes a first shape measurement step (step S1), a second shape measurement step (step S2), and a shape data acquisition step (step S3). , a contact point calculation step (step S4), an inclination angle calculation step (step S5), and a machining step (step S6).

<First shape measurement process>
In the first shape measurement step, the shapes of the grindstones 14 and 18 before tilting are measured (step S1). Specifically, in the first shape measurement step, the cup-shaped grindstones 14 and 18 are not tilted with respect to the center axis of rotation Ac for turning the grindstones 14 and 18 (see A in FIG. 1). , the shapes of the grindstones 14 and 18 are measured by the shape measuring mechanism 22. Furthermore, in the first shape measurement step, the shapes of the grindstones 14 and 18 arranged upward are measured from above by the shape measurement mechanism 22.

<Second shape measurement process>
In the second shape measurement step, the shapes of the grindstones 14 and 18 after tilting are measured (step S2). Specifically, in the second shape measurement step, the shapes of the grindstones 14 and 18 are measured by the shape measurement mechanism 22 in a state where the grindstones 14 and 18 are tilted with respect to the rotation center axis Ac. In the second shape measurement step, the shapes of the grindstones 14 and 18, which are arranged to be inclined at a predetermined angle, are measured from above by the shape measurement mechanism 22. Further, in the second shape measurement step, it is preferable to measure the shape data while tilting the grindstones 14 and 18 to a state close to the inclination angle during actual processing.

<Shape data acquisition process>
In the shape data acquisition step, as shown in FIG. 6, the shape data of the grinding wheels 14 and 18 acquired in the first shape measurement step and the shape data of the grindstones 14 and 18 acquired in the second shape measurement step are combined. By doing so, estimated shape data when the grindstones 14 and 18 are tilted with respect to the rotation center axis Ac is obtained (step S3). Note that "shape data" refers to point sequence data indicating the shapes of the grindstones 14 and 18. This shape data also includes position data (coordinate data) of each point.

Specifically, the shape data acquisition step includes a feature point extraction step and an estimated shape data acquisition step. In the feature point extraction process, for example, as shown in part C of FIG. Extract feature points common to the data. Subsequently, in the estimated shape data acquisition step, the shape data of the grinding wheels 14, 18 acquired in the first shape measurement step and the shape data of the grinding wheels 14, 18 acquired in the second shape measurement step are calculated based on the feature points. Estimated shape data is obtained by combining the shape data.

Here, the shape data of the whetstones 14, 18 obtained in the second shape measurement step is obtained by measuring the whetstones 14, 18 at an angle, so a portion (one end) of the whetstones 14, 18 is The data is only about the shape, and the overall shape and position of the grindstones 14 and 18 are unknown. On the other hand, in the shape data acquisition step, in order to fit the shape data obtained in the second shape measurement step to the shape data obtained in the first shape measurement step, the overall shape and position of the grinding wheels 14 and 18 are accurately grasped. It becomes possible to do so.

In the first shape measurement step, for example, as shown in section D in FIG. 7, the shape data of the upper surface of both ends of the grindstone 14 before tilting and its center position (grindstone rotation axis At1) are measured. I can do it. Further, in the second shape measurement step, for example, as shown in section E in FIG. 8, shape data of the upper surface of one end (left side in the paper) of the grindstone 14 after tilting can be measured. In the shape data acquisition step, by combining these shape data, as shown in FIG. 9, estimated shape data of the grindstone 14 after tilting and its center position (grindstone rotation axis At1) can be obtained. can. Note that although FIGS. 7 to 9 show an example in which the shape data of the grindstone 14 is measured and synthesized, the shape data of the grindstone 18 is also measured and synthesized in the same manner.

Further, as shown in FIG. 7, for example, the vicinity of the contact point between the grindstone 14 (and the grindstone 18) and the workpiece W is often inclined, and there is a strong tendency for errors in shape measurement to become large. Therefore, in the second shape measurement step, it is preferable to measure the shape data while tilting the grindstones 14 and 18 to a state close to the inclination angle during actual processing. By combining the shape data measured in this way with the shape data acquired in the first shape measurement step, the shape data of the entire grindstones 14 and 18 can be acquired with high precision. As a result, in the contact point calculation step to be described later, the contact point during processing can be calculated with high accuracy.

<Contact point calculation process>
In the contact point calculation step, the contact points between the grindstones 14 and 18 and the workpiece W having a desired curvature are calculated based on the estimated shape data acquired in the shape data acquisition step (step S4). Note that the "contact point" specifically refers to the trajectory of the contact point between the grinding wheels 14 and 18 (also referred to as the rotation trajectory) when processing the workpiece W by rotating the grindstones 14 and 18 around the rotation center axis Ac. It shows.

