JPH08336701A - Surface processing method - Google Patents

Abstract

(57) [Summary] [Purpose] A curved surface of any shape is machined with high surface accuracy. [Structure] A workpiece W such as a toric lens is held on an XY stage 10, and a diamond cutter 2 held by a spindle 1 in the Z-axis direction parallel to the workpiece W is swung while rotating the Z.
The belt-shaped portion A ₁ of the workpiece W is cut into a predetermined curved surface by moving it in the axial direction and simultaneously moving the X stage 12 of the XY stage 10 up and down. The entire curved surface of the workpiece W is processed into a mirror-like state by repeating the process of feeding the Y stage 11 by one pitch in the Y-axis direction and processing the same band-shaped portion A ₂ as described above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface processing method capable of processing a surface of an optical component such as a toric lens or its molding die into a mirror surface state with high surface accuracy.

[0002]

2. Description of the Related Art Conventionally, as long as the surface shape of an optical component such as a lens or its molding die is axially symmetric, a double-axis control precision processing machine as shown in FIG. Can be used to process the mirror surface with high precision. this is,
The workpiece P is held on a machining table 102 that is integral with the main shaft of the rotating unit 101, and while the workpiece P is rotated around the Z axis, the workpiece P is moved in the Z axis direction, while the arcuate cutting edge is used. Z diamond R bite 103 having 103a
By feeding in the X-axis direction orthogonal to the axis, an axially symmetric curved surface Pa is machined around the Z-axis. If the processed surface of the work piece is axially symmetric, a curved surface with high surface accuracy can be processed by this method. Further, a toric lens or a cylindrical lens having a non-axially symmetric curved surface is as shown in FIG. To three
A high-precision ball end mill 202 is attached to a spindle 201 of an NC machine tool whose position is controlled in the axial direction.
While rotating the Z axis, the Z axis of the surface of the work piece Q is obtained by feeding the Z axis in a predetermined axial direction (Z axis direction) orthogonal to the rotation axis (X axis).
By repeating the process of cutting the belt-shaped portion Qa in the axial direction and then shifting the spindle 201 or the workpiece Q by a predetermined pitch in the Y-axis direction and similarly cutting the next belt-shaped portion Qb, Generally, the entire surface of Q is processed into a predetermined curved surface shape.

[0003]

However, according to the above conventional technique, it is difficult to obtain a uniform curved surface with high surface accuracy when manufacturing an optical component such as a toric lens which is not axially symmetric. . The reason is as follows.

Since a ball end mill is attached to the main shaft of an NC machine tool which is controlled in three positions and is rotated, the peripheral speed of the cutting edge of the ball end mill becomes zero at the center of rotation and therefore the machinability of this portion is zero. That is, the peripheral speed is increased and the machinability is increased in the portion located radially outward. If the machinability greatly changes depending on the position where the blade end of the ball end mill hits, the surface of the workpiece cannot be machined into a uniform mirror surface.

The present invention has been made in view of the problems of the above-mentioned prior art, and even optical components such as toric lenses having a curved shape that is not axially symmetric have a uniform mirror surface state with high surface accuracy. It is an object of the present invention to provide a surface processing method capable of processing.

[0006]

In order to achieve the above object, the surface processing method of the present invention provides a cutting tool, which is swung around a turning axis parallel to a holding surface for holding a workpiece, along the holding surface. It is characterized in that a step of feeding the cutting tool in the second direction along the holding surface is repeated after cutting a predetermined band-shaped portion of the workpiece by feeding in the first direction.

It is advisable to advance and retract the workpiece toward the cutting tool while feeding the cutting tool in the first direction.

The pitch for feeding the cutting tool in the second direction may be controlled on the basis of the tolerance of the curvature or surface roughness of the machined surface of the workpiece.

The cutting tool is preferably a single crystal diamond cutter having an arcuate cutting edge with a shape error of 0.1 μm or less.

The bite may be mounted on the spindle of a three-position controlled ultra-precision NC machine tool.

