JPH0349867A - Surface polishing method - Google Patents

Abstract

PURPOSE:To form a flat surface of less irregularity in the intermediate part or the full part in the radial direction of a grinding wheel by using a dresser, in which pellets in a point end protruding condition are circumferentially arranged in the peripheral end part or in the vicinity thereof in a dresser main unit while with no pellet existing in the inner position from these pellets, to perform dressing of the grinding wheel. CONSTITUTION:Pellets 32 are circumferentially arranged in the peripheral end part or in its vicinity of a disk-shaped main unit 31 of a dresser 30 with no pellet existing in the inner position from these pellets 32. The dresser 30, thus formed, is used, and by rotating the dresser 30, while it is revolved on its own axis, around the center of rotation in a condition that the pellets 32 are brought into press contact with surfaces of grinding wheels 3, 4, their dressing is performed. By this dressing, a flat surface of less irregularity in the intermediate or total part in the radial direction of the grinding wheels 3, 4 is utilized, and a workpiece is polished.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a double-sided or single-sided precision flat surface polishing method used to obtain a high-precision finished surface as required for magnetic disk substrates and the like.

2. Description of the Related Art As one type of surface polishing machine for polishing objects to be polished, such as aluminum substrates for magnetic disks, the one shown in FIGS. 3 and 4 is known. That is, (A) in the figure is a flat surface polishing machine, and this polishing machine has a pair of upper and lower opposed surface plates (1
) (2), donut-shaped upper and lower grindstones (3) (4) attached to the inner surface of each surface plate, and a sun gear arranged at the axis of the grindstone between each grindstone (3) (4). (5), an internal gear (6) disposed concentrically outward of the sun gear (5), and an outer peripheral surface meshed with both the sun gear (5) and the internal gear (6). The polishing object holder (7) is provided with one or more thin plate spur gear-shaped object holders (7) arranged in the same manner. Also,
Each retainer (7) is formed with a plurality of holes, into which a disc-shaped object to be polished (B) having a thicker wall than the retainer is fitted and held. Furthermore, the upper and lower surface plates (1) and (2) are connected to the first motor (
11), and is rotated by the drive of the motor (11). The upper surface plate (1) is supported by a cylinder (not shown) so that it can be raised and lowered, and the fifth
In the lowered position shown in the figure, it engages with an engaging portion (la') at the upper end of the drive shaft (la) to apply a rotational force in the opposite direction to that of the lower surface plate (2). On the other hand, the sun gear (5) is connected to the second motor (12) via the drive shaft (5a) and sprocket (5b), and the internal gear (6) is connected to the second motor (12) via the drive shaft (Ga) and sprocket (6b). These motors (12) and (13) are each connected to a third motor (13), and are rotated at different rotational speeds by driving these motors (12) and (13), thereby allowing the retainer (7) to revolve while rotating like a planetary gear. It is said that Chino. In addition, the upper and lower surface plates (1) (2), the sun gear (5), and the internal gear (
The number of revolutions in step 6) is set in advance at a desired ratio so that both sides of the object to be polished (B) can be processed equally.

In the illustrated surface polishing machine, the workpiece to be polished (B) is first set in the workpiece holder (7), and then the upper and lower surface plates (1) (2)
) are brought close together and the grindstones (3) and (4) are brought into pressure contact with the object to be polished (B) with a predetermined pressure. Next, each of the first to third motors (
11) Drive (12) and (13) to move the upper and lower surface plates (1
)(2), rotate the sun gear (5) and internal gear (6).

Due to the rotation of the sun gear (5) and internal gear (6), the workpiece holder (7) rotates and revolves around the rotation centers of the upper and lower grindstones (3) and (4), and the rotating grindstone (3) The polishing process of the object to be polished (B) is accomplished by the action of (4).

