JP6190654B2 - Method for uniformizing machining allowance and peripheral grinding apparatus for plate material - Google Patents

Description

  The present invention relates to an apparatus for grinding a peripheral edge of a glass substrate or other plate material used for a display panel of a portable terminal, and more particularly to a method for uniforming a machining allowance during grinding and the apparatus for carrying out the method.

  The plate material grinding apparatus includes a machining center type apparatus (orthogonal coordinate system, see Patent Document 1) that performs processing by moving the relative position of the grindstone with respect to the workpiece in two orthogonal directions, and a rotation angle of a table that holds the workpiece. There is an apparatus of a contouring system (polar coordinate system, see Patent Document 3) that performs processing by associating and controlling the position of the grindstone that moves in the radial direction of the rotation. The rectangular coordinate system apparatus is suitable for processing a large and rectangular plate material such as a glass plate for a display panel of a television receiver. On the other hand, polar coordinate system devices are suitable for processing small plates such as glass plates used in display panels of portable terminals, and have a greater degree of freedom in processing shape and smaller devices than rectangular coordinate system devices. There is a feature that can be done.

  The plate material grinding apparatus cannot position the workpiece on the table by a method such as positioning the workpiece by bringing the reference side of the workpiece into contact with a protrusion provided on the table. For this reason, it is necessary to perform processing by setting a correction value for processing the workpiece held on the table at a position shifted (biased) from the correct position into a correct shape in the controller.

  Therefore, a camera is provided in the apparatus, and each time the work is carried into the grinding apparatus and fixed on the table, an image of the work corner or positioning mark on the table is acquired by the camera, and the corner or The deviation from the position where the positioning mark should be detected is detected, the correction value of the rotation angle of the table and the position of the grindstone is calculated from the detected deviation, and processing is performed while correcting the command value from the controller with the correction value. (Patent Document 3).

  On the other hand, the machining accuracy of the workpiece decreases due to aging of the machine, thermal deformation, abrasion of the grindstone, and the like. In order to prevent such a decrease in machining accuracy over time, a workpiece that has been machined every predetermined number of workpieces is measured, workpiece dimensions are measured, and correction to correct machining accuracy from the measured values A desired machining accuracy is maintained by calculating a value and inputting it to the controller.

  Regarding this mechanical accuracy correction, in Patent Document 1, in the rectangular coordinate system grinding apparatus, the position and the chamfering width of the processed workpiece are measured by using a camera provided for detecting a carry-in error, A means for automatically setting a correction value for machine accuracy is shown. Patent Document 2 discloses a technique for correcting the machine accuracy by measuring the machining shape of a machined workpiece using such a camera.

  On the other hand, the grinding speed is slow, and the risk of cracking or chipping of the workpiece increases when the cutting of the grindstone is increased in the processing of the plate material. For this reason, in the grinding of the periphery of the plate material, it is preferable that the machining allowance is uniform over the entire periphery, thereby improving the processing accuracy and processing efficiency and reducing the grinding wheel wear.

  In a rectangular coordinate system grinding device, in particular, a device equipped with two grindstones that simultaneously process opposite sides of a workpiece as shown in Patent Document 1 and equipped with a camera on each grindstone feed table, images were taken simultaneously with the camera. The cutting allowance can be made uniform by making the cutting dimensions of the left and right grindstones (the feed amount in the direction perpendicular to the side to be machined) the same with respect to the position of the side of the workpiece.

  However, in the polar coordinate system, even if a high resolution camera is used, there is a relationship in which the rotational center of the table cannot be detected by the camera and the positional relationship between the table, the grindstone, and the camera cannot be determined. The machining allowance cannot be made uniform by a simple method such as an apparatus. Therefore, conventionally, a reference line is placed at a certain distance from the periphery of the workpiece, and the distance from the workpiece periphery to the reference line is measured with a non-contact measuring instrument such as a microscope before processing. After that, measure the distance from the periphery of the workpiece to the reference line with a similar measuring instrument, calculate the correction value so that the machining allowance is uniform from the measured value before and after machining, and set it in the controller Therefore, the cutting allowance on the entire periphery of the workpiece was made uniform.

JP 2009-1225876 A JP2012-121100A JP2013-35089A

  However, with such conventional means, it is necessary to remove the workpiece from the device when measuring the workpiece after machining, to insert a reference line into the material workpiece, to measure the amount of cutting and to calculate the correction value and to the controller Since the setting is performed manually, the skill of the operator is required, and there is a problem that a measurement error or an input error may occur. In addition, with the conventional mechanical accuracy correction method as disclosed in Patent Document 2, it has not been possible to correct the machining allowance to be uniform.

