JP2007175803A - Manufacturing method for optical part or its mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an optical part or its mold, obtaining uniform machined surface in short-time machining. <P>SOLUTION: According to this manufacturing method for an optical part or its mold, a tool is rotated round its axis with the cutting edge directed to the outside, a machining object surface of a workpiece is cut by one portion of a circle drawn by the cutting edge, and simultaneously the tool and the workpiece are relatively linearly moved at a predetermined feed rate in the line direction to perform cutting for one line. Subsequently, the tool and the workpiece are relatively moved in the pitch direction intersecting the line direction only by pick feed amount to perform cutting for the next one line. The rotating speed of the tool is set to 10,000 (rotation/min), and the movement in the line direction is reversed line by line to perform cutting in reciprocation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a manufacturing method for manufacturing an optical component having a free-form surface or a mold for molding the optical component. For example, it is suitable for a manufacturing method of a mold for forming a free-form surface mirror for an fθ lens or a projection TV.

  In recent years, projection mirrors for projection TVs and the like having a free-form surface on the mirror surface have been used. In particular, in rear projection televisions and the like, free-form curved mirrors are important because it is necessary to make the optical system as thin as possible. In order to mold an optical component having such a free-form surface, it is first necessary to manufacture a mold in which the free-form surface is copied. In general, when cutting a free-form surface having no rotating shaft, a fly-cut machine as shown in FIG. 1 is used (for example, see Patent Document 1 and Patent Document 2).

  In such a fly-cut processing machine 1, an X-axis direction slide table 12 and a Z-axis direction slide table 13 are provided on a surface plate 11 in an overlapping manner. A tool spindle 15 is attached to the Y-axis direction slide table 14. A tool 16 is attached to the tip of the tool spindle 15. Each of the axial slide tables 12, 13, and 14 is controlled to move in the respective axial direction, and the tool spindle 15 is controlled to rotate so that the tool 16 rotates about its main axis.

  According to this fly cutting machine 1, the workpiece 20 placed on the Z-axis direction slide table 13 is controlled in two axes in the XZ plane. Further, the tool 16 is rotated at a predetermined rotation speed and controlled in one axis in the Y-axis direction. Thereby, cutting can be performed while the tool 16 and the workpiece 20 are relatively controlled in three axes. In addition, there is a three-axis control processing machine in which the workpiece table is controlled by one axis and the tool table is controlled by two axes.

In the cutting by the fly-cut machine 1, generally, for example, as shown in FIG. 4 of Patent Document 1, the tool 16 and the workpiece 20 are relatively moved in the rotational circumferential direction of the tool 16 to make one line. Cut. When the cutting of one line is completed, the tool 16 and the workpiece 20 are once separated, the tool 16 is moved by a predetermined amount in the direction of the rotation axis, and the workpiece 20 is moved to the start position of the next line. Then, the tool 16 and the workpiece 20 are moved relative to each other to perform the next one line cutting. That is, cutting is always performed only in one direction in one direction. This is because the relationship between the rotation direction of the tool 16 and the movement direction of the workpiece 20 is made constant so that the machined surface characteristics become uniform.
JP 2000-94270 A JP 2000-298509 A

  However, in the conventional mold core manufacturing method described above, since processing is performed only in one direction as described above, it takes extra time for simple return movement. As a result, the processing time as a whole becomes longer and the productivity is poor. Furthermore, since the machining time is long, the ambient temperature tends to change during machining, and the workpiece or device may be slightly deformed due to temperature changes. In that case, there is a problem that waviness may occur on the machined surface. On the other hand, however, when reciprocating is performed, the machined surface characteristics change between the forward path and the return path, and a uniform machined surface cannot be obtained.

  The present invention has been made to solve the problems of the above-described conventional mold core manufacturing method. That is, an object of the present invention is to provide a method of manufacturing an optical component or a mold thereof that can obtain a uniform processed surface in a short time.

  In order to solve this problem, the optical component of the present invention or the method of manufacturing the mold thereof is the method of rotating the tool around the axis with the cutting edge facing outward, and at one place of the circle drawn by the cutting edge. While cutting the surface to be machined, the tool and workpiece are moved relative to each other in the line direction at a predetermined feed speed to perform one line cutting, and then the tool and workpiece are relatively moved. A method of manufacturing an optical component or a mold thereof by moving the next one line by moving the pick feed amount in the pitch direction intersecting the line direction, and the tool rotation speed (S) is set to 10,000 (rotation / Min)), and the reciprocal cutting is performed by reversing the movement in the line direction for each line.