[0011]

The tool, which turns about a turning axis parallel to the holding surface, cuts the surface of the workpiece on the holding surface by means of a cutting edge that is arranged outward on a cylindrical surface coaxial with the turning axis. Since the peripheral speed of the cylindrical surface is constant, the cutting property of the cutting tool is uniform, and there is no possibility that the cutting property becomes uneven depending on the position where the cutting edge abuts, as in the case of using a ball end mill. Therefore, the band-shaped portion of the workpiece can be processed into a mirror surface state with high surface accuracy.

By sending the cutting tool to the work piece in the second direction and repeating the cutting step, the entire surface of the work piece can be processed into a mirror surface state with high surface accuracy.

By advancing and retracting the work piece with respect to the cutting tool while feeding the cutting tool in the first direction, the band-shaped portion of the work piece can be processed into a curved surface having a predetermined undulation. By repeating this step, the entire surface of the workpiece can be processed into a uniform mirror-like curved surface shape.

[0014]

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

FIG. 1 illustrates a surface processing method according to an embodiment, which is applied to a step of manufacturing a toric lens used in an optical system of an image forming apparatus such as a laser printer or a laser facsimile.

As shown in FIG. 1A, the workpiece W is held on the surface of the XY stage 10, which is the holding surface of the ultra-precision NC machine tool M, and is rotated around the Z axis, which is the turning axis. Together with the spindle 1 that reciprocates in the Z-axis direction, which is the first direction, the single-crystal diamond cutter 2 that is a bite
Attach the bite holder 3 for holding. The XY stage 10 has a Y stage 11 that reciprocates in the Y axis direction (horizontal direction) that is the second direction, and an X stage 12 that reciprocates in the X axis direction (vertical direction) on the Y stage 11. The position in the Y-axis direction and the position in the X-axis direction of the X stage 12 are respectively monitored by the laser interferometer, and the workpiece W can be positioned with extremely high accuracy within an error range of 0.01 μm.

The main shaft 1 is supported by a hydrostatic bearing and rotates with extremely high rotational accuracy, for example, a shake amount of 0.05 μm or less, and the position of the main shaft 1 in the Z-axis direction is also monitored by a laser interferometer. It is controlled with high precision as well as.

The shape of the cutting edge of the diamond cutter 2 is
For example, with a radius of 5 mm, the roundness which is a shape error is 0.1 μ.
It is a circular arc shape of m and the turning radius is set to 25 mm.

The surface of the workpiece W is cut as follows. First, the Y stage 11 is fixed at a predetermined Y position, and the workpiece W is moved in the Z axis direction while rotating the spindle 1 around the Z axis. At the same time, the X stage 12 is moved to the X position according to a predetermined program. By moving the workpiece W in the axial direction, the workpiece W is moved back and forth toward the diamond cutter 2, and the Z-axis strip portion A ₁ on the surface of the workpiece W is cut. Since the present embodiment is to process a toric lens, the inclination of the cutting surface of the strip-shaped portion A ₁ has a cross section along the vertical plane including the Z axis as shown in FIG. It is an arc shape formed by vertical movement, and as shown in (c) of the figure, the cross section along the vertical plane including the Y axis is cut into an arc shape of a fine width by the turning of the diamond cutter 2, It becomes a strip-shaped mirror surface with extremely high surface accuracy.

Next, the Y stage 11 is moved in the Y-axis direction by a predetermined pitch, and the strip-shaped portion A ₂ adjacent to the strip-shaped portion A ₁ is cut in the same manner as the strip-shaped portion A ₁ . By repeating this process, the entire width of the workpiece W in the Y-axis direction can be processed into a predetermined curved surface.

As shown in FIG. 2, the pitch ΔY of the Y stage 11 must be set so that the surface roughness of the machined surface of the workpiece W in the Y-axis direction is below an allowable value. Therefore, the pitch ΔY of the Y stage 11 is controlled as follows.

As shown in FIG. 3, the following relationship is established between the turning radius R of the diamond cutter 2, the curvature ρ of the machined surface of the workpiece W and the surface roughness δ.

Δ = ΔY ² (1 / 8R-1 / 8ρ) (1) ρ = (1 + f ₁ ² ) ^3/2 / f ₂ (2) R <ρ (3 ) Where f ₁ and f ₂ are toric generatrix shapes X, respectively.
= F (Y) is the first and second derivative.

