Abstract: There is described a method, apparatus and shaping tool for shaping a workpiece. The tool comprises a flexible support surface on which are mounted a number of rigid pellets (84) carrying abrasive material. The tool is driven, in contact with the workpiece surface (S), to perform a ductile grinding operation which results in a finished surface of reduced roughness as compared to conventional grinding operations, while achieving significantly higher material removal rates than comparable ultra-precision grinding techniques. A procedure for preparing the tool for operation by conditioning the tool against a conditioning surface is also described. An exemplary application for the method and apparatus is in the preparation of moulds for moulding curved glass components for use in display screens, in which process a silicon carbide mould cavity surface is shaped using the method to produce a mould cavity surface with a smooth surface finish.

Abstract: There is described a method, apparatus and shaping tool for shaping a workpiece. The tool comprises a flexible support surface on which are mounted a number of rigid pellets (84) carrying abrasive material. The tool is driven, in contact with the workpiece surface (S), to perform a ductile grinding operation which results in a finished surface of reduced roughness as compared to conventional grinding operations, while achieving significantly higher material removal rates than comparable ultra-precision grinding techniques. A procedure for preparing the tool for operation by conditioning the tool against a conditioning surface is also described. An exemplary application for the method and apparatus is in the preparation of moulds for moulding curved glass components for use in display screens, in which process a silicon carbide mould cavity surface is shaped using the method to produce a mould cavity surface with a smooth surface finish.

Abstract: A lapping tool for localized optical polishing of a workpiece, the tool having a flexible working surface and being characterized by means for selectively varying the pressure applied, in use, on the workpiece by different regions of the tool working surface whereby to vary the effective area of contact with the workpiece. A method of optical polishing and optical workpiece using a lapping tool whose maximum working surface area is substantially smaller than the workpiece, comprising determining the path to be travelled by the tool across the workpiece, and determining the pressure and effective area of contact of the tool on the workpiece, in order to achieve the next stage of polishing, and then driving the tool over that path while dynamically varying the said applied pressure and effective contact area.