JP4576255B2 - Tool whetstone shape creation method - Google Patents

Description

  The present invention relates to grinding technology, and in particular, a grinding wheel suitable for grinding high-precision optical elements such as lenses and prisms used in optical equipment, or grinding of an optical element molding die for molding them. It relates to technology for creating shapes.

  Optical parts such as lenses and prisms are required to have very high shape accuracy and surface roughness accuracy. As a method of processing such a high-precision optical component, for example, as described in Non-Patent Document 1, using a grindstone having an arc cross-sectional shape, the grindstone is moved in a direction crossing the rotation direction of the workpiece. A method (so-called parallel grinding method) is disclosed in which aspherical grinding is performed with a grindstone machining surface having an arc envelope with respect to a workpiece. In this processing method, as shown in FIG. 5, since the cross-sectional shape of the tool grindstone 109 is transferred to the workpiece 110, it is necessary to use the tool grindstone 109 having a highly accurate arc cross-sectional shape.

  As a method for creating and sharpening such a high-precision tool grindstone 109, for example, there is a truing / dressing method for a spherical grindstone disclosed in Patent Document 1. This method will be described with reference to FIG. 6. A cup-shaped generating grindstone 108 is cut in one direction with respect to a tool whetstone 109 for creating a shape (cut from left to right in FIG. 6A). A spherical shape is created, and thereafter, as shown in FIG. 6 (b) by the slurry 111, a spherical shape having the outer diameter of the tool grindstone 109 to be created as a diameter can be created.

  Recently, for the purpose of improving the optical performance, the shape of the aspherical lens and the shape of the free-form surface prism have been diversified. Therefore, when a spherical tool grindstone 109 as shown in FIG. 7 is used, the tool grindstone 109 may interfere with the aspherical workpiece 110. Here, if the radius of the tool grindstone 109 is reduced in order to avoid interference, the machining load on the tool grindstone 109 increases, so that there is a problem that wear is increased and sufficient machining accuracy cannot be obtained. Therefore, it is necessary to use an annular grindstone having an annular curvature radius a smaller than the grindstone diameter b of the tool grindstone 109 as shown in FIG.

Conventionally, as a means for creating the processing surface of the tool grindstone 109 in an annular shape, for example, a single stone diamond dresser method or a stainless roll method is known as disclosed in Patent Document 2.
A method of creating a tool grindstone in an annular shape by the single stone diamond dresser method will be described with reference to FIG. 9A. In this method, the processing surface of the rotating tool grindstone 109 is brought into contact with the single stone diamond dresser 112. However, the tool stone 109 is created in an annular shape by relatively moving the single stone diamond dresser 112 and the tool grindstone 109 so that the processed surface has a desired curvature shape.

In addition, a method for creating a tool grindstone in an annular shape by the stainless roll method will be described with reference to FIG. 9B. This method is based on a relatively circular arc while the rotating grindstone 109 and the stainless roll 113 are in contact with each other. By making it move, the tool grindstone 109 is created in an annular shape.
JP 2001-260023 A JP 2003-260646 A Saeki, Yodogawa, Shoji, “Study on Aspherical Die Machining by Parallel Grinding Method”, Journal of Precision Engineering, Japan Society for Precision Engineering, August 2002, Vol. 68, No. 8, p. 1067-1071

  In order to obtain a high-precision machining result by the parallel grinding method, in addition to the high-precision cross-sectional shape of the grindstone, in order not to form waviness on the machined surface of the workpiece, as shown in FIG. It is necessary that there are no periodic irregularities in the grinding wheel rotation direction and the vertical direction on the 109 processed surface. However, in the conventional method of creating an annular grindstone as described above, uniform machining marks are formed by the single stone diamond dresser 112 and the stainless roll 113 in the rotational direction of the tool grindstone 109 as shown in FIG. Will be. When such a tool grindstone 109 is used for aspherical grinding, the processing marks on the surface of the grindstone are transferred to the workpiece, so that waviness is formed on the surface of the processed optical element and sufficient optical performance is obtained. There is a problem that can not be.

  This invention is made | formed in view of the problem mentioned above, The subject which it is going to solve is providing the method of creating an annular-shaped grindstone with high precision.