By the way, if you use the above polishing machine (A) for a long time, the grinding wheel (3
) (4) may become clogged or crushed, and as a result, it becomes impossible to obtain good straightness and flatness of the object to be polished, so it is necessary to regularly sharpen the grindstones (3) and (4) using a dresser. be. This dresser (20), as shown in FIG.
A plurality of cylindrical pellets (22) of the same size are provided for dressing, which are embedded in the upper and lower end surfaces of the main body with their tips protruding. Note that (21a) shown in Fig. 11 is the dresser body (21a).
1) is a toothed portion provided on the outer peripheral surface. Then, after setting the dresser (20) in place of the object holder (7) and pressing the grindstones (3) and (4) against the pellet, the sun gear (5) and the internal gear (6) are operated. Dresser (20)
By rotating the grindstones (3) and (4) while rotating and revolving around them, the tips of the pellets (22) scrape off the surface of the grindstones, thereby sharpening the grindstones (3) and (4). .

Problem to be Solved by the Invention However, the grindstone (
3) In the case of sharpening in (4), the surface of the whetstone was not flat, resulting in large irregularities in the entire radial direction. When polishing is performed using such a grindstone, the pressure distribution of the grindstone on the object to be polished becomes uneven, which causes unevenness in the amount of polishing and, in turn, non-uniformity in the surface properties of the object to be polished. For this reason, conventionally, the irregularities on the grindstone surface have been manually corrected after sharpening, which is a complicated process.

The present invention has been made in view of this technical background, and is a polishing method capable of obtaining a polished product with excellent straightness and flatness without having to manually correct irregularities on the surface of the grindstone after sharpening. The purpose is to provide a processing method.

Means for Solving the Problems In order to achieve the above object, the inventor investigated and researched the reasons why the surface of the grinding wheel did not become a uniform flat surface after dressing, and found that in the past, pellets were arranged over the entire surface of the dresser. Therefore, it was found that the rate at which pellets pass through the whetstone surface during sharpening differs at each part of the whetstone surface, and the areas where the pellets pass through the wheel with a high rate are concave, and the areas with a low rate of passage are convex. This invention has been made based on this knowledge, and will be explained using the reference numerals in FIGS. The pellets (32) are arranged in a circumferential manner at or near the peripheral edge of the pellets (32), and no pellets exist inwardly from these pellets (32). And the dresser (3
0), the dresser (30) is rotated and revolved around the center of rotation of the rotating whetstones (3) (4) with the pellets (32) in pressure contact with the whetstone surface. Perform 4) sharpening. By this sharpening, the radial intermediate portions or all of the grindstones (3) and (4) become flat surfaces (3a) and (4a) with less unevenness. Next, the object to be polished (B) is polished using this flat surface.

Operation When dressing is performed using the above-mentioned dresser (30), each pellet (32) passes evenly through the middle or all of the grindstones (3) and (4) in the radial direction, and in that part the surface of the grindstone becomes flat. (32) and flat surface (3a)
(4a). The object to be polished (B) using this flat surface.
Since the polished object (B) is polished, excellent straightness and flatness are imparted to the polished object (B).

Embodiment First, a dresser used in the present invention will be explained. In FIG. 1, (30) is a dresser, and the dresser (30) consists of a dresser body (31) and a plurality of dressing pellets (32).

The dresser main body (31) has a disc shape with a predetermined thickness, and the sun gear (5) of the polishing machine (A) shown in FIG. 3 is mounted on its outer peripheral surface.
and a tooth portion (31) that meshes with both the internal gear (6) and the internal gear (6).
a) is formed. This dresser main body (31) is made of SUS, and its weight is reduced by providing a hollowed-out portion (33) in the center in the thickness direction.

On the other hand, the pellets (32) are attached to the dresser body (31).
The pellets are densely arranged in a single layer circumferentially along the peripheral edge of the pellet body (31), and no pellets are provided in other parts of the pellet body (31) except for the peripheral edge. By arranging the pellets in this manner, each pellet (32) uniformly passes over the entire surface of the grindstones (3) and (4), including the middle part excluding the inner and outer circumferential edges, or the inner and outer circumferential edges, during sharpening. Each pellet (32) is made of the same large cylindrical diamond sintered body, and as shown in FIG.
The dresser body (31) is fitted into a fitting recess (31b) provided on the end face of the dresser body (31) with its tip protruding, and is joined to the dresser body (31) by silver soldering. The number (34) shown in the figure is the wax part. In addition, the protruding end surface of the pellet (32) has fine irregularities (3) for sharpening the grindstones (3) and (4).
2a) is formed.

