JPH05329762A - Method and device for polishing curved surface - Google Patents

Abstract

PURPOSE:To provide a curved surface polishing method and device which improves shape precision of a work by suppressing the occurrence of partial wear of a polishing tool. CONSTITUTION:A polishing tool 2 having a spherical crown having a curvature different from any curvature of a work 1 is pressed against the surface to be machined of the work 1 through the energizing force of a compression spring 33 as it is rotated around a first axis L with the aid of a tool rotating motor 32. Simultaneously therewith, the polishing tool 2 is caused to cross the first axis L with the aid of a tool oscillating motor 45 and reciprocatively oscillate around a second axis M extending the center of the curvature of the spherical crown of the polishing tool 1. This method and constitution cause equal pressing of the spherical crown of the polishing tool 2 against the surface to be machined of the work l and suppresses partial wear of the polishing tool 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curved surface polishing method for partially polishing a work surface of a work which requires highly precise shape and surface finishing such as an optical surface of an optical lens and a cavity surface of a mold. And equipment.

[0002]

2. Description of the Related Art Conventionally, as this type of curved surface polishing method,
A method is known in which a spherical polishing tool is rotated and pressed against a surface of a workpiece to be processed, and the polishing tool and the workpiece are relatively scanned to slide the two. At this time, the larger the peripheral speed of the polishing tool, the larger the removal amount by the polishing tool and the more efficient polishing can be performed. Polishing is performed by inclining and using a portion as far as possible from the center of rotation of the polishing tool.

[0003]

However, in the above-described conventional curved surface polishing method, since the pressing portion of the polishing tool with respect to the workpiece is substantially constant, the polishing tool is pressed in the form of a ring on the workpiece to polish the workpiece. The tool is prone to uneven wear in the shape of a ring.
Therefore, as the machining is repeated, the radius of curvature of the pressing portion of the polishing tool with the workpiece is gradually increased.
When the polishing tool is unevenly worn and the curvature of its sliding portion is increased, the contact width of the polishing tool with the workpiece may be increased, and even a portion that does not need to be polished may be polished. There has been a problem that it is difficult to polish a work piece into a predetermined curved surface.

It is an object of the present invention to provide a curved surface polishing method and apparatus for improving the shape accuracy of a workpiece by suppressing uneven wear of a polishing tool.

[0005]

To achieve the above object, a curved surface polishing method of the present invention uses a polishing tool having a spherical crown having a radius of curvature different from any radius of curvature of a surface to be processed of a workpiece. While rotating the tool around the first axis passing through the center of curvature of the spherical crown of the polishing tool, the spherical crown of the polishing tool is pressed against the workpiece, and at the same time, the polishing tool is moved to the first axis. While relatively reciprocatingly swinging about a second axis that intersects and passes through the center of curvature of the spherical crown of the polishing tool, the polishing tool and the workpiece are relatively scanned and slid relative to each other. Characterize.

Further, when the surface to be processed is concave, the radius of curvature of the spherical crown of the polishing tool may be smaller than the minimum radius of curvature of the surface to be processed, or the polishing tool is pressed against the object to be processed. The rotation speed of the polishing tool may be changed according to the swing angle of the polishing tool about the second axis so that the peripheral speed in the section becomes constant.

The curved surface polishing apparatus of the present invention comprises a polishing tool having a spherical crown and a rotating means for rotating the polishing tool around a first axis passing through the center of curvature of the spherical crown. In a curved surface polishing apparatus that presses the spherical crown against the workpiece while rotating, and at the same time relatively scans the polishing tool and the workpiece so as to slide the two, the rotating means includes: A support shaft that rotatably supports a second axis that intersects with the first axis and that passes through the center of curvature of the spherical cap, and a swinging unit that reciprocally swings the support shaft around the second axis. It is characterized by having.

[0008]

According to the invention as set forth in claim 1, which is configured as described above, the polishing tool is configured to pass through the first center of curvature of the spherical crown of the polishing tool.
At the same time as rotating around the axis of, passing through the center of curvature,
Further, by reciprocally swinging about the second axis that intersects the first axis, the ring position of the polishing tool pressed against the workpiece by the rotation of the polishing tool continuously changes, and the ball of the polishing tool is changed. The crown is evenly slid relative to the work piece. As a result, the spherical crown of the polishing tool is evenly worn, and uneven wear of the polishing tool is suppressed.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

First, the overall construction of an embodiment of the curved surface polishing apparatus of the present invention will be described.

