JPH01140959A - Tin stool in contactless polishing device - Google Patents

Abstract

PURPOSE:To make it possible to hold polishing liquid in several small spiral grooves during rotation of a tin stool by forming these small spiral grooves in the upper surfaces of spiral raised ridges, and by inclining the small grooves toward the center axis of the stool so as to be asymmetric. CONSTITUTION:Spiral raised ridges 10 are formed on the upper surface of a tin stool in a contactless polishing device. Several small spiral grooves 12 are formed in the upper surfaces of the raised ridges 10, and a large groove 11 is formed between each adjacent ridges 10. The cross-sectional shape of the small grooves 12 has a saw tooth-like shape inclined toward the center axis of the stool, having its apex angle of valley angle (r) is set to 30 to 60deg. while the inclination angle theta of the surfaces of the grooves facing the center axis is set to 80 to 120deg. with respect to a horizontal plane. With thus formed small grooves 12, a larger amount of polishing liquid may be reserved in these small grooves 12 so as to exert a higher rotational speed to the polishing liquid, thereby it is possible to increase the dynamic pressure of the polishing liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION (7) Technical Field The present invention relates to an improvement in the groove shape of a tin surface plate of a non-contact polishing device.

The non-contact polishing method uses a polishing liquid containing free abrasive grains, and polishes the workpiece only by bringing the workpiece into contact with the polishing liquid. There is no contact between the surface plate, etc. and the workpiece.

In order to avoid contact, the polishing liquid must have strong dynamic pressure.

There are several types of non-contact polishing methods depending on the means for generating dynamic pressure.

Among these, the object of the present invention is float polishing.

Polishing liquid is continuously supplied onto a high-speed rotating tin surface plate. The workpiece is attached to the bottom of a rotatable work holder and set on a tin surface plate.

Rotate the work holder and rotate the tin surface plate. It is the same as a typical conventional contact polishing method, except that the workpiece is polished by double rotation.

The difference is that the work holder is supported so that it can be moved up and down, and a spiral groove is cut into the tin surface plate.

Due to the spiral groove, the polishing liquid obtains a large rotational speed.

Dynamic pressure increases, which is proportional to the square of the speed. Since the polishing liquid with a large dynamic pressure passes under the work holder, the work holder is lifted. Therefore, the workpiece is not in contact with the surface plate.

The workpiece is gradually polished by the action of free abrasive grains contained in the polishing liquid. It is called float polishing because the workpiece is floated by the polishing liquid.

Although the polishing speed is slow, it is possible to finish highly flat surfaces with high accuracy.

There is a lot of literature on float polishing. For example, Y, Namba and H, Tsuwa, “Ud
tra-Fine Polishing of Sapp
hire Single Crystal,” Anna
lsofCIRP, 26 1°Y, Namba an
d H, Tsuwa, “Mechanism a.
nd Some Applications of Ul
tra-Fine Finishing,” Anna
ls of CIRP, 27 1° (a) Conventional technology A tin surface plate is used as a polishing surface plate.

A spiral groove is carved into the top surface of the tin surface plate.

FIG. 4 shows the groove structure of a conventional tin surface plate.

A large groove 11 is spirally carved on the tin surface plate 1.

Further above the major groove 11, several minor grooves 12 are carved.

As shown in FIG. 5, the large groove 11 is actually a single spiral groove that extends from the center in a spiral pattern to the outer periphery.

Although the small groove 12 is also spiral, it is a plurality of grooves.

In this example, the width M of the raised strip 10 is 2 mm, and the width of the large groove is 2 mm.
m shoulder, the height K of the raised stripes 10 is 1 to 2 mm.

The small groove 12 carved on the upper surface of the raised strip 10 has a height H of 0.
It is 1-02MM. What is important is that the groove is triangular and has a symmetrical cross section.

The widening angle θ of the groove valley is 60 to 90°. The bisector of the divergent angle is a vertical line. θ can be called an apex angle or a trough angle.

In order to apply dynamic pressure to the polishing liquid, a large groove 11 is installed on the tin surface plate.
, small grooves 12 are carved. If there is no groove,
The centrifugal force generated by the rotation of the surface plate dominates, and the polishing liquid immediately flows in the radial direction. For this reason, the speed of the polishing liquid does not increase and sufficient dynamic pressure cannot be obtained.

