JPS63196368A - Polishing method using magnetic fluid - Google Patents

Abstract

PURPOSE:To improve the extent of efficiency, by dipping a float in a magnetic fluid containing abrasive grains, giving buoyance to this float in making an external magnetic field act on the magnetic fluid, while pressing these abrasive grains between a float acting surface and a workpiece to this workpiece by dint of the buoyancy, and giving relative motion to an interval between the workpiece and the magnetic fluid. CONSTITUTION:A workpiece 3 is attached to the underside of a disc 6 as a driving jig free of rotation, and it is dipped in the vicinity of a level of a magnetic fluid 2 containing abrasive grains in a vessel 1. Here, a float 5 is dipped in the magnetic fluid 2, and if an external magnetic field is made to act on by a magnet 4 from the lower part of the magnetic fluid 2, buoyancy acts on these abrasive grains, floating them upward, and thereby an abrasive grain layer of high density is formed in the upper part of the magnetic fluid 2. Simultaneously with this, the buoyancy is given to the float 5 as well, and the float 5 is floated upward, strongly pressing these abrasive grains existing in the upper part to a surface of the workpiece 3. Under this state, when the driving disc 6 is rotated with a vertical shaft 61 as the center, the under side being contacted with these abrasive grains is polished. In this case, the polishing rate is improved by action of the float 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for polishing the surface of an object to be polished using a magnetic fluid containing abrasive grains under the action of a magnetic field. M
The force is controlled by a combination of a magnetic fluid, a float, and a magnetic field.
The present invention relates to a highly efficient polishing method.

A method of polishing the surface of an object using a polishing liquid containing abrasive grains in magnetic fluid under the action of a magnetic field is described in Japanese Patent Application Laid-open No. 5
1-10499, JP-A-57-183057, JP-A-57-158280, JP-A-58-77447,
JP-A-5i9-102589, JP-A-80-8705
No. 7, JP-A No. 6O-11848B, JP-A No. 80-18
No. 7781, JP-A No. 80-188388, JP-A-80
Various proposals have been made in specifications such as No.-191759 and Japanese Patent Application Laid-open No. 80-242983.

The basic principle of the method of polishing the surface of an object using a polishing liquid containing abrasive grains in a magnetic fluid under the action of a magnetic field is explained using Fig. 8. An object 3 to be polished is placed so that its surface to be polished is immersed in a magnetic fluid z containing grains, and a magnet 4 is placed below the container 1 to apply an external magnetic field from below the magnetic fluid. In this way, the abrasive grains float to the top and form a high-density abrasive grain layer that comes into contact with the surface to be polished. Therefore, when relative motion is applied between the object to be polished and the magnetic fluid containing abrasive grains, in the case shown in the figure, the object to be polished is rotated around a vertical axis, so that it comes into contact with the abrasive grain layer. The surface to be polished is polished.

Alternatively, there is a method of applying relative motion between the object to be polished and the magnetic fluid containing abrasive grains by rotating an external magnetic field to rotate the magnetic fluid containing abrasive grains.

However, although these conventional methods can achieve the purpose of polishing, the polishing rate (amount of polishing per unit time) is very small and inefficient, so even though they are stable in principle, they have not been put into practical use. There are no examples.

Problems to be Solved by the Invention An object of the present invention is to provide a method for efficiently polishing the surface of a workpiece in a polishing method using a magnetic fluid containing abrasive grains.

In the polishing method of the present invention, a float is immersed in a magnetic fluid containing abrasive grains, and an external magnetic field is applied to the magnetic fluid to impart buoyancy to the float. The method consists of pressing the abrasive grains between the working surface of the workpiece and the object to be polished onto the object to be polished, and giving relative motion between the object to be polished and the magnetic fluid containing the abrasive grains.

The method of the present invention will be specifically explained using one typical application example.

1A and 1B show one specific example of simultaneous polishing of a plurality of objects to be polished, with FIG. 1A being a view seen from above and FIG. 1B being a side sectional view.

As shown in FIGS. 1A and 1B, the object to be polished 3 is rotatably attached to the lower surface of a disk 6 as a driving jig, and is placed near the liquid level of the magnetic fluid 2 containing abrasive grains in a container l. immersed in. Here, when the float 5 is immersed in the magnetic fluid 2 containing abrasive grains and an external magnetic field is applied by the magnet 4 from below the magnetic fluid, buoyancy acts on the abrasive grains and they float upwards. A high-density abrasive grain layer is formed at the same time, and buoyancy is also given to the float 5, so that the float 5 floats and strongly presses the abrasive grains present above it against the surface of the object to be polished. When the drive disk 6 is rotated about the vertical axis 61 in this state, the lower surface in contact with the abrasive grains is polished. In this case, due to the action of the float 5, the polishing rate is significantly improved compared to the case where no float is used.