As shown in FIG. 1, the surface plate 5 is mounted on three vibration isolation units 3 (one is not shown) via a frame 13. Below the surface plate 5, there are three seismic stoppers 4 (1
The surface of the surface plate 5 is provided with a known XY table 6 for scanning the workpiece 1. Further, a tool attitude control mechanism 20 described later is supported on the surface plate 5 via three polishing frames 11 having an inverted L shape and a hexagonal mounting plate 16. A polishing head 30 is attached to the tool attitude control mechanism 20, and the polishing head 30 is located above the XY table 6.

Next, the detailed structure of each part such as the XY table 6, the tool posture control mechanism 20, the polishing head 30 and the like will be sequentially described.

As shown in FIG. 1, an XY table 6 includes a Y table 7 provided on a surface plate 5 so as to be capable of reciprocating in an arrow Y direction, and an Y table 7 in an arrow X direction (a direction perpendicular to the arrow Y direction). ) And an X table 9 which is reciprocally movable. The Y table 7 is provided with a ball nut (not shown), and the ball screw shaft 19a screwed to the ball nut is integrally provided with the output shaft of the Y-axis motor 8 fixed to the surface plate 5. It is connected. On the other hand, X table 9
Is also provided with a ball nut (illustrated), and the output shaft of the X-axis motor 10 fixed to the Y table 7 is integrated with the ball screw shaft 19b screwed to the ball nut via a coupling. Are linked together.

In the XY table 6 having this structure, the Y table 7 is reciprocated in the arrow Y direction with respect to the surface plate 5 by driving the Y axis motor 8 to rotate the ball screw shaft 19a forward and backward. Further, by driving the X-axis motor 10 to rotate the ball screw shaft 19b in the forward and reverse directions, the X table 9 is reciprocated in the arrow X direction with respect to the Y table 7, and the workpiece 1 is moved to a predetermined position. Positioned.

A working table 12 is mounted on the upper surface of the X table 9 through a rotation driving means (not shown), and the working table 12 is normally or reversely rotated in the arrow R direction by this rotation driving means. Has become. Further, the processing table 12 has a structure in which the workpiece 1 is attached to the upper surface thereof and also has a trough 15. The tub 15 surrounds the workpiece 1 and is configured to be able to receive the polishing liquid therein.

The tool posture control mechanism 20 provided at the upper portion of the curved surface polishing apparatus has a triangular mounting plate 21 as shown in FIG.
The three corners of the triangular mounting plate 21 are fitted and fixed in the openings of the hexagonal mounting plate 16 (see FIG. 1).
Three shafts 22 (one of which is not shown) are fixed to the triangular mounting plate 21 in parallel with the respective sides thereof, and a block 25 is mounted for each shaft 22 so as to be rotatable about each axis. Has been. A polishing arm 24, which is a frame body surrounding each block 25, is attached to each block 25 so as to be reciprocally movable in the vertical direction (the arrow Z direction) in the drawing through a known slide means. A ball screw shaft 36 parallel to the arrow Z direction is rotatably supported on each polishing arm 24. Each ball screw shaft 36 is inserted through each block 25 and provided inside each block 25. It is screwed into a ball nut (not shown). Further, the upper ends of the ball screw shafts 36 in the drawing are the polishing arms 2 respectively.
4 is integrally connected to an output shaft of a motor 27 attached to the upper side of the figure. A universal joint 26 is attached to the lower side of each polishing arm 24 in the drawing, and the polishing head attachment plate 23 is connected via each universal joint 26.

Each polishing arm 24 has a ball screw shaft 36.
Are respectively rotated in the forward and reverse directions by driving of the respective motors 27, so that they are reciprocally moved in the arrow Z direction with respect to the respective blocks 25. For example, by moving the polishing arms 24 by the same distance in the same direction, the polishing head mounting plate 23 can be moved by the distance while maintaining the same posture, and the polishing arms 24 can be moved by different distances. By only moving the polishing head 23, the polishing head 23 can be freely tilted in any direction. That is, the polishing head 30 attached to the polishing head attachment plate 23
Is tilted in an arbitrary direction with respect to the workpiece 1 by the tool attitude control mechanism 20 and is freely raised and lowered.

