Polishing method and polishing apparatus

Abstract

To provide a polishing method and a polishing device which can suppress the occurrence of a defective workpiece.SOLUTION: A polishing method comprises the steps of: performing the first polishing processing; acquiring the height position in the center axis direction of a workpiece holding mechanism that holds a workpiece after the first polishing processing; calculating the height of a polishing surface of a grindstone on the basis of the height position of the workpiece holding mechanism and the previously-acquired thickness of the workpiece; calculating a height change amount of the polishing surface of the grindstone after the first polishing processing on the basis of the height of the polishing surface of the grindstone before and after the first polishing processing; acquiring a curvature radius of the polishing surface of the grindstone; calculating a change amount of an area of the polishing surface of the grindstone after the first polishing processing on the basis of the height change amount of the polishing surface of the grindstone and the curvature radius of the polishing surface of the grindstone; adjusting a polishing processing condition of the workpiece on the basis of the change amount of an area of the polishing surface of the grindstone; and performing the second polishing processing on the basis of the polishing processing condition after adjustment.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a polishing method and a polishing apparatus.

Background Art

[0002] Patent Document 1 discloses a technique for determining polishing conditions such as processing pressure and processing rotational speed based on the contact area between a workpiece to be polished and a grindstone.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the polishing of a workpiece, polishing is performed by rubbing a rotated workpiece against a grindstone that is oscillated and rotated, so that the shape of the grindstone approaches the shape of the workpiece. As a result, the shape of the workpiece is made into a desired spherical shape. In this polishing process, if a plurality of workpieces are processed with the same grindstone, the grindstone also gradually wears, so that the shape of the workpiece processed later also changes.

[0005] When the polishing surface of the grindstone wears due to repeated polishing, the height (depth) of the polishing surface of the grindstone changes, and the area of the polishing surface also changes. When the area of the polishing surface of the grindstone changes in this way, even if polishing is performed under the same polishing conditions as before, the polishing amount of the workpiece changes. As a result, the processing quality of the workpiece may differ from the assumption, leading to the risk of defects.

[0006] The present invention has been made in view of the above, and an object thereof is to provide a polishing method and a polishing apparatus capable of suppressing the occurrence of defective workpieces.

Means for Solving the Problems

[0007] In order to solve the above-described problems and achieve the object, a polishing method according to the present invention includes a step of performing first polishing by bringing a swinging grindstone into contact with a workpiece rotated about a central axis; a step of obtaining a height position in the central axis direction of a workpiece holding mechanism that holds the workpiece after the first polishing; a step of calculating the height of the polishing surface of the grindstone based on the height position of the workpiece holding mechanism and the thickness of the workpiece obtained in advance; a step of calculating a change amount of the height of the polishing surface of the grindstone after the first polishing based on the height of the polishing surface of the grindstone before and after the first polishing; a step of obtaining a radius of curvature of the polishing surface of the grindstone; a step of calculating a change amount of the area of the polishing surface of the grindstone after the first polishing based on the change amount of the height of the polishing surface of the grindstone and the radius of curvature of the polishing surface of the grindstone; a step of adjusting polishing conditions of the workpiece based on the change amount of the area of the polishing surface of the grindstone; and a step of performing second polishing based on the adjusted polishing conditions.

[0008] The polishing method according to the present invention further includes, in the above invention, a step of obtaining the thickness of the workpiece after polishing performed before the first polishing as the thickness of the workpiece.

[0009] In the polishing method according to the present invention, in the above invention, in the step of adjusting the polishing conditions, when the change amount of the area of the polishing surface of the grindstone exceeds a predetermined threshold value, the area of the polishing surface is corrected to the area of a predetermined polishing surface by processing the grindstone.

[0010] In the polishing method according to the present invention, in the above invention, in the step of adjusting the polishing conditions, when the change amount of the area of the polishing surface of the grindstone exceeds a predetermined threshold value, the contact pressure between the grindstone and the workpiece or the swing angle of the grindstone is changed.

[0011] In the polishing method according to the present invention, in the above invention, in the step of adjusting the polishing conditions, further, based on the relationship between the radius of curvature of the workpiece and the area of the polishing surface of the grinding wheel, it is determined whether adjustment of the polishing conditions is necessary, and when it is determined that adjustment of the polishing conditions is necessary, the polishing conditions are adjusted.

