Fixturing Stiffness Analysis

This chapter introduces a method for modeling work-piece boundary conditions and applied loads during a machining process, analyzing the work-piece deformation, and optimizing support locations using finite element analysis (FEA). Work-piece boundary conditions are defined through locators and clamps that are in contact with the work piece. The locators are placed in a 3-2-1 fixture configuration, constraining all six DOF of the work piece, and are modeled using linear spring-gap elements. Clamps are modeled as point loads, the cutting force in drilling and milling operations are modeled as quasi-static load acting on the work piece. Machining fixtures are used to locate and constrain a work piece during a machining operation. To ensure that the work piece is manufactured according to specified dimensions and tolerances, it must be located and clamped. Production quality depends considerably on the relative position of the work piece and machine tools. Minimizing work piece and fixture tooling deflections because of clamping and cutting forces in machining is critical to machining accuracy. The work-piece deformation during machining is directly related to the work-piece fixture system stiffness.

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