  According to the method for manufacturing an optical component or a mold thereof according to the present invention, the movement in the line direction, which is the relative movement direction of the tool and the workpiece, is reversed in each line, and cutting is performed in both directions. Therefore, it is not necessary to move to return the position of the tool, compared to cutting with only one way. Therefore, the time required for processing is short. Furthermore, since the tool rotation speed (S) is set to 10,000 (rotations / minute) or more, even when reciprocating as described above, the difference in the cutting state depending on the moving direction is small, and a uniform machined surface can be obtained. Therefore, it is a method for manufacturing an optical component or its mold that can obtain a uniform processed surface in a short time. Here, the method according to the present invention includes a method for manufacturing a mold by cutting under the above conditions, a direct manufacturing of an optical component by cutting under the above conditions, and an optical component using a mold by cutting under the above conditions. Is included.

  Furthermore, in the present invention, it is desirable to perform cutting under the condition that the relationship between the feed rate (F, mm / min) and the tool rotation speed (S, rotation / min) is F / S ≦ 0.1 mm / rotation. . In this way, since the ratio of the feed speed to the tool rotation speed is small, the amount of cutting by one rotation of the tool is very small. Therefore, the difference in the cutting state depending on the moving direction is small.

  Furthermore, in the present invention, to the workpiece of the tool in the down line, the direction of movement of the cutting edge of the tool scraping the workpiece at the cutting point coincides with the direction of movement by line movement of the workpiece with respect to the rotation center of the tool. It is desirable that the amount of cut of is greater than the amount of cut in the reverse upline. In this way, the difference in cutting state depending on the moving direction becomes smaller.

  According to the method for manufacturing an optical component or its mold of the present invention, a uniform processed surface can be obtained in a short time.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to a method of manufacturing a mold for molding an optical component having a free-form surface.

  As shown in FIG. 1, the fly-cut processing machine 1 used in the present embodiment is provided with an X-axis direction slide table 12 and a Z-axis direction slide table 13 which are stacked on a surface plate 11. A tool spindle 15 is attached to the Y-axis direction slide table 14. A tool 16 is attached to the tip of the tool spindle 15. Each of the axial slide tables 12, 13, and 14 is controlled to move in the respective axial direction, and the tool spindle 15 is controlled to rotate so that the tool 16 rotates about its main axis. The basic configuration of the fly-cut machine 1 is the same as that of the conventional one.

  According to the fly-cut processing machine 1, the workpiece 20 placed on the Z-axis direction slide table 13 is moved to a predetermined position in the XZ plane by the X-axis direction slide table 12 and the Z-axis direction slide table 13. Placed in position. Alternatively, the workpiece 20 can be controlled to move in a predetermined direction at a predetermined speed. Further, the tool 16 is rotated at a predetermined rotational speed by the tool spindle 15 and is position-controlled in the Y-axis direction by the Y-axis direction slide table 14.

  In this embodiment, as shown in FIG. 1, while rotating the tool 16, the tool 16 and the workpiece 20 are relatively brought close to each other to cut the workpiece 20. In this figure, the surface on the back left side of the workpiece 20 is a cutting surface. Then, the workpiece 20 is moved in the XZ plane while being cut by the tool 16. For example, the tool 16 is rotated in the direction indicated by the arrow in the figure, and one line is cut while moving the X-axis direction slide table 12 from the right rear side to the left front side in the figure. At this time, the Z-axis direction slide table 13 is simultaneously controlled in accordance with the required cutting surface shape.

  Hereinafter, this movement in the XZ plane is referred to as feed movement. The direction of this feed movement corresponds to the line direction. The moving speed of the workpiece 20 in the XZ plane at the time of cutting (relative speed with the tool 16) is referred to as a feed speed F. The movement direction of the tool 16 in the Y-axis direction is referred to as a pick feed direction. The pick feed direction is only one direction. Further, a single movement amount in the pick feed direction is referred to as a pick feed amount f.

  When the cutting of one line is finished, the tool 16 is moved by a predetermined amount in the Y-axis direction. Then, the next one line is cut while moving the workpiece 20 in the reverse direction. Here, on the contact surface between the tool 16 and the workpiece 20, the direction of movement due to the rotation of the tool 16 and the direction of feed movement of the workpiece 20 are substantially the same direction, and the case of the opposite direction is the up direction. It is called processing. Since the cutting direction of the tool 16 into the workpiece 20 differs between the down direction and the up direction, strictly speaking, the cutting characteristics are different. In the past, machining was performed only by cutting in the down direction.

  In the manufacturing method of this embodiment, the rotational speed S of the tool 16 is set to 10,000 rpm or more. Further, the feed speed F is controlled so that the feed speed F (mm / min) / tool rotation speed S (rpm) = 0.1 mm / r or less. That is, at the tool rotation speed S = 10000 rpm, the feed speed F is set to 1000 mm / min or less. By doing so, since the length of the workpiece 20 cut by one rotation of the tool 16 becomes very small, the difference in cutting load depending on the feed direction becomes very small.

  However, if the rotational speed S of the tool 16 is 50000 rpm or more, mechanical vibration due to the swing of the rotating shaft of the tool 16 tends to occur, and the processing accuracy is lowered. It is worse than the above surface roughness. For this reason, it is desirable that the tool rotation speed S be in the range of S = 10000 to 50000 rpm.

