JP2013036804A - Method of measuring pitch error of work table - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible, even during consecutive machining of a work, automatic measurement of errors in the rotational angle (pitch errors) of a turntable suitable for a processing machine which performs consecutive processing of a large number of boards.SOLUTION: A method uses a measuring board that is substantially in the same shape as a work and whose surfaces bears radial measurement lines drawn at prescribed angular intervals and a mark for enabling the center of radiation of the measurement lines to be detected. Any positional deviation and angular deviation of the center of the measuring board delivered onto a table are detected by delivery error detecting means disposed on a processing machine; next the position of each measurement line on an image shot by a camera when the table is turned at a prescribed angle at a time is detected; and any pitch error of the table is measured from the difference between the direction of each measurement line corrected with the earlier detected deviations of the board center and its inherent direction.

Description

  The present invention relates to a method for measuring a rotation angle error (pitch error) of a work table of a processing machine, in particular, a table mounted with a work, and particularly for a processing machine that automatically and continuously processes a large number of plate materials. The present invention relates to the above method suitable for a rotary table.

  The process of making the shape of the liquid crystal panel into a rounded trapezoidal shape or a barrel shape is performed by scraping the periphery of the substrate fixed to the table with a rotating grindstone. Such a peripheral processing machine for hard and brittle plates has conventionally been provided with a feed base for feeding a rotating grindstone in two directions (XY directions) orthogonal to each other, and the rotating grindstone is formed in a two-dimensional plane according to the peripheral shape to be processed. Machining was performed in the same way as workpiece machining by a machining center.

  On the other hand, as shown in FIG. 3, the applicant of the present application has a rotation angle θ around the rotation center P of the table to which the work w is fixed, and one direction approaching and separating from the rotation center P (X in the figure). A device is proposed that performs free-form peripheral machining on the workpiece w (hereinafter referred to as “contouring method”) by controlling the movement of the rotating grindstone 3 in the direction. The contouring type peripheral processing machine is characterized in that the installation area of the apparatus can be greatly reduced as compared with the conventional machining center type peripheral processing machine.

  In the case of this contouring type machining, if there is a pitch error in the rotation of the table, a machining error such as a straight side being curved occurs. Therefore, when performing edge processing of a plate material that requires high accuracy, measure the pitch error of the table for each processing machine, and perform processing while controlling the rotation of the table in association with the tool position. Processing is performed while correcting the angle of the table based on the measured pitch error.

  As a method for measuring the pitch error of this table, conventionally, as schematically shown in FIG. 8, a polygon mirror (regular polygon mirror) 81 is mounted, the mirror surface is irradiated with laser light, and the table 12 is moved at a predetermined angle. Rotate by (angle between adjacent mirror surfaces of the polygon mirror) and detect the position of the reflected light r of the laser beam i with the light receiving array 82 or the like, thereby measuring the pitch error of the table 12 for each predetermined angle, Based on the measured value, the angle of the table 12 when machining the workpiece was corrected.

  The work table 12 in a glass substrate processing machine or the like is configured to fix a work mounted on the table onto the table 12 by vacuum suction or the like. Therefore, the automatic centering function, that is, the function of aligning the center of the workpiece with the center of the table does not work as when the workpiece is fixed to the table with the chuck. For this reason, when the polygon mirror 81 is mounted on the table 12 in order to measure the pitch error, it is necessary to mount the polygon mirror 81 with its center accurately matched, and skill is required for the work.

  In addition, special devices such as laser transmitters, polygon mirrors, and light receiving arrays are required to measure the pitch error, and it is difficult to re-measure after the machine is shipped or installed. In addition, it is difficult to cope with a change in pitch error that occurs suddenly, and it is impossible to prevent an increase in machining error due to aging of the machine. In addition, there is a problem that an apparatus necessary for the measurement is expensive and a work load necessary for the measurement is large.

  The present invention has been made to solve the problems of the conventional method as described above, and can measure the pitch error of the table with a simple device. Even during continuous machining, it is possible to automatically measure the pitch error of the work table. Therefore, by using the measured value and automatically changing the correction value set in the controller, the error over time It is an object of the present invention to obtain technical means that can correct the occurrence or fluctuation of the above and maintain high machining accuracy.

