Patent ID: 6173948
Filing Date: 2001-01-16
Classification: B25B

Abstract:
A vacuum fixture for retaining a workpiece on a surface during processing of said workpiece while implementing dimensional compensation of distortions caused by thermal changes; said vacuum fixture comprising:(a) a frame structure housing a rigid porous plate;(b) a vacuum line connected to a vacuum source communicating with said porous plate for creating a flow of suctioning air through said plate;(c) an apertured interposer member supported on said porous plate, said apertured interposer member comprising a thin plate member having a coefficient of thermal expansion generally equal to that of the porous plate, and forming a thermal insulator between the workpiece and the porous plate, said workpiece being positionable on a planar upper surface of said interposer member and retained thereon in surface contact by a vacuum created by said suctioning air; and(d) heat-controllable means being arranged below said porous plate in operative engagement therewith, whereby controlling the thermal conditions of said means selectively expands or contracts said porous plate in correlation with thermal distortions of said workpiece so as to dimensionally compensate said workpiece to facilitate accurate processing thereof.