<Inclination angle calculation process>
In the inclination angle calculation step, the inclination angle of the grindstones 14 and 18 around the rotation center axis Ac, which is set in actual machining, is calculated based on the contact point calculated in the contact point calculation step (step S5).

<Processing process>
In the machining process, the grindstones 14 and 18 are set to the inclination angle calculated in the inclination angle calculation process, and the workpiece W is spherically ground (step S6).

Here, in the spherical grinding of the workpiece W, as mentioned above, due to the limits of equipment accuracy, for example, the theoretical (simulation) center axis of rotation Ac and the actual center axis of rotation (true center axis of rotation) Ac may differ. There may be errors between the two. Therefore, in the spherical surface grinding method according to the embodiment, the true pivot axis Ac may be determined.

In this case, in the second shape measurement step, the shape of the grindstones 14 and 18 is measured by the shape measurement mechanism 22 while the grindstones 14 and 18 are tilted at a plurality of different angles with respect to the rotation center axis Ac. do. Then, based on the shape data of the grindstones 14 and 18 before tilting measured in the first shape measurement process and the shape data of the plurality of grindstones 14 and 18 measured in the second shape measurement process, the true turning A turning center axis estimation step for estimating the center axis Ac is carried out. Note that this turning center axis estimation step may be performed after the second shape measurement step and before the inclination angle calculation step.

Subsequently, in a fifth step, the true turning center axis Ac estimated in the turning center axis estimation step is further used to calculate the inclination angle of the grinding wheels 14, 18 with respect to the turning center axis Ac, which is set in actual machining. .

A method for estimating the true turning center axis Ac in the turning center axis estimation step will be described with reference to FIGS. 10 to 12. Below, as shown in the same figure, the distance between the theoretical center axis of rotation (denoted as "center axis of rotation (Sim)") and the true center axis of rotation (described as "center axis of rotation (actual)"). The explanation is based on the assumption that there is an error. Moreover, FIG. 11 shows a case where the inclination angle θ of the grindstone is set to “20°”, and FIG. 12 shows a case where the inclination angle θ of the grindstone is set to “40°”.

First, as shown in Fig. 10, there is a circle with radius rt from the turning center axis (Sim) to the end (corner) of the grinding wheel, and a circle with radius rf from the turning center axis (actual) to the end of the grinding wheel. Draw each. Next, the angles θt0 and θf0 from the turning center axis (Sim) and the turning center axis (actual) to the end of the grinding wheel before tilting, and the inclination angle θ=20° of the grinding wheel shown in FIG. Based on the equation of the circle, we can calculate the coordinates (yct1, zct1) of the theoretical grinding wheel position (denoted as "grinding wheel position (Sim)") and the actual grinding wheel position ("grinding wheel position (actual)"). The coordinates (yft1, zft1) of the notation) are determined. Then, based on these coordinates, deviation amounts Δy1 and Δz1 of the grindstone position (actual) with respect to the grindstone position (Sim) are determined.

Next, the angles θt0 and θf0 from the turning center axis (Sim) and the turning center axis (actual) to the end of the grinding wheel before tilting, and the inclination angle θ=40° of the grinding wheel shown in FIG. Based on the equation of the circle, we can calculate the coordinates (yct2, zct2) of the theoretical grinding wheel position (denoted as "grinding wheel position (Sim)") and the actual grinding wheel position ("grinding wheel position (actual)"). The coordinates (yft2, zft2) of the notation) are determined. Then, based on these coordinates, the deviation amounts Δy2 and Δz2 of the grindstone position (actual) with respect to the grindstone position (Sim) are determined. The true turning center axis Ac is estimated using the deviation amounts Δy1, Δz1, Δy2, and Δz2 obtained as described above.

In this way, by comparing the shape data when the whetstones 14 and 18 are tilted around the theoretical center axis of rotation Ac and the shape data when the whetstones 14 and 18 are tilted around the true center axis of rotation Ac, The coordinates of the true center axis of rotation Ac can be determined. This makes it possible to grasp the shapes and accurate trajectories of the grinding wheels 14, 18 using the coordinates of the true turning center axis Ac. ) can be accurately grasped. As a result, the inclination angles of the grindstones 14 and 18 necessary for grinding to a desired curvature can be determined with high precision. Furthermore, higher precision machining quality can be obtained in terms of the curvature of the workpiece W and the amount of grinding.