If the pitch of the Y stage 11 is controlled based on the equations (1) to (3) each time the position of the workpiece W in the Y axis direction changes, the machining surface of the workpiece W in the Y axis direction can be controlled. The surface roughness can be finished below the allowable value. That is, the entire processed surface of the workpiece W can be processed into a mirror surface with high surface accuracy. Further, the processed surface of the workpiece W is divided into strip-shaped portions having a uniform width along the undulations, and the Y stage 11 is
You may comprise so that each strip | belt-shaped part may be advanced intermittently every time a pitch is sent. In this case, the feed pitch of the Y stage 11 is controlled based on the curvature of the processed surface of the workpiece W.

According to this embodiment, since the diamond cutter is attached to the horizontal spindle of the ultra-precision NC machine tool and the diamond cutter is rotated to perform the curved surface machining, the entire width of each strip-shaped portion of the machined surface is processed. Can be cut at a uniform cutting speed and can be mirror-finished uniformly with high surface accuracy. Unlike the conventional example using a ball end mill, there is no possibility that the peripheral speed of the cutting edge will change in the radial direction and the surface accuracy will not vary, so that it is suitable for the production of optical components that require extremely high surface accuracy.

The process of processing the curved surface of the toric lens according to this embodiment will be described with reference to the flowchart of FIG.

First, in step S1, the curved surface shape data of the toric lens is input to the ultra-precision NC machine tool. In step S2, the pitch of the Y stage is calculated based on the equations (1) to (3), the center position of the tool is set in step S3, and in step S4, rotation of the spindle, movement in the Z axis direction, and XY.
The stage is controlled to cut the machined surface of the work piece. In step S5, it is confirmed that the entire machined surface of the workpiece has been machined, and the machining cycle ends.

Since the toric lens is machined in this embodiment, the section taken along the plane perpendicular to the Z-axis direction of the machined surface has an arc shape with a uniform curvature. It goes without saying that any curved surface can be cut by controlling the position of the workpiece in the X-axis direction.

[0029]

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

Even an optical component such as a toric lens having a curved surface shape which is not axially symmetrical can be processed into a uniform mirror surface state with high surface accuracy. As a result, a toric lens or the like having excellent optical characteristics can be manufactured.

[Brief description of drawings]

1A and 1B are views for explaining a curved surface processing step according to an embodiment, in which FIG. 1A is a perspective view showing a workpiece to be processed and a cutting device, and FIGS. FIG. 3 is a schematic partial cross-sectional view showing the workpiece, the diamond cutter, and the bite holder in different cross sections.

FIG. 2 is a diagram illustrating a workpiece and a pitch in the Y-axis direction.

FIG. 3 is a graph showing the relationship between the surface roughness of the processed surface of the workpiece and the pitch in the Y-axis direction.

FIG. 4 is a flowchart illustrating a curved surface processing process according to the present embodiment.

FIG. 5 is a schematic cross-sectional view illustrating a conventional example.

FIG. 6 is a perspective view illustrating another conventional example.

[Explanation of symbols]

 1 Spindle 2 Diamond cutter 3 Tool holder 10 XY stage 11 Y stage 12 X stage

Claims (5)

[Claims] 1. A cutting tool which swivels about a swivel axis parallel to a holding surface for holding a work piece along the holding surface.
A predetermined band-shaped portion of the work piece is cut by feeding the cutting tool in the second direction, and then the step of feeding the cutting tool in the second direction along the holding surface is repeated. 2. The surface processing method according to claim 1, wherein the workpiece is moved toward and away from the cutting tool while feeding the cutting tool in the first direction. 3. The pitch according to claim 1, wherein the pitch for feeding the cutting tool in the second direction is controlled based on the tolerance of the curvature or surface roughness of the machined surface of the workpiece. Surface processing method. 4. The surface processing method according to claim 1, wherein the cutting tool is a single-crystal diamond cutter having an arcuate cutting edge with a shape error of 0.1 μm or less. 5. The surface processing method according to claim 1, wherein the cutting tool is attached to a spindle of a three-position controlled ultra-precision NC machine tool.