JP2507793B2 - Precision metal disk manufacturing method - Google Patents

Description

The present invention relates to a method for producing a precision metal disc by coining.

[Conventional technology and its problems]

Precision metal disks, such as aluminum substrates for memory disks, mirror plates and rotary reflectors for encoders, that require a smooth surface finish are usually manufactured by precision cutting using a natural diamond bite, etc. Since the processing takes time and the productivity is low, a method of performing this by coining has recently been proposed (Patent Application Publication No. 61-502787).

In order to manufacture a precision metal disc by coining, as shown in Fig. 2, the disc-shaped metal material 1 is placed in the space between the die ring 2 and the mandrel 3 in two dies having a smooth pressing surface. Four
・ It is sandwiched between 4 and pressed, and die ring 2 and mandrel 3
In this method, the smooth surface of the dies 4 is imprinted on the metal material 1 in a state where the radial expansion limit of the metal material 1 is regulated. This is the case of a disc with holes, but in the case of a disc without holes, no mandrel is required and a die with no hole in the center is used.

In coining, friction between the pressing die and the metal material is the biggest problem. Specifically, if this friction condition is bad, the fixed area (the part where the material does not move horizontally)
Occurs, and the amount of metal flow is different from that in other regions, resulting in a difference in plate thickness, which deteriorates the flatness of the obtained precision metal disc. Increasing the amount of lubricant applied is an effective way to improve the friction state and reduce the sticking area, but increasing the amount of lubricant applied deteriorates the surface roughness of the precision metal disk obtained. There is a problem of doing.

[Means for solving the problem and its action]

As described above, it is difficult to manufacture a precision metal disk having good flatness and small surface roughness only by adjusting the amount of lubricant applied. Therefore, the inventors of the present invention have shown that in order to obtain good flatness and surface roughness in a range where the amount of lubricant applied is small,
A die 4 (which has a slight bulge from the surface edge portion to the center portion) having a crown on the pressing surface A as described in 3 (hereinafter referred to as a crown die) was examined. By using such a crown die, a precision metal disk with good flatness can be manufactured with a smaller amount of lubricant, compared to the case of using a conventional die with a flat pressing surface (hereinafter referred to as a flat die). I knew I could do it.

However, this crown die also has the following problems,
There was a need for improvement.

○ It takes longer to process the pressure surface (grinding and polishing) and costs more than a flat die.

○ It is difficult to stably form a crown of the same shape.

○ Depending on the shape of the crown, processing may not be possible. For example, a die made of cemented carbide and having a weight of about 50 kg has a limit of R = 1000 mm in the current grinding machine.

Based on the above-mentioned examination results, the present invention uses the die 4 having the concave portions 5 formed on the outer peripheral surface and the inner peripheral surface of the portion closer to the base than the pressing surface A as shown in FIG. It solves the problem of crown dies. Figure-1
The dies are for discs with holes, but those for discs without holes have a shape without a central hole.

By forming the concave part of the die as described above, even if the die processing surface is processed flat, the pressure surface elastically deforms to the same shape as the crown die at the time of coining, and the crown die is used. The same effect as in the case of doing is obtained.

〔Example〕

 Examples of the present invention will be described below.

As shown in FIG. 1, the die has a flat pressing surface, and the radius of curvature R of the semicircular recess 6 on the outer peripheral surface and the inner peripheral surface is 3 mm, 7 mm,
Three types of 15mm dies were made. Also for comparison-
With a crown die like 3, the crown height h of the pressing surface is 2
Three types of crown dies of μm, 5 μm and 10 μm, and a conventional flat die with a flat pressing surface were manufactured. However, a crown die having a crown height of 2 μm could not be manufactured because the radius of curvature of the crown was too large. The sizes of the three types of R in the die of FIG. 1 are determined by FEM analysis so that the same crown height as that of the above three types of crown dies can be obtained by the pressure during coining. The dies are all made of cemented carbide, and the pressed surfaces have the same finish.

The coining process was performed using the above-mentioned 6 types of dies manufactured. The disc-shaped metal material used is an aluminum blank material (5086-O material) with a plate thickness of 1.300 mm, an outer diameter of 95 mm, and an inner diameter of 25 mm.
The amount of lubricant applied was 50 mg / m ² , and the pressure was 300 tons. After coining, the flatness and surface roughness Ra of the obtained precision metal disk were measured. The flatness is obtained by obtaining a profile curve in the radial direction and expressing it as a distance from the reference line to the top of the curve.

 Table 1 shows the results of coining.

As is clear from Table-1, the method of the present invention using the die of FIG. 1 has the same effect as that of using the crown die, and compared with the conventional method using the flat die, The roughness Ra is the same, but the flatness is improved. The degree of improvement increases as the crown height under pressure decreases, but with a crown die, the crown height is 2 μm.
Since it is impossible to process (1), it is not possible to manufacture a precision metal disk corresponding to the first aspect of the present invention.

Further, comparing the processing time and cost of the die pressing surface, the die used in the present invention is similar to the conventional flat die, and the processing time is shorter and the cost is lower than the crown die.

〔The invention's effect〕

As described above, according to the present invention, it is possible to manufacture a precision metal disc having both good flatness and surface roughness, and since the die pressing surface may be flat, the die die can be used as compared with the case of using a crown die. The pressing surface can be easily processed, and the cost of the die can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a die used in the method of the present invention, FIG.
2 is an explanatory view showing a method for manufacturing a precision metal disk by coining, and FIG. 3 is a vertical cross-sectional view of a crown die examined in the course of reaching the present invention. 1: Disc-shaped metal material, 2: Die ring, 3: Mandrel, 4: Dice, 5: Recess, A: Pressurized surface.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Saito 1677-24 Takaragi Honcho, Utsunomiya City, Tochigi Prefecture (72) Inventor Tomokatsu Hata 610 Kiyotaki Tanse Town, Nikko City, Tochigi Prefecture (72) Inventor Yoshito Inabayashi, Tochigi Prefecture 610 Kiyotaki, Tanse-cho, Nikko-shi (72) Inventor, Akemi Yoshida Minami-Biery Center, Yokohama-shi, Kanagawa 21-1-206 (72) Inventor, Masanori Kitahama 1351-508, Chiba-shi, Chiba-shi

Claims (2)

(57) [Claims] 1. A disc-shaped metal material is sandwiched between two dies having a smooth pressing surface in a die ring that regulates a radial expansion limit, and coining is performed to form a die-processed surface. In the method for producing a precision metal disk whose dimensions are regulated on the inner peripheral surface of a die ring, the precision die characterized by using a concave portion formed on the outer peripheral surface of the portion closer to the base than the pressing surface as the die. Manufacturing method of metal disk. 2. A coin-shaped metal material is sandwiched between two dies having a smooth pressing surface in a space between a die ring and a mandrel for restricting a radial expansion limit to perform coining. In the method for producing a precision metal disk whose dimensions are regulated by the inner surface of the die pressing surface and the outer surface of the mandrel, as the die, a concave portion is formed on the outer peripheral surface and the inner peripheral surface of the portion closer to the base than the pressing surface. A method for producing a precision metal disc, characterized in that a product formed with the above is used.