  The present invention solves the above-described problems, and even in a polar coordinate system grinding apparatus, the work cutting allowance is made uniform over the entire periphery of the work by using a camera provided for detecting a work carry-in error. It is an object of the present invention to obtain a grinding apparatus that can automatically set a correction value for achieving the correction.

  The method of equalizing the machining allowance according to the present invention includes a table 12 for holding a plate-like workpiece w and a rotating device 15 for the table, a grindstone 3 for grinding the periphery of the workpiece w, and the grindstone as a rotation center P of the table 12. A feed device 23 that linearly moves in the direction of approaching and moving away, a controller 4 that controls the rotation device 15 and the feed device 23 in association with the rotational angle θ of the table 12 and the movement position s of the grindstone 3, and the table 12 This is a method for equalizing a machining allowance used in a peripheral grinding apparatus for a plate material provided with a camera 5 that acquires an image of the upper workpiece w.

In the method of the present invention, before and after the work w held on the table 12 is processed, three or more peripheral portions A to H including two positions facing each other across the predetermined work center of the work with the camera 5 are processed. The image is acquired, and the difference (side interval) Δx (Δxa to Δxf) and Δy (Δya to Δyh) between the positions of the two orthogonal directions of the workpiece before and after the processing at each peripheral edge is detected, Correction values at which the side position differences Δx and Δy at the three or more peripheral portions are uniform are obtained and set in the controller 4. The controller 4 has corrected the command values given to the table rotating device 15 and the grindstone feeding device 23 with the set correction value, and controls the rotating device 15 and the feeding device 23 to solve the above problem. Is.

  In the above method, the peripheral edge image obtained after processing is corrected to include the workpiece peripheral error after processing by correcting the material workpiece carry-in error to the table 12 so as not to include the workpiece carry-in error. A value can be set. In addition, the correction value can be set more correctly by obtaining the correction value from the average value of the side position differences measured from the peripheral images before and after the processing obtained for a plurality of workpieces.

  The peripheral grinding apparatus according to the present invention for carrying out the method of the present invention includes a table 12 for holding a plate-shaped workpiece w and a rotating device 15 for the table, a grindstone 3 for grinding the peripheral edge of the workpiece w on the table 12, and the grinding stone. , And a controller 4 that controls the rotation angle θ of the table 12 and the moving position s of the grindstone 3 in association with each other. The camera 5 for acquiring the images of the peripheral portions A to H of the upper workpiece w, the image acquiring means 43, the storage means 44 for storing the peripheral image of the workpiece before processing, and the analysis of the images before and after processing Means 45 and means 46 for correcting the rotational angle θ of the table or the moving position s of the grindstone are provided.

  The image acquisition means 43 acquires images of three or more predetermined peripheral portions A to H of the workpiece with the camera 5 before and after the processing of the workpiece w held on the table 12. The image storage means 44 stores images of the three or more peripheral portions before processing. The image analysis means 45 detects the difference Δx, Δy between the positions of the sides of the workpiece before and after the processing at the respective peripheral portions A to H. The correction means 46 stores a correction value at which the side position differences Δx and Δy at the three or more peripheral portions A to H are uniform, and gives the correction value from the controller 4 to the rotating device 15 or the feeding device 23. Correct the command value.

  The three or more peripheral edges are three or four corners including two opposite corners, so that the number of images to be acquired can be reduced and only the rotation of the table that does not move the camera. Since images at all locations can be acquired, correction values can be set in a short time.

  This invention uses a camera provided in the machine to compare the shape of the material workpiece before processing and the shape of the workpiece after processing with images, thereby detecting deviations in the machining allowance and uniforming the machining allowance of the entire workpiece. Thus, the processing accuracy is improved and the grinding wheel wear is reduced.

  According to the present invention, the machining allowance can be measured and the correction value can be set using a camera installed in the machine during the continuous machining of the workpiece, so that it is not necessary to remove the workpiece from the machine, and the number of measurement steps can be reduced. Measurement errors and input errors can be prevented. Further, since the camera for measuring the machining allowance can use a positioning confirmation camera when the material workpiece is carried into the machine, it is not necessary to prepare an expensive measuring instrument for measuring the machining allowance.

  In addition, by periodically carrying out the method of the present invention, it becomes possible to keep the machining allowance of the workpiece uniform, and the machining load becomes constant. Therefore, machining is improved by improving the dimensional accuracy of the workpiece and reducing chipping. The accuracy is improved, the product quality is stabilized, and the life of the grindstone is extended.

