Research On Quality Improvement Of The Domestic Automobile Considering Economic Quality Of Auto-parts

China has become the first country with most auto production and marketing for nine years,who has become a big but not a powerful automobile contry.However,the late strat of domestic brand vehicle manufactures,lack of technology for core components and the imperfect post market service system have made a significant difference in quality between domestic and foreign brands.The procurement cost of auto parts accounts for 70%-80% of a total vehicle cost.In addition,low price has been the main characteristic between auto assembly firms and auto part factories in China,which contributes to the competitive advantage of domestic vehicle product with lower cost.To improve the quality of domestic automobile products,the domestic automobile industries begin to perform quality improvement practice.However,how to improve the quality under the low cost advantage is a very complex issue that industries concern.Statistically,the failures occurred of domestic auto products are caused by auto parts has reached to about 80%.The soaring quality defects and failures of auto parts and components,not only contribute to maintenance expenditure,but also lead to the customer compalints which causes hidden quality loss.Therefore,how to improve the economy of quality(EOQ)of domestic automobile products,from auto parts perspective in a scientific and efficient way,is an urgent task for automobile industry and domestic auto factories,promoting China to become a powerful automobile country.According to the above-mentioned analysis,this dissertation performs on quality improvement research of domesic automobile products considering the economic quality of auto parts,and the study follows the main line of vehicle quality improvement from auto part perspective.Based on the index analysis of EOQ,this disseratation starts with the crucial auto parts.According to the influence ruel of quality input on EOQ index of automobile products,the management decision model and practice is put forward for economy of quality improvement.The main research contents of the dissertation are as follows:(1)An EOQ index system including R/1000@3MIS,TGW/1000@3MIS and total cost related two-dimensional quality is built,providing a guidance for domestic automobile industry for quality improvement.In addition,the question issue unit(QIU)including failure unit(FU)and customer complaint unit(CCU)is established to obtain failure frequency and customer complaint frequency of parts and automobiles from the point of view of the consumer.In order to reflect EOQ in different stages,twodimensional PAF-LCC total cost related quality framework is established from PAFbased quality cost and lifecycle dimesions.The Taguich loss function is introduced to quantize stealth loss arising in customer complaint.The economy of quality within warranty period is addressed from quality invst and quality loss perspectives.(2)To improve the quality improvement efficiency from auto part perspective,the “crucial parts” quality improvement strategy is proposed,which means the EOQ improvement of automobile is promoted by the EOQ performance enhancemen of crucial auto parts.The method how to chose the crucial auto parts has been addressed in this chapter.Based on the risk priority number when performing FMEA,the quality improvement priority coefficient is deinfed and used to refeclet the priority for improvement.Firstly,the rough set-based attribute reduction(RSAR)is employed to establish the influence factors.Then,the combined weight integrating fuzzy DEMATEL with entropy-based method is embedded into fuzzy VIKOR steps.The comprehensive utility value Q,as the quality improvement priority coefficient,provides to select crucial parts under static quality information.After that,to resolve the curcial part selection under dynamic environment,the dynamic triangular fuzzy weighting average operator,(DTFWA)is introduced to propose the new quality improvement priority coefficien ζ.(3)To determine the quality input mode in a scientific and effective way,the interactive systems dynamic model of EOQ indexes is constructed to guide quality improvement practice,also contributing to the influecence identification of quality input on EOQ index of the vehicle.Firstly,based on the quality formation of domestic vehicle and quality improvement procedure,the causality diagram and flow graph among EOQ indexes are analyzed,and the SD model is established based on logic relationship of variables.Besides,R/1000@3MIS、TGW/1000@3MIS and elements of total quality related cost framework are treated as key criteria to reflect EOQ of vehicle.Secondly,the hypothesis test and ANOVA are performed to verify the validation of the constructed simulation model.Finaly,the Vensim PLE is used to simulate the variation of EOQ under different quality input mode,which provides guidance for quality input and quality plan durng the quality improvement of vehicle.(4)To achieve quality improvement by the enhancement of crucial parts,the twostage decision-making optimization model on supplier portfolio of crucial parts is established by addressing economy of quality within warranty period.This model consists of two steps,including FVIKOR-based primary selection and nonlinear integer multi-objective programming model-based portfolio selection.In the first stage,the extended fuzzy VIKOR with respect to qualitative criteria is used to determine the supplier candidate set.Then,the RPN value is modified to calculate the relative importance of part by concerning the nonlinear characteristics of severity of part failure.At the second stage,the nonlinear multi-objective optimization programming model is formulated concerning total quality related cost,system reliability,delivery time and customer complaint attributes.To improve the search efficiency,the local serach strategy is embedded into adaptive genetic algorithm.And the hybrid adaptive genetic algorithm(HAGA)is designed to solve this complex problem,which help domestic auto factory to achieve quality improvement by systematic optimization method in the next manufacturing cycle.In summary,this dissertation perfoms researches on the key problems of quality improvement from the viewpoint of crucial parts,which enriches the theories and methods related to quality manamgent area,and provides guidance on quality improvement practice of domestic vehicle products.