Shape creating method of a tool grinding wheel, which is one aspect of the present invention, X-axis, pivots Z axis is an axis perpendicular to the X axis, and an axis perpendicular to both of the X-axis and the Z-axis as the center A machining apparatus capable of moving in three directions of the B axis, which is the axis, and a tool rotation axis that can be rotated by the B axis in a plane constituted by the X axis and the Z axis. A tool that uses a tool grindstone that grinds an object, and a creation grindstone that is held on a workpiece rotating shaft and has a flat portion in a portion facing the tool grindstone, and creates a shape of the tool grindstone A method for creating a shape of a grindstone, wherein the tool grindstone is rotated about the tool rotation axis and the creation grindstone is rotated about the work piece rotation axis to swing the tool grindstone in the rotation direction of the B axis. Move it in the direction of the X axis while moving In this state, the tool grindstone is created in an annular shape by giving a certain amount of incision to the tool grindstone in the direction of the Z-axis. Resolve.

  In the above-described method for creating the shape of the tool grindstone according to the present invention, the position of the tool grindstone is adjusted so that the center of curvature of the annular portion of the tool grindstone coincides with the turning center of the B axis. It may be.

Further, in the above-described method for creating the shape of the tool grindstone according to the present invention, the movement of the tool grindstone in the X-axis direction and the swing of the tool grindstone in the rotation direction of the B-axis may be performed asynchronously.
Moreover, in the shape creation method of the tool grindstone according to the present invention described above, the swing of the tool grindstone in the rotation direction of the B axis and the movement of the tool grindstone in the direction of the X axis are repeated a plurality of times. You may make it change the starting position of the contact with the said tool grindstone and the said creation grindstone in the said repetition each time.

  According to the present invention, the ring-shaped grindstone can be created with high accuracy because the processing surface of the circular grindstone does not have periodic irregularities in the rotation direction and the vertical direction of the grindstone. There is an effect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A first embodiment of the present invention will be described. First, the configuration of the present embodiment will be described.
In FIG. 1, an ultra-precision machining lathe 1 is a machine tool for machining an optical surface of an optical element itself or a mold for creating the optical surface of the optical element. The ultra-precision machining lathe 1 can move at least three axes of the X axis, the Z axis, and the B axis indicated by arrows in FIG.

  In the ultra-precision machining lathe 1, a workpiece rotation driving device 2 having a rotation axis parallel to the Z axis is installed on a Z axis stage 3 that can be controlled to move in the Z axis direction. Further, on the X stage 4 which can be controlled to move in the X-axis direction perpendicular to the Z-axis, the B-axis has a B-axis which is an axis turning around an axis perpendicular to both the X-axis and the Z-axis. Stage 5 is arranged.

  On the B-axis stage 5, a tool rotation driving device 6 including a rotation axis on a plane stretched between the X-axis and the Z-axis is installed. Further, on the side of the B-axis stage 5, a B-axis drive device 7 for performing movement control in the B-axis direction, which is different from the movement control device in the X-axis direction and the Z-axis direction, of the lathe 1 for ultraprecision machining. Is installed.

  The B-axis drive device 7 may have, for example, a structure in which the B-axis stage is swung by a DC motor via a crank, that is, a simple structure having no control such as B-axis rotation angle control and swing movement speed control. Absent. Moreover, the movement control of the B-axis stage 5 by the ultra-precision machining lathe 1 can be canceled, and the rotational movement can be freely performed by canceling this movement control.

  A columnar generating grindstone 8 having a flat surface facing the tool rotation driving device 6 is attached to the tip of the workpiece rotation driving device 2. At this time, it is attached to the workpiece rotation axis so that the plane portion of the generating grindstone 8 is adjusted so that no rotational deviation occurs in either the thrust direction or the radial direction.

  A tool grindstone 9 for grinding an actual optical surface or mold is attached to the tip of the tool rotation driving device 6. The tool grindstone 9 is installed at a position where the center of curvature of the workpiece side coincides with the rotation axis center of the B-axis stage. Note that the binding material of the generating grindstone 8 is harder than the binding material of the tool grindstone 9.