[0012] The polishing method according to the present invention, in the above invention, further includes a step of making the swing center of the grinding wheel coincide with the center of curvature of the polishing surface of the grinding wheel based on the amount of change in the height of the polishing surface of the grinding wheel.

[0013] In the polishing method according to the present invention, in the above invention, the step of obtaining the height position is a step of measuring the change in the total of the thickness of the workpiece and the thickness of the grinding wheel that changes after the first polishing, and the change in the total of the thickness of the workpiece and the thickness of the grinding wheel is measured by a displacement sensor provided in the workpiece holding mechanism and measuring the displacement of the workpiece in the central axis direction.

[0014] In order to solve the above-described problems and achieve the object, a polishing apparatus according to the present invention includes a workpiece holding mechanism that holds a workpiece to be polished, a grinding wheel for polishing the workpiece, a grinding wheel holding mechanism that holds and swings the grinding wheel, a height measuring mechanism that measures the height position of the workpiece holding mechanism, a correction processing mechanism for correcting the area of the polishing surface of the grinding wheel, a grinding wheel area calculation mechanism that calculates the amount of change in the area of the polishing surface of the grinding wheel based on the thickness of the workpiece after polishing and the height position of the workpiece holding mechanism, and a correction necessity determination mechanism that determines whether correction of the grinding wheel by the correction processing mechanism is necessary based on the amount of change in the area of the polishing surface of the grinding wheel.

[0015] In the polishing apparatus according to the present invention, in the above invention, the correction necessity determination mechanism determines whether correction of the grinding wheel by the correction processing mechanism is necessary based on the amount of change in the area of the polishing surface of the grinding wheel and the radius of curvature of the workpiece before processing that is input into the polishing process.

Advantages of the Invention

[0016] In the polishing method and polishing apparatus according to the present invention, by adjusting the polishing conditions of the workpiece based on the change amount of the area of the polishing surface of the grindstone, the workpiece can be processed with the expected quality, so that the generation of defective workpieces can be suppressed.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the polishing method and polishing apparatus according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and the constituent elements in the following embodiments include those that can be replaced and are easy for those skilled in the art, or those that are substantially the same.

[0019] (Polishing Apparatus) The polishing apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. The polishing apparatus 1 is for polishing the workpiece W. This polishing apparatus 1 can perform polishing on both the convex-worked workpiece W and the concave-worked workpiece W. In the present embodiment, as shown in FIG. 1, the polishing apparatus 1 for polishing the convex-worked workpiece W will be described.

[0020] The grinding device 1 includes a work holding mechanism 11, a pressing cylinder 12, a work rotating mechanism 13, a height measuring mechanism 14, a grindstone 15, a grindstone holding mechanism 16, a grindstone rotating mechanism 17, a grindstone area calculating mechanism 18, a correction necessity determination mechanism 19, a correction processing mechanism 20, and a shape evaluation mechanism 21. In FIG. 1, the grindstone area calculating mechanism 18, the correction necessity determination mechanism 19, and the shape evaluation mechanism 21 are illustrated as separate devices, but these mechanisms may be configured by one device.

[0021] The work holding mechanism 11 is a mechanism for holding a work W to be processed. Examples of the work W include a glass lens having a diameter of about Φ1 to 3 mm. The pressing cylinder 12 is a mechanism for pressing the work holding mechanism 11 in the direction of the central axis of the work W (hereinafter referred to as the "work rotation axis") Aw with a predetermined pressure. The work rotating mechanism 13 is a mechanism for rotating the work holding mechanism 11 around the work rotation axis Aw.

[0022] The height measuring mechanism 14 is a mechanism for measuring the height position of the work holding mechanism 11. The height measuring mechanism 14 is provided on the work holding mechanism 11. Further, the height measuring mechanism 14 is constituted by, for example, a displacement sensor (such as a Z-axis scale) that measures the displacement of the work W in the direction of the work rotation axis Aw.

[0023] Here, when the grinding process of the work W is performed, both the grindstone 15 and the work W are worn. As a result, the work holding mechanism 11 is pressed by the pressing cylinder 12 by the amount of wear of both, and the position of the work holding mechanism 11 drops downward. Therefore, as shown in FIG. 1, by installing the height measuring mechanism 14 on the work holding mechanism 11, the total wear amount of the work W and the grindstone 15 can be detected.