For example, as shown in FIG. 13, if there is no undulation in the orbits of the whetstones 14 and 18 around the pivot axis Ac, the contact point is calculated in the contact point calculation process or the pivot axis estimation process is performed as described above. By estimating the true center axis of rotation Ac, the inclination angles of the grindstones 14 and 18 can be determined with high precision. On the other hand, as shown in FIG. 14, for example, if there are undulations in the orbits of the whetstones 14 and 18 around the rotation center axis Ac, the contact points are calculated in the contact point calculation process, or the true rotation center is determined in the rotation center axis estimation process. There may be cases in which the inclination angles of the grindstones 14 and 18 cannot be determined with high precision simply by estimating the axis Ac.

In this case, as described above, in the second shape measurement step, by using the shape data obtained by tilting the grinding wheels 14 and 18 to a state close to the inclination angle during actual machining, it is possible to detect undulations in the orbit. Even in this case, the inclination angles of the grindstones 14 and 18 can be determined with high precision.

Further, it is also conceivable that the inclination angle when actually machining the workpiece W is slightly changed (corrected) from the inclination angle at the time of measurement in the second shape measurement step. In this case, as described above, by estimating the true turning center axis Ac in the turning center axis estimation step, the inclination angles of the grindstones 14 and 18 can be determined with high precision.

According to the spherical surface grinding method and spherical surface grinding apparatus according to the present embodiment described above, it is possible to estimate the shape data of the grindstones 14, 18 when the grindstones 14, 18 are inclined with respect to the rotation center axis Ac. Accordingly, data on accurate contact points between the grindstones 14 and 18 and the workpiece W can be obtained. Thereby, the workpiece W can be ground with high precision.

Further, according to the spherical surface grinding method and spherical surface grinding apparatus according to the present embodiment, even when processing a micro diameter lens such as Φ1 mm for endoscopes that requires high precision of 1 μm or less, the workmanship can be evaluated and repeatedly adjusted. Grinding can be completed in one go without repeating machining and follow-up work. Therefore, it is possible to improve productivity and significantly reduce costs.

Moreover, in the spherical surface grinding method and spherical surface grinding apparatus according to the present embodiment, the shape data near the contact point between the grinding wheels 14, 18 and the workpiece W, where optical measurement errors are likely to occur, is converted into measurement data at a plurality of inclination angles. A more accurate grindstone shape can be obtained by synthesizing and correcting. As a result, errors in estimating the contact points between the grindstones 14 and 18 and the workpiece W are reduced, and highly accurate machining is achieved.

Further, by using the spherical surface grinding method and spherical surface grinding apparatus according to the present embodiment, the shape of the grindstones 14 and 18 after processing the workpiece W, that is, the amount of wear of the grindstones 14 and 18 can be calculated. Therefore, for example, correction of curvature when continuously machining the workpiece W can be automated and highly accurate.

That is, conventionally, a quality inspection was performed after processing a workpiece, and the curvature of the next workpiece was corrected each time based on the quality inspection results. On the other hand, in the spherical grinding method and spherical grinding apparatus according to the present embodiment, the amount of wear of the grinding wheels 14 and 18 is calculated based on the shape measurement results performed before processing the work W, and the amount of wear of the grinding wheels 14 and 18 is calculated based on the amount of wear. The curvature of the workpiece W can be automatically corrected.

Furthermore, in the past, the curvature of the workpiece was corrected by, for example, adjusting the swivel angle of the grinding wheel, but in the spherical grinding method and spherical grinding apparatus according to the present embodiment, the workpiece W is moved in the Y-axis direction. Thereby, the curvature of the workpiece W can be corrected with high precision. That is, by shifting the workpiece W in the Y-axis direction (for example, see FIG. 1) using the workpiece holding mechanism 11, the curvature of the workpiece W can be finely adjusted.

Furthermore, in the past, the shape of the grindstone was measured each time a workpiece was processed, but in the spherical grinding method and spherical grinding apparatus according to the present embodiment, the grindstones 14, 18 are measured after processing several workpieces W, for example. It becomes possible to measure the shape of the workpiece W, and perform correction if necessary to correct the curvature of the workpiece W.

Above, the spherical surface grinding method and spherical surface grinding apparatus according to the present invention have been specifically explained using the mode for carrying out the invention, but the gist of the present invention is not limited to these descriptions, and the scope of the claims must be interpreted broadly based on the description in Furthermore, it goes without saying that various changes and modifications based on these descriptions are also included within the spirit of the present invention.

For example, in this embodiment, as shown in FIG. 3, the spherical grinding device 1 was introduced as an example, which includes the grindstone 14 for rough grinding and the grindstone 18 for fine grinding. The structure may include only one of the grindstones 18 for fine grinding, or may include three or more types of grindstones.