The presence of the spiral groove suppresses the radial flow of the polishing liquid due to centrifugal force. Since viscous force in the rotational direction is applied to the polishing liquid, the polishing liquid has a velocity component in the rotational direction.

However, no matter how many grooves there are, the liquid will flow toward the outer circumference beyond the grooves. Polishing liquid is constantly replenished to the center of the surface plate, so there is no chance of the liquid running out.

The polishing liquid supplied to the center enters the large groove 11 and the small groove 12. Although the surface plate is rotating, the angular velocity N of these polishing liquids does not immediately become equal to the angular velocity Ω of the surface plate because the viscosity is small.

Due to the action of viscosity, the polishing liquid in the small grooves gradually gains an angular velocity N. Since viscosity only works in extremely thin layers, major groove 1
Acquisition of angular velocity at 1 is slow. In the small groove, the polishing liquid gradually gains angular velocity.

Since the square of the angular velocity gives centrifugal force, the centrifugal force eventually becomes dominant, and it passes over the peak of the small groove 12 and enters the small groove at the outer corner. This small groove further accelerates the rotational direction due to viscosity. The centrifugal force increases, it goes over the mountain of the small groove and enters the small groove in the outer corner.

In the same way, cross the small groove outward.

The large groove 11 is provided so that a sufficient amount of polishing liquid can be retained on the surface plate. If the amount of liquid is insufficient, the dynamic pressure will be insufficient, so the workpiece will not float.

The dynamic pressure is the sum of the square of the velocity in the radial direction and the square of the velocity in the rotational direction.

In order to obtain large dynamic pressures, these velocities must be increased. However, the radial speed is determined by the amount of polishing liquid supplied. It does not depend on the rotation speed of the tin surface plate or the shape of the groove.

Therefore, in order to increase the dynamic pressure, it is necessary to
It is important to apply sufficient force in the rotational direction.

For this purpose, it is necessary that the polishing liquid stays between the small grooves for a long time.

(1) Problems to be Solved by the Invention Although viscous force is a small force, the impulse given by the product of the force and the time during which it is applied is the rotational speed of the polishing liquid. For this reason, it is desirable to have a long residence time in the small groove.

To achieve this, the grooves may be made deeper and the difference between the peaks and valleys may be increased. However, this reduces the contact area between the liquid and the surface plate, making it difficult for viscous forces to act.

Conversely, if you want to increase the viscosity, you can make the grooves shallower, but this will reduce the amount of liquid.

If you want to increase the amount of time the liquid stays in the small grooves without reducing the amount of liquid, it may be possible to make the small grooves 12 sharper. In other words, the apex and trough angles are made smaller. However, it is difficult to narrow the apex angle of the groove in terms of processing. Also, since the surface tension becomes more effective, the amount of polishing liquid stored will decrease.

It may seem like increasing the rotation speed of the surface plate Ω, but that is not the case. The centrifugal force increases quickly, and the polishing liquid is quickly blown away to the outer periphery.

A symmetrical small groove shape as shown in FIG. 4 has the advantage of being easy to process. However, if the polishing liquid is left to stay for a long time,
It is not the best shape in terms of transmitting rotational force through viscosity.

2) Structure The tin fixing pin of the present invention is asymmetrical with the small groove tilted in the direction of the axial center.

FIG. 1 shows the cross-sectional shape of the small groove of the tin surface plate of the present invention. Second
The figure is an enlarged view.

Let T be the apex angle (or trough angle). Make the minor grooves asymmetrical instead of symmetrical. If it is made asymmetrical, the shape cannot be specified just by the size of the apex angle. Therefore, the angle between the surface facing the axis center and the horizontal is θ. If they are complementary, let Φ be the angle between the surfaces that do not face the axis and the horizontal.

In FIG. 2, the cross-sectional shape of the small groove is indicated by ABC.

AC is parallel to the surface of the surface plate and lies in the same horizontal plane. A
B is the surface facing the axial center. The apex angle EAB is T1 and the trough angle ABC is also T. You can call it either way, but here it is called the apex angle.

The inclination angle/ABE of the opposing surface AB is θ. Non-facing surface BC
The inclination angle/CBF is Φ. Of course, θ+T+Φ
=180° (1). Since the conventional one is symmetrical, e=o=9oO-T/2
There was a relationship (2).