Schematic side view showing an embodiment of a peripheral grinding device FIG. 1 is a plan view showing the main equipment arrangement of the apparatus of FIG. Explanatory drawing showing processing method of polar coordinate system Schematic diagram showing superimposed images before and after processing of the corner A of the workpiece obtained by the camera A view similar to FIG. A view similar to FIG. Schematic diagram showing superimposed images before and after processing of the entire workpiece obtained with the camera

  Embodiments of the peripheral grinding apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic side view of a peripheral edge grinding apparatus of a polar coordinate system, and FIG. 2 is a plan view showing an equipment arrangement.

  In the figure, a work shaft 1 is a vertical hollow shaft and is rotatably supported by a bearing 11 on a machine frame (not shown). A table 12 is fixed to the upper end of the work shaft 1, and the upper surface of the table is a horizontal work holding surface 13. Negative pressure is supplied to the work holding surface 13 through the hollow hole of the work shaft 1, and the work w placed on the work holding surface 13 is fixed to the table 12 by vacuum suction of the lower surface. A spindle motor (servo motor) 15 is connected to the lower end of the work shaft 1. The spindle motor 15 is connected to the controller 4 via the servo amplifier 41, and the rotation angle of the work shaft 1 is controlled by a command from the controller 4.

  A lateral feed base 21 is provided above the work shaft 1. The lateral feed base 21 is movably guided by a horizontal lateral guide provided on the machine frame, and is screwed to a lateral feed screw 24 that is rotationally driven by a lateral feed motor (servo motor) 23. The lateral feed motor 23 is connected to the controller 4 via a servo amplifier 42, and the movement position of the lateral feed base 21 is controlled by the controller 4.

  The horizontal feed table 21 is provided with a vertical feed table 25. The vertical feed base 25 is movably mounted on a vertical guide (not shown) fixed in the horizontal feed base 21, that is, in a direction parallel to the workpiece axis 1, and is driven to rotate by a vertical feed motor 26. The feed screw 27 is screwed.

  A grindstone shaft 31 is pivotally supported on the vertical feed base 25, and the grindstone 3 is mounted on the lower end of the grindstone shaft. The grindstone shaft 31 is supported by a vertical bearing 32 in parallel with the workpiece shaft 1. The upper end of the grindstone shaft 31 is connected to a grindstone drive motor 34 via a toothed belt 33.

  The axis of the work shaft 1 and the axis of the grindstone shaft 31 are located on the same vertical plane S parallel to the moving direction of the lateral feed base 21. FIG. 3 is a diagram schematically showing the peripheral grinding of the workpiece w by the polar coordinate system apparatus. The controller 4 controls the movement amount s of the lateral feed table 21 and the rotation angle θ of the workpiece shaft 1 in association with each other. Thus, the peripheral processing of a desired planar shape is performed. Although not shown in the figure, in a device that processes a through hole and an inner diameter in a workpiece, a small diameter grindstone that can be moved up and down relative to the grindstone 3 is provided on the vertical feed base 25 to perform the through hole and inner diameter processing. .

  A camera 5 that acquires an image of the peripheral edge of the work on the table 12 is mounted at a fixed position of the lateral feed base 21. The workpiece w is loaded onto the table 12 with the workpiece center, which is the point where the distances from the four corners A to D are equal, coincide with the rotation center P of the table 12. The optical axis O of the camera 5 is set on a vertical plane S connecting the rotation center P of the table 12 and the axis Q of the grindstone 3. Since the camera 5 cannot recognize the rotation center P of the table 12 from an image obtained by photographing the center of the table 12, the positions of the rotation center P of the table 12, the axis Q of the grindstone 3, and the optical axis O of the camera 5 are This includes processing errors and assembly errors.

  The controller 4 obtains images of three predetermined corners A to C among the corners A to D of the workpiece before and after the processing of the workpiece w held on the table 12 by the camera 5. Acquisition means 43, image storage means 44 for storing the images of the three or more corners before processing acquired by the acquisition means, and the X direction of the workpiece before and after processing at the corners A to C, and orthogonal thereto. And image analysis means 45 for detecting differences in side positions (side intervals) Δx (Δxa to Δxc) and Δy (Δya to Δyc) in the Y direction. Further, the controller 4 stores correction values that make the difference Δx, Δy between the sides of the three corners A to C before and after the machining uniform, and from the controller 4 to the rotating device 15 or the feeding device 23. Correction means 46 for correcting the command value to be applied is provided.

