Method for polishing slight area of surface of workpiece and tool therefor

Claim 1

A method for polishing a slight region of a surface of a workpiece, comprising the steps of: applying a magnetic field, in a Z-direction perpendicular to the surface of the workpiece, to a space between a polishing portion disposed at a leading end of a polishing tool and the workpiece to magnetically hold a polishing material in the space between the polishing portion and the workpiece, the polishing material including magnetic fluid and nonmagnetic abrasive grains disposed in the magnetic fluid; applying pressure mechanically in the space between the surface of the workpiece and the polishing portion; operating an actuator or actuators, each actuator comprising a piezoelectric element, to cause the polishing portion disposed at the leading end of the polishing tool to undergo a slight movement in at least one of an XY-direction parallel with the surface of the workpiece and the Z-direction to polish the slight region of the surface of the workpiece with the polishing material; and stepwise reducing an amount of abrasion per period of time by stepwise decreasing a frequency of the slight movement of the polishing portion while the workpiece is being polished.

Claim 2

A method for polishing a slight region of a surface of a workpiece, comprising the steps of: applying a magnetic field, in a Z-direction perpendicular to the surface of the workpiece, to a space between a polishing portion disposed at a leading end of a polishing tool and the workpiece to magnetically hold a polishing material in the space between the polishing portion and the workpiece, the polishing material including magnetic fluid and nonmagnetic abrasive grains disposed in the magnetic fluid; applying pressure mechanically in the space between the surface of the workpiece and the polishing portion; operating an actuator or actuators, each actuator comprising a piezoelectric element, to cause the polishing portion disposed at the leading end of the polishing tool to undergo a slight movement in at least one of an XY-direction parallel with the surface of the workpiece and the Z-direction to polish the slight region of the surface of the workpiece with the polishing material; and stepwise reducing an amount of abrasion per period of time by stepwise decreasing a frequency of the slight movement of the polishing portion while the workpiece is being polished.

Claim 3

A method for polishing a slight region of a surface of a workpiece, comprising the steps of: applying a magnetic field, in a Z-direction perpendicular to the surface of the workpiece, to a space between a polishing portion disposed at a leading end of a polishing tool and the workpiece to magnetically hold a polishing material in the space between the polishing portion and the workpiece, the polishing material including magnetic fluid and nonmagnetic abrasive grains disposed in the magnetic fluid; applying pressure mechanically in the space between the surface of the workpiece and the polishing portion; operating an actuator or actuators, each actuator comprising a piezoelectric element, to cause the polishing portion disposed at the leading end of the polishing tool to undergo a slight movement in at least one of an XY-direction parallel with the surface of the workpiece and the Z-direction to polish the slight region of the surface of the workpiece with the polishing material; stepwise reducing an amount of abrasion per period of time by stepwise decreasing a frequency of the slight movement of the polishing portion while the workpiece is being polished; moving the polishing portion away from the surface of the workpiece for a short period of time to let nonmagnetic abrasive grains flow in the space between the surface of the workpiece and the polishing portion; and wherein the leading end of the polishing portion comprises a rotatable sphere.

Claim 4

A method for polishing a slight region of a surface of a workpiece, comprising the steps of: applying a magnetic field, in a Z-direction perpendicular to the surface of the workpiece, to a space between a polishing portion disposed at a leading end of a polishing tool and the workpiece to magnetically hold a polishing material in the space between the polishing portion and the workpiece, the polishing material including magnetic fluid and nonmagnetic abrasive grains disposed in the magnetic fluid; applying pressure mechanically in the space between the surface of the workpiece and the polishing portion; operating an actuator or actuators, each actuator comprising a piezoelectric element, to cause the polishing portion disposed at the leading end of the polishing tool to undergo a slight movement in at least one of an XY-direction parallel with the surface of the workpiece and the Z-direction to polish the slight region of the surface of the workpiece with the polishing material; stepwise reducing an amount of abrasion per period of time by stepwise decreasing a frequency of the slight movement of the polishing portion while the workpiece is being polished; moving the polishing portion away from the surface of the workpiece for a short period of time to let nonmagnetic abrasive grains flow in the space between the surface of the workpiece and the polishing portion; and wherein the leading end of the polishing portion comprises a rotatable sphere.