In the present invention, θ≠Φ. Moreover, 30°≦T≦60° (3) 80°≦
θ≦120' (4) Φ(e
(5). In other words, it is asymmetrical and has a shape tilted toward the axial center.

The most desirable one is one in which the axis-center facing surface AB is perpendicular to the horizontal line, θ=90° (6) T=45° (7).

Thus, in the present invention, the cross section of the small groove has a sawtooth shape.

The present invention is not exactly represented by (3) to (5), but (5) is actually redundant. If (3) and (4) hold true, then (5) definitely holds true.

The sum of θ and T1 is 180°. From this, (3
), (4) can be used to prove (5).

Considering the inequality (3) + 2 X (4), 1
90°≦T+28 (8). From now on 10°+180°−T−〇≦θ (9)10
'+Φ≦θ α1 and Φ×θ (11) In other words, (5) is proven. However, inequality (5) is
This clearly shows the content of the present invention.

In Figs. 1 and 4, only three small grooves are drawn on one raised strip, but this is for the sake of simplicity. In reality, there are many small grooves of about 10 to 20 grooves.

In this way, if you create a shape that is slightly tilted toward the center of the axis,
More polishing liquid can be stored in the small groove 12 during the rotation operation.

(4) Function During rotation operation, more polishing liquid can be stored in the small groove.

Assuming that the supply amount of polishing liquid is constant, as the amount stored in the small groove increases, the time that the polishing liquid is in contact with the small groove of the surface plate increases. In proportion to the time it is in contact with the small groove,
Due to the viscous force, the polishing liquid gains speed in the rotational direction.

Therefore, the tin surface plate of the present invention can give a much higher rotational speed to the polishing liquid. Therefore, the dynamic pressure of the polishing liquid increases.

The reason why the small groove shape of the present invention can hold more polishing liquid during rotation operation will be explained with reference to FIG.

When at rest, the entire small groove can hold liquid. The retention cross section Σ is ABC.

If the height h of the grooves is the same, the total holding cross-sectional area does not change, and the amount of liquid stored does not change either. No matter what T2O and Φ are, the cross-sectional areas of groove ABC and small protuberance AEB are the same. Therefore, if the area of the portion of the upper surface of the surface plate in which the small grooves are carved is S, the amount of liquid stored is always Sh/2.

As the apex angle T becomes smaller, the cross-sectional area ABC becomes smaller, but
Conversely, the number of small grooves increases inversely.

Therefore, the amount of liquid stored is Sh/2 when the vehicle is stationary, regardless of T2O and Φ.

However, when the surface plate rotates, the water surface tilts due to centrifugal force. Let the inclination angle from the horizontal be a.

The part where liquid can be stored becomes ABD.

In actual float polishing, there is polishing liquid on the ADC area, and a thin film of polishing liquid is also formed on the horizontal surface AC.

However, the polishing liquid in the ADC part and the part above AC is not captured in the small grooves. This is the part that flows outward beyond vertex A.

The cross-sectional area Σ of the portion caught in the small groove is ΔABD. If AC-a, ΔABC=ha/2.

Consider ΔABD by normalizing it with the cross-sectional area of ΔABC. Let Σ be the normalized cross-sectional area of ΔABD.

= 1−− H BC Applying the law of sine to ΔABC, BCAC − knee (+4) nθ s
in T Applying the sine theorem to ΔACD, CD AC −= −(l average sin aI sin (Φ ten α) is obtained from this.

The inclination angle α is given by the ratio of the gravitational acceleration to the radial acceleration v2/r.

-α=□ (1 kg) ■ is the velocity of the liquid in the rotational direction, and r is the radius of curvature of the small groove.

From (16), find what can make Σ large for the same α.

There is sin T in the molecule. Therefore, the smaller T is, the larger Σ can be.

Conventionally, T was 60° to 90°. In the present invention, as already stated, the apex angle T is 30° to 60'.

It is preferable if the angle is less than 30°, but as already explained, this is limited by the difficulty of processing and the surface tension of the polishing liquid.

As long as T is small, the minor grooves may be symmetrical in the medial and medial directions. However, the denominator is sin (Φ+α)si
Since there is nO, it is desirable that the structure be asymmetrical.

The reason for the sawtooth shape is in the sin(Φ+α)sinO part.