[0024] The grinding wheel 15 is a tool for polishing the workpiece W. A flat portion 151 for preventing chipping is provided at the edge of the grinding wheel 15. Further, the grinding wheel 15 has a polishing surface 152 for polishing the workpiece W. The grinding wheel holding mechanism 16 is a mechanism for holding the grinding wheel 15 and swinging it around a predetermined swing center. The grinding wheel rotation mechanism 17 is a mechanism for rotating the grinding wheel holding mechanism 16 around the central axis (hereinafter referred to as the "grinding wheel rotation axis") At of the grinding wheel 15.

[0025] Further, when the grinding wheel 15 wears due to polishing and the height of the polishing surface 152 of the grinding wheel 15 changes as shown in FIG. 2, for example, the grinding wheel holding mechanism 16 corrects the position of the grinding wheel 15 upward based on the amount of change in the height of the polishing surface 152 of the grinding wheel 15. Thereby, the swing center of the grinding wheel 15 is made to coincide with the curvature center of the polishing surface 152 of the grinding wheel 15.

[0026] The grinding wheel area calculation mechanism 18 is a mechanism for calculating the amount of change in the area of the polishing surface 152 of the grinding wheel 15. The grinding wheel area calculation mechanism 18 calculates the amount of change in the area of the polishing surface 152 of the grinding wheel 15 based on the thickness of the workpiece W after polishing, the radius of curvature of the workpiece W, and the height position of the workpiece holding mechanism 11 measured by the height measurement mechanism 14. Specifically, the amount of change in the height of the grinding wheel 15 is calculated using the thickness of the workpiece W after polishing this time and the previous time, and the data of the height positions of the workpiece holding mechanism 11 this time and the previous time. Further, assuming that the radius of curvature of the workpiece W and the radius of curvature of the polishing surface 152 are substantially the same, the grinding wheel area is calculated from the amount of change in the height of the grinding wheel and the radius of curvature of the polishing surface 152.

[0027] Note that for the "thickness of the work W" and the "radius of curvature of the work W", for example, the measured values measured by a thickness measuring device (not shown) and the shape evaluation mechanism 21 can be used. Also, the calculated grinding wheel area is a value obtained by evaluating and calculating the work W as a result of processing. Therefore, in order to reflect the information of the calculated grinding wheel area in the next processing, it is necessary to interrupt the grinding process until the calculation of the grinding wheel area is completed. However, since the change in the grinding wheel area due to processing per piece is not necessarily large, it is possible to perform continuous production by starting the next processing without waiting for the calculation of the grinding wheel area, and productivity can be further improved.

[0028] The correction necessity determination mechanism 19 is a mechanism for determining whether correction of the grinding wheel 15 is necessary. The correction necessity determination mechanism 19 determines whether correction of the grinding wheel 15 by the correction processing mechanism 20 is necessary based on the change amount of the area of the grinding surface 152 of the grinding wheel 15.

[0029] The correction processing mechanism 20 is a mechanism for correcting the area of the grinding surface 152 of the grinding wheel 15. As shown in FIG. 3, the correction processing mechanism 20 corrects the area of the grinding surface 152 of the grinding wheel 15 by grinding the flat portion 151 of the grinding wheel 15.

[0030] The shape evaluation mechanism 21 is also a mechanism used to evaluate the shape of the work W before processing that is input into the grinding device 1 this time. The shape evaluation mechanism 21 evaluates the shape of the work W based on, for example, a chart (see FIG. 5 described later) prepared in advance for managing the processing quality of the work W. Note that the "shape of the work W" specifically refers to the radius of curvature of the work W.

[0031] (Grinding Method) A polishing method according to an embodiment of the present invention will be described with reference to FIGS. 4 and 5. In the polishing method according to the embodiment, as shown in FIG. 4, a first polishing process (step S1), a height position acquisition process (step S2), a thickness acquisition process (step S3), a height calculation process (step S4), a height change amount calculation process (step S5), a grindstone inner diameter calculation process (step S6), an area change amount calculation process (step S7), a processing condition adjustment process (step S8), and a second polishing process (step S9) are performed.

[0032] In the polishing method according to the embodiment, the first polishing process (step S1) is a process of performing a polishing process on the first workpiece W, and the second polishing process (step S9) is a process of performing a polishing process on a second workpiece W different from the first workpiece W.

[0033] Further, the first polishing process (step S1) is performed based on the polishing process conditions determined by the processing condition adjustment process (step S8) performed after the previous polishing process. Also, the processing condition adjustment process (step S8) is performed to determine the polishing process conditions for the second polishing process (step S9). Among the polishing methods according to the embodiment, the height calculation process, the height change amount calculation process, the grindstone inner diameter calculation process, and the area change amount calculation process are mainly performed by the grindstone area calculation mechanism 18.

