Simultaneous fixturing layout and sequence optimization based on genetic algorithm and finite element method

Abstract

Dimensional and geometrical precision of industrial parts in the manufacturing process depend heavily on several items such as material, tool, machine tool and fixturing strategy. The workpiece deformation depends on several issues such as workpiece elastic deformation, geometric error of fixcles (we will call locators and clamps as “fixcles” afterwards), fixturing layout, external forces like clamping and machining forces, and variation of contact forces during machining. The optimization of locator and clamp positions, as well as their sequence, are crucial factors in minimizing the deformation error in workpiece machining. This research tries to introduce a new viewpoint toward genetic algorithm (GA) optimization method in order to introduce fixturing regions and fixturing sequence, which minimize the workpiece deformation error in 3-2-1 locating approach. A new concept, namely “Fixturing Clearance (FC)” has been proposed in this study. FC is a criteria which evaluates fixturing layout. All layouts which lead to fewer machining errors than FC have the potential to be accepted in the final fixturing regions. Although GA method originally results in an individual optimum point, the proposed strategy in this study introduces continuous fixturing regions as well as the functional fixturing sequence. An integration between GA and finite element is used to optimize the elastic deformation of the workpiece under clamping and machining loads. The effectiveness of this method has been illustrated on a 2D case study.