Since Φ1θ+γ2180°, if γ is constant,
The sum of Φ and θ is constant.

When α takes a positive value, the denominator sin (Φ+α) sin
What should be done to maximize the value of θ? That's what it means.

sin (Φ+α) sinθ knee (cos (Φ+α
−θ) −cos (Φ1θ+α)). Φ+e is a constant. (The second term of the country does not depend on the selection of Φ and θ.

Then, the question becomes (what should be done to increase the first term of the country? cos is the largest when the variables in it become 0. α is a positive variable, and Φ and θ are parameters. Therefore, the whole of (18) can be increased by setting Φ< 8 (19). Inequality (I9) is the same as (5) and (11).

The value of T is 30 to 60 degrees (conventionally 60 degrees to 900).

From (19), when T = 30°, θ is 75° ~ 150°
It can take the value of °. When T=60', θ is 60°~1
1) Obtain the value of 20°.

Therefore, when T is between 30° and 600, θ is 75
It can take any value between 120° and 120°.

If T=30'h when θ-75°, Φ=75°, and there is room for symmetry.

Therefore, the range of θ is set to 80° to 120°.

Now, assuming that it is asymmetric, the apex angle T is 30°
Another reason for the above restrictions becomes clear. In addition to the processing difficulties and surface tension problems mentioned earlier, small grooves are prone to collapse. FIG. 6 shows such an example.

If it is asymmetrical and the apex angle T is small, the small grooves will overlap in one direction and will be easily destroyed by a force from above.

(B) Effect: The small grooves on the tin surface plate can hold more polishing liquid during rotation.

In other words, the polishing liquid requires more time to pass through the small grooves. Therefore, it becomes easier to obtain speed in the rotational direction due to the action of viscosity. This increases the speed of the polishing liquid.

The dynamic pressure, which is proportional to the square of the speed, also increases.

As the speed of the polishing liquid increases and the dynamic pressure also increases, the floating blade of the workpiece becomes larger and more stable.

Furthermore, since the flow of the polishing liquid becomes stronger, the polishing speed becomes faster.

(1) Example A tin surface plate of the present invention was made. T=45°, e=900,
The pitch of the small grooves was 0.2 yxw. The small groove was cut using a diamond cutting tool.

The workpiece is BK7 glass.

The polishing liquid used was a mixture of 70 5i-02 microparticles as abrasive grains in a few percent of pure water.

The rotation speed of the surface plate was 1100 rpm. The rotation speed of the work holder was also 100 rpm. Polishing was performed in this way.

Polishing was performed under the same conditions using a tin surface plate with symmetrical small grooves (isosceles triangular grooves). Figure 3 shows the measurement results regarding the relationship between time and polishing amount.

Compared to the conventional tin surface plate, the polishing rate of the present invention was improved by about 40%.

Further, no scratches were observed on the surface of the workpiece.

This is considered to be because the floating state of the workpiece became stable. The surface roughness was 15 people R, but 1oARa.

.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the groove shape of the surface plate of the non-contact polishing apparatus of the present invention. Figure 2 is an enlarged view of the cross section of the small groove. FIG. 3 is a graph showing measurement results of polishing time and polishing amount in the present invention and the conventional example. FIG. 4 is a cross-sectional view of grooves in a conventional surface plate. Figure 5 is a plan view of the tin surface plate. FIG. 6 is a sectional view of an example in which the groove apex angle is too small. 1......Tin surface plate 10......Elevated strip 11......Large groove 12...・・・
...Komizo Inventor Miki Kusao Patent Applicant Sumitomo Electric Industries Co., Ltd. Application I + Raccoon #, Kiki II + Kiku Hatake Book σ",
i borrow i-1:'4i,':::f 1st figure 2nd figure gabatsuj1

Claims (1)

[Claims] The upper surface has a spiral ridge 10, a large number of spiral small grooves 12 carved on the upper surface of the ridge 10, and a large groove 11 formed between adjacent ridges 10, 10, and the small groove 12 is located on the axis. It has a serrated cross section tilted toward the center, the apex angle or valley angle Υ of the small groove is 30 to 60°, and the inclination angle Θ of the surface facing the axis with respect to the horizontal plane is 80 to 120°. Features a tin surface plate of non-contact polishing equipment.