Next, to explain the polishing method of the present invention, first, using the dresser (30) shown in FIGS. 1 and 2, the grinding wheel (3) (
Carry out the sharpening in step 4 as follows. That is, as shown in FIG. 5, the dresser (30) is
) are the sun gear (5) and internal gear (6) of the polishing machine (A).
The grindstone (3) is placed so that it meshes with both of the
(4) is brought into pressure contact with the pellet (32) of the dresser (30). In this state, the sun gear (5) and internal gear (6)
By rotating the dresser (30), the dresser (30) is rotated and revolved, and at the same time, the surface plates (1) and (2), that is, the grindstone (3) (
4) Rotate. Then, based on the relative motion between the grinding wheels (3), (4) and the dresser (30), the pellets (32) passing through the surfaces of the grinding wheels (3), (4) one after another scrape off the surfaces of the grinding wheels, thereby performing dressing. . In this invention, since the pellets (32) are arranged circumferentially at the peripheral end of the dresser body (31) as described above, each pellet (32)
) passes through the middle part of the grindstone at a uniform rate, excluding the inner and outer circumferential ends of the grindstone (3) and (4), which have a small inner diameter and a large outer diameter. Therefore, as shown in Fig. 6, the grinding wheels (3) and (4) are
While this part is averagely shaved to become a flat surface (3a) (4a), the ratio of pellets (32) passing through the inner and outer circumferential ends (3b) (4b) is higher than that in the middle part, so-called Sagging occurs and a flat surface cannot be obtained. This means that
Conversely, as shown in FIG.
) (4b') beforehand.
) (4') This means that when a grindstone with a large inner diameter and a small outer diameter is used, the entire surface becomes a flat surface. Of course, any grindstone may be used.

By the way, the rate at which the pellet (32) passes through any arbitrary surface of the grinding wheels (3) and (4) can be calculated by calculating the distance M (hereinafter simply referred to as "passing distance") that the pellet passes from each point on the grinding wheel surface. You can ask for it. That is, as shown in FIG. 8, if it is assumed that one circular pellet of radius Rp exists at a distance of radius R from the center of the dresser (OT), a point Z at a radius of r from the center of the grinding wheel (Ow) (r
, θ), the circumferential direction average value f (r
) is given by the following formula.

[Left below] 1) When C-R+Rp Cr<C+R-Rp, f Cr)
= (t/π)! ':, q v (r, θ)・β(
r, Re ) dθ However, v (r, θ) − (π/30) v'Ct + r v
-T12CrNr (Nv-Nt)cosθ β(r, Re)= (1/π)cos-11CRa
” 10R'-Rp2)/2Ra・R) u) C-R-Rp≦r≦C-R+Rp or C+R-R
When p≦r≦C+R+Rp, f (“) = (t/π) f: 2v (r, θ)・
β(r, Re) dθ1u) r<C-R-Rp or C+R+Rp<rf) and *f (r) = 0 However, in the above equation, N (rps): rotation speed of the dresser Nv (rpm): of the grinding wheel Rotational speed R (m)
: Distance Rp (m) from dresser center (OT) to pellet center (Op) : Pellet radius C (a+) : Distance t (sec) from grinding wheel center (Ov) to dresser center (0 teeth): Dressing time v (r,
θ): Relative speed between the grinding wheel and the dresser (pellets) β(r, Re): Ratio of pellets on the circumference of the dresser with radius R6 ) shows the passing distance when one circular pellet (32) of radius Rp exists at a distance of radius R from ), but when there are χ pellets at a distance of R from the center of the dresser (OT), is the passing distance F at each point of the grinding wheels (3) and (4)
(r) may be obtained by multiplying the passing pressure 1f(r) for one pellet by seven times. If the passing distance F(r) of each point of the grindstone is equal, the amount of grinding by the pellet (32) will be equal, and the surface of the grindstone will be flat.

