JP2761010B2 - Mold insert processing method for streamlined exterior optical parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for nesting a flow-surface type exterior optical component in a mold.

[Conventional technology]

In recent years, plastic molded parts using curved surfaces for exterior parts such as cameras have been frequently used. Among them, for example, in a 35 mm lens / shutter camera, there is a component having an optical function called a finder, such as a transparent component of a finder portion, which is an exterior component using a curved surface in design. Since such a part is an optical part molded in a three-dimensional shape, it is an external part,
High precision processing is required.

For example, in the case of a product having a design based on the flow surface shape, the shape of the transparent plastic part (front mold) provided on the front surface of the finder portion is shown in FIG. 5 (perspective view) and FIG. 6 (plan view). It has become. That is, the exterior surface is formed on the toric optical surface 1 and its bus 2
It is inclined by an angle θ with respect to the center line 3 of the outer shape (rectangle) of a curve of radius R _1. 4 is a sagittal toric optical surface 1, sagittal 4 is a curve of radius R _2. Such a transparent plastic part has a very complicated shape and is fitted on the front of the finder. Therefore, the surface thickness t of the outside and the interior is made uniform so as not to have a lens effect. It is a part that must be very accurate.

Such parts are manufactured by plastic injection molding. At this time, the mold inserts for molding the complicated toric optical surfaces of the exterior and interior are also inverted in shape, and the bus bar is inclined to a rectangular outer shape and the toric is formed. Optical surfaces have been created. In particular, since the predetermined optical performance must be ensured in the molded part, the curvature R accuracy, surface accuracy and surface properties of the convex and concave busbars and the sagittal wires are determined by the mold insert for the finder plastic lens. Must be machined with the same precision as.

Conventionally, a three-dimensional shape such as the above-mentioned mold insert has been cut by a machining center or a die-sculpting machine equipped with XYZ three-axis drive control, and then processed by a skilled engineer's hand finishing. .

[Problems to be solved by the invention]

However, in the above-mentioned conventional technology, since the cutting process is performed with an NC-controlled machining center or a die-sinking machine, the processing accuracy is not very accurate as an optical surface, and it occurs during cutting even in the polishing process of hand finishing by a skilled person. It is difficult to completely remove the trace of the cutting edge, and it has not been possible to obtain desired optical surfaces in terms of shape accuracy, surface accuracy and surface properties. Further, since the polishing is performed by hand finishing by a skilled person, there is a disadvantage that enormous processing time is required, reproducibility is poor, and the quality variation of each mold insert is large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an optical mirror surface such as a toric optical surface, a cylindrical optical surface, and a curved surface symmetrical with one axis that is inclined at an angle θ with respect to the center line of the outer shape without polishing. It is an object of the present invention to provide a method for die insert machining of a streamlined exterior optical component that can be created with high precision, high quality and in a short time only by machining.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a method for processing a mold insert for molding a plastic exterior optical component having a flow surface shape on an outer surface. And the mold insert preform is inclined at a predetermined angle with respect to the center axis of the spundle, and is detachably attached to the spindle via a positioning toy provided rotatably around the center axis of the spindle. The cutting tool is moved in a plane including the central axis of the cutting tool as a straight or curved feed path for supporting the cutting part, thereby forming a cylindrical optical surface, a toric optical surface, or a uniaxially symmetric curved surface.

In the present invention, a processing machine that rotates a mold insert preform is equipped with a spindle having a high-precision rotation accuracy secured by an aerostatic pressure structure (hydrostatic bearing structure) called, for example, an ultra-precision lathe. Use a processing machine. The optically processed surface of the mold insert base material, such as toric or cylindrical, which is to be processed, is previously electrolessly phosphorous (P) -nickel (N
i) It is good to coat amorphously by plating, and it is good to form with a copper system metal.

[Action]

In the processing method having the above-described configuration, the mold insert preform is provided around the rotation axis by, for example, a cylindrical positioning jaw supported by the main spindle. The mold insert preform is inserted into the positioning toy and fixed to the toy with a screw on the base material bottom surface, or the mold insert insert preform is fixed by pressing the side of the mold with a screw so that it can be inserted into and removed from the positioning toy. I do. The work surface of the mold insert base material protrudes in the outer circumferential direction in the case of a convex shape and in the inner circumferential direction in the case of a concave shape, and the center axis of the main spindle is parallel to the generating line of the toric or cylindrical surface. In such a manner, it is installed and fixed in a state inclined at an angle θ, and rotated by a spindle.