  The work w is fixed to the table 12, the table 12 is rotated by an angle α determined by the aspect ratio of the work, and the horizontal axis 21 of the horizontal feed base 21 is the diagonal dimension of the work w from the rotation center P of the table 12. The camera 5 can be set to the photographing positions of the corners A to D of the workpiece w by moving so as to come to a position of half L. Further, the camera 5 has a photographing area of about 20 mm × 25 mm, for example, and the amount of deviation of the work fixed on the table 12 and the machining allowance by grinding are sufficiently smaller than the photographing area of this camera. Therefore, the corners A to D of the workpiece before and after machining fixed to the table in a biased state can be put into the photographing area of the camera 5 held at a fixed position by rotating the table 12.

  After the loaded work w is fixed to the table 12, the camera 5 has the optical axis O positioned at the desired corner position of the work (the corner position when the work is placed at the correct position on the table). An image a1 (FIG. 4) of the corner A before processing the workpiece is acquired. Next, the table 12 is rotated with the position of the camera 5 fixed (180 degrees when the work is rectangular), and an image b1 (FIG. 5) of the second corner B of the work w is acquired. Further, the table 12 is rotated at an angle determined by the aspect ratio of the workpiece, and an image c1 (FIG. 6) of the third corner C of the workpiece w is acquired and stored. The image center O is the position of the corner of the workpiece when the workpiece is correctly placed on the table.

  Next, a correction value for correcting the work carry-in error on the table is obtained from the deviation between the images a1 and b1 of the diagonal corners A and B and the image origin O and set in the controller (Patent Document 3). (Refer to FIG. 4), and using the correction value to control the rotation angle θ of the table 12 and the position s of the lateral feed base 21 in association with each other, the grindstone 3 grinds the periphery of the workpiece w.

  When the processing of the workpiece is completed, images a2, b2, and c2 of the corners A, B, and C after processing are acquired by the camera 5 with the table rotation angle and the position of the horizontal feed base set to the same angle and position as before the processing. . FIGS. 4 to 6 are diagrams in which the corners A to C acquired before and after the processing are displayed in an overlapping manner, and Δxa to Δxc and Δya to Δyc are orthogonal to the X direction (movement direction of the grindstone) at each corner. This is the cutting allowance in the Y direction.

  Accordingly, with the long side of the workpiece as the X direction, the deviation of the rotation angle of the table 12 is obtained from the difference between Δya and Δyb and the diagonal dimension L of the workpiece, and from the difference between Δxa and Δxc and the difference between Δyb and Δyc, respectively. The deviations of the machining allowances in the X direction and the Y direction are obtained, and correction values for correcting these deviations are set in the controller.

  In the above-described embodiment, correction values are set from the images of the three corners A to C of the workpiece. However, any three locations of the four corners A to D (which must be diagonally located). 2 locations are included), or all four locations may be selected and their average value may be used as the correction value. In consideration of variations in dimensions or shapes of workpieces before machining, it is preferable to set a correction value obtained from an average value of deviations detected for a plurality of workpieces.

  When the size of the work is small, half or the whole of the work enters the photographing area of the camera 5. In such a case, images of three or more locations are obtained from half or the entire image of the workpiece acquired by the camera 5. FIG. 7 is a diagram showing an example of an image of the entire workpiece before and after machining acquired by the camera 5. In this example, the image w1 of the entire workpiece before processing and the image w2 of the entire workpiece after processing acquired with the camera 5 set at the same position are overlapped, and from the eight images A to H, locations A, B, For E and F, the X-direction deviations Δxa, Δxb, Δxe, and Δxf of the sides are obtained. For the locations C, D, G, and H, the Y-direction deviations Δyc, Δyd, Δyg, and Δyh of the sides are obtained. The distances Lab, Lcd, Lef, and Lgh between the portions where the deviation is measured are acquired.

Then, from these obtained deviations, the deviation Δθ of the table rotation angle is the average of the difference in inclination of each side before and after machining, that is,
Δθ = (Δθab + Δθcd + Δθef + Δθgh) / 4
Δθab = Atan (Δxa-Δxb) / Lab)
Δθcd = Atan (Δyc-Δyd) / Lcd)
Δθef = Atan (Δxe-Δxf) / Lef)
Δθgh = Atan (Δyg-Δyh) / Lgh)
Calculate with.