  In the method of the present invention, a measurement substrate for measuring a pitch error is used. As shown in FIG. 4, the measurement substrate wo is substantially the same shape as the workpiece to be processed, and a radial measurement line L drawn on the surface every predetermined angle (for example, 15 degrees) and the center of the radial measurement line. A mark M (Ma, Mb) for detecting Q (a point through which all measurement lines pass) is displayed.

  A processing machine that performs processing by fixing a work on the table 12 by vacuum suction or the like includes means for detecting a deviation between the center of the work fixed on the table and the rotation center of the table 12. This means, for example, reads the mark provided at or near the corner of the workpiece with the camera 5 provided in the processing machine, and detects the workpiece on the table 12 by the deviation from the reference position of the corner or the mark on the camera image. The center position deviation and angular deviation of w are detected.

  The measurement of the pitch error of the work table according to the present invention is carried out by a loading error (a positional deviation of the substrate on the table) of the measuring substrate wo that is automatically loaded onto the table 12 by a hand or by a loader and fixed on the table 12. And angle deviation) and detection of deviation in the direction of the measurement line L at each position where the table 12 is rotated by a predetermined angle.

  That is, after the measurement substrate wo is loaded onto the table 12 and fixed, the center of the measurement substrate wo on the table 12 (radiation center of the measurement line) Q is measured by the loading error detection means provided in the processing machine. An image of the camera 5 when a positional deviation and an angular deviation with respect to the table center P are detected, and then the table is rotated by an angle (for example, 15 degrees) corresponding to the division angle of the measurement line L displayed on the measurement substrate wo. The position of each measurement line L above is detected, and from the difference between the original direction and the direction of the measurement line corrected by the position deviation and the angle deviation of the substrate center, each measurement line on the image previously detected, The angle error (pitch error) of the table 12 at the angle is measured.

  The measurement line L and the mark M may be printed on a single film, pasted on one of the workpieces to be processed as a measurement substrate, and the measurement line L and the mark M can be displayed at an accurate position. Is possible. The carry-in error detecting means for detecting the position deviation and the angle deviation between the mark and the table by detecting a mark provided at or near the corner of the workpiece includes a camera for photographing the corner or the mark. What is necessary is just to detect the measurement line L in this invention using the said camera. The mark M for measuring the center of the substrate provided on the measurement substrate is provided in conformity with the carry-in error detection means provided in the processing machine.

  When performing continuous automatic machining of workpieces, the loading error of each loaded workpiece is performed for each loaded workpiece. Therefore, by adding a means for determining whether the loaded substrate is a material workpiece or a pitch error measurement substrate to the workpiece loading error detection means, the workpiece loading error detection means is only used when the loaded substrate is a measurement substrate. Instead of processing, measurement of the pitch error of the table and correction of the correction value based on the measurement value may be performed. The determination as to whether or not the substrate is a measurement substrate can be made by determining whether or not the camera of the carry-in error detection means has detected a measurement line or mark provided on the measurement substrate when detecting the carry-in error. Good.

  By carrying the measurement program that records the procedure for carrying out the method of the present invention by transporting the measurement substrate onto the table, it becomes possible to automatically measure the value of the angle error (pitch error) of the table, It is possible to automatically correct the pitch error using the measured value.

  And in continuous processing that repeats automatic conveyance and processing of the workpiece to the processing machine, by placing one measurement substrate in the material workpiece before processing that is sequentially transferred to the processing machine, It is possible to automatically correct the pitch error of the table during the continuous machining, and it is possible to quickly correct the machining error due to the pitch error that occurs over time or suddenly after installation.

  That is, according to the present invention, it is possible to greatly reduce the time and work load for adjusting or correcting the table rotation angle at the time of shipment or installation of the processing machine, and to cope with errors in the table rotation angle after installation or during continuous machining of workpieces. Since the correction value can be corrected, high machining accuracy can be easily maintained.

