Improved algorithm for tolerance-based stiffness optimization fixtures of machining

Current fixture design methods rely extensively on heuristics and lack a fo rmal engineering approach to determine the necessary stiffness, dimensions, etc. This paper presents a model for stiffness optimization of machining f ixtures based on the tolerance limit specified for the machined part surfac e. Specifically, the model allows systematic determination of the optimum f ixture stiffness needed to keep the contribution of fixture deflection to t he machined feature tolerance within a designer-specified level. Based on t he stiffness optimization model presented here, the optimum dimensions of t he fixture elements can also be determined. The model development relies on rigid body analysis methods, contact mechanics principles, and considerati on of bulk elasticity of the fixture. The model is generic enough to be use d for the design of dedicated or flexible fixtures consisting of mechanical elements. Two examples, one involving a pin-array type flexible fixture an d another involving a dedicated fixture, are presented to illustrate the ap plicability of the model.