JP2007276081A - Polishing device and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing device capable of easily keeping a balance of a tool holding member which is held freely to swing. <P>SOLUTION: The polishing device is provided with a first base 3, a second base 5 and a third base 7 placed on a horizontal rack 1 freely to be moved in three axial directions crossing one another, a support member 13 provided in the third base 7, the tool holding member 35 rotatably provided in the support member 13, and a polishing tool 14 provided in the tool holding member 35. The support member 13 is provided with a proximity sensor 51 for confirming whether the tool holding member 35 is horizontal or not. A metal fixture 53 detected by the proximity sensor 51 is fixed to the tool holding member 35 so as to be positioned on the axis of the proximity sensor 51 when the tool holding member 35 is rotated in relation to the support member 31 and the axial direction of the tool holding member 35 becomes horizontal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing apparatus and a polishing method used for polishing a mold of a small-diameter lens. In particular, the present invention relates to a polishing apparatus and a polishing method in which a polishing tool vibrates slightly with ultrasonic waves.

  Conventionally, for example, a lens mold has been processed by cutting or grinding. However, lens molds require processing with very high precision, while cutting and grinding processes are fast and efficient, but can be achieved with respect to surface roughness and surface texture uniformity. There was a limit.

On the other hand, polishing processing is inferior to cutting and grinding in terms of efficiency, such as processing speed, but it can process minute amounts with high accuracy, and reachable surface roughness and surface property uniformity are also better than cutting and grinding. . For this reason, as a previous step, it is necessary to obtain a certain degree of shape accuracy by cutting or grinding, and finally correct an error that remains very slightly by polishing and improve the surface roughness. And the invention shown in the following patent document 1 is proposed about the polisher which grind | polishes.
JP-A-2005-96016

  In the polishing apparatus shown in Patent Document 1, a tool holding member (ultrasonic polishing head) is supported by a single fulcrum and is held so as to be swingable. When polishing is performed, a balance is achieved around that point, but it is difficult to achieve this balance.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing apparatus and a polishing method that can easily balance a tool holding member that is swingably held.

  The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 is directed to a base that is movable in the front and rear, right and left, up and down, that is, in three orthogonal directions, and front and rear of the base. A tool holding member that is swingably held around a rotation axis provided in a direction, a polishing tool that is provided on the tool holding member and polishes a workpiece, and applies ultrasonic vibration to the polishing tool. Ultrasonic vibration applying means for detecting, detecting means for detecting the level of the tool holding member, and holding the tool holding member horizontally by moving the tool holding member up and down while monitoring detection by the detecting means. It is possible to provide a polishing device comprising a control unit for operating the base.

  The invention described in claim 2 is the polishing apparatus according to claim 1, further comprising a load adjusting means for adjusting a load applied to the workpiece.

  According to a third aspect of the present invention, in the tool holding member held on the base so as to be swingable in a vertical plane, the polishing tool is provided at one end thereof, and the tool and the tool holding member The polishing apparatus according to claim 2, wherein a coil spring is provided between the coil springs so that the biasing force can be adjusted.

  According to a fourth aspect of the present invention, the polishing tool is formed in a rod shape, and is held by the tool holding member in an inclined state so as to be rotatable around its axis. 4. The polishing apparatus according to any one of up to 3.

  According to a fifth aspect of the present invention, the amplitude, frequency, or vibration direction of the ultrasonic vibration of the polishing tool can be variably controlled. This is a polishing apparatus.

  The invention according to claim 6 is a method for obtaining the center of the object to be processed in the polishing apparatus according to any one of claims 1 to 5, wherein a step of determining the temporary center A, from the temporary center A The step of moving the polishing tool to the point B separated by the distance a, the step of drawing the first circle by rotating the workpiece with the polishing tool placed at the point B, and the point C separated from the temporary center A by the distance b A step of moving the polishing tool, a step of rotating a workpiece to draw a second circle with the polishing tool placed at point C, a step of obtaining the radius of each circle, the distance a, the distance b, and the circles A method for determining the center of a workpiece, comprising a step of obtaining a correction amount based on the radius of the workpiece.

  Furthermore, the invention described in claim 7 is a method for polishing an object to be processed by the polishing apparatus according to any one of claims 1 to 5, wherein a polishing tool is used in accordance with a coordinate value in a feed direction. The polishing method is characterized by changing any one or more of the feed speed, the load on the workpiece, the amplitude of the ultrasonic vibration, or the frequency of the ultrasonic vibration.

  According to the polishing apparatus and the polishing method of the present invention, it is possible to easily balance the tool holding member that is rotatably held.

  Hereinafter, an example of a polishing apparatus and a polishing method of the present invention will be described in more detail with reference to the drawings.

  FIG. 1 is a schematic perspective view showing an embodiment of the polishing apparatus of the present invention. 2 is a partially enlarged view of the polishing apparatus of FIG. 1, showing a part thereof in cross-section, and FIG. 3 is a cross-sectional view of FIG. 4 and 5 are a left side view and a right side view of FIG.

  The polishing apparatus of the present embodiment is used, for example, for polishing a small-diameter lens mold. The mold has a short cylindrical shape, and a curved concave portion is processed in advance on the upper surface by cutting, grinding, or the like, and finishing polishing is performed by the polishing apparatus of this embodiment.

  The polishing apparatus of the present embodiment is placed on a horizontal base 1 and is movable in the left-right direction (x direction), and placed on the first base 3 in the front-rear direction (y direction). ) Movable on the second base 5, a third base 7 placed on the second base 5 and movable in the vertical direction (z direction), and the third base 7. The main portion includes a support member 13, a tool holding member 35 rotatably provided on the support member 13, and a polishing tool 41 provided on the tool holding member 35. The third base 7 is configured to move up and down along a column portion 9 erected on the second base 5.

  The first base 3, the second base 5, and the third base 7 are driven and moved by motors (not shown). In this embodiment, a pulse motor is used as a motor for driving the bases 3, 5, and 7. The bases 3, 5, and 7 are controlled in moving speed and moving distance by a controller 11 including a controller and a personal computer. The polishing apparatus of this embodiment is an NC control apparatus.

The support member 13 is substantially L-shaped and has one end fixed to the third base 7. Specifically, the support member 13 includes a rectangular plate-like piece 15 extending forward from the third base 7 and a rectangular plate-like other piece 17 extending downward from the tip of the one piece 15. Composed.
As described above, the support member 13 fixed to the third base 7 moves up and down as the third base 7 moves up and down.

  As shown in FIG. 3, a cylindrical portion 19 is formed at the lower end portion of the other piece 17 of the support member 13 along the front-rear direction. The cylindrical portion 19 is provided with two bearings 21 and 21 that are separated from each other in the front-rear direction. Each bearing 21 is disposed such that the axial direction of the central hole 21 a is along the front-rear direction, and the outer ring 23 is fitted into the cylindrical portion 19 and fixed.

  A round bar-shaped rotating shaft 25 is fitted in the center hole 21 a of the bearing 21. That is, the rotary shaft 25 is fitted and fixed to the inner ring 27 of the bearing 21. A substantially annular fastener 29 is provided at the tip of the rotating shaft 25.

  The fastener 29 is provided such that its axial direction is orthogonal to the axial direction of the rotary shaft 25. The fastener 29 of this embodiment is composed of a pair of curved members 31, 31 and the end portions of the members 31, 31 are bent outward in the radial direction. Then, the end portions of the members 31 and 31 are overlapped with each other and fixed with screws 33.

The tool holding member 35 has a substantially cylindrical shape and is fixed by being fitted into the fastener 29 and tightening the members 31 and 31 of the fastener 29 with screws 33. As described above, the tool holding member 35 is held by the fastener 29 fixed to the distal end portion of the rotating shaft 25, and is rotatably provided around the rotating shaft 25 on the support member 13.
In the present embodiment, the tool holding member 35 is swingably held by the support member 13 so as not to rotate more than a certain amount around the rotation shaft 25 from a state where the axis is horizontal.
That is, the tool holding member 35 is held so as to be swingable in the vertical plane (xz plane).

  As shown in FIG. 2, a vibrator 37 is built in the tool holding member 35. A substantially rod-shaped horn 39 is coaxially inserted into the tool holding member 35. The base end portion of the horn 39 is connected to the vibrator 37, and the tip end portion of the horn 39 protrudes from the tip end of the tool holding member 35 toward the tip end side.

  The polishing tool 41 has an elongated round bar shape, is inserted into a through hole formed at the tip of the horn 39, and is detachably held on the horn 39. In the present embodiment, the polishing tool 41 is fixed so as to be orthogonal to the axial direction of the tool holding member 35. Specifically, the polishing tool 41 is provided at the tip of the horn 39 so as to be along the vertical direction in a state where the tool holding member 35 is held horizontally.

  In addition, an inverted conical polishing portion 43 is integrally provided at the lower end portion of the polishing tool 41. The lower end portion of the polishing portion 43 is formed in a rounded shape, and for example, the tip has a diameter of 0.3 to 2.0 mm.

  In the polishing apparatus of the present embodiment, the horn 39 is vibrated by the vibrator 37 built in the tool holding member 35, and accordingly, the polishing tool 41 is slightly vibrated along the axial direction of the tool holding member 35. That is, in the state where the tool holding member 35 is held horizontally, the polishing tool 41 vibrates slightly in the left-right direction (x direction). In this embodiment, the amplitude of the polishing tool 41 is about 10 to 40 μm.

  The mold 45 to be polished by the polishing apparatus of this embodiment is attached to a mounting base 47 provided on the gantry 1. The mounting base 47 is rotatable around an axis along the vertical direction. The mounting base 47 of this embodiment has a chuck structure, and the mold 45 is fixed by three claws 49, 49, 49. The rotation speed of the mounting base 47 is also controlled by the controller 11. Note that the mounting base 47 may have a structure other than the chuck.

  When the mold 45 is polished by the polishing apparatus of this embodiment having such a configuration, first, a shape definition numerical value in which the shape of the mold 45 that has been cut or ground is predetermined is input to the controller 11. The controller 11 calculates the trajectory of the polishing tool 41 and the feed speed of the polishing tool 41 from the numerical values, creates an NC program for driving the tool based on the calculated trajectory, and controls the scanning of the polishing tool 41. That is, the motor etc. which move each base 3, 5, 7 drive according to the instruction | indication of the controller 11. FIG. Note that scanning may be performed a plurality of times depending on the processing amount.

  Further, when the mold 45 is polished by the polishing apparatus of the present embodiment, the tool holding member 35 is held so that the axial direction thereof is horizontal, and the polishing tool 41 is held vertically. The polishing part 43 is brought into contact with the surface of the mold 45. Then, the polishing tool 41 moves, for example, from left to right along the x direction, and the surface of the mold 45 is polished. In the present embodiment, the first base 3 moves from the left to the right along the x direction with respect to the gantry 1, so that the support member 13 and the tool holding member 35 move, and as a result, the polishing tool 41 moves. The mold 45 is polished. At this time, the polishing tool 41 polishes the mold 45 while performing minute ultrasonic vibration in the left-right direction.

  During the polishing process by the polishing apparatus of the present embodiment, the mounting base 47 is rotated, and the mold 45 is also rotated around its axis. Therefore, the polishing tool 41 moves along the radial direction while slightly vibrating in the left-right direction with respect to the rotating mold 45. In addition, the rotation speed of the mounting base 47 shall be 20-500 rpm, for example. In this way, a series of movements of the bases 3, 5, 7 and the mounting base 47, that is, a feed speed, a moving distance, a rotational speed, and the like are controlled by the controller 11 as described above to polish the mold 45. The

By the way, in the polishing apparatus of this embodiment, the tool holding member 35 is swingably held by the support member 13. Further, the tool holding member 35 is heavier on the tip side (the polishing tool 41 side) than the rotary shaft 25. Therefore, in the initial state, as shown in FIG. 6, the tool holding member 35 is held by the support member 13 in a state in which the tool holding member 35 is inclined downward toward the distal end side.
As described above, the polishing apparatus according to the present embodiment is configured such that the tool holding member 35 is swingably held by the support member 13 so that polishing can be performed with a load applied to the mold 45. .

  When polishing a plurality of dies having the same shape, it is necessary to make the inclination of the tool holding member 35 constant in order to make the load for each process constant. For this reason, the polishing apparatus of the present embodiment is provided with position detecting means for measuring or confirming the inclination angle of the tool holding member 35.

In the present embodiment, as described above, the mold 45 is polished in a state where the tool holding member 35 is held horizontally, so that the load for each processing is made constant.
Therefore, in the present embodiment, the proximity sensor 51 is used as position detection means for confirming whether or not the tool holding member 35 is horizontal. The proximity sensor 51 of the present embodiment is of a high frequency oscillation type and detects the presence or absence of a magnetic metal.

In the present embodiment, the proximity sensor 51 is fixed to the support member 13. A metal jig 53 detected by the proximity sensor 51 is fixed to the outer peripheral surface of the tool holding member 35.
Specifically, the proximity sensor 51 is fixed to the support member 13 in a state in which the detection unit faces the tool holding member 35 along the y direction. The metal jig 53 is positioned so that the tool holding member 35 is positioned on the axis of the detection unit when the tool holding member 35 rotates with respect to the support member 13 and the axial direction of the tool holding member 35 becomes horizontal. It is fixed to.

  Further, the proximity sensor 51 of the present embodiment is provided with a lamp 55. When the metal jig 53 is on the axis of the detection unit, for example, the lamp 55 is lit in blue, and the metal jig 53 is detected by the detection unit. When it is not on the axis line, the lamp 55 is lit red. Note that the tool holding member 35 and the like are made of a magnetic material such as a resin and have no influence on the detection of the proximity sensor 51.

  With such a configuration, when the axial direction of the tool holding member 35 is horizontal, the proximity sensor 51 senses the metal jig 53 and the lamp 55 is lit blue, and when the tool holding member 35 is not horizontal. The lamp 55 is lit red. Thus, the polishing apparatus of the present embodiment is provided with the proximity sensor 51, so that it is easy to check whether or not the tool holding member 35 is in a horizontal state. That is, it is easy to balance the tool holding member 35.

Here, in order to make the axial direction of the tool holding member 35 horizontal, first, the third base 7 is moved upward, and the tool holding member 35 and the polishing tool 41 are disposed above the mold 45, The third base 7 is lowered so that the polishing portion 43 of the polishing tool 41 contacts the mold 45.
If the third base 7 is further lowered and the descent is stopped when the lamp 55 of the proximity sensor 51 turns blue, the tool holding member 35 is in a horizontal state.

  In the present embodiment, the controller 11 has an operation unit. For example, a keyboard connected to a personal computer is used as the operation unit, and the third base 7 can be moved up and down by controlling the rotation of a motor that drives the third base 7 by key operation of the keyboard. Therefore, the operation unit may be operated by moving the third base 7 up and down while monitoring the proximity sensor 51, and the operation of the operation unit may be stopped when the lamp 55 of the proximity sensor 51 turns blue.

Moreover, the tool holding member 35 can be automatically leveled by sending the detection signal of the proximity sensor 51 to the controller 11.
That is, the controller 11 controls the rotation of the motor that drives the third base 7 while comparing with the detection signal of the proximity sensor 51 to move the third base 7 up and down, so that the proximity sensor 51 is moved to the tool holding member 35. Is detected, the controller 11 stops the rotation of the motor and stops the third base 7 from moving up and down. Thus, by providing the proximity sensor 51, the tool holding member 35 can be leveled manually or automatically.

  During the polishing process, the polishing tool 41 moves up and down slightly by moving the curved concave portion of the mold 45, but the controller 11 grasps the shape of the mold 45 so that the controller 11 As the polishing tool 41 moves up and down, the third base 7 is moved up and down so that the tool holding member 35 is kept horizontal.

  As described above, the polishing apparatus according to the present embodiment holds the tool holding member 35 horizontally to keep the load for each process constant, but the load adjustment provided at the base end portion of the tool holding member 35 is performed. The load applied to the mold 45 can be adjusted by the member 57.

  In this embodiment, the main body 61 of the load adjusting member 57 is fixed to the mounting plate 59 that is horizontally fixed to the support member 13. The main body 61 has a structure similar to that of a micrometer. When the dial 63 is turned, the shaft portion 65 at the lower end is moved up and down. The shaft portion 65 is integrally provided with an elongated round bar 67 protruding downward.

  The tool holding member 35 is provided with a plate material 69 along its axial direction. In the present embodiment, a plate material 69 is provided at a position on the left side of the rotary shaft 25 in a state where the tool holding member 35 is held horizontally. A through hole (not shown) is formed in the plate material 69 along the vertical direction, and the tip of the round bar 67 is inserted into the through hole. The through hole is formed in such a size that the round bar 67 does not hit when the tool holding member 35 rotates. For example, the through hole is formed in an elongated hole in the axial direction of the tool holding member 35.

  A coil spring 71 is inserted into the round bar 67, the upper end portion of the coil spring 71 is fixed to the shaft portion 65 of the main body 61, and the lower end portion of the coil spring 71 is fixed to the plate material 69. Thereby, the coil spring 71 expands and contracts by turning the dial 63 of the main body 61 to move the shaft portion 65 up and down.

  As described above, since the coil spring 71 is interposed between the support member 13 and the tool holding member 35, a load is applied when the tool holding member 35 swings around the rotation shaft 25 with respect to the support member 13. . Further, by rotating the dial 63 to expand and contract the coil spring 71, it is possible to adjust the load in the rotational direction of the tool holding member 35, and thus it is possible to adjust the load applied to the mold 45.

  The load applied to the mold 45 can be measured by using a plate-shaped electronic balance 73. In order to measure the load, first, the electronic balance 73 is placed horizontally on the mounting base 47. Next, the bases 3, 5 and 7 are moved to bring the polishing portion 43 of the polishing tool 41 into contact with the upper surface of the electronic balance 73, and as shown in FIG. To do. And if the scale of the electronic balance 73 in this state is read, the load in the state in which the tool holding member 35 was leveled will be measured. At this time, as described above, the load can be adjusted by turning the dial 63 of the main body 61 of the load adjusting member 57 and holding the tool holding member 35 horizontally.

  After the measurement, the electronic balance 73 is removed, the mold 45 is attached to the mounting base 47, the polishing portion 43 of the polishing tool 41 is brought into contact with the mold 45, and the tool holding member 35 is leveled to obtain a desired load. That is, the measured load is applied to the mold 45. As described above, the polishing apparatus of this embodiment can perform polishing by adjusting the load applied to the mold 45.

  The position of the urging member made of a coil spring or the like can be changed as appropriate. In the case of a coil spring, if one end is fixed to the support member 13 (third base 7) side and the other end is fixed to the tool holding member 35 side, the load in the rotation direction of the tool holding member 35 is adjusted. Is possible. For example, the rotation shaft 25 may be provided.

  Moreover, the load applied to the mold 45 can be adjusted by placing a weight on the tool holding member 35 instead of the coil spring. That is, by placing a weight on the left side of the rotary shaft 25 of the tool holding member 35 (the base end side of the tool holding member 35), the load applied to the mold 45 can be reduced, and the weight can be placed on the right side. The load can be increased.

  By the way, in the polishing apparatus of this embodiment, on the assumption that the polishing portion 43 of the polishing tool 41 passes through the center (rotation center) of the mold 45, the feed speeds and feed amounts of the bases 3, 5, and 7 etc. Is controlled. Therefore, when the polishing portion 43 of the polishing tool 41 does not pass through the center of the mold 45, the planned polishing process cannot be performed.

  Therefore, it is necessary to adjust so that the polishing portion 43 of the polishing tool 41 passes through the center of the mold 45 before polishing. This adjustment may be performed once when the polishing tool 41 is attached to the tool holding member 35 (horn 39), and thereafter, the center position of the mold 45 may be stored in the controller 11. That is, when the polishing tool 41 is replaced, the center position is easily shifted. When the controller 11 recognizes the center position of the mold 45 by performing adjustment at the time of replacement, the polishing tool 41 can be used for subsequent polishing. It is possible to control the polishing unit 43 so as to pass through the center of the mold 45.

Hereinafter, a method for determining the center of the mold 45 will be described. When determining the center, a mold having a flat upper surface that is not cut or the like is used.
8 and 9 are reference diagrams showing a method of determining the center. FIG. 10 is a flowchart showing the steps of a method for obtaining the center.

First, as shown in FIG. 8, an arbitrary temporary center A is determined on the upper surface of the mold 45, and the polishing tool 41 is moved to the temporary center A. At this time, the coordinates (x ₁ , y ₁ ) of the temporary center A are not clear. Next, the polishing tool 41 is moved from the temporary center A to the point B shifted by a predetermined distance a in the x direction. Then, with the polishing portion 43 of the polishing tool 41 in contact with the mold 45 and the tool holding member 35 being leveled, the position of the polishing tool 41 is fixed, the mold 45 is rotated, and the upper surface of the mold 45 is The first circle C1 is processed. At this time, the first circle C1 is a circle centered on the true center of rotation O (0, 0). Further, since the tip of the polishing part 43 of the polishing tool 41 has a width, the contour line of the first circle C1 has a processing width.

  After processing the first circle C1, the polishing tool 41 is temporarily returned to the temporary center A. Next, the polishing tool 41 is moved from the temporary center A to a point C shifted by a predetermined distance b in the y direction. Then, in the same manner as before, the mold 45 is rotated while the position of the polishing tool 41 is fixed, and the second circle C <b> 2 is processed on the upper surface of the mold 45. This second circle C2 is also a circle centered on the true center of rotation O (0, 0). The contour line of the second circle C2 also has a processing width.

  Next, the radii X and Y of the first circle C1 and the second circle C2 are obtained. In this embodiment, using a microscope, as shown in FIG. 9, the intersections X1, X2,... Of the straight line HH passing through the center O of the mold 45 and the contour lines of the first circle C1 and the second circle C2. , X8 is measured. For example, in FIG. 9, the x-coordinate of each point X1, X2,. Since the microscope is provided with a cross scale S, the coordinates of the points X1,..., X8 can be easily measured.

  Then, by substituting these numerical values into the following formulas 1 and 2, the radius X of the first circle C1 and the radius Y of the second circle C2 are obtained.

By substituting X and Y obtained from Equations 1 and 2 and a and b into Equations 3 and 4 below and solving the simultaneous equations, the coordinates (x ₁ , y ₁ ) of the temporary center A are obtained, This is the correction amount to be obtained. That is, if the polishing tool 41 is moved from the temporary center A by this correction amount (x ₁ , y ₁ ), the polishing portion 43 of the polishing tool 41 can be arranged at the true center O.

In order to finally confirm whether or not the polishing tool 41 is located at the center of the mold 45 after the adjustment, it is only necessary to draw a circle at the position after the adjustment.
Specifically, as shown in FIG. 11, the polishing tool 41 is moved left and right along the x-axis direction from the adjusted center position to process the lines L <b> 1 and L <b> 2 on the surface of the mold 45. Next, the polishing tool 41 is moved up and down along the y-axis direction from the adjusted center position to process the lines L3 and L4 on the surface of the mold 45.

Then, in the same manner as when the first circle C1 is processed, the mold 45 is rotated and the third circle C3 is processed on the surface of the mold 45 with the polishing tool 41 fixed at the adjusted center position.
At this time, the center of the third circle C3 is the true center, and the third circle C3 is drawn with a deviation from the position of the polishing tool 41 (polishing portion 43). By seeing this, it is possible to grasp how much the adjusted center position is deviated from the true center.
For example, if the error is within 10 μm (0.01 mm), the adjusted center position is regarded as the true center O within the standard. If the error is out of specification, the operation may be performed again to obtain the center position.

  In addition, although the case where a circle is actually processed on the surface of the mold has been described, instead of performing the processing, a thin paint is applied to the surface of the mold, and a circle is drawn on the surface of the paint as described above. It is also possible to obtain the correction amount.

  By the way, when the polishing apparatus of this embodiment performs polishing so that the polishing amount (processing amount) is uniform, the scanning speed of the polishing tool 41 is derived as follows.

  First, the processing amount δ is expressed by Equation 5 from Preston's law. Here, k is a proportional constant, P is a load (pressure), V is a relative speed between the polishing tool and the mold, and t is a residence time. Further, in Formula 5, the power of ultrasonic waves is not considered.

  Here, when the polishing tool 41 is scanned at a speed F (x) in the radial direction (x direction) while rotating the mold 45 at a constant rotational speed ω (radian / second), the polishing time t (per unit area) = Residence time) is given by Equation 6.

  Further, A is the area (constant) of the polishing mark of the polishing portion 43, and there is a relationship of Equation 7 between the pressure P and the load W.

  Equation 8 is derived from Equation 5, Equation 6, and Equation 7.

  When it is desired to keep the machining amount δ constant, it can be seen from Equation 8 that the machining is performed while controlling the scanning speed F (x) of the polishing tool 41 to a value inversely proportional to the radius x.

FIG. 12 is a part of a flowchart showing how to send the polishing tool.
In the polishing apparatus of this embodiment, the trajectory of the polishing tool 41 is finely divided, and the polishing tool 41 is sent step by step as shown in FIG. Then, in each step of the stepwise feeding, when the next step position is called and the polishing tool 41 is sent, the polishing amount is reduced by sending the polishing tool 41 to the next position at a speed calculated from Equation 8. Can be even.

However, if the polishing tool 41 is fed stepwise at the scanning speed calculated from Equation 8, the amount of processing at the central portion of the mold 45 becomes too large, and an error shape with the central portion being easily removed tends to occur. This is considered to be because the radius x decreases near the center, and the velocity F (x) becomes a very large value according to Equation 8.
That is, under the condition of Expression 8, the polishing tool 41 must be scanned in the radial direction at a very high speed near the center of the mold 45 where the radius x is small, and both the speed and acceleration increase. An excessive load is applied to an actuator such as a motor for driving the base 3, and the actuator cannot be driven at the required speed. As a result, a machining error occurs near the center.

  As described above, the speed calculated from Expression 8 cannot be realized near the center due to limitations on the feed speed and acceleration due to the power limit of the motor that drives the feed in the radial direction (x direction) of the polishing apparatus. When the scanning speed of the polishing tool 41 is lower than the speed calculated from the equation 8, the residence time of the polishing tool 41 is correspondingly increased, and the processing error is caused by being processed excessively than the set value. Will occur.

In order to prevent such excessive machining in the vicinity of the center, the polishing apparatus of the present embodiment is provided with a fast feed function.
Here, some processing machines have two kinds of feed speeds of cutting feed and rapid feed. The cutting feed is controlled within a safe range where sufficient feedback control can be performed, and the fast feed moves the tool to the initial position at a high speed at a speed exceeding that.
And the polishing apparatus of a present Example is provided with the rapid feed function which performs this fast feed, and the excessive process of a center part is prevented.

Hereinafter, a method for preventing the excessive processing of the central portion during the polishing process by the polishing apparatus of the present embodiment having the fast-forward function will be described.
In this embodiment, the x coordinate of the center of the mold 45 is set to 0, and the polishing tool 41 is polished while moving from the negative side along the x direction to the positive side through the center of the mold 45. The case will be described. That is, in FIG. 1, the case where the polishing tool 41 moves from the left to the right for polishing will be described.

  First, through measurement, from where and how the error increases when the mold 45 is polished by feeding the polishing tool 41 stepwise at the scanning speed calculated from the above equation 8 with the processing conditions fixed. To grasp. If data is accumulated, over-processing can be estimated even for similar shapes.

FIG. 13 is a diagram showing an error distribution near the center of the mold.
As a result of the above measurement, it is assumed that the location where excessive machining occurs is identified. For example, as shown in FIG. 13, it is specified that excessive machining becomes significant within the radius R0 of the mold 45.
That is, when it is determined that excessive machining becomes significant in the range where the x coordinate is −R0 to + R0, the polishing tool 41 is sent as follows.

FIG. 14 is a part of a flowchart showing how to feed the polishing tool for preventing excessive machining near the center of the mold.
First, after reading the next feed position of the polishing tool 41, it is determined whether or not the x coordinate N of the feed position is in the range of −R0 to + R0. That is, it is determined whether or not the absolute coordinate | N | in the x direction of the next feed position is larger than R0.

As a result of the determination, if the absolute coordinate | N | of the next feeding position is larger than the radius R0, the polishing tool 41 is fed to the next position at a speed obtained from the normal processing, that is, Expression 8.
In other words, when the x coordinate N of the next feeding position is smaller than −R0, the polishing tool 41 is fed to the next position at the speed obtained from Expression 8.

If the absolute coordinate | N | in the x direction of the next feed position is equal to or less than the radius R0 as a result of the determination, the polishing tool 41 is sent to the x coordinate + R0 using the fast feed function.
That is, when the x coordinate N of the next feed position is within the range of −R0 to + R0, the polishing tool 41 is fed to the x coordinate + R0 using the fast feed function.
Then, after the polishing tool 41 is sent to the x coordinate + R0, the polishing tool 41 may be sent stepwise at a speed obtained from Equation 8.

  As described above, the polishing apparatus according to the present embodiment avoids excessive processing by not reaching the required speed because the polishing tool 41 is fed at a higher speed than the feedback control through the central portion of the mold 45. can do.

  In addition, although the case where polishing was performed by moving the polishing tool 41 from left to right along the x direction has been described, the polishing tool 41 may be similarly sent when polishing from right to left.

In this embodiment, the polishing tool 41 is vibrated with ultrasonic waves. Therefore, in order to prevent excessive machining, the following control is possible in addition to the above method or alone.
FIG. 15 is a part of a flowchart showing how to feed the polishing tool when adjusting the ultrasonic vibration to prevent over-processing near the mold center.

  First, after the next feed position is read, if the absolute coordinate | N | in the x direction of the feed position is larger than the radius R0, the polishing tool 41 is driven with a normal ultrasonic vibration intensity.

As a result of the determination, if the absolute coordinate | N | of the next feed position in the x direction is smaller than the radius R0, it is further determined whether or not the absolute coordinate | N | is larger than the radius R1. Note that R0> R1 (FIG. 13).
As a result of the determination, if it is larger than the radius R1, it is determined that the absolute coordinate | N | of the next feed position is between the radii R0 to R1, and the attenuation level 1 is lower than the normal ultrasonic vibration intensity. The polishing tool 41 is driven.

As a result of the determination, if the absolute coordinate | N | of the next feed position in the x direction is smaller than the radius R1, it is determined that it is in the deep inner periphery, and the ultrasonic vibration intensity is determined from the attenuation level 1. Further, the polishing tool 41 is driven at a reduced attenuation level 2.
Naturally, the amplitude of the attenuation level 2 is smaller than that of the attenuation level 1, and in some cases, the control can be performed by stopping the oscillation of the ultrasonic wave.

  In this way, by reducing the ultrasonic vibration intensity in the vicinity of the center of the mold 45, excessive machining in the vicinity of the center can be prevented.

Further, the load applied to the mold 45 may be adjusted in order to prevent excessive machining near the center.
FIG. 16 is a part of a flowchart showing how to feed the polishing tool when the load is adjusted to prevent excessive machining near the center of the mold.

First, after reading the next feed position of the polishing tool 41, it is determined whether or not the absolute coordinate | N | of the position in the x direction is larger than the radius R0.
As a result of the determination, if the absolute coordinate | N | in the x direction of the next feeding position is larger than the radius R0, the polishing tool 41 is fed rightward with a normal load.

As a result of the determination, if the absolute coordinate | N | in the x direction of the next feed position is equal to or less than the radius R0, the third base 7 is moved upward to temporarily retract the polishing tool 41 to the sky. . At this time, the polishing tool 41 may be completely separated from the mold 45, or the polishing tool 41 may be retreated to the sky as long as the polishing portion 43 of the polishing tool 41 contacts the mold 45.
When retracted, movement in the x direction is controlled by the read value, and when the absolute coordinate | N | of the next feed position in the x direction is outside the radius R0 again, the load position is returned to control of the normal position. . That is, the third base 7 is lowered to return the tool holding member 35 to the horizontal position, and the polishing portion 43 is brought into contact with the mold 45.

  In this way, by adjusting the load applied to the mold 45 in the vicinity of the center of the mold 45, excessive processing in the vicinity of the center of the mold 45 can be prevented.

  As described above, the polishing apparatus of the present embodiment can prevent excessive processing of the central portion by changing the processing method in the vicinity of the center of the mold.

By the way, in the said Example, although the polishing tool 41 is vibrating along the advancing direction, in order to attain leveling of grinding | polishing and to suppress generation | occurrence | production of grinding | polishing unevenness etc., the direction of the vibration of the grinding tool 41 is demonstrated. It is preferable to change or to have a plurality of scanning modes.
Hereinafter, modified examples of the polishing apparatus of the present invention will be described. Note that the polishing apparatus of this modification example has basically the same configuration as the polishing apparatus of the above-described embodiment, and will be described with a focus on different parts.

  FIG. 17 is a view showing a state in which the ultrasonic oscillator is attached to the tool holding member.

In the above embodiment, the vibrator 37 is provided inside the tool holding member 35, but in this modification, the ultrasonic oscillator 81 is provided at the tip of the tool holding member 35.
Specifically, a rectangular cylindrical attachment portion 83 is provided at the tip of the tool holding member 35, and the ultrasonic oscillator 81 is attached in the attachment portion 83.
The attachment portion 83 is formed such that the central rectangular hole is along the vertical direction when the tool holding member 35 is horizontal.

The ultrasonic oscillator 81 of this modification is formed by attaching piezoelectric elements 89, 91, 93, and 95 that are expanded and contracted by applying a voltage to each side surface of a rectangular parallelepiped oscillator 87 made of metal or ceramic. Yes. At this time, the piezoelectric element 89 and the piezoelectric element 91, and the piezoelectric element 93 and the piezoelectric element 95 are provided on opposite side surfaces, respectively.
These facing directions are defined as an x direction and a y direction, respectively, as shown in FIG. This is made to correspond to the x and y directions in FIG. 1 for convenience, but the story is the same even if x and y are interchanged. The oscillator 87 may be a laminated type other than the type that expands and contracts.

In this modification, as shown in FIG. 17, the polishing tool 41 is fitted and fixed in the center of the oscillator 87 of the oscillator 81 along the vertical direction.
In this modification, the polishing tool 41 vibrates when the ultrasonic oscillator 81 operates in the attachment portion 83 of the tool holding member 35.

FIG. 18 is a diagram showing the internal structure of the piezoelectric element 89 (91, 93, 95), where (a) shows a normal state, (b) shows an expanded state, and (c) shows a reduced state. FIG.
As shown in FIG. 18A, the piezoelectric element 89 (91, 93, 95) includes an electrode 89B (91B, 93B, 95B) (anode) and an electrode 89C so as to sandwich the piezoelectric material 89A (91A, 93A, 95A). (91C, 93C, 95C) (cathode) is connected and formed. In practice, a pair of piezoelectric material and electrode is laminated so that the strain is increased at the same applied voltage, but the operation principle is the same.

Then, as shown in FIG. 18B, when the electrodes 89B and 89C are connected to an external power source and a positive voltage is applied to the electrode 89B and a negative voltage is applied to the electrode 89C, the piezoelectric element is elongated in the vertical direction. Stretches.
Conversely, as shown in FIG. 18C, when a negative voltage is applied to the electrode 89B and a positive voltage is applied to the electrode 89C, the length of the piezoelectric element is reduced in the vertical direction.

FIG. 19 is a schematic view of the ultrasonic oscillator as viewed from the front.
FIG. 20 is a diagram illustrating the operation of the ultrasonic oscillator.
Next, focusing on the piezoelectric element 89 and the piezoelectric element 91, the operation of the surface where the piezoelectric element 89 and the piezoelectric element 91 face each other will be described with reference to FIGS.

In FIG. 19, reference numeral 103 denotes a power supply device (or an oscillation circuit having a sufficiently large output capacity), which can generate a desired voltage (waveform) at its output O1 and output O2.
In this embodiment, as shown in FIG. 19, the output O1 of the power supply device 103 is connected to the anode 89B of the piezoelectric element 89 and the cathode 91C of the piezoelectric element 91, and the output O2 is connected to the cathode 89C of the piezoelectric element 89 and the piezoelectric element. 91 is connected to the anode 91B.

  In this state, when a negative voltage is applied to the output O1 and a positive voltage is applied to the output O2, the piezoelectric element 89 contracts and the piezoelectric element 91 expands. Accordingly, from the state of FIG. 20A, the oscillator 81 is deformed so that the upper and lower ends move to the left and the central portion to the right, and protrudes to the right as shown in FIG. 20B. Curved in a shape.

  Conversely, when a positive voltage is applied to the output O1 and a negative voltage is applied to the output O2, the piezoelectric element 89 expands and the piezoelectric element 91 contracts. As a result, as shown in FIG. 20C, the oscillator 81 is deformed so that the upper and lower ends relatively move to the right and the central portion moves to the left, and is curved convexly to the left.

  When the polarity of the voltage applied to the output O1 and the output O2 is periodically changed using the power supply device 103 as an oscillation circuit, FIGS. 20B and 20C are periodically repeated to generate ultrasonic oscillation. The child 81 vibrates in the x direction.

  Further, if the piezoelectric element 93 and the piezoelectric element 95 are connected to another power supply device or an oscillation circuit with the same configuration as in FIG. 19, the ultrasonic oscillator 81 can be vibrated in the y direction. Furthermore, by devising the waveform of the oscillation circuit, it is possible to make the time change of the amplitude in each direction sinusoidal.

Next, a circuit for driving the ultrasonic oscillator 81 will be described with reference to FIG.
FIG. 21 shows an electric circuit for driving the ultrasonic oscillator shown in FIG. 17, and reference numeral 111 denotes an oscillation circuit.

If the relationship between the voltage and strain of the piezoelectric element is linear, the oscillation waveform can be a sine wave.
In addition, if there is nonlinearity in the voltage and strain of the piezoelectric element, waveform shaping can be performed to correct it. Normally, the output capacity of the oscillation circuit is insufficient for driving the piezoelectric element in terms of voltage and current, and is supplied to the piezoelectric element 115 via the amplifier circuit 113.
It is assumed that the piezoelectric element 115 in FIG. 21 is the piezoelectric elements 89 and 91 in FIG.

The output of the oscillation circuit 111 is connected to the input of the 90 ° phase circuit 117, and the output of the 90 ° phase circuit 117 is further connected to the 90 ° phase circuit 119. The output of the 90 ° phase circuit 117 is connected to the piezoelectric element 123 via the amplifier circuit 121.
It is assumed that the piezoelectric element 123 in FIG. 21 is the piezoelectric elements 93 and 95 in FIG.

  In this embodiment, a switch 125 is connected in parallel with the 90 ° phase circuit 117. Further, a switch 127 is connected in parallel with the 90 ° phase circuit 119. When these switches 125 and 127 become conductive, the 90 ° phase circuits 117 and 119 are short-circuited and do not operate, so that they do not operate as phase circuits. When these switches 125 and 127 are open (non-conducting), they operate as normal 90 ° phase circuits 117 and 119.

  Next, the function of the series circuit of the 90 ° phase circuit 117 and the 90 ° phase circuit 119 will be described.

  (I) When both the switch 125 and the switch 127 are conductive, both the 90 ° phase circuits 117 and 119 are inoperative, and the waveform of the oscillation circuit 111 is supplied to the amplifier circuit 121 as it is.

  (ii) When one of the switch 125 and the switch 127 is conductive and the other is open, one 90 ° phase circuit is inoperative, the other 90 ° phase circuit is in operation, and the 90 ° phase shift waveform of the oscillation circuit 111 is This is supplied to the amplifier circuit 121.

  (Iii) When both the switch 125 and the switch 127 are open, both the 90 ° phase circuits 117 and 119 are operated, and the 180 ° phase shift waveform, that is, the sign inversion waveform of the oscillation circuit 111 is supplied to the amplifier circuit 121.

  In this embodiment, independent switches (not shown) are provided between the amplifier circuit 113 and the piezoelectric element 115 and between the amplifier circuit 121 and the piezoelectric element 123, respectively. By opening this switch, the vibration of the axis (x or y) of the piezoelectric element can be prevented.

  The above is the configuration of the electric circuit for driving the ultrasonic oscillator of the present embodiment shown in FIG. 17. Next, the operation of this electric circuit will be described with reference to FIG.

(Case 1) First, both the switch 125 and the switch 127 are turned on, the switch (not shown) between the amplifier circuit 113 and the piezoelectric element 115 is turned on, and the switch (not shown) between the amplifier circuit 121 and the piezoelectric element 123 is turned off. The case will be described.
In this case, only the piezoelectric element 115 is driven, and only the piezoelectric elements 89 and 91 in FIG. 17 are driven to vibrate, so that the ultrasonic oscillator 81 vibrates only in the x direction, resulting in the vibration in FIG. .

(Case 2) Next, the switch 125 and the switch 127 are both turned on, the switch (not shown) between the amplifier circuit 113 and the piezoelectric element 115 is turned off, and the switch (not shown) between the amplifier circuit 121 and the piezoelectric element 123 is turned on. The case where it is doing is demonstrated.
In this case, only the piezoelectric element 123 is driven, and only the piezoelectric elements 93 and 95 of FIG. 17 are driven to vibrate, so that the ultrasonic oscillator 81 vibrates only in the y direction, resulting in the vibration of FIG. .

(Case 3) Next, both the switch 125 and the switch 127 are turned on, the switch (not shown) between the amplifier circuit 113 and the piezoelectric element 115 is turned on, and the switch (not shown) between the amplifier circuit 121 and the piezoelectric element 123 is turned on. The case will be described.
In this case, since the piezoelectric element 115 and the piezoelectric element 123 are driven with the same waveform and vibrate, the ultrasonic oscillator 81 vibrates in the Y = X direction, resulting in the vibration of FIG.

(Case 4) Next, both the switch 125 and the switch 127 are opened, the switch (not shown) between the amplifier circuit 113 and the piezoelectric element 115 is turned on, and the switch (not shown) between the amplifier circuit 121 and the piezoelectric element 123 is turned on. The case will be described.
In this case, since the piezoelectric element 115 and the piezoelectric element 123 are driven to vibrate with a sign inversion waveform and vibrate, the ultrasonic oscillator 81 vibrates in the Y = −X direction, resulting in the vibration of FIG.

(Case 5) Furthermore, one of the switch 125 and the switch 127 is conductive and the other is open, the switch (not shown) between the amplifier circuit 113 and the piezoelectric element 115 is conductive, and the switch between the amplifier circuit 121 and the piezoelectric element 123 is not shown. A case where the switch is conductive will be described.
In this case, since the piezoelectric element 115 and the piezoelectric element 123 are driven to vibrate with a 90 ° phase shift waveform and vibrate, the ultrasonic oscillator 81 is a vibration that combines Y = Acos (ωt) and X = Asin (ωt), That is, the (elliptical) circular vibration of FIG.

As described above, by using the drive electric circuit of FIG. 21 for the ultrasonic oscillator having the configuration of FIG. 17, it is possible to perform circular vibration or linear vibration orthogonal to each other.
The switches 125, 127, and the switches (not shown) inserted between the amplifier circuits 113, 121 and the piezoelectric elements 115, 123 are power semiconductors called commercially available power MOSFETs, photo MOS relays, etc. Detailed description will be omitted because it can be easily realized by a composite element.

By the way, if the oscillation voltage of the oscillation circuit 111 of FIG. 21 can be controlled, the voltage applied to the piezoelectric element 115 and the piezoelectric element 123 can also be controlled. As a result, the vibration amplitude of the ultrasonic oscillator 81 of FIG.
The vibration amplitude control function will be described with reference to FIGS. 23 and 24. FIG.

FIG. 23 is a diagram showing an inverting amplifier circuit of the most basic operational amplifier.
In the figure, reference numeral 131 denotes an operational amplifier, which comprises three terminals: an inverting input terminal a, a non-inverting input terminal b, and an output terminal c.

In order to amplify the voltage of the difference between the voltage of the non-inverting input terminal b and the voltage of the inverting input terminal a with a very large gain, when the connection is made as shown in FIG. 23, the voltage of the non-inverting input terminal b and the inverting input terminal a A strong negative feedback action works so that the voltages of the two become equal.
The voltage of the input 133 is applied to the resistor 135 (resistance value R1) connected between the input 133 and the inverting input terminal a and the resistor 139 (resistance value R) connected between the output 137 and the inverting input. When Vin and the voltage of the output 137 are Vout, the relationship of Equation 9 is established.

If the resistance values R1 and R of the resistor 135 or 139 can be controlled from the relationship of Equation 9, the output amplitude can be controlled for an oscillation circuit that oscillates at a fixed amplitude.
Hereinafter, an electric circuit example of an amplifier circuit capable of controlling the output amplitude with respect to an oscillation circuit oscillating with a fixed amplitude will be described.

FIG. 24 is a diagram illustrating an example of an electric circuit of an amplifier circuit that can change gain discretely. The basic circuit configuration is the same as in FIG. 23, and the same symbols are used for the same elements.
23 differs from FIG. 23 in that only one resistor 135 is connected between the input 133 and the inverting input terminal a in FIG. 23, but in FIG. 24, the switch Si and the resistor 141i (where i = a, b, c, d, and e) connected in series are connected in parallel. Note that the resistance values of the resistor 141 i (i = a, b, c, d, e) in the illustrated example are R, 2R, 4R, 8R, and 16R, respectively.

  The resistance of this portion is expressed by Equation 10 assuming that the resistance when the switch Si is conductive = 0 and the resistance when the switch Si is open = ∞.

  However, since i = a, b, c, d, e is given by Si = 0 when the switch Si is open and Si = 1 when the switch is conductive, applying Equation 10 to Equation 9 results in Equation 11 become that way.

From equation 11, it is clear that the gain can be adjusted by the combination of conduction or open of the switch Si. By this function, the oscillation voltage can be reduced by connecting this circuit to the output of the oscillation circuit 111 of FIG. Can be controlled.
Accordingly, the voltage applied to the piezoelectric element 115 and the piezoelectric element 123 can be controlled, and as a result, the vibration amplitude of the ultrasonic oscillator 81 shown in FIG. 17 can be controlled.
Although the polarity is inverted in Expression 11, no problem occurs in sine wave oscillation because it can be regarded as the same waveform in the long run.

  By the way, although the processing amount when the ultrasonic power is not taken into account has been described above, the processing amount δ by the polishing apparatus of this modification when the ultrasonic power is taken into consideration is expressed by Equation 12 from Preston's law. Here, k is a proportional constant, P is a load (pressure), V is a relative speed between the polishing portion and the mold, t is a residence time, and u is an ultrasonic power.

  The scanning speed F (x) of the polishing tool is expressed by Expression 13 from Expression 12, Expression 6, and Expression 7.

Here, assuming that the ultrasonic power u is constant and the processing amount of the entire upper surface of the mold is to be polished to be constant (δ = constant in Expression 13), the scanning speed of the polishing tool 41 becomes a value inversely proportional to the radius x. It must be processed while being controlled.
However, as described above, the radius x decreases near the center of the mold 45, and the speed F (x) becomes a very large value, resulting in a processing error.

Therefore, if the ultrasonic power u in Equation 13 is controlled to be proportional to the radius X using the circuit of FIG. 24, the scanning speed is constant and the processing amount can be kept constant.
If the control resolution is taken, the power can be controlled to a level close to zero. As an extreme case, it may be possible not to perform processing with the ultrasonic power off and the power set to zero.

This is particularly useful in the case of processing only a portion that is insufficiently processed without performing processing of a portion where a sufficient amount of processing has already been performed in shape correction processing or the like.
In reality, when a system is configured at low cost with a power control member having a small resolution, it is also possible to use the control of the speed F (x) and the control of the ultrasonic power u together.
In this example, the gain control is also described with an inverting amplifier circuit of an operational amplifier that is easy to explain, but it goes without saying that other types may be used.

For example, when performing polishing so that the polishing amount becomes uniform, processing is performed while controlling the scanning speed F (x) and the ultrasonic power u in accordance with Expression 13, and scanning is performed a plurality of times according to the processing amount.
In this case, the vibration mode of the polishing tool 41 can be selected and changed from (a) to (e) of FIG.

For example, by alternately performing (a) and (b) in FIG. 22 at a specific ratio, polishing that draws out the advantages of both polishings is possible.
Further, by alternately performing (c) and (d) in FIG. 4, polishing can be leveled more than when only one is performed.
Furthermore, it is conceivable to further equalize by adding (e) in FIG. 4 to the scanning.

22 (c) and 22 (d), the amplitudes in the two directions are the same in the figure, and the vibration is inclined 45 degrees with respect to the x direction. However, the ratio of the amplitudes in each direction is controlled. By doing so, this angle can be freely controlled.
When polishing is performed in several scans, leveling can be improved by changing this angle for each scan.

  By the way, in this modified example, by using the ultrasonic oscillator shown in FIG. 17, vibrations in a plurality of directions as shown in FIG. 22 are possible. Even if it is possible only, functions other than FIG.22 (e) are realizable by devising control by the controller 11. FIG.

Specifically, when the polishing tool 41 is scanned along the x-axis and the direction of vibration of the polishing tool 41 is changed from the state shown in FIG. 22A, the scanning direction of the polishing tool 41 is changed along the y-axis. The vibration state shown in FIG. That is, while the polishing tool 41 is vibrated in the x direction, the first base 3 is moved and the tool holding member 35 is moved along the x direction. What is necessary is just to move the two bases 5 and to move the tool holding member 35 to ay direction.
This can be realized simply by replacing X in the NC code (G code) with Y.

Further, the scanning direction of the polishing tool 41 is controlled in the form of (Xn, 0, Zn) (where n = 0, 1, 2,..., N), (Xn, If the same set of values of Zn) is adopted as it is and replaced with the following formula 14 or formula 15 to perform scanning control, the scanning direction in the radial direction can be rotated 45 degrees in the xy plane. At 25, what was initially scanning in the p direction can be changed to scanning in the q and r directions.
In other words, the relative vibration of the polishing tool with respect to the mold can be polished corresponding to the vibration state of FIGS. 22 (c) and 22 (d).

  If the NC code is generated as (Xn · cos θ, Xn · sin θ, Zn) by generalization, the scanning direction during polishing can be freely rotated in the xy plane (in the above case, θ degree: variable) The direction of vibration with respect to the radial direction can be freely controlled.

In this way, polishing by changing the power of ultrasonic waves reduces the burden on the scanning speed control member rather than changing only the scanning speed by making the ultrasonic power constant, and comes from the limit of the scanning speed control member. Errors can be avoided.
In addition, when scanning is performed a plurality of times in processing, polishing can be performed more uniformly and with less processing unevenness by changing the vibration mode for each scanning.

The polishing apparatus of the present invention is not limited to the configuration of each of the above embodiments, and can be changed as appropriate.
For example, in the above embodiment, the proximity switch is used as a method for confirming the horizontal state of the tool holding member, but other means may be used.
Moreover, the circuit shown in the said Example is an example, The structure can be changed.

  Further, as shown in FIG. 26, the polishing tool 41 is rotatably held in an inclined state at the tip end portion of the horn 39 provided on the tool holding member 35 in a state where the tool holding member 35 is horizontal, It is good also as a structure which connects the upper end part of 41 to the drive shaft of the motor 151. FIG. Thereby, during the polishing process, the polishing tool 41 vibrates and rotates around its axis, so that the surface roughness of the surface of the mold 45 and the uniformity of the surface properties can be improved.

It is a schematic perspective view which shows one Example of the grinding | polishing apparatus of this invention. It is the elements on larger scale of the polish device of Drawing 1, and shows a section in part. FIG. 3 is a sectional view taken along line III-III in FIG. 2. FIG. 3 is a left side view of FIG. 2. FIG. 3 is a right side view of FIG. 2. It is a schematic front view which shows the state in which the tool holding member of the grinding | polishing apparatus of FIG. 1 inclined. It is a schematic front view which shows the state which is measuring the load. It is the reference figure which showed the method of calculating | requiring a center. It is a reference figure showing a method of obtaining the center. It is the flowchart which showed the process of the method of calculating | requiring a center. It is the reference figure which showed the method at the time of confirming whether the center after adjustment is within a specification. It is a part of flowchart which shows how to send an abrasive tool. It is a figure which shows the error distribution in the center vicinity of a metal mold | die. It is a part of flowchart which shows how to send the grinding | polishing tool for preventing the excessive process of mold center vicinity. It is a part of flowchart which shows how to send the grinding | polishing tool at the time of adjusting ultrasonic vibration and preventing the excessive process of mold center vicinity. It is a part of flowchart which shows how to send the grinding | polishing tool at the time of adjusting a load and preventing the excessive process of the center vicinity of a metal mold | die. It is a figure which shows the modification of the grinding | polishing apparatus of this invention. It is a figure which shows the internal structure of a piezoelectric element, (a) is a normal state, (b) is the expanded state, (c) has shown the contracted state. It is the schematic sectional drawing which looked at the ultrasonic oscillator of the polisher of Drawing 17 from the front. It is a figure which shows operation | movement of the ultrasonic oscillator of the grinding | polishing apparatus of FIG. It is a figure which shows the electric circuit which drives an ultrasonic oscillator. It is a figure which shows the vibration direction of a polishing tool. It is a figure which shows the inverting amplifier circuit of a basic operational amplifier circuit. It is a figure which shows the electric circuit example of the amplifier circuit which can change a gain discretely. It is a reference drawing which shows the scanning direction and vibration direction of an abrasive tool. It is a figure which shows another modification of the grinding | polishing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stand 3 1st base 5 2nd base 7 3rd base 11 Controller 13 Support member 25 Rotating shaft 35 Tool holding member 37 Vibrator 39 Horn 41 Polishing tool 43 Polishing part 45 Mold 47 Mounting stand 51 Proximity sensor 53 Metal jig 57 Load adjusting member 71 Coil spring 73 Electronic scale 81 Ultrasonic oscillator

Claims (7)

A base that can move back and forth, left and right and up and down;
A tool holding member held on the base so as to be swingable about a rotation axis provided along the front-rear direction;
A polishing tool provided on the tool holding member for polishing a workpiece;
Ultrasonic vibration applying means for applying ultrasonic vibration to the polishing tool;
Detecting means for detecting the level of the tool holding member;
A polishing apparatus comprising: a control unit that operates the base so that the tool holding member can be held horizontally by moving the tool holding member up and down while monitoring detection by the detection means. . The polishing apparatus according to claim 1, further comprising a load adjusting unit that adjusts a load applied to the workpiece. The tool holding member held on the base so that it can swing in the vertical plane is provided with the polishing tool at one end thereof,
The polishing apparatus according to claim 2, wherein a coil spring is provided between the base and the tool holding member so as to adjust an urging force. The polishing tool according to any one of claims 1 to 3, wherein the polishing tool is formed in a rod shape, and is held by the tool holding member in an inclined state so as to be rotatable around an axis thereof. apparatus. The polishing apparatus according to any one of claims 1 to 4, wherein the amplitude, frequency, or vibration direction of the ultrasonic vibration of the polishing tool can be variably controlled. A method for obtaining a center of an object to be processed in the polishing apparatus according to any one of claims 1 to 5,
Determining the temporary center A;
Moving the polishing tool to a point B separated from the temporary center A by a distance a;
A process of drawing a first circle by rotating the workpiece with the polishing tool placed at point B;
Moving the polishing tool to a point C spaced from the temporary center A by a distance b;
A process of drawing a second circle by rotating the workpiece with the polishing tool placed at point C;
Determining the radius of each circle;
A method for determining a center of a workpiece, comprising: calculating a correction amount based on the distance a, the distance b, and the radius of each circle. A method for polishing a workpiece by the polishing apparatus according to any one of claims 1 to 5,
A polishing method comprising changing at least one of a feed speed of a polishing tool, a load on a workpiece, an amplitude of ultrasonic vibration, and a frequency of ultrasonic vibration according to a coordinate value in a feed direction.

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