Polishing apparatus

Abstract

A polishing apparatus for polishing a workpiece by utilizing a fluid including abrasive particles having a dielectric property. The polishing apparatus includes an electrode for applying processing pressure to the abrasive particles on the workpiece and having electrode elements for collecting and arranging the abrasive particles by a Coulomb force produced by application of an alternating-current voltage to the electrode, and a driving device for driving the electrode.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a polishing apparatus in which polishing of a workpiece is effected using dielectric abrasive particles located at a position at which processing pressure is applied by a Coulomb force produced when a voltage is applied across electrodes. [0003] 2. Description of the Prior Art [0004] Polishing apparatuses having various configurations have been proposed. A polishing apparatus generally has a polishing pad holding abrasive particles that is affixed to a surface plate, and effects polishing by moving one of the plate and the workpiece with respect to the other. In recent years, progress has been made with research into functional fluids that respond to an electrical field or a magnetic field, and there are polishing apparatuses that utilize such functional fluids. [0005] In processing such as polishing and surface finishing, for example, use has been made of magnetic fluids, which are ...

AI Technical Summary

Benefits of technology

"The present invention provides a polishing apparatus that uses a Coulomb force to collect abrasive particles on a sample and applies processing pressure to the collected particles. The apparatus includes an electrode with multiple electrode elements, a driving means for the electrode, and abrasive particles with a dielectric property disposed between the electrode and the workpiece. The electrode elements can have different diameters and different voltages can be applied to them to achieve uniform polishing. The apparatus can also include a cylindrical electrode and a low-frequency alternating-current electrical field. The invention provides a more efficient and energy-saving polishing process."

Problems solved by technology

Although polishing using a magnetic fluid is suitable when the workpiece to be polished has a spherical or other such special shape, magnetic fluid polishing has a number of problems.

For example, magnetic fluid induction produces a small processing pressure that results in a low polishing efficiency.

Other problems include scratching caused by fragments of removed material that become entrained in the magnetic fluid, and the fact that in the case of a magnetic workpiece, movement of the abrasive particles is constrained, making it impossible to achieve the required polishing effect.

Such problems have limited the application of polishing using magnetic fluids.

However, because it has been considered difficult to control the shape, position and apparent viscosity of the formations, it is thought that there is a high risk that applying pressure to the formations will produce scratching of the workpiece surface.

Thus, it has been considered that these MR fluids are usable for primary rough grinding but are not readily usable for fine and finish polishing.

The large size of the iron particles generally used in the MR fluids has posed another obstacle to their use for fine and finish polishing.

In this case, there is a mutual repulsion between adjacent clusters, and in order to maintain a certain spacing, the positioning of the abrasive particles can readily become uneven, giving rise to non-uniformity in the surface roughness of the polished surface.

With the polishing apparatus of the prior art thus configured, the movement of the abrasive particles from the rotary electrode 1 onto the conductive specimen 3, and the uneven positioning of the abrasive particles, makes it difficult to achieve a high-quality polished surface in the case of large products.

Moreover, having to apply a voltage between the rotary electrode and a conductive workpiece makes it difficult to apply the apparatus to insulating materials.

That is, the thickness of a workpiece having insulation properties has the same effect as an air-gap, so a high polishing effect cannot be obtained without using an electrical field strength that is high enough to control the position of the abrasive particles, which means the work is dangerous and there is a risk of the workpiece being damaged by an electrical discharge.

Also, centrifugal force generated by the rotation of the polishing part tends to cause the abrasive particles to accumulate around the periphery of the polishing area, reducing polishing efficiency.

However, the aforementioned spacing between adjacent clusters of abrasive particles has made it impossible to achieve a highly uniform arrangement of the particles.

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