[0034] <First Polishing Process> In the first polishing process, the grindstone 15 and the workpiece W are brought into contact with each other to perform a polishing process (step S1). In the first polishing process, the grindstone holding mechanism 16 rotates and swings the grindstone 15 around the grindstone rotation axis At. Also, the workpiece holding mechanism 11 rotates the workpiece W around the workpiece rotation axis Aw. Then, the workpiece W is polished by rubbing the rotated and swung grindstone 15 against the rotated workpiece W.

[0035] <Height Position Acquisition Process> In the height position acquisition step, after the first polishing step, the height position in the direction of the workpiece rotation axis Aw of the workpiece holding mechanism 11 that holds the workpiece W is acquired (step S2). In the height position acquisition step, for example, by a height measurement mechanism 14 composed of a displacement sensor, the change in the total thickness of the workpiece W and the grinding wheel 15 that changes after the first polishing step is measured.

[0036] That is, the height measurement mechanism 14 measures the total value of the thickness of the workpiece W and the thickness of the grinding wheel 15 (hereinafter referred to as the "total thickness value") by measuring the height position of the workpiece holding mechanism 11. Further, each time the workpiece W is polished by the polishing apparatus 1, the height measurement mechanism 14 measures the total thickness value, thereby measuring the difference between the total thickness value in the current polishing process and the total thickness value in the previous polishing process, that is, the change amount of the total thickness value.

[0037] <Thickness acquisition step> In the thickness acquisition step, the thickness (wall thickness) of the polished workpiece W is acquired (step S3). In the thickness acquisition step, the thickness of the workpiece W after polishing is measured by a thickness measurement mechanism (not shown). At that time, together with the thickness of the workpiece W, the radius of curvature of the workpiece W may be measured using the shape evaluation mechanism 21.

[0038] Here, in the thickness acquisition step, the workpiece W during polishing may be temporarily removed from the polishing apparatus 1 to measure the thickness of the workpiece W, but it is more preferable to acquire the thickness of the workpiece W after the polishing step performed before the first polishing step. This is because when the height of the workpiece holding mechanism 11 is acquired in the height position acquisition step, the thickness of the workpiece W during polishing cannot be acquired. Therefore, since it is necessary to remove the workpiece W from the workpiece holding mechanism 11 for measurement, the polishing process will be interrupted. In addition, when the workpiece W is attached and detached during the polishing process, processing defects are likely to occur. On the other hand, in the thickness acquisition step, by acquiring the thickness of the workpiece W that has already been polished, it is possible to acquire the information necessary for adjusting the polishing conditions of the workpiece W without interrupting the polishing process.

[0039] <Height calculation step> In the height calculation step, based on the height position of the work holding mechanism 11 obtained in the height position acquisition step and the thickness of the work W obtained in the thickness acquisition step, the height of the polishing surface 152 of the grinding wheel 15 is calculated (step S4). In the height calculation step, the height of the polishing surface 152 of the grinding wheel 15 is calculated by subtracting the thickness of the work W from the total thickness of the work W and the grinding wheel 15, that is, the height position of the work holding mechanism 11.

[0040] <Height change amount calculation step> In the height change amount calculation step, based on the height of the polishing surface 152 of the grinding wheel 15 before and after the first polishing process, the height change amount of the polishing surface 152 of the grinding wheel 15 after the first polishing process is calculated (step S5). In the height change amount calculation step, the height change amount of the polishing surface 152 of the grinding wheel 15 is calculated by subtracting the height of the polishing surface 152 of the grinding wheel 15 after the polishing process (previous polishing process) performed before the first polishing process from the height of the polishing surface 152 of the grinding wheel 15 after the first polishing process (current polishing process). Note that the above is a method of calculating the height change amount from the absolute value of the grinding wheel height, but the height change amount may also be calculated from the relative change amount. Specifically, the height change amount of the polishing surface 152 of the grinding wheel 15 is calculated by subtracting the difference between the thickness of the work W after the current polishing and the thickness of the work W after the previous polishing from the difference between the height of the work holding mechanism 11 at the time of the current polishing and the height of the work holding mechanism 11 at the time of the previous polishing.

