Design optimisation of the head of a high-precision optical polishing machine

A highly deformable polishing tool has been specified for a revolutionary aspheric polishing system. This rubber tool is required to retain a spherical outer surface with minimal change in shape when subjected to internal pressure. It is proposed here that using a variable wall thickness around the tool will reduce deviations from the spherical shape. This paper describes a theoretical study carried out using finite element analysis to determine the optimum wall thickness variation. The component performance was judged against the three criteria of change in radius, center of curvature drift and loss of sphericity. A multi-criteria optimization code linked to a parametric finite element model was used to analyze the problem and generate a set of Pareto optimal solutions. The characteristics of this Pareto set are described in this paper and used to explain the various deformation modes of the tool. It is concluded that varying the wall thickness will achieve the desired objective.