JPS63300849A - Grinding method for disc - Google Patents

Abstract

PURPOSE:To obtain a disc with high accuracy in which each of the grinding unevenness and sagging on the edge surface is small and the deviation of the plate thickness is exceedingly small, by setting the position relation between a ring-shaped narrow width grindstone and the disc and setting the grindstone width to the certain relations. CONSTITUTION:Grinding is performed by setting the position relation between a ring-shaped grindstone 5 and a disc (workpiece) 4 and the grindstone width so that the equations I, II, III, and IV are satisfied (RD is the radius of a circle which is formed by the centers of a plurality of discs 4 in the simultaneous grinding, GI is the inside diameter of a ring-shaped grindstone 5 whose center is set at the center position of the above-described circle, G0 is the outer peripheral radius, DI is the inner peripheral radius of the disc 4, and D0 is the outer peripheral radius). Therefore, the formation of polishing pattern on the outer or inner peripheral part of the disc and formation of sagging on the edge surface of the disc can be prevented, and the smooth rotation of the disc is permitted, and the disc having a flat plane form with high accuracy can be obtained.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for grinding a disk processed into a donut-shaped disk, such as an aluminum alloy magnetic disk substrate, and more specifically, the present invention relates to a method for grinding a disk processed into a donut-shaped disk, such as an aluminum alloy magnetic disk substrate. Disc grinding uses a narrow-width grindstone double-sided surface grinder that performs rotational motion, and the disc placed between them rotates on its own axis by receiving rotational force from a surface plate, to obtain a finished surface with excellent surface shape accuracy. Regarding the method. (Prior Art) In recent years, magnetic disks used in external storage devices for computers have become thinner and the flying height of the head has been reduced in order to achieve higher recording densities. Requirements for surface smoothness and shape accuracy of disk substrates are becoming increasingly sophisticated. Conventionally, in order to manufacture such a disk base with excellent surface properties, a mirror cutting method using an ultra-precision lathe and a precision grinding method using a grindstone have been generally carried out industrially. The latter method of grinding using a grinding wheel involves the upper surface plate, lower surface plate, sun gear, and internal gear each performing its own rotational movement, and by rotating the upper and lower surface plates in opposite directions. The carrier (the jig that holds the workpiece) placed between the surface plate and the lower surface plate rotates while moving (revolving) in the same direction as the lower surface plate due to the rotation of the sun gear and internal gear, and A double-sided surface grinder that simultaneously grinds both sides of a held disk (workpiece) is commonly used. However, this machine has a large grinding wheel area,
In addition, in order to manufacture a disk base with excellent shape accuracy, it is necessary to maintain the surface shape of the grindstones attached to the upper and lower surface plates with high precision. To do this, the grindstone must be dressed, but dressing requires skill. Furthermore, with this method, it is difficult to automate the loading of the disk and the removal of the disk after grinding is completed. (Problems to be Solved by the Invention) On the other hand, there is a grinding method that is the same as the above-mentioned grinding method in that it uses a grindstone, but uses a narrow grindstone. In this grinding method, as shown in Fig. 1, a donut-shaped disk (workpiece )
This is a method in which the grinding wheel is supported by the disk support ring 1 and the rolls 2.3, but compared to the above polishing method, the grinding wheel area is smaller and has self-dressing properties, so it is difficult to ensure the planar shape of the grinding wheel. Although dressing does not require skilled skills and is relatively easy to automate, it has traditionally had a large disc thickness deviation and a polished pattern on the surface compared to the above-mentioned grinding methods. This is because there are problems such as the occurrence of The quality was insufficient to meet the required quality of magnetic disk substrates for computers, and it had not been put into practical use. The present invention has been made in order to solve the problems of the above-mentioned prior art method of simultaneously grinding both surfaces of a plurality of disks using a narrow grindstone, It is an object of the present invention to provide a disk grinding method capable of obtaining a disk having a highly accurate surface shape with a small polishing pattern and no polishing pattern on the surface. (Means for Solving the Problems) In order to achieve the above object, the present inventor has conducted intensive research to clarify the cause of the above problems in the conventional narrow-width grindstone double-sided surface grinding method, and to find countermeasures. As a result, we found that this is possible by setting the positional relationship between the ring-shaped narrow-width grindstone and the disk and the width of the grindstone in a constant relationship. That is, as shown in FIGS. 1 and 2, the radius of the circumference formed by the centers of the plurality of disks (workpieces) 4 to be simultaneously ground is set as RD, and the center is set at the center position of this circumference. Assuming that the inner radius of the ring-shaped grindstone 5 is GI, the outer radius is Go, and the inner radius of the disc 4 is DI, and the outer radius is Do, first, if G machining≦RD-DI, that is, the inner circumference of the grindstone CG ) is the disc outer diameter (Do) and the disc inner diameter (
DI) (see Figure 3 (a)), problems such as: ■ polishing patterns occurring on the outer or inner circumference of the disk, and ■ sagging occurring on the edge surface of the disk occur. Therefore, it is not suitable for processing a disk having a finished surface with excellent surface quality as desired. Therefore, it is necessary to satisfy GI>RD-DI (see FIG. 3(b)). Note that the inner circumference (GI) of the grinding wheel may be made larger than the center position (Ro) of the disk, but since this increases the size of the grinding machine and increases the equipment cost, it is not economical, so GI < RD (Fig. 3). (see (b)). In addition, the disc is sandwiched between the upper and lower surface plates and rotates on its own axis under pressure while receiving the rotational force of the surface plate, and both sides are ground simultaneously. To complete the process, the disk must rotate smoothly. For that, place the disc in the center! Increase the distance between (RD) and the center position of the grinding wheel width ((G + Go) / 2),
It is better to increase the rotational force received from the surface plate. Therefore, RD>(Gz+Go)/2 (see FIG. 4). At that time, if the grindstone outer diameter position (GO) is set to (RD+DI/2) or more, that is, if the grindstone outer diameter position is set to 0172 or more from the disk center position and the disk is placed too far inside (see Fig. 5 (a) )), it becomes difficult to perform smooth rotation, so set Go<RD+D/2 (see 5th
(See figure (b)). Furthermore, the disk area (RD-DI) is located inside the disk center position [e(RD) by the disk inner radius (DI)].
First, the outer diameter of the grinding wheel (it needs to be inside than (GO), so Go > RD - Dl, see Figure 4), and the center position of the grinding wheel width (G + Go)
It needs to be inside than /2, so (G + GO)
/2>RD-Dx (see Fig. 4). The dimensions of the donut-shaped disk that is the workpiece are determined by the use of the disk, etc., but the width (
The inner radius of the grindstone is designed so that DoDz) is smaller than the inner radius G of the ring-shaped grindstone. In view of the above points, the gist of the present invention is to set the positional relationship between the ring-shaped grindstone and the disk and the width of the grindstone to conditions that satisfy the following relational expressions (1), (2), and (2). RD-DI<G engineering<Ro・・・・・・・・・・・・・・・
・・・・■Do-DI<G Engineering・・・・・・・・・・・・
......0 Next, examples of the present invention will be shown. (Example) Using a narrow-width grindstone double-sided surface grinder having upper and lower surface plates with an inner diameter of 650 mφ and an outer diameter of 790 mmφ, the outer diameter (Do) made of JIS 5086 aluminum alloy was 130++ fatφ. Fifteen disk substrates each having an inner diameter (DI) of 40 mmφ and a thickness of 2 mm were simultaneously polished. Grinding wheel: PVA grinding wheel $1500 Grinding fluid: Water-soluble lubricant Surface plate rotation speed: 30 rpm, pressure 1 kg/cwt" Polishing time: 5 minutes Also, the size of the circumference formed by the center of the disk is 780 a
m (RD=390a+m). During grinding, the position and width of the grinding wheel were varied as shown in Table 1. After cutting, the surface properties and thickness deviation of the obtained discs were investigated. The results are shown in Table 1. As is clear from the table, RD-p engineering<a engineering and RD-
Comparative Example 1, which does not satisfy DI<(G+Go)/2<Ro, has large grinding unevenness and end face sagging, and also has a large plate thickness deviation. Furthermore, in Comparative Example 2, which does not satisfy R, -DI, G machining, the grinding unevenness, end face sag, and plate thickness deviation are slightly smaller than those in Comparative Example 1, but these are of a size that poses a practical problem. Furthermore, Comparative Example 3 which does not satisfy Go<R work+DI/2
Similar to Comparative Example 2, there are uneven grinding and sag on the end surface. The plate thickness deviation is large. On the other hand, the examples of the present invention satisfy all of the conditions, so they can obtain discs with excellent accuracy with small grinding irregularities and end face sag, and extremely small plate thickness deviations, as well as high grinding speeds. High efficiency.