[0041] <Grinding wheel inner diameter calculation step> In the grinding wheel inner diameter calculation step, the inner diameter of the polishing surface 152 of the grinding wheel 15 is calculated (step S6). In the grinding wheel inner diameter calculation step, based on the radius of curvature of the work W obtained together with the thickness in the thickness acquisition step, the inner diameter of the polishing surface 152 of the grinding wheel 15 is calculated. Note that in the grinding wheel inner diameter calculation step, the measured radius of curvature of the work W may be used as the radius of curvature of the polishing surface 152 of the grinding wheel 15, or a measured value directly measuring the radius of curvature of the polishing surface 152 of the grinding wheel 15 may be used.

[0042] <Area change amount calculation step> In the area change amount calculation step, based on the height change amount of the polishing surface 152 of the grinding wheel 15 calculated in the height change amount calculation step and the inner diameter of the polishing surface 152 of the grinding wheel 15 calculated in the grinding wheel inner diameter calculation step, the change amount of the area of the polishing surface 152 of the grinding wheel 15 after the first polishing process is calculated (step S7). In this embodiment, the area of the polishing surface 152 of the grinding wheel 15 is calculated from the calculated inner diameter of the polishing surface 152 of the grinding wheel 15 and the height change amount of the polishing surface 152. However, it is also possible to calculate the area of the grinding wheel 15 using the radius of curvature of the polishing surface 152 instead of the inner diameter of the polishing surface 152 of the grinding wheel 15.

[0043] <Processing condition adjustment step> In the processing condition adjustment step, based on the change amount of the area of the polishing surface 152 of the grinding wheel 15 calculated in the area change amount calculation step, the polishing processing conditions of the workpiece W in the second polishing process are adjusted (step S8).

[0044] In the processing condition adjustment step, for example, as shown in FIG. 3, by processing the flat portion 151 of the grinding wheel 15 with the correction processing mechanism 20, the area of the polishing surface 152 of the grinding wheel 15 is corrected to a predetermined (desired) area of the polishing surface 152. The processing of the flat portion 151 of the grinding wheel 15 in the processing condition adjustment step is performed, for example, when the change amount of the area of the polishing surface 152 of the grinding wheel 15 exceeds a predetermined threshold value. In this way, in order to maintain the processing quality of the workpiece W, the polishing amount of the workpiece W can be adjusted by correcting the area of the polishing surface 152 of the grinding wheel 15. In this embodiment, since the inner diameter of the polishing surface 152 of the grinding wheel 15 is calculated, it is also possible to utilize the correction processing mechanism 20 to prevent chipping of the grinding wheel 15 due to the disappearance of the flat portion 151 and the sharp angle of the edge portion of the inner diameter of the grinding wheel 15.

[0045] In addition, in the processing condition adjustment step, for example, the polishing processing conditions may be adjusted by changing the contact pressure between the grindstone 15 and the workpiece W or the swing angle of the grindstone 15. In this case, when the change amount of the area of the polishing surface 152 of the grindstone 15 exceeds a predetermined threshold value, the contact pressure between the grindstone 15 and the workpiece W or the swing angle of the grindstone 15 is changed. In this way, in order to maintain the processing quality of the workpiece W, the polishing amount of the workpiece W can be adjusted by changing the contact pressure between the grindstone 15 and the workpiece W and the swing angle of the grindstone 15.

[0046] In addition, in the processing condition adjustment step, further, based on the relationship between the radius of curvature of the workpiece W and the area of the polishing surface 152 of the grindstone 15, it is determined whether adjustment of the polishing processing conditions is necessary. When it is determined that adjustment of the polishing processing conditions is necessary, the polishing processing conditions may be adjusted. In this case, the shape evaluation mechanism 21 determines whether adjustment of the polishing processing conditions is necessary based on a previously prepared chart as shown in FIG. 5, for example.

[0047] That is, in the processing condition adjustment step, when the radius of curvature of the workpiece W input into the polishing apparatus 1 or the area of the polishing surface 152 of the grindstone 15 is within the management range (denoted as "Area1" in the figure) defined in the chart, it is determined that adjustment of the polishing processing conditions is unnecessary. On the other hand, in the processing condition adjustment step, when the radius of curvature of the workpiece W input into the polishing apparatus 1 or the area of the polishing surface 152 of the grindstone 15 is outside the management range defined in the chart, it is determined that adjustment of the polishing processing conditions is necessary. Hereinafter, a more specific method of using the chart will be described with reference to FIG. 5.