Next, the operation of this embodiment will be specifically described with reference to FIGS. However, these do not limit the present invention.
First, the tool wheel 9 is combined (position adjustment of the tool rotation driving device 6) so that the center of circular curvature of the workpiece on the workpiece side becomes the center of the rotation axis of the B-axis stage 5 (the center of rotation of the B-axis). FIG. 2 shows a state in which this combination has been completed.

  Thereafter, the tool grindstone 9 is axially rotated by the tool rotation driving device 6 and the generating grindstone 8 is axially rotated by the workpiece rotation driving device 2. At this time, the control of the B-axis angle of the lathe 1 for ultraprecision machining that moves the B-axis stage 5 is released.

  Next, power is supplied to the B-axis drive device 7, and the B-axis stage 5 is caused to swing by the B-axis drive device 7. Since this oscillating motion uses a drive source that is independent of the movement control device for the ultra-precision machining lathe 1, each axis of the X stage 4 and the Z stage 3 controlled to move in the ultra-precision machining lathe 1 is used. The movement and the swinging of the B-axis stage 5 in the B-axis direction are asynchronous movement operations.

  While swinging the tool grindstone 9 in this way, a certain amount of cut is given in the Z-axis direction from the position where the tip of the tool grindstone 9 and the tip of the generating grindstone 8 are in contact. In this state, the tool grindstone 9 is moved forward or backward in the X-axis direction by controlling the movement of the super-precision lathe 1 with respect to the X-axis stage 4. As a result, the contact point between the generating grindstone 8 and the tool grindstone 9 moves as shown in FIG. 3, and processing for creating the tip of the tool grindstone 9 in an annular shape is performed.

  Note that the moving speed in the X-axis direction at this time may be changed so as to be inversely proportional to the contact diameter of the generating wheel 8, whereby the processing load per unit area at the working point of the generating wheel 8 is uniform. Therefore, the flat surface portion of the generating grindstone 8 is uniformly worn.

  Further, since the X-axis movement by the X stage 4 and the B-axis direction swing by the B-axis stage 5 are asynchronous movements, the coordinate position in the X-axis direction and the swing angle in the B-axis direction coincide with each other twice. There is nothing. As a result, since the surface shape of the flat portion of the generating grindstone 8 is not transferred to the generating surface of the tool grindstone 9, the tip of the annular tool grindstone 9 can be created with high accuracy.

By repeating the above-described processing steps for creating the tool grindstone 9 in an annular shape a plurality of times, the tip shape of the tool grindstone 9 is created in an annular grindstone.
As described above, according to this embodiment, the tool grindstone can be created in an annular shape by moving in the X-axis direction and swinging in the B-axis angle. In addition, since the position in the X-axis direction and the angle of the B-axis are not made to coincide with each other, the surface shape of the uneven surface portion of the generating grindstone 8 is not transferred to the generating surface of the tool grindstone 9. .

  As a result, the processing surface of the tool grindstone 9 does not cause periodic irregularities in the grindstone rotation direction and the vertical direction, and an annular tool grindstone is created with high accuracy.

Next, a second embodiment of the present invention will be described.
In the present embodiment, the B-axis drive device 7 installed on the ultra-precision machining lathe 1 according to the first embodiment is eliminated. Since the configuration of the present embodiment other than the above is the same as the configuration of the first embodiment shown in FIG. 1, FIG. 1 is used as it is as the configuration diagram of the present embodiment, and description thereof is omitted.

Next, the operation of this embodiment will be specifically described with reference to FIG. However, these do not limit the present invention.
The B axis is swung by the movement control device of the lathe 1 for ultra-precision machining. At this time, since the swing of the B-axis by the B-axis stage 5 and the movement of the X-axis by the X-axis stage 4 are moved by the same control, both are synchronized in the present embodiment.

  Next, while rotating the workpiece rotation starting device 2 and the tool axis rotation driving device 6 on each axis, a certain amount from the position where the tip of the generating grindstone 8 and the tip of the tool grindstone 9 contact each other in the Z-axis direction. In the state where the B-axis stage 5 is reciprocally swung in the B-axis direction, the X-axis stage 4 is moved once in the X-axis direction to make the tool grindstone 9 into an annular shape. Create a process to create.

