Research On Quality Improvement Of Product A In M Company

The auto parts industry is becoming increasingly competitive,and OEMs have more and more strict requirements to their suppliers,so the enterprise takes the pursuit of small product quality to total quality management as its strategy,and brings zero defect into the quality management culture of the company.At the same time,Six Sigma theories is introduced to reduce unqualified quality cost,reduce waste,improve enterprise management ability and competitiveness.In this thesis,the expansion tank of product A in M company