Next, the polishing head 30 which is a feature of the present invention.
The structure will be described with reference to FIGS. 3 and 4.

FIG. 3 is a partially cutaway front view of the polishing head of the curved surface polishing apparatus shown in FIG. 1, and FIG. 4 is a part of the periphery of the polishing head of the curved surface polishing apparatus shown in FIG. It is the side view which fractured. As shown in FIGS. 3 and 4, a tool swing shaft support member 41 is fixed to one end of the polishing head mounting hole 23a of the polishing head mounting plate 23 of the tool attitude control mechanism 20 (see FIG. 2) described above. The boss 40 is fitted and fixed. The tool swing shaft support member 41 has an arm portion extending in the horizontal direction, and a hanging portion extending downward in the vertical direction and integrally provided at both ends of the arm portion. One end of an L-shaped tool rocking shaft 43 as a support shaft is rotatably supported at the lower end of each hanging part in the figure via a bearing 44, and the rotation of each tool rocking shaft 43 is rotated. Both centers are on the second axis M. At the other end of each tool rocking shaft 43, a tool rotation motor support member 4 that extends in the horizontal direction and supports the tool rotation motor 32 as a rotating means.
2 is fixed, and a tool swing motor 45 as swing means is connected to one end of one tool swing shaft 43 of each tool swing shaft 43 via a speed reducer 46. ..

The tool rotation motor 32 has its output shaft (not shown) rotated about a first axis L orthogonal to the second axis M with respect to its housing, and is movable in the direction of the first axis L. The tool rotation shaft 31 is provided, and the tool rotation shaft 31 is integrally connected to one end of the output shaft of the tool rotation motor 32. A flange 31a is provided so as to project along the outer periphery of the upper end portion of the tool rotation shaft 31 in the drawing, and the flange 31a is integrally formed on the lower end surface of the tool rotation motor 32 when the workpiece 1 is not attached to the machining second. The tool rotating shaft 31 is prevented from falling by coming into contact with a stopper 37 provided on the. The polishing tool 2 having a hemispherical spherical crown is fixed to one end of the tool rotation shaft 31 with an adhesive or the like. This polishing tool 2
Is made of polyurethane resin and has a sphericity of 1 μm or less. The center of curvature of the spherical crown of the polishing tool 2 is located at the intersection of the rotation center of the tool rotation shaft 31, that is, the first axis L, and the rotation center of each tool swing shaft 43, that is, the second axis M. Further, the radius of curvature of the spherical crown of the polishing tool 2 is a value that is not equal to any radius of curvature of the surface to be processed of the workpiece 1.

On the other hand, an inverted L-shaped holding plate 34 is integrally provided on the upper end surface of the tool rotation motor 32 in the figure, and a spring support is provided on the upper end surface 32a of the output shaft of the tool rotation motor 32 via a thrust bearing 36. A member 35 is provided, and the compression coil spring 3 is provided between the pressing plate 34 and the spring support member 36.
3 is sandwiched. The output shaft of the tool rotation motor 32 is urged downward along the first axis L direction by the urging force of the compression coil spring 33, and as a result, the polishing tool 2 is pressed against the work surface of the work piece 1. ..

When the tool rotation motor 32 is driven based on the configuration described above, the polishing tool 2 is rotated about the first axis L, and the tool swing motor 45 is rotated in the normal direction and the reverse direction at a predetermined cycle. Then, the polishing tool 2 is reciprocally swung about the second axis M in the arrow θ direction shown in FIG. At this time, since the center of curvature of the spherical crown of the polishing tool 2 becomes the center of rotation and the center of reciprocal swing of the polishing tool 2, theoretically the position of the center of curvature of the spherical crown does not change.