[0048] FIG. 5 shows a chart when processing a workpiece W having a diameter of Φ1 mm. In the figure, the vertical axis represents the radius of curvature of the workpiece W to be input into the polishing apparatus 1 from now on, and the horizontal axis represents the area of the grindstone 15. In addition, the chart in the figure is prepared in advance using a general statistical method (for example, multiple regression analysis, etc.) before implementing the polishing method according to the embodiment. When using multiple regression analysis, the quality (number of Newton rings) of the workpiece W after polishing is used as the objective variable, and the quality (number of Newton rings) of the workpiece W to be input and the area of the grindstone 15 are used as the explanatory variables.

[0049] For example, consider the case where the radius of curvature of the workpiece W input into the polishing apparatus 1 and the area of the grindstone 15 are within the range of Area1 in FIG. 5, and the workpiece W after polishing becomes a good product (a workpiece W having a desired radius of curvature). In this case, set the radius of curvature of the workpiece W input into the polishing apparatus 1 and the area of the grindstone 15 within any range within this Area1.

[0050] Specifically, in FIG. 5, the radius of curvature R1 of the workpiece W was set to "NR1 pieces", and the radius of curvature R2 was set to "NR2 pieces". Also, the area S1 of the grindstone 15 was set to "0.70 mm 2 ", and the area S2 was set to "0.78 mm 2 ". In this case, as shown by A in the same figure, by maintaining the area of the grindstone 15 between S1 and S2, the workpiece W within the range of the radius of curvature R1 to R2 after polishing is a good product.

[0051] Also, the chart in FIG. 5 can be used as follows. For example, when the radius of curvature of the workpiece W input into the polishing apparatus 1 deviates from R1 to R2 and is R4 (for example, NR4 pieces), if the area of the grindstone 15 is maintained between S1 and S2, the polished workpiece W will be defective. Therefore, as shown by B in FIG. 5, in the processing condition adjustment step, by correcting the area of the grindstone 15 to S3, it is possible to obtain a good product. Conversely, if the area of the grindstone 15 becomes S3 as a result of the previous polishing process, by inputting the workpiece W with a radius of curvature R4 into the polishing apparatus 1 accordingly, it is possible to obtain a good product.

[0052] Here, since the size of the area of the polishing surface 152 of the grindstone 15 is related to the correction ability of the radius of curvature of the workpiece W input into the polishing apparatus 1, when the radius of curvature of the input workpiece W is close to the target radius of curvature after polishing, even if the area of the polishing surface 152 of the grindstone 15 is somewhat small, it is possible to obtain good polishing quality.

[0053] Therefore, in the processing condition adjustment step, as shown in FIG. 5, it is preferable to determine whether correction processing of the grindstone 15 is necessary according to the quality (radius of curvature) of the workpiece W input into the polishing apparatus 1. That is, by preparing a chart as shown in the figure in advance, the quality of the workpiece W after polishing can be estimated from the radius of curvature of the input workpiece W and the area of the grindstone 15. Utilizing this mechanism, the quality of the workpiece W can be feed-forward stabilized by estimating the quality of the workpiece W after polishing in advance and performing correction processing of the grindstone 15 when it is estimated to be defective. Further, even if workpieces W with varying shapes are input into the polishing apparatus 1, workpieces W with a desired shape can be continuously and automatically processed, improving productivity.

[0054] <Second polishing process> In the second polishing process, polishing of the workpiece W is performed based on the polishing conditions adjusted in the processing condition adjustment step (step S9). In the second polishing process, similar to the first polishing process, the workpiece W is polished by rubbing the rotated and oscillated grindstone 15 against the rotated workpiece W.

[0055] <Spherical center alignment step> Here, in the polishing method according to the embodiment of the present invention, for example, a spherical center alignment step may be performed after the area change amount calculation step and before the second polishing process. In the spherical center alignment step, based on the height change amount of the polishing surface 152 of the grindstone 15 calculated in the height change amount calculation step, the oscillation center of the grindstone 15 is made to coincide with the curvature center of the polishing surface 152 of the grindstone 15. In this case, for example, by the grindstone holding mechanism 16, the position of the grindstone 15 is moved upward (in the case of FIG. 1) by the amount of wear (the amount of height change) of the polishing surface 152 of the grindstone 15, so that the oscillation center of the grindstone 15 coincides with the curvature center of the polishing surface 152 of the grindstone 15. Note that the spherical center alignment step is performed for each workpiece W polished.