Schematic side view showing an example of a contouring processing machine 1 is a plan view showing the main equipment arrangement of the processing machine of FIG. Explanatory drawing showing contouring process Perspective view of measurement board The figure which shows the image of the corner of the work typically The figure which shows typically the image of the corner of the measurement board Flow chart showing the procedure for automatic measurement of pitch error Explanatory drawing showing a conventional pitch error measurement method

  Hereinafter, a method for measuring a pitch error of a work table according to the method of the present invention will be described in detail by taking as an example a processing machine that processes the periphery of a plate material by a contouring method. The peripheral processing machine shown in the figure is the contouring method shown in FIG. 3, that is, the rotation angle θ around the rotation center P of the table on which the workpiece w is mounted and the amount of movement in the one-dimensional direction of the tool 3 in the direction approaching and separating from the center P. It is an apparatus that processes the peripheral edge a of the workpiece w by controlling in association with x.

  1 and 2 are diagrams schematically showing the equipment configuration of such a peripheral processing machine. Referring to FIGS. 1 and 2, the work shaft 1 is a vertical hollow shaft, and is rotatably supported on a frame by a bearing 11. 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 table 21 is movably guided by a horizontal lateral guide provided on a frame (not shown), 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 outer periphery machining of the workpiece w by the contouring method. By controlling the movement amount x of the lateral feed base 21 and the rotation angle θ of the workpiece shaft 1 by the controller 4 in association with each other. Then, 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 images of corners A and B of the workpiece on the table 12 is mounted on the lateral feed base 21. In the example of FIGS. 1 and 2, the camera 5 is mounted on the lateral feed base 21 via a movable base 51 that is moved and positioned on the lateral feed base 21 in the Y direction (perpendicular to the plane of FIG. 1). The moving table 51 is screwed into a feed screw 53 that is driven by a moving motor 52, and the moving motor 52 is connected to the controller 4 via a servo amplifier 43.

  As shown in FIG. 4, the measurement substrate wo is provided with a measurement line L in the radial direction in increments of 15 degrees from the center Q (not necessarily coincident with the center of the substrate wo). A mark M (Ma, Mb) is attached to one corner A and a second corner B on the opposite side of 180 degrees. These measurement lines L and marks M can be attached in an accurate positional relationship by printing on a transparent sheet and attaching the sheet to a material workpiece.

  The carry-in error detecting means in the peripheral processing machine shown in the drawing detects one camera 5 and the work corners Ca and Cb (FIG. 5) in the image of the camera, and the X direction and Y from the position Co where it should be. Means for detecting direction deviations δxa, δya, δxb, δyb. Since the size of the workpiece to be loaded and the position of the mark M attached to the measurement substrate are known, the corner of the workpiece w loaded on the table 12 and the position where the mark should be can be obtained by calculation. By controlling the lateral feed motor 23 and the moving motor 52 with the controller 4, the image area acquired by the camera 5 can be positioned in the corner areas A and B of the workpiece w.

  Therefore, the deviations δxa and δya at the first angle Ca of the workpiece on the image shown in FIG. 5A acquired by the camera 5 and on the image shown in FIG. 5B when this is rotated 180 degrees. From the four deviations of the deviations δxb and δyb at the second angle Cb, the position deviation of the workpiece center and the workpiece angular deviation with respect to the table center are detected using an arithmetic expression registered in the controller.

  Since the camera 5 has a photographing area of, for example, about 20 mm × 25 mm, the mark M on the measurement substrate can be attached at a position within the photographed image at this time. Therefore, the presence / absence of the mark M can be detected by the operation of detecting the corner portion of the loaded workpiece, and it can be determined whether the loaded substrate is a material workpiece or a measurement substrate.

  Next, the pitch error measuring method of the present invention in the above-described peripheral edge processing machine will be described with reference to FIGS. In FIG. 7, when the workpiece w is loaded onto the table 12 and fixed to the table 12, the camera 5 moving to the image acquisition position acquires an image of the first corner A of the workpiece (step 61). ). Since the center detection mark M is attached to the corner of the measurement substrate wo, the controller 4 can recognize whether or not the loaded substrate is the measurement substrate based on the presence or absence of this mark. If the work is a material work, the process branches at step 62 and the work is processed at step 63.

  If the workpiece is a measurement substrate, in step 64, an error in loading the substrate is detected. That is, as shown in FIG. 6A, the deviations δxa and δya in the X direction and the Y direction between the mark Ma of the image at the first corner A acquired by the camera 5 and the position Mo where it should be detected are detected. Next, the table 12 is rotated by 180 degrees, and the deviation δxb in the X direction and the Y direction from the position Mo should be similarly applied to the mark Mb at the second corner B shown in FIG. δyb is detected, and the positional deviations in the X and Y directions of the substrate Q (more precisely, the radiation center of the measurement line L) with respect to the table center P from these four detection values, and the measurement substrate on the table 12 The angular deviation of wo is obtained by an arithmetic expression registered in advance in the controller 4. This calculation formula can be the same as the calculation formula of the carry-in error detecting means.