Incidentally, the dresser (30
), a grindstone with a small inner diameter and a large outer diameter (4)
If the calculation results of the passing distance of each point in the radial direction are illustrated, the shape is roughly shown in Figure 1O.
It can be seen that the inner and outer circumferential edges are largely shaved, and the radial middle portion is uniformly shaved. Also, actually, the diameter is 42
When a grinding wheel was sharpened by arranging 144 pellets densely in a circumferential manner around the peripheral end of an 8M dresser, the radial middle part of the grinding wheel became a flat surface with a waviness of 10 μm or less. On the other hand, when dressing was performed using the same pellets placed over the entire surface of the dresser, undulations of 30 to 40 μm were observed in the radial intermediate portion.

Next, the object to be polished (B) is polished using the sharpened whetstones (3) and (4).
3) Perform using only the flat surfaces (3a) and (4a) of (4). As a means for this purpose, for example, as shown in FIGS. 4 and 9, a fitting hole (7a) for holding the workpiece to be polished is provided in the workpiece holder (7) at a position near the center of the inside, Always place the object to be polished (B) on the flat surface (3a) of the grindstones (3) and (4).
A method of rotating within the range of (4a) can be mentioned. As a result, the entire object to be polished (B) is polished evenly and uniformly with uniform pressure applied from the grindstones (3) and (4).

In the above embodiment, both grindstones (3) and (4) are sharpened at the same time, and both surfaces of the object (B) to be polished are polished at the same time. The same applies to cases where the same applies. Also,
To increase dressing efficiency, install two or more dressers (30
) may be used at the same time for sharpening.

Effects of the Invention In accordance with the above, firstly, pellets with protruding tips are arranged in a circumferential manner at or near the peripheral end of the dresser body, and pellets are present at positions inward from the pellets. Since the dressing of the grindstone is carried out by using a dresser that does not rotate and revolve around the rotating grindstone, it is possible to form a flat surface with few irregularities in the middle part or the entire part of the grindstone in the radial direction. Therefore, it is possible to eliminate the need for manual correction of irregularities, which was conventionally applied to the grindstone after sharpening in order to obtain a flat surface, so that the efficiency of the entire polishing process can be improved. Next, since the object to be polished is polished using the flat surface of the grindstone obtained as described above, the pressure distribution of the grindstone to the object to be polished can be made uniform, and as a result, a polished product with excellent surface texture and quality can be provided. .

[Brief explanation of drawings]

FIG. 1 is a plan view of a dresser used in the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. Figure 4 is the third
Fig. 5 is a perspective view of the main part showing the usage state of the surface polishing machine shown in Fig. 3, Fig. 5 is a perspective view of the main part to explain the sharpening method of the grinding wheel in the grinding machine shown in Fig. 3, and Fig. 6 is a part of the grinding wheel after sharpening. 7 is a cross-sectional view showing a modified example of the grinding wheel, FIG. 8 is a schematic plan view showing the relationship between the dresser and the grinding wheel when calculating the pellet passing distance on the grinding wheel surface, and FIG. 9 is a cross-sectional view showing a modified example of the grinding wheel. FIG. 10 is a plan view showing the positional relationship between the grinding wheel and the object to be polished held in the grinding object holder; FIG. 1st
FIG. 1 is a perspective view of essential parts showing a conventional method in which dressing is performed using a dresser. (30)...dresser, (31)...dresser body, (32)...pellet, (3)(4)...grindstone,
(3a) (4a)...Flat surface. That's all~ (with: 1it); Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Distance between the stones and the inside Figure 10 Figure 11

Claims (1)

[Claims] A dresser is used in which pellets with protruding tips are arranged in a circumferential manner at or near the peripheral end of a disc-shaped dresser body, and there are no pellets inward of the pellets, and a rotating grindstone is used. The grindstone is sharpened by rotating and revolving the dresser while rotating the dresser with the pellets pressed against the surface of the grindstone with respect to the center, and then the object to be polished is polished using the flat surface of the grindstone. A flat surface polishing method.