  Next, when the tool grindstone 9 is moved forward in the B-axis direction, a length 0.15 times the distance that the tool grindstone 9 is moved in the X-axis direction is added to the X-axis position coordinates, and then the position coordinates are changed. In the same manner as described above, the tool grindstone 9 is processed to create an annular shape. Thereafter, this process is repeated a plurality of times.

  In this way, when the contact position at the start of contact between the generating grindstone 8 and the tool grindstone 9 is changed every time, as shown in FIG. 4, the X-axis position where the generating grindstone 8 and the tool grindstone 9 are in contact, and B Since the swing angle of the shaft is shifted at every step, the X-axis position where the generating grindstone 8 and the tool grindstone 9 are in contact with the swing angle of the B-axis does not match twice.

  As described above, also in the present embodiment, as in the first embodiment, the tool grindstone can be created in an annular shape by moving in the X-axis direction and swinging in the B-axis angle. In addition, since the position in the X-axis direction and the angle of the B-axis are not made to coincide with each other, the surface shape of the uneven surface portion of the generating grindstone 8 is not transferred to the generating surface of the tool grindstone 9. .

As a result, the processing surface of the tool grindstone 9 does not cause periodic irregularities in the grindstone rotation direction and the vertical direction, and an annular tool grindstone is created with high accuracy.
In addition, the present invention is not limited to the above-described embodiments, and various improvements and changes can be made.

It is a figure which shows the example of schematic structure of the lathe for ultraprecision machining used for implementation of this invention. It is a figure explaining the creation method of the tool grindstone in Example 1. FIG. It is a figure which shows the mode of the movement of the tool grindstone in Example 1. FIG. It is a figure which shows the mode of a change of the X-axis origin position of the tool grindstone in Example 2. FIG. It is a figure explaining the outline | summary of the grinding process by a parallel grinding method. It is a figure explaining the outline | summary of the creation method of the spherical shape grindstone by a truing / dressing method. It is a figure explaining the problem of interference with a spherical-shaped tool grindstone and an aspherical surface workpiece. It is a figure which shows the example of the shape of an annular shape grindstone. It is a figure which shows the example of the creation method of an annular shape grindstone. It is a figure explaining the problem of the waviness which arises in an annular grindstone with the conventional creation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lathe for ultra-precision machining 2 Workpiece rotation drive device 3 Z-axis stage 4 X-axis stage 5 B-axis stage 6 Tool rotation drive device 7 B-axis drive device 8 Creation wheel 9 Tool wheel 108 Creation wheel 109 Tool wheel 110 Workpiece 111 Slurry 112 Monolithic diamond dresser 113 Stainless steel roll a Circular radius of curvature b Wheel diameter

Claims (4)

The X axis, the Z axis that is perpendicular to the X axis, and the B axis, which is an axis that pivots about an axis perpendicular to both the X axis and the Z axis, can be moved in each direction. A machining tool, a tool grindstone for grinding a workpiece having a tool rotation axis that can be rotated by the B axis in a plane constituted by the X axis and the Z axis , and held by the workpiece rotation axis A tool for creating a shape of a tool grindstone using a creating grindstone for creating a shape of the tool grindstone having a flat portion at a portion facing the tool grindstone,
Rotating the tool grindstone with the tool rotation axis and rotating the generating grindstone with the workpiece rotation axis,
The tool grindstone is moved back and forth in the X-axis direction while swinging in the rotation direction of the B-axis, and in this state, a certain amount of cut is given to the tool grindstone in the Z-axis direction. The tool grindstone is created in an annular shape,
A method for creating a shape of a tool grindstone characterized by the above.   The method for creating a shape of a tool grindstone according to claim 1, wherein the position of the tool grindstone is adjusted so that the center of curvature of the annular portion of the tool grindstone coincides with the turning center of the B axis. 2. The method for generating a shape of a tool grindstone according to claim 1, wherein the movement of the tool grindstone in the X-axis direction and the swing of the B-axis rotation direction of the tool grindstone are performed asynchronously. The swinging of the tool grindstone in the rotation direction of the B-axis and the movement of the tool grindstone in the X-axis direction are repeated a plurality of times, and the start position of contact between the tool grindstone and the generating grindstone in the repetition The method for creating a shape of a tool grindstone according to claim 1, wherein the shape is varied each time.