[Left below]

Furthermore, from the results in Table 1, it is presumed that similar results can be obtained in cross polishing in which a cloth and free abrasive grains are used instead of a grindstone. (Effects of the Invention) As described in detail above, according to the disk grinding method of the present invention, a double-sided surface grinder using a ring-shaped narrow-width grindstone is used to produce a highly efficient, low-cost, and highly accurate surface. You can get a disc with the shape. It is particularly suitable for polishing various types of disks that require highly accurate planar shapes, such as computer disk substrates.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a narrow-width grindstone double-sided surface grinding method according to the present invention, and FIG. 2 is an explanatory diagram generally showing the positional relationship between the grindstone and the disk and the grindstone width in the above method. Figures 3(a) and 5(a) show cases in which the conditions of the present invention are not met, and Figures 3(b), 4, and 5(b) show cases in which the conditions of the present invention are met. Indicates when DESCRIPTION OF SYMBOLS 1... Disc support ring, 2.3... Disc support roll, 4... Disc (workpiece), 5... Ring-shaped grindstone.

Claims (1)

[Claims] (1) By rotating the ring-shaped upper and lower surface plates, a plurality of disks (workpieces) placed between the two surface plates receive rotational force from the surface plates and rotate on their own axis. A narrow-width grindstone double-sided surface grinder is characterized by obtaining a disk with an excellently accurate surface shape by setting the positional relationship between the ring-shaped grindstone and the disk and the grindstone width so as to satisfy the following conditions. Disc grinding method. R_D-D_I<G_I<R_D R_D-D_I<G_O<R_D+(D_I)/2RD
-D_I<(G_I+G_O)/2<R_DD_O-D
_I<G_I where, R_D: radius of the circumference formed by the centers of the plurality of disks G_I: inner radius of the ring-shaped grindstone having the same center as the center of the above circumference G_O: same center as the center of the above circumference Outer radius of ring-shaped grindstone D_I: Inner radius of disk D_O: Outer radius of disk