  Tool 16 is a single crystal diamond tool. The cutting edge portion of the tool 16 is formed in an arc shape as shown in FIG. This arc-shaped radius is called a tool nose radius. Although it is shown quite large in this figure, in practice, a very large tool 16 cannot be used due to the limitation due to the material. This is because obtaining a large tool 16 is very difficult as well as costly. Therefore, the tool nose radius r is substantially in the range of r = 5 to 20 mm.

  Further, if the pick feed amount f is 0.01 mm or less, the number of lines becomes too large, and the processing time increases, so the productivity is lowered. If the pick feed amount f is 0.04 mm or more, the tool nose r needs to be 20 mm or more in order to make the theoretical roughness within 10 nm, which is not practical. For this reason, it is desirable that the pick feed amount f be in the range of 0.01 mm to 0.04 mm.

  Further, in this embodiment, the cut surface can be made more uniform by changing the cutting amount between the down direction and the up direction. The cutting depth is a depth at which the tool cutting edge bites into the workpiece 20 and corresponds to a distance between the workpiece 20 and the tool 16 in the Z-axis direction. Here, the cutting amount of the tool 16 with respect to the workpiece 20 is cut so as to be slightly smaller in the up direction than in the down direction. That is, in the up direction, the distance in the Z-axis direction between the workpiece 20 and the tool 16 is made slightly larger over the entire range of one line. This is because if the cutting amount is controlled to be the same value, the cutting result tends to increase the actual cutting amount in the up direction compared to the down direction. Therefore, by controlling in this way, even if reciprocating cutting is performed at the same rotational speed and the same feed speed, there can be almost no difference in the processed surface.

  As a method of changing the cutting amount, there is a method in which a cutting program in which the control value of the Z-axis direction slide table 13 is changed in the forward path and the backward path is created in advance and cutting is performed by the program. Alternatively, when the Z-axis direction slide table 13 has a mechanism capable of moving the feedback scale of the table back and forth, control is also performed by temporarily moving only the feedback scale during cutting in the up direction. it can.

Thus, in the manufacturing method of this embodiment, each parameter to be used is set as follows.
Tool rotation speed (S): 10,000 to 50,000 rotations / minute feed speed (F): 300 to 2000 mm / minute Tool edge rotation radius (D): 5 to 15 mm
Pick feed amount (f): 0.01 to 0.04 mm
Tool nose diameter (r): 5 to 20 mm
Cutting depth: 1 to 20 μm

  As described above in detail, according to the manufacturing method of the present embodiment, the difference in cutting load is very small even when the feed direction is the reciprocating direction by increasing the rotation speed of the tool 16 and reducing the feed speed. Furthermore, if the cutting amount is changed according to the feed direction, the difference in cutting load is further reduced. That is, even if reciprocating cutting is performed, the cutting characteristics can be made almost the same. Therefore, the cutting surface of each part can be made substantially uniform. Thereby, it is a mold manufacturing method that can obtain a uniform processed surface in a short time.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, a lens may be used as an optical component manufactured by this mold. In the above embodiment, the mold manufacturing method is used. However, the present invention can also be applied to a manufacturing method for manufacturing an optical component by directly cutting an optical component material using similar manufacturing conditions.

It is a perspective view which shows schematic structure of a fly cut processing machine. It is a side view which shows schematic structure of a fly cut processing machine. It is explanatory drawing which shows the feed direction by the manufacturing method of this form.

Explanation of symbols

1 Fly cutting machine 16 Tool S Tool rotation speed F Feed rate

Claims (3)

The tool is rotated around its axis with the cutting edge facing outward, and the tool and workpiece are relatively aligned in the line direction while cutting the workpiece surface at one location of the circle drawn by the cutting edge. The line is moved at a feed rate of 1 line to perform one line of cutting, and then the tool and workpiece are moved by a pick feed amount in a pitch direction that intersects the line direction relatively to perform the next line of cutting. In the manufacturing method of the optical component or its mold by performing,
The tool rotation speed (S) is set to 10,000 (rotations / minute) or more,
A method of manufacturing an optical component or a mold thereof, wherein the movement in the line direction is reversed for each line and the reciprocating cutting is performed. In the manufacturing method of the optical component of Claim 1, or its metal mold | die,
The relationship between feed rate (F, mm / min) and tool rotation speed (S, rotation / min) is
A method of manufacturing an optical component or a mold thereof, wherein cutting is performed under the condition of F / S ≦ 0.1 mm / rotation. In the manufacturing method of the optical component of Claim 1, or its metal mold | die,
The amount of cutting of the tool into the workpiece in the downline, where the direction of movement of the cutting edge of the tool scraping the workpiece at the cutting point coincides with the direction of movement of the workpiece by line movement with respect to the rotation center of the tool, A method of manufacturing an optical component or a mold thereof, wherein the amount of cut is larger than the amount of cut in an upline in the reverse direction.

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