JP2507792B2 - Method for manufacturing memory-disk substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a memory having a smooth surface from a blank material (hereinafter simply referred to as a blank material) made of an aluminum plate having a hole in the center, an aluminum alloy plate or a composite material thereof. The present invention relates to a method for manufacturing a disk substrate.

(Prior Art) A memory disk used in an external storage device of an electronic computer usually has a structure in which an aluminum plate (substrate) is coated with a magnetic material. The memory disk requires a high degree of flatness and smoothness in order to read and write accurately with a magnetic head, but the surface condition of the memory disk depends on the surface condition of the aluminum substrate, so the aluminum substrate has extremely high dimensions. Precision and high quality surface conditions are required.

Conventionally, as a method for manufacturing such a memory disk substrate, (a) a method of ultra-precision cutting a blank material with a natural diamond cutting tool, (b) a method of simultaneously polishing both surfaces with a grindstone, and (c) a lapping machine There is a method in which both surfaces are simultaneously polished with abrasive grains and warm water.

(Problems to be Solved by the Invention) Since all of the above-described substrate manufacturing methods are processing by cutting or grinding, there is a problem in that processing takes time and productivity is poor. Therefore, the use of coining, which is usually used for manufacturing coins, is being considered. The coining technique is usually a technique to form a concavo-convex pattern on the machined surface, but unlike the conventional method of forming a concavo-convex pattern, a smooth die is used to impress a smooth surface on the blank material. Attempts have been made to obtain a substrate for a memory disk (Japanese Patent Laid-Open No. 61-502787).

By the way, a normal memory disk substrate is a donut-shaped disc having a hole in the center, and it is necessary to form chamfered portions at the corners of the outer peripheral edge and the inner peripheral edge. However, coining is usually performed in a tice ring that regulates the spread limit of the material.Therefore, when coining is performed with a die with a smooth surface, a memory disk substrate with raised peripheral corners can be formed. Becomes The chamfering of the peripheral edge can be performed after the coining, but the chamfering is not a preferable method because the smooth surface formed by the coining is likely to be damaged or soiled. Furthermore,
When performing chamfering, it is usually attached to a lathe by a vacuum chuck, but at that time, mechanical properties such as straightness corrected by coining may deteriorate.

The present invention solves the problems of the prior art as described above,
It is an object of the present invention to provide a method for manufacturing a memory disk substrate, which has extremely high productivity by coining.

(Means for Solving the Problem) The present inventors have found that the degree of reduction rate of the chamfered portion due to the flow of material accompanying the reduction of sheet thickness in coining has a close relationship with the reduction rate of sheet thickness. Based on this finding, the present invention has been completed based on this finding.

That is, according to the present invention, a blank material made of an aluminum plate having a hole in the center, an aluminum alloy plate or a composite material thereof is sandwiched between two dies having a smooth pressing surface, and the spread limit of the blank material is regulated. A method of manufacturing a memory disk substrate for coining in die ring, which is 1 to 1.7 times the chamfering width to be obtained as a product in advance on the outer peripheral edge and the inner peripheral edge of the blank material in performing coining. The present invention provides a method for manufacturing a memory disk substrate, characterized in that a chamfered portion having a size is formed and coining is performed at a plate thickness reduction rate of 1 to 4%.

As shown in FIG. 1, the chamfered portion 2 of the memory disk substrate is formed on the outer peripheral edge and the inner peripheral edge of the blank material 1 when blanking the blank material 1, and the chamfered width W ₀ thereof.
In general, there is a tolerance of ± 50%. That is, 0.5
A chamfer width of ~ 1.5W ₀ is acceptable for the product. Usually, in coining, the chamfered portion becomes smaller due to the flow of material accompanying the reduction in plate thickness, and the degree thereof has a close relationship with the reduction rate of plate thickness.

In addition, this plate thickness reduction rate is an important factor in obtaining a flat surface that is a characteristic of coining. If the plate thickness reduction rate is less than 1%, the flat surface that is the purpose of the main body will be obtained. If the blank cannot be given a sufficient amount of plastic working, and if the reduction rate of the sheet thickness is larger than 4%, the flatness is rather deteriorated due to the excessive flow of material. Normal product flatness is 10 μm
It is the following.

For the above reasons, in the present invention, the reduction rate of the plate thickness is set in the range of 1 to 4%.

Considering the flow of material within this range of plate thickness reduction, the width of the chamfer formed on the blank material is smaller than the chamfer width to be obtained as a product, or the required chamfer is obtained with a dimension larger than 1.7 times. Is impossible. For the above reason, in order to manufacture a chamfered portion having a tolerance of ± 50%, the chamfered width formed in advance on the blank material is 1 to 1.7 times the chamfered width to be obtained.

The blank material used in the present invention may be an aluminum material, an aluminum alloy material, or a composite material thereof, and the plate thickness thereof is preferably 2 mm or less. This is because the original plate thickness required to obtain a predetermined plate thickness as a product.

(Example) The present invention will be described in more detail based on the following examples.

Blank materials having various widths of the chamfered portions 2 formed in advance on the outer peripheral edge and the inner peripheral edge of the blank material 1 shown in FIG. 1 were prepared, and the chamfer width and flatness after coining were confirmed.

The blank material has a thickness of 1.3 mm, an outer diameter of 95 mm, and an inner diameter of 25 m.
The flatness of the blank is about 30 μm. Lubricating oil was applied at about 100 mg / m and coined with a load of 300 tons. Then, the dimension of the end of the molded product was measured and the flatness was measured by an optical interference fringe meter. The results are shown in Table 1.

As shown in the results in Table 1, when considering only the chamfer width of the product, there are some cases where the plate thickness reduction rate falls within the tolerance even if it is outside the range of 1 to 4% specified by the method of the present invention. It is difficult to obtain good flatness, which is a feature of the processing method, and it is not of a quality that can be used as a memory disk substrate.

(Effect of the invention) As described above, according to the present invention, a large chamfered portion having a chamfering width of 1 to 1.7 times is formed in advance on a blank material, and coining is performed at a plate pressure reduction rate of 1 to 4%. Since this is done, the desired chamfered portion can be formed simultaneously with the coining without impairing the flatness, and there is an advantage that a good memory disk substrate can be efficiently manufactured.

[Brief description of drawings]

 FIG. 1 is a sectional view of the blank material of the present invention. 1 ... Blank material, 2 ... Chamfer

 ─────────────────────────────────────────────────── ─── 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 Jun Yamazaki Utsunomiya City, Tochigi Prefecture 7-62 Tsuruta-cho (72) Inventor Akimoshi Yoshida 26-1-206 (56) Nakazatodai, Minami-Biery Center, Yokohama-shi, Kanagawa Reference JP-A-61-502787 (JP, A)

Claims (1)

(57) [Claims] 1. A blank material made of an aluminum plate having a hole in the center, an aluminum alloy plate or a composite material thereof is sandwiched between two dies having a smooth pressing surface, and the spread limit of the blank material is regulated. A method of manufacturing a memory disk substrate for coining in a die ring, the chamfering width of which is 1 to 1.7 times as large as a product to be preliminarily obtained as a product on an outer peripheral edge and an inner peripheral edge of the blank material in performing coining. A method for manufacturing a substrate for a memory disk, characterized in that a chamfered portion is formed and coining is performed at a thickness reduction rate of 1 to 4%.