The generated polishing force is determined by the buoyant force acting on the float and the rigidity of the float as a resistance force in the polishing direction. The rigidity in the polishing direction is determined by factors such as the material, mass, shape, and fluid resistance of the float.

As the material of the float, various materials such as metal, plastic, ceramics, rubber, etc. can be selected depending on the purpose.

The buoyant force acting on the float is determined by the strength of the external magnetic field acting from below, the size of the float, the distance to the float, etc., and by changing these factors, the required processing pressure can be arbitrarily controlled.

It is not an absolutely necessary condition that the specific gravity of the float is lighter than the specific gravity of the magnetic fluid containing abrasive grains, but it is sufficient that it generates buoyancy by the action of an external magnetic field acting from below.

The shape of the float depends on the shape of the surface to be polished of the object to be polished, for example, a flat surface, a curved surface, an uneven surface, etc.

It is preferable that the shape is such that the distance between the object to be polished and the surface to be polished is constant in all parts.

The surface of the float may be smooth, but as shown in FIG. 6A or FIG. 6B as a partially enlarged sectional view, a float with a large number of grooves or recesses on its upper surface to facilitate retention of abrasive grains is used. Alternatively, as shown in FIG. 6C as a partially enlarged sectional view, one having a large number of communicating holes may be used to facilitate the replenishment of abrasive grains.

The relative motion between the object to be polished and the abrasive grains mixed in the magnetic fluid is
This is performed by rotation, reciprocation, vibration and other movements of the object to be polished, movement of a magnetic fluid containing abrasive grains, fluctuations in the magnetic field, movement of a float, and movements that combine these movements.

As the abrasive grains contained in the magnetic fluid, known polishing abrasive grains can be appropriately selected and used. For example, AJ1203
(corundum), 5iC (silicon carbide: carporundum), diamond, etc., or abrasive grains with added magnetism may be used.

The magnet 4 used as the external magnetic field may be a single magnet or a group of magnets arranged with the same polarity, but it is rather arranged so that the polarities of adjacent magnets are different from each other (as indicated by the arrows in the figure).
A combined magnet group is preferable. Combining the magnet groups so that the poles of adjacent magnets are different from each other increases the buoyancy of the abrasive grains and the float, and also causes a magnetic ejection force to act in the horizontal direction, thereby reducing the This is to hold the abrasive grains against the direction of movement of the polishing object.

This magnet or group of magnets may be a permanent magnet or an electromagnet.

In addition to the lower part of the container l, the magnet may also be placed on one side to generate a magnetic field gradient in an appropriate direction, such as horizontally or in an inclined direction. In either case, an external magnetic field is applied from one side of the magnetic fluid. All you have to do is to apply this force to generate buoyancy on the opposite side.

FIGS. 2A and 2B are diagrams for explaining another specific example of simultaneously polishing a plurality of objects to be polished, similar to FIGS. 1A and 1B, and FIG. 2A is a view from above. Fig. 2
Figure B is a side sectional view. In this case, the plurality of objects 3 to be polished are placed between the drive disk 6 and the float 5 so as to float in the magnetic fluid z containing abrasive grains. When an external magnetic field is applied to this from below, the magnetic fluid containing abrasive grains 2
The float 5 immersed therein floats up, and the abrasive grains present above are pressed against the lower surface of the object 3 to be polished. When the driving disk 6 is rotated about the vertical axis 61, the object to be polished 3 is rotated by the disk 6.
, the outer peripheral wall 62 and the float 5 float in a magnetic fluid containing abrasive grains, and the lower surface or upper and lower surfaces of the object 3 to be polished are polished.

3A and 3B are diagrams for explaining the case of polishing the side surface of a ring or disk, with FIG. 3A being a view seen from above and FIG. 3B being a side sectional view.

A ring or disk-shaped object 3 to be polished is attached to a horizontal rotating shaft 61 and rotated, and a float 5 immersed in a magnetic fluid 2 containing abrasive grains floats to rotate the abrasive grains present above it. Alternatively, if it is pressed against the side surface of the disc-shaped object 3 to be polished, that side surface will be efficiently polished. In this case, it is desirable to provide the rotating shaft 7 at the center of the float 5.