However, in reality, various vibrations are generated in the polishing tool 2 due to its rotation and rocking. Of the vibrations, for high-frequency vibrations caused by the rotation of the polishing tool 2, it is desirable to suppress the deflection of the tool rotation shaft 31 to 1 μm or less and the amplitude to 1 μm or less. This is because when the amplitude of the vibration caused by the rotation of the polishing tool 2 is large, the polishing tool 2 resists the urging force of the compression coil spring 33 and the workpiece 1
This is because the polishing tool 2 may not reliably follow the shape of the work surface of the work piece 1 due to being repelled. On the other hand, with respect to the low-frequency vibration caused by the oscillation of the polishing tool 2, the force against the biasing force of the compression coil spring 33 does not act on the polishing tool 2 by itself, so that the polishing tool 2 exerts a force on the workpiece 1. It does not affect the followability. For this reason,
The positional deviation between the center of curvature of the spherical crown of the polishing tool 2 and the second axis M is set to 10 μm or less, and the amplitude of vibration caused by the swing of the polishing tool 2 may be suppressed to 10 μm or less.

Next, the operation of the curved surface polishing apparatus of this embodiment will be described.

First, the tool attitude control mechanism 20 raises the polishing head 30 in advance to separate the polishing tool 2 from the surface to be processed of the workpiece 1, and the polishing tool 2 is rotated in this state. The rotation speed of the polishing tool 2 is in the range of 200 to 5000 rpm, but in normal polishing it is 500 to 1000 rpm.
The range is good.

Next, the tool attitude control mechanism 20 lowers the polishing head 30, and at the same time, the polishing tool 2 is reciprocally rocked to press the spherical crown of the polishing tool 2 against the surface to be processed of the workpiece 1. .. The swing angle of the polishing tool 2 is θ shown in FIG.
Can be arbitrarily set within the range of 90 ° or less. Further, the rocking speed of the polishing tool 2 is preferably as slow as possible within a speed range in which the polishing tool 2 can reciprocate at least 3 times during polishing, and specifically, a cycle of 1 to 10 seconds per reciprocation. Speed is preferred. This is because when the swing speed of the polishing tool 2 is high, the polishing tool 2 may resonate due to this swing, and the removal amount of the workpiece 1 by the polishing tool 2 becomes unstable. ..

Then, while rotating and swinging the polishing tool 2 as described above, the processing table 12 is moved to scan the workpiece 1, and the workpiece 1 and the polishing tool 2 slide relative to each other. As a result, the workpiece 1 is polished. In this way, by rotating the polishing tool 2 about the first axis L and swinging it about the second axis M, the spherical crown of the polishing tool 2 of the ring zone pressed against the workpiece 1 is rotated. The position is continuously moved, and the spherical crown of the polishing tool 2 is uniformly pressed by the workpiece.
As a result, the polishing tool 2 does not wear unevenly in the shape of a ring and the radius of curvature of that portion does not increase, and the contact width with the workpiece 1 is also kept constant. It is possible to surely polish only the part of the object 1 to be polished,
The shape accuracy of the work piece can be improved.

In the present embodiment, an example in which the polishing tool 2 is rotated at a constant rotation speed to polish the workpiece 1 is shown. However, when the rotation speed of the polishing tool 2 is constant, the polishing tool 2 is rotated. The peripheral speed at the pressing portion (processing portion) against the workpiece 1 changes depending on the inclination of the polishing tool 2. When the peripheral speed in the processing part of the polishing tool 2 changes, the removal amount of the workpiece 1 also changes accordingly. Therefore, the number of revolutions of the polishing tool 2 may be changed so that the peripheral speed of the polishing tool 2 at the portion where the workpiece 1 is processed becomes constant. In particular,
When the radius of curvature, the swing angle and the number of rotations of the spherical crown of the polishing tool 2 are r, θ and N, respectively, the peripheral velocity V at the processing portion of the polishing tool 2 is represented by V = Nπr · sin θ. Here, when the peripheral speed V is constant, this formula is modified to obtain N = V / (πr · sin θ) to obtain the rotation speed N corresponding to the swing angle θ, and based on this value, The rotation speed N of the polishing tool 2 may be changed.

As described above, the number of revolutions of the polishing tool 2 is changed so that the peripheral speed at the processing portion of the polishing tool 2 is constant, so that the workpiece to be processed by the polishing tool 2 is independent of the inclination of the polishing tool 2. Since the removal amount of the object 1 becomes constant, the shape accuracy of the workpiece 1 can be further improved.

[0030]

Since the present invention is configured as described above, it has the following effects.