Further, the workpiece holding mechanism 11 (see FIG. 3) in this embodiment may adjust the thickness of the workpiece W by controlling the workpiece W in the Z-axis direction. Furthermore, although the present embodiment has been described assuming that the work W to be machined is mainly a lens, it may be any object other than lenses as long as it can be spherically ground. Further, the material of the workpiece W can be selected as appropriate, and for example, a grindable material such as sapphire or ceramic may be selected as well as glass.

In addition, in this embodiment, a laser displacement meter is illustrated as the shape measuring mechanism 22 (see FIG. 3), but there are other types of displacement meters that can measure optically, mechanically, planarly, in a band shape, or linearly. Various measurement mechanisms can be used. Further, in this embodiment, cup-shaped grinding wheels are used as the grinding wheels 14 and 18, but the grain size and type of the grinding wheels can be selected as appropriate depending on the required quality of the workpiece W.

1 Spherical grinding device 11 Work holding mechanism 12 Work rotating mechanism 13 Retracting mechanism 14 Grinding wheel (first grinding wheel)
15 Grindstone holding mechanism 16 Grindstone rotation mechanism 17 Grindstone turning mechanism 18 Grindstone (second grindstone)
19 Grindstone holding mechanism 20 Grindstone rotation mechanism 21 Grindstone rotation mechanism 22 Shape measurement mechanism 23 NC movement mechanism 24 Measurement control mechanism 25 Data processing device 26 Processing control mechanism 27 Reference surface Ac Rotation center axis Ao Optical axis At1 Grindstone rotation axis At2 Grindstone rotation axis O Equipment origin St1, St2 Grinding wheel reference W Workpiece

Claims (4)

A first step of measuring the shape of the cup-shaped whetstone with a shape measuring mechanism in a state where the whetstone is not tilted with respect to a central axis of rotation for turning the whetstone;
a second step of measuring the shape of the whetstone with the shape measuring mechanism in a state where the whetstone is tilted with respect to the rotation center axis;
By combining the shape data of the whetstone acquired in the first step and the shape data of the whetstone acquired in the second step, when the whetstone is tilted with respect to the center axis of rotation. a third step of acquiring estimated shape data;
a fourth step of calculating a contact point between the grindstone and a workpiece having a desired curvature based on the estimated shape data;
a fifth step of calculating an inclination angle of the grindstone with respect to the rotation center axis, which is set in actual processing, based on the contact point;
a sixth step of setting the grindstone at the inclination angle and spherically grinding the workpiece;
Spherical grinding method including. The third step is
a feature point extraction step of extracting feature points common to the shape data of the grindstone obtained in the first step and the shape data of the grindstone obtained in the second step;
An estimated shape in which the shape data of the grindstone obtained in the first step and the shape data of the grindstone obtained in the second step are combined based on the feature points to obtain the estimated shape data. a data acquisition process;
The spherical surface grinding method according to claim 1, comprising: In the second step, the shape of the whetstone is measured by the shape measuring mechanism in a state where the whetstone is tilted at a plurality of different angles with respect to the rotation center axis,
A turning center axis estimation step of estimating a true turning center axis based on the shape data of the grindstone measured in the first step and the shape data of the plurality of grindstones measured in the second step. Furthermore, it includes
The fifth step further includes calculating the inclination angle using the true center axis of rotation.
The spherical surface grinding method according to claim 1 or claim 2. a work holding mechanism that holds the work;
a work rotation mechanism that rotates the work holding mechanism around a work rotation axis;
A grindstone holding mechanism that holds a cup-shaped grindstone;
a grindstone rotation mechanism that rotates the grindstone around a grindstone rotation axis;
a grindstone rotation mechanism that rotates the grindstone rotation mechanism around a rotation center axis that is perpendicular to the grindstone rotation axis;
a shape measuring mechanism whose optical axis is an axis parallel to the work rotation axis;
an NC moving mechanism that moves the shape measuring mechanism in a three-dimensional direction;
a retraction mechanism that retracts the workpiece holding mechanism to a position away from the grindstone rotation axis;
To measure the shape of the whetstone in a state where the whetstone holding mechanism is not inclined with respect to the turning center axis, and the shape of the whetstone in a state where the whetstone holding mechanism is inclined with respect to the turning center axis, respectively. , a measurement control mechanism that controls the shape measurement mechanism and the NC movement mechanism;
Synthesize the shape data of the grindstone acquired by the measurement control mechanism, and use data on the contact point between the workpiece and the grindstone when the grindstone holding mechanism is tilted at a desired angle with respect to the rotation center axis. , a data processing device that calculates an inclination angle of the grindstone holding mechanism to obtain a workpiece with a desired curvature;
a processing control mechanism that controls the grindstone rotation mechanism based on the output result of the data processing device;
A spherical grinding device equipped with

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