Geometric error control of workpiece during drilling through optimisation of fixture parameter using a genetic algorithm

Abstract

Fixtures are an essential component of manufacturing and production. They are used to accurately position a component or workpiece within a machine-tool coordinate system. During material removal, the function of the fixture is to ensure the stability of the workpiece which is constrained to meet the design requirements. The fixture performs this function by providing accurate and repeatable location of the component with respect to the machine tool, and by resisting motions, deflections, and distortions of the workpiece under the influence of the cutting forces. Therefore, the focus of this paper is to develop a methodology that analyses and optimises the fixture parameter configurations using a genetic algorithm (GA) with an ANSYS parametric design language (APDL) of a finite element analysis that minimises the geometric dimensional tolerance errors of the final component dimensions. Here, the workpiece is located and constrained in a fixture, as it undergoes material removal owing to the insertion of a drill bit. The deformations and distortions of the workpiece are modelled at discrete intervals throughout the drilling process. Three case studies were used to illustrate the application of the proposed approach. The first explains the methodology used in this research. The second and third explain the control of deformation and geometric error of the hole in sequential and simultaneous drilling operations by optimising the fixture parameters using GA. This work minimises the deformation of the workpiece using a GA–ANSYS integrated tool. Then, the same layouts given by the integrated tool are used in the experimental setup, and it is found that the errors found in the perpendicularity and circularity of the drilled holes are minimal when the above geometric dimensional tolerances were checked using a coordinate measuring machine.

Keywords:

• deformation
• finite element analysis
• geometric error

Acknowledgements

The authors would like to thank Dr Kalyanmoy Deb, KanGal, IIT, Kanpur, for the GA code used in this study.