  Next, the camera 5 is moved to a position where an image of the measurement line L attached to the measurement substrate wo is acquired, and the table 12 is rotated at a division angle (for example, 15 degrees) of the measurement line L starting from a table angle of 0 degrees. Each time an image of the measurement line L is acquired (step 65), the position of the image of the measurement line is corrected based on the deviation of the center position of the workpiece and the angle deviation detected earlier, and the corrected direction and The pitch error of the table at the angle is measured from the difference from the direction of the measurement line that should be. This operation is performed every time the table 12 is rotated by a predetermined angle to calculate a pitch error of the table every 15 degrees between 0 degrees and 360 degrees (step 66). If the calculated pitch error is so small that it is not necessary to register it as a correction value, it is determined in step 67 that adjustment (rewriting) of the correction value is unnecessary, and the procedure ends. If adjustment is necessary, the correction value registered in the NC device is rewritten so that the measured pitch error is corrected (step 68).

  In the example of FIG. 7, the pitch error measurement and correction value calibration procedure is performed five times (step 69), and if no adjustment unnecessary determination is made in step 67 (using the calibrated correction value). If the pitch error does not become smaller than the criterion of step 67 even if it is corrected, the measured pitch error value is not reliable. Therefore, the correction value set in the NC device in steps 71 and 72 is the original value. Then, a flag indicating that the automatic measurement of the pitch error has failed is set, and the procedure is terminated (the measurement substrate is unloaded and the next workpiece is loaded).

  In machining the workpiece after the pitch error has been normally calibrated, the rotation angle command value for the table 12 is corrected based on the newly set correction value, and applied to the table drive motor 15. If the angle command given to the table drive motor is an angle between the angles where the correction values are registered, the correction value at the angle is calculated by linear interpolation of both correction values, and the controller command value Correct.

  As described above, the command value of the angle given from the controller 4 to the table 12 is corrected with the correction value for the measured pitch error, and the center position deviation and angle deviation of the workpiece on the table 12 detected for each workpiece. By performing the correction with the correction value corresponding to the above, it is possible to process the peripheral edge processing for each loaded workpiece into an accurate shape with no error.

5 Camera
12 Table L Measuring line
M (Ma, Mb) Mark P Table center Q Measurement line center w Work wo Measurement board

Claims (5)

  A measurement substrate displaying a plurality of measurement lines in the radial direction passing through the same point on the surface and a mark for detecting the point is fixed to a table for measuring an error of the rotation angle, and a camera set at a predetermined position. After reading the mark, measuring a two-dimensional positional deviation between the turning center of the table and the point from the reading position, and then setting the camera to a predetermined position for reading a measurement line, the table is then moved to the predetermined angle. Measuring the rotation angle error of the work table, characterized by measuring the deviation between the direction of the measurement line photographed by the camera and the direction in which it should be at each turn by correcting the position deviation and the angle deviation. Method.   The measuring method of the rotation angle error of the work table of Claim 1 which is a board | substrate which affixed the film which printed the said measurement line and the mark on one board | substrate for a measurement or the workpiece | work to be processed.   3. The method for measuring a rotation angle error of a work table according to claim 1, wherein the marks are provided symmetrically with respect to the point at both diagonal portions of the measurement substrate.   Whether the substrate loaded from the image of the camera used to detect the loading error of the material workpiece carried into the table is the same material workpiece as the workpiece to be processed while being fixed to the table. 4. The method for measuring a rotation angle error of a work table according to claim 1, wherein the rotation angle error of the table is measured when it is determined that the substrate is a measurement substrate, and when it is determined that the substrate is a measurement substrate.   The table rotation angle error is automatically measured when performing continuous automatic machining of a plurality of workpieces by placing measurement substrates in a large number of material workpieces that are automatically carried into the table and continuously processed. 4. A method for measuring a rotation angle error of a work table according to 4.

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