Information-based Manufacturing for Selective Assembly via a Coordinated Statistical Tolerancing and Spc Model

Aimed at overcoming the disadvantages of traditional selective assembly and improving the manufacturing processes of mating parts, a new approach of information-based manufacturing for the mating parts of selective assembly via a coordinated statistical tolerancing (ST) and SPC model is presented. On the basis of studies on quality indices and process capability index (PCI), particularly, the matchable degree of selective assembly, the quality-oriented PCIbased statistical tolerancing using response surface method is introduced, which provide an interface between customer’s quality expectation and the process parameter design. A coordinated ST and SPC model under information-based manufacturing condition is discussed. Compared with independent ST and SPC model, the innovative method can achieve the maximum matchable degree and minimum defective ratio by fully utilizing ST zone and the known information of manufactured mating parts via a local network and information system. Thus, production cost for selective assembly can be reduced obviously. Notation USL upper specification limit LSL lower specification limit MST midpoint of USL and LSL t dimensional tolerance, t = USL-LSL T target of process mean Subscripts H hole S shaft * designated value Cp process capability index k ratio of the bias of process mean to its allowable bias σ standard deviation of process output μ mean of process output ∆ bias of process mean to its target, ∆ = μ − Τ Pmd matchable degree of mating parts in selective assembly, Pd percentage of defective in process output