On the other hand, a cutting tool (diamond tool)
Is set in a plane including the center axis of the main spindle, and when the feed movement is straight, the cylindrical surface
When a circular motion is performed by numerical control and scanning control, a toric optical surface is formed.

In particular, when an electroless P-Ni surface or a copper-based metal surface is cut with a diamond bite, an extremely good mirror surface can be obtained, and a desired optical surface can be cut without a polishing step.

〔Example〕

(First Embodiment) This embodiment is an embodiment in which a convex toric surface is formed on a mold insert preform, and will be described with reference to FIGS. 1 and 2. FIG.

That is, as shown in FIG. 2, bus bars 2 and the curvature radius of the outer shape becomes the radius of curvature R ₁ in the mold insert preform 5 of a substantially rectangular column
This is a processing method for obtaining an optical mirror surface in which the convex toric optical surface 1 having the sagittal wire 4 of R _{2 is} inclined by a predetermined angle θ with respect to the center line 3 of the outer shape of the mold insert preform 5.

The processing machine used in this embodiment has a spindle 6 having an aerostatic pressure structure (hydrostatic bearing structure) and ensuring high rotational accuracy.
Is a so-called super-precision lathe equipped with a main shaft (not shown). In the hydrostatic bearing structure, high precision rotation is obtained by flowing aerostatic pressure through a minute gap between the housing and the core of the bearing and rotating the core in a floating state. On the other hand, the mold insert preform 5 is made of SUS420J2
The surface 5a to be processed is subjected to electroless P-Ni plating.

A cylindrical positioning toy 7 is coaxially supported and fixed to the spindle 6 which can be rotated with high precision by a motor (not shown). The positioning toy 7 can rotate around the central axis A of the spindle 6. It is provided in. A mold insert base material 5 is detachably fitted to and held by the positioning toy 7 with screws. Work surface of mold insert base material 5
5a is then turned away with respect to the central axis A of the spindle 6, with which protrudes from a radius R ₂ or sagittal curvature of tolling optical surface 1 by the central axis A, the bus 2 of the toric optical surface 1 The mold insert preform 5 is circumferentially fixed to the positioning toy 7 in a state of being inclined at a predetermined angle θ with respect to the central axis A so as to be parallel to the central axis A.

On the other hand, a tool holder 9 is erected on the processing machine table 8, and a diamond tool 10 is fixedly mounted on the upper part of the tool holder 9 as a cutting tool. The cutting edge of the diamond cutting tool 10 is provided so as to be in a horizontal plane including the central axis A of the spindle 6. Processing machine table 8
Is parallel to the central axis A of the spindle 6,
The robot can be controlled to be able to move in an arc by numerical control or copying.

According to the processing machine having such a configuration, when the spindle 6 is rotated by the motor, the work surface 5a of the mold insert preform 5 with it the central axis A of the spindle 6 at the outer diameter at a radius R ₂ or Rotate (number of rotations 500 to 10,000 rpm). On the other hand, the cutting edge of the diamond tool 10 which is held through the tool holder 9 on the machine table 8 comes into contact with the work surface 5a of the mold insert preform 5 which is rotating, comprising radius R ₁ arc in and controlled by the feed movement, it is subjected to cutting to a radius of sagittal curvature radius R _2. Since the diamond tool 10 is used for the cutting tool, the work surface 5a which is an electroless P-Ni surface
Is turned (rotated, turned) into a surface property having an extremely good optical mirror surface. After processing, by removing the mold insert preform 5 from the positioning lens holder unit 7, the mold insert preform 5 to be processed surface 5a, the radius of curvature R ₁ becomes bus 2, the radius of curvature
A toric optical surface having a sagittal line 4 of R ₂ and inclined at a predetermined angle θ with respect to the center line 3 of the outer shape is formed.

It should be noted that a plurality of the mold insert preforms 5 are arranged in the positioning toy 7 in the same configuration as described above, or one positioning toy 7 is used.
A large amount of processing is also possible by fitting and detaching only the mold-inserted base material 5 a plurality of times by mounting. Also, the radii of curvature R ₁ , R
₂ may be reversed.

In the present embodiment, since it is possible to configure with a precision of μm (micron order), a desired optical surface can be formed with high precision.
A large amount can be obtained with high quality and without variation.

Second Embodiment This embodiment is an embodiment in which a concave toric surface is formed on a mold insert preform, and will be described with reference to FIGS. 3 and 4. FIG.

That is, as shown in FIG. 3, a bus bar 2 having a radius of curvature R ₁ and a radius of curvature
This is a processing method for obtaining an optical mirror surface in which the concave toric optical surface 1 having the sagittal wire 4 of R _{2 is} inclined by a predetermined angle θ with respect to the center line 3 of the outer shape of the mold insert preform 5.