The deviation in the X direction is the average value of the workpiece center coordinates (0,0), Δxa, Δxb as positive dimensions, Δxe, Δxf as negative dimensions,
Δx = (Δxa + xb + Δxe + Δxf) / 4
Is calculated. The deviation in the Y direction is the average value of the workpiece center coordinates (0,0), Δc and Δd as positive dimensions, and Δg and Δh as negative dimensions,
Δy = (Δyc + Δyd + Δyg + Δyh) / 4
Is calculated.

  Then, the obtained deviations of Δθ, Δx, and Δy are converted into the tool path correction value by converting the deviation into the tool cutting axis (S axis) and the table rotation axis (C axis) and set in the controller. For the subsequent machining of the workpiece, the machining is performed by correcting the command values for table rotation and tool position.

  In the above embodiment, the rectangular workpiece has been described. However, in addition to barrel shapes and rounded rectangles other than rectangles, pentagons, hexagons, and the like are used, and three or more corners are selected from the same as described above. The machining allowance can be made uniform by this method.

  The correction value set as described above is stored, and the rotation angle command value given to the spindle motor 15 and the feed motor 23 are given by the correction value and the correction value of the carry-in error detected each time the work is carried. If the workpiece w is machined by correcting the command value of the grinding wheel position, the workpiece can be ground with a uniform machining allowance for subsequent workpieces.

DESCRIPTION OF SYMBOLS 3 Grinding wheel 4 Controller 5 Camera 12 Table 15 Spindle motor 23 Cross feed motor 43 Image acquisition means 44 Image storage means 45 Image analysis means 46 Correction means A to H Workpiece peripheral edge P Rotation center w Work s Grindstone movement position θ Rotation Angle Δx, Δy Difference in workpiece side position

Claims (5)

A table for holding a plate-like workpiece and a rotating device for the table;
A grindstone that grinds the periphery of the workpiece, and a feed device that linearly moves the grindstone toward and away from the rotation center of the table;
A controller for controlling the rotation device and the feeding device in association with the rotation angle of the table and the moving position of the grindstone;
A method for uniformizing a machining allowance of a peripheral grinding device comprising a camera that acquires an image of a peripheral part of a workpiece on the table,
Acquiring an image of a plurality of positions of the peripheral portion of at least one of the predetermined two orthogonal directions of the workpiece by the camera after processing the previous machining of the workpiece held by the table is separated from each other, wherein at their locations 2 detecting the position of the edges after processing the previous direction of the processing for each of the two directions, the distance between processing before and after the sides of three or more points including the two positions opposite to each other across the workpiece center becomes uniform A machining allowance uniforming method in which a correction value is obtained and set in the controller. 2. The machining allowance uniforming method according to claim 1, wherein the plurality of predetermined peripheral edge portions are three to four places including two corners in the diagonal direction. A method for uniformizing the machining allowance of a peripheral grinding apparatus provided with a carry-in error correction means for setting a correction value for correcting a carry-in error of a workpiece on a table based on an image acquired by the camera,
A correction value for correcting the carry-in error is set in the controller based on the images of the two corners in the diagonal direction acquired before processing the workpiece, and after processing the workpiece using the correction value, The machining allowance uniforming method according to claim 2, wherein images of corner portions after processing at three to four locations are acquired. A table for holding a plate-like workpiece and a rotating device for the table;
A grindstone that grinds the periphery of the workpiece, and a feed device that linearly moves the grindstone toward and away from the rotation center of the table;
A controller for controlling the rotation device and the feeding device in association with the rotation angle of the table and the moving position of the grindstone;
A camera that acquires an image of the peripheral edge of the workpiece on the table, an acquisition unit for the image, a storage unit, and an analysis unit; and a correction unit for a rotation angle of the table or a moving position of the grindstone,
The acquisition means acquires images of a plurality of peripheral portions where at least one of two predetermined orthogonal directions of the work is separated from each other by the camera before and after the work held on the table, storage means stores an image of the periphery of the plurality of locations of pre-processing, the analyzing means detects the edges of the position of the workpiece after machining and before the processing of the two directions in their <br/> locations And
For each of the two directions , the correction means is configured to feed the rotating device or the feed from the controller so that the interval between sides before and after machining at three or more locations including two locations facing each other across the workpiece center is uniform. Correct the command value given to the device,
Periphery grinding device for plate material. Three or more peripheral edge images acquired by the acquisition means are three to four images including two corners in the diagonal direction, and the storage means has three to four before processing. The image of the location is stored, and the correction means corrects the command value given from the controller to the rotating device or the feeding device so that the interval between the sides before and after the processing at the 3 to 4 locations is uniform.
The peripheral grinding apparatus for a plate material according to claim 4.

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