Computer Aided Fixture Design Oriented Analysis Methods For Fixture Layout Attachment/Detachment

With the rapid development and advancement of manufacturing industry, the machining technology has been promoted, and fixturing, which has an influence on precision in product processing and fabricating cost, is still a significant tooling of machining technology. The estimate of the performance of a fixture layout is a key to guarantee that the fixture design satisfies actual processing. The fixture layout attachment/detachment is an important index of the fixture layout performance, it can reflect the possibility of placing a workpiece in contact with the fixture layout or displacing a workpiece from the fixture layout. The objective of attachment/detachment analysis is helping the correct selection of fixturing surfaces and fixturing points on workpiece. Therefore, this paper has made a detailed analysis of the fixture layout of ‘workpiece-fixture’.First, according to the practical contact or assembly of workpiece with the fixture layout performing the math modeling, hence, Taylor theorem is used to formulate the attachment/detachment kinematic model of the fixture layout of ‘workpiece-fixture’, referred to as the A/D model. Then, after analyzing the A/D model and equalizing the possibility of placing a workpiece in contact with the fixture layout or displacing a workpiece from the fixture layout to the solution existence of A/D model, a mathematics trick is created to express an arbitrary number in the A/D model as a difference of two nonnegative numbers. Only by doing so can the analysis of solution existence of A/D model be identified as a linear programming problem and in turn, a judgment method is proposed for the fixture layout attachment/detachment. Next, specially under the condition that the A/D model has solutions, the feasible direction of attachment/detachment of workpiece to/from the fixture layout is further considered. By equivalently transforming seeking the feasible direction of attachment/detachment into solving the general solution of A/D model, Γ-algorithm is suggested for solving a set of linear inequalities. Last, using Matlab as the carrier, developed the attachment/ detachment GUI analysis system, and realized the automatic evaluation of fixture performance on attachment /detachment of the fixture layout.The presented "seeking solutions if equations are solvable" algorithm only concerns on the coordinates and unit normal vectors of workpiece at fixturing points. It can not only be carried out for a workpiece with complex surfaces, but also avoid the solving process of the A/D model without solutions. It is more important, it can develop and enrich the theoretical basis of automated fixture design.