The fourth rI4 is a diagram for explaining the case of polishing a cylinder having a deep groove. A cylindrical workpiece 3 having deep grooves is horizontally supported and rotated by a jig 63, and a float 51 having an uneven shape corresponding to the deep grooves is used to rotate the abrasive grains present above the workpiece. 3, the side surface will be efficiently polished down to the deep grooves. In this case, the guide bin 71 restricts the lateral movement so that the float 51 does not swing irregularly.

FIG. 5 is a diagram for explaining the case of polishing the inside of the pores of the object 3 to be polished, which has pores. Pore 3
A needle-shaped float 52 is inserted into the inside of 5. When the object 3 to be polished is horizontally reciprocated, the inside of the pore 35 is efficiently polished.

When the cross section of the pore 35 is circular and the outer shape is also a cylinder or a regular polygonal prism, the object 3 to be polished may be rotated.When polishing the inner surface of a ring or pipe, the surface to be polished This can be accomplished in a similar manner by applying the buoyant force of a magnetic field to the inner surface of a float adapted to the shape.

The polishing method using a float according to the present invention is not limited to the above specific example, but can be applied to various polishing methods using a magnetic fluid containing abrasive grains.

Example 1 Using the apparatus shown in FIG. 7, polishing was carried out under the conditions shown in Table 1. The test results are shown in Table 2.

Table 1 The polishing rate was determined from the cross-sectional curve of the end of the lower surface of the test piece.

Comparative Example 1 A polishing test was conducted under the same conditions using the same equipment as in Example 1, except that no float was used. The results are shown in Table 2. The polishing rate in this case was also determined from the cross-sectional curve of the end of the lower surface of the test piece in the same manner as in Example 1.

Table 2 When a float is used (Example 1), a polishing rate 60 times higher than when no float is used (Comparative Example 1) is obtained.

C8 Effects of the Invention Since the polishing method of the present invention is carried out in a magnetic fluid containing abrasive grains, the loading system for applying processing force to the object to be polished has a flexible structure, and therefore overload and impact force do not occur. It is possible to polish difficult-to-work materials such as brittle materials such as ceramics and ductile materials such as aluminum while minimizing the occurrence of damage or deterioration due to processing.

Furthermore, since the heat generated by polishing can be efficiently removed, combined with the effect of the soft structural load mentioned above, high-speed polishing becomes possible and polishing efficiency improves.

Furthermore, the greatest feature of the present invention is that in the conventional polishing method using magnetic fluid, the processing pressure is mainly due to the buoyancy of the abrasive grains, but the buoyancy of the abrasive grains is small as a processing pressure, so the polishing rate is very small. In the present invention, since a float is used, the abrasive grains are strongly pressed against the surface to be polished by the buoyant force, and the processing pressure is significantly increased. At the same time, the float acts as a resistance body in the polishing direction, and as a result, the polishing rate is significantly improved. That's true.

Further, by appropriately changing the shape of the float depending on the shape of the surface to be polished, it is possible to polish a complicated surface.

[Brief explanation of the drawing]

Figure 1A and Figure 1B, Figure 2A and Figure 2B, Figure 3A
Figures 3B, 4, and 5 are diagrams for explaining specific embodiments of the present invention, respectively, and Figures 6A, 6B, and 6C are partially enlarged views of the float used in the present invention. FIG. 7 is a diagram showing an example of a cross-sectional structure, FIG. 7 is a diagram showing the apparatus used in Example 1, and FIG. 8 is a diagram for explaining a conventional method.

Claims (1)

[Claims] 1. A float is immersed in a magnetic fluid containing abrasive grains, and an external magnetic field is applied to the magnetic fluid to give a buoyant force to the float. A method for polishing an object to be polished, which comprises pressing abrasive grains between the objects to be polished and applying relative motion between the object to be polished and a magnetic fluid containing abrasive grains. 2. The polishing method according to claim 1, wherein relative motion is imparted between the object to be polished and the magnetic fluid containing abrasive grains by horizontally reciprocating, rotating or vibrating the object. 3. The polishing method according to claim 1, wherein relative motion is imparted between the object to be polished and the magnetic fluid containing abrasive grains by varying an external magnetic field and causing the magnetic fluid containing abrasive grains to flow. 4. The polishing method according to claim 1, wherein a float having a large number of grooves or recesses on its working surface is used. 5. The polishing method according to claim 1, wherein a float having a large number of communication holes for the magnetic fluid and the abrasive grains is used. 6. Claim 1, in which the object to be polished is sandwiched between a float and a driving jig and suspended in a magnetic fluid containing abrasive grains.
Polishing method described in section. 7. The polishing method according to claim 1, which uses a group of magnets in which adjacent magnets have different poles as the external magnetic field that acts on the magnetic fluid.