[0056] When the height of the polishing surface 152 of the grinding stone 15 changes, not only the area of the polishing surface 152 but also the center of curvature of the polishing surface 152 will change. Therefore, as described above, by correcting the position of the grinding stone 15 according to the wear of the polishing surface 152 of the grinding stone 15, the work W can be polished with higher accuracy without changing the swing center and swing radius of the grinding stone 15.

[0057] In the polishing method and polishing apparatus according to the present embodiment described above, the height of the polishing surface 152 of the grinding stone 15 is calculated based on the height position of the work holding mechanism 11 and the thickness of the work W. Further, based on the height of the polishing surface 152 of the grinding stone 15 and the radius of curvature of the polishing surface 152 of the grinding stone 15, the change amount of the area of the polishing surface 152 of the grinding stone 15 is calculated. Then, based on the change amount of the area of the polishing surface 152 of the grinding stone 15, the polishing processing conditions of the work W are adjusted to process the work W with the expected quality. Thereby, the occurrence of defective work W can be suppressed and the processing quality of the work W can be maintained.

[0058] Further, in the polishing method and polishing apparatus according to the present embodiment, the shape of the grinding stone 15 (the area of the polishing surface 152) that changes over time is estimated from the height position of the work holding mechanism 11 and the thickness of the work W, and if necessary, correction processing of the grinding stone 15 or a change in the contact pressure with the work W is performed before the next polishing of the work W.

[0059] Thereby, without stopping the polishing apparatus 1 and measuring the height and area of the polishing surface 152 of the grinding stone 15, the change in the area of the polishing surface 152 of the grinding stone 15 can be grasped. As a result, the work W can be continuously processed while always maintaining an appropriate shape of the grinding stone 15. In addition, since the correction processing of the grinding stone 15 can be automatically performed, the occurrence of defective work W can be suppressed. That is, every time a defective work W occurs, good products can be continuously obtained without stopping the polishing apparatus 1 and having an operator perform condition adjustment or correction processing, so that a highly productive polishing apparatus 1 can be realized.

[0060] For example, conventionally, the polishing apparatus was periodically stopped, and a sensor was pressed against the grindstone to directly measure the height of the grindstone. In this case, it was necessary to remove the grindstone from the polishing apparatus, and the height could only be known at the timing when the grindstone was removed. On the other hand, in the polishing method and polishing apparatus according to the present embodiment, the area of the polishing surface 152 of the grindstone 15 can be obtained only from the information on the height position of the work holding mechanism 11, the thickness of the work W, and the information on the radius of curvature of the work W or the grindstone 15. Further, in order to obtain the area of the polishing surface 152 of the grindstone 15 every time a new work W is processed, the change amount of the area of the polishing surface 152 of the grindstone 15 can be grasped in real time.

[0061] As described above, the polishing method and polishing apparatus according to the present invention have been specifically described by way of embodiments for carrying out the invention. However, the gist of the present invention is not limited to these descriptions and should be broadly interpreted based on the descriptions in the claims. Needless to say, various changes and modifications based on these descriptions are also included in the gist of the present invention.

[0062] For example, as the work W to be polished, in addition to a glass lens, it is essentially widely applicable to objects to be processed into a lens shape or a spherical shape. Further, as the work W, mainly glass materials are applicable targets, but as long as the material can be polished, for example, glass, sapphire, ceramics such as alumina, metal, resin, stone, etc. are not limited.

[0063] Further, the device configuration of the polishing apparatus 1 may be integrally configured for each component, or may be installed separately for each component, as long as it can exhibit the same operation as the present invention.

[0064] Also, in the processing condition adjustment step, as shown in FIG. 5, the logic for determining the necessity of corrective machining of the grindstone 15 is preferably obtained statistically from the curvature accuracy of the work W and the parameters of the processing conditions for each specific shape of the work W. However, a generalized determination criterion may be set so as to be applicable to various shapes of the work W.

[0065] In addition, there is a means of inspecting all the workpieces W input into the grinding apparatus 1 in advance for the curvature accuracy of the workpiece W. However, for example, making use of the inspection results in lot inspection is also useful for improving efficiency.

[0066] In addition, according to the area of the polishing surface 152 of the grindstone 15, workpieces W that can yield good products are input. When there are no more corresponding workpieces W, various management methods can be devised according to the convenience of production, such as performing correction processing on the grindstone 15. Needless to say, it becomes possible by making use of the present invention.

