Optimization of fixture flexibility for irregular geometries of workpiece based on metamorphic mechanisms

Abstract

This paper proposes a novel flexible fixture for workpiece with irregular geometries like non-axisymmetric cylinder. According to the processing condition and geometric characteristics, a new 3-2-1 locating principle, which is different with the 4-1-1 in the case of axisymmetric cylindrical workpiece, is proposed. Based on this, a novel flexible fixture containing locating and clamping systems is designed. The core part of it is the clamping system based on a metamorphic mechanism that consists of specially designed “spring balls” and “chasing turntables” which provide strong flexibility for indenters. The spring balls are capable to change connection state between indenters automatically with respect to whether single indenter is resisted by workpiece or not, while the chasing turntables are able to automatically connect indenters again after all of them have been resisted. Therefore, the flexible fixture is adaptable to different geometries by enabling the indenters to approach the irregular surface synchronously, touch it asynchronously, clamp it synchronously, and release it synchronously. The main contribution of this paper is the application of metamorphic mechanism to fixture designing that has not been widely concerned yet. This work significantly improves the clamping efficiency of fixture and its adaptability to irregular workpieces.