The main configuration is the same as that of the first embodiment, and will not be described, and the characteristic points will be described.

In this embodiment, similarly to the first embodiment, the positioning toy 7 held by the mold insert base material 5 is supported and fixed to the spindle 6 of the main shaft, but the work surface 5a of the mold insert base material 5 is processed. Is positioned opposite the center axis A of the spindle 6 and
There is a sagittal wire 4 of the toric surface 1 in the inner circumferential direction, and the central axis A
From the center axis A so that the distance from the center axis A is parallel to the center axis A while projecting from the positioning toy 7 so that the distance from the center line is smaller than the sagittal curvature radius R ₂ . In this state, the mold insert preform 5 is fixed around the positioning toy 7.

On the other hand, the diamond cutting tool 10, which is a cutting tool, is supported by the cutting tool 9a by the cutting tool arm 9a such that the cutting edge infiltrates the inner peripheral surface side of the positioning toy 7, is flush with the central axis A, and is oriented substantially perpendicularly. . The tool arm 9a is fixed on the processing machine table 8 via a tool holder 9.

According to the processing machine having such a configuration, by rotating the spindle 6, the processing surface 5a of the mold insert preform 5 fitted on the inner peripheral surface of the positioning toy 7 is rotated around the central axis A. . Then, to control the feed movement in an arc comprising a radius R ₁ against the cutting edge of the diamond tool 10 to be processed surface 5a, subjected to cutting to a radius of sagittal curvature radius R _2.
After the processing, the mold insert preform 5 is removed from the positioning toy 7 to produce a bus curvature radius R ₁ , as shown in FIG.
A concave toric optical surface in which the toric optical surface having the sagittal radius of curvature R _{2 is} inclined by an angle θ with respect to the outer shape is formed.

Also in this embodiment, similarly to the first embodiment, a large number of desired optical surfaces can be obtained with high accuracy, high quality, and without variation.

In each of the above embodiments, the mold nesting base material 5 is SU
Since it is made of S420J2, electroless P-Ni plating was applied to the work surface 5a. However, when the mold insert base material 5 is made of oxygen-free copper or Shinchu, the work surface 5a is formed of a copper-based metal. Good to do.

Also, in the processing machine shown in FIGS. 1 and 4, by making the cutting edge feed movement of the diamond bite 10 linear, the cylindrical optical surface can be similarly formed at an angle θ. Further, the cutting edge feed motion can be freely controlled such as a non-circular arc, and various shapes can be formed.

〔The invention's effect〕

As described above, according to the present invention, for example, such as a viewfinder cover of a 35 mm LS camera, when processing a mold insert of an exterior optical component having optical performance and having a flow surface shape, the outer shape is reduced. The toric optical surface and the cylindrical optical surface inclined at an arbitrary angle θ can be machined as high-precision and high-quality optical surfaces. Further, even in a plurality of processes, it is possible to process a large amount at a low cost while maintaining high accuracy and having a small quality. Therefore, the performance of the exterior optical component such as the cover can be improved and the cost can be reduced. Furthermore, if either the bus bar or the sagittal line draws a circular arc, the orthogonal direction can form a free shape such as a non-circular arc, and the degree of freedom in design increases.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a processing machine used in the first embodiment of the present invention, FIG. 2 is a perspective view of a mold insert processed in the first embodiment of the present invention, and FIG. FIG. 4 is a perspective view of a mold insert processed in the second embodiment, FIG. 4 is a perspective view showing a processing machine used in the second embodiment of the present invention, and FIGS. 5 and 6 each have a toric optical surface. It is the perspective view and top view of a transparent plastic component. 1 ...... toric optical surface, 2 ...... busbar 4 ...... sagittal, 5 ...... mold insert preform 6 ...... spindle 10 ...... diamond cutting tool R _1, R ₂ ...... curvature radius, theta ...... angle A …… Center axis of spindle

Claims (1)

(57) [Claims] In processing a mold insert for molding a plastic exterior optical component having a flow surface shape on an outer surface, a surface to be processed of a mold insert base material is turned backward or opposed to a center axis of a spindle. At the same time, the mold insert preform is tilted at a predetermined angle with respect to the center axis of the spindle, and is detachably attached to the spindle via a positioning jaw rotatably provided around the center axis of the spindle. The cutting surface of the cutting tool that supports the cutting edge is moved linearly or curvedly to move the cutting tool to form a cylindrical optical surface, toric optical surface, or a uniaxially symmetric curved surface. Mold insert processing method.