[0067] In addition, in response to a change in the area of the polishing surface 152 of the grindstone 15, instead of the correction processing mechanism 20 that changes the area of the polishing surface 152 of the grindstone 15, in response to the increased area of the polishing surface 152, means for changing the pressure so that the contact pressure between the grindstone 15 and the workpiece W is constant, or means for changing the relative speed between the grindstone 15 and the workpiece W, such as the rocking angle and rocking speed of the grindstone 15, may be employed.

Explanation of Reference Numerals

[0068] 1 Grinding apparatus 11 Workholding mechanism 12 Pressurizing cylinder 13 Work rotating mechanism 14 Height measuring mechanism 15 Grindstone 151 Flat portion 152 Polishing surface 16 Grindstone holding mechanism 17 Grindstone rotating mechanism 18 Grindstone area calculating mechanism 19 Correction necessity determination mechanism 20 Correction processing mechanism 21 Shape evaluation mechanism At Grindstone rotation axis Aw Work rotation axis W Workpiece

Claims

1. A step of performing a first polishing process by bringing a swung grindstone into contact with a workpiece rotated about a central axis; A step of obtaining a height position in the central axis direction of a workpiece holding mechanism that holds the workpiece after the first polishing process; A step of calculating the height of the polishing surface of the grindstone based on the height position of the workpiece holding mechanism and the thickness of the workpiece obtained in advance; A step of calculating a change amount of the height of the polishing surface of the grindstone after the first polishing process based on the height of the polishing surface of the grindstone before and after the first polishing process; A step of obtaining the radius of curvature of the polishing surface of the grindstone; A step of calculating a change amount of the area of the polishing surface of the grindstone after the first polishing process based on the change amount of the height of the polishing surface of the grindstone and the radius of curvature of the polishing surface of the grindstone; A step of adjusting the polishing conditions of the workpiece based on the change amount of the area of the polishing surface of the grindstone; A step of performing a second polishing process based on the adjusted polishing conditions; A polishing method including the above.

2. The polishing method according to claim 1, further including a step of obtaining the thickness of the workpiece after a polishing process performed before the first polishing process as the thickness of the workpiece.

3. In the step of adjusting the polishing conditions, when the change amount of the area of the polishing surface of the grindstone exceeds a predetermined threshold value, the area of the polishing surface is corrected to the area of a predetermined polishing surface by processing the grindstone. The polishing method according to claim 1 or claim 2.

4. In the step of adjusting the polishing conditions, when the change amount of the area of the polishing surface of the grindstone exceeds a predetermined threshold value, the contact pressure between the grindstone and the workpiece or the swing angle of the grindstone is changed. The polishing method according to claim 1 or claim 2.

5. The step of adjusting the polishing conditions further includes determining whether adjustment of the polishing conditions is necessary based on the relationship between the radius of curvature of the workpiece and the area of the polishing surface of the grinding wheel, and adjusting the polishing conditions when it is determined that adjustment of the polishing conditions is necessary. The polishing method according to claim 3.

6. The polishing method according to claim 5, further including a step of aligning the swing center of the grinding wheel with the center of curvature of the polishing surface of the grinding wheel based on the amount of change in the height of the polishing surface of the grinding wheel.

7. The step of obtaining the height position is a step of measuring the change in the total thickness of the workpiece and the grinding wheel that changes after the first polishing process. The change in the total thickness of the workpiece and the grinding wheel is measured by a displacement sensor provided in the workpiece holding mechanism and measuring the displacement of the workpiece in the central axis direction. The polishing method according to claim 1.

8. A workpiece holding mechanism for holding a workpiece to be polished; A grinding wheel for polishing the workpiece; A grinding wheel holding mechanism for holding and swinging the grinding wheel; A height measuring mechanism for measuring the height position of the workpiece holding mechanism; A correction processing mechanism for correcting the area of the polishing surface of the grinding wheel by grinding the grinding wheel; A grinding wheel area calculation mechanism for calculating the amount of change in the area of the polishing surface of the grinding wheel based on the thickness of the workpiece after polishing and the height position of the workpiece holding mechanism; A correction necessity determination mechanism for determining whether correction of the grinding wheel by the correction processing mechanism is necessary based on the amount of change in the area of the polishing surface of the grinding wheel; A polishing apparatus comprising:

9. The correction necessity determination mechanism determines whether correction of the grinding wheel by the correction processing mechanism is necessary based on the amount of change in the area of the polishing surface of the grinding wheel and the radius of curvature of the workpiece before processing that is input into the polishing process. The polishing apparatus according to claim 8.

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