In the curved surface polishing method of the present invention, the polishing tool is rotated about the first axis and at the same time reciprocally rocked about the second axis, whereby the spherical crown of the polishing tool is uniformly pressed by the workpiece. Wear evenly. Therefore, the radius of curvature of the working portion of the polishing tool will not increase and the contact width with the workpiece will not increase due to uneven wear of the polishing tool.Therefore, the polishing tool should polish only the necessary parts of the workpiece. It is possible to improve the shape accuracy of the workpiece.

Further, the rotational speed of the polishing tool is changed in accordance with the swing angle of the polishing tool around the second axis so that the peripheral speed of the pressing portion of the polishing tool against the workpiece is constant. As a result, the removal amount of the work piece by the polishing tool becomes constant, and the shape accuracy of the work piece can be further improved.

In the curved surface polishing apparatus of the present invention, a support shaft for rotatably supporting the rotating means for rotating the polishing tool about the first axis and the second shaft, and the support shaft reciprocating about the second axis. Since the polishing tool has the swinging means for swinging,
Since it is rotated about the axis and is reciprocally swung about the second axis, the curved surface polishing method of the present invention can be easily implemented.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of an embodiment of a curved surface polishing apparatus of the present invention.

FIG. 2 is an enlarged perspective view of a tool attitude control mechanism of the curved surface polishing apparatus shown in FIG.

FIG. 3 is a front view in which a part of the periphery of a polishing head of the curved surface polishing apparatus shown in FIG. 1 is cut away.

FIG. 4 is a side view in which a part of the periphery of the polishing head of the curved surface polishing apparatus shown in FIG. 1 is cut away.

[Explanation of symbols]

 1 Workpiece 3 Vibration Isolation Unit 4 Seismic Stopper 5 Surface Plate 6 XY Table 7 Y Table 8 Y-axis Motor 9 X-table 10 X-axis Motor 11 Polishing Frame 12 Processing Table 13 Frame 15 Facsimile 16 Hexagonal Mounting Plate 19a, 19b, 28 Ball screw shaft 20 Tool posture control mechanism 21 Triangular mounting plate 22 Axis 23 Polishing head mounting plate 24 Polishing arm 25 Block 26 Universal joint 27 Motor 30 Polishing head 31 Tool rotating shaft 31a Collar 32 Tool rotating motor 32a Output shaft upper end surface 33 compression coil spring 34 pressing plate 35 spring support member 36 thrust bearing 37 stopper 40 boss 41 tool swing shaft support member 42 tool rotation motor support member 43 tool swing shaft 44 bearing 45 tool swing motor 46 reducer

Claims (4)

[Claims] 1. A polishing tool having a spherical crown having a radius of curvature different from any radius of curvature of a surface to be processed of a workpiece, wherein the polishing tool is rotated around a first axis passing through a center of curvature of the spherical crown of the polishing tool. While pressing the polishing tool, the spherical crown of the polishing tool is pressed against the workpiece, and at the same time, the polishing tool intersects the first axis, and
Curved surface polishing, wherein the polishing tool and the workpiece are relatively scanned and slid relative to each other while reciprocally swinging about a second axis passing through the center of curvature of the spherical crown of the polishing tool. Method. 2. The curved surface polishing method according to claim 1, wherein the radius of curvature of the spherical crown of the polishing tool is smaller than the minimum radius of curvature of the surface to be processed when the surface to be processed is a concave surface. 3. The number of revolutions of the polishing tool is adjusted according to the swing angle of the polishing tool around the second axis so that the peripheral speed of the polishing tool at the pressing portion against the workpiece is constant. The curved surface polishing method according to claim 1 or 2, which is changed. 4. A polishing tool having a spherical crown and rotating means for rotating the polishing tool around a first axis passing through a center of curvature of the spherical crown, the spherical crown being rotated while rotating the polishing tool. In a curved surface polishing apparatus that presses against the work piece and at the same time relatively scans the polishing tool and the work piece and slides them relative to each other, wherein the rotating means intersects the first axis. And a support shaft that rotatably supports a second axis that passes through the center of curvature of the spherical cap, and a swinging unit that swings the support shaft back and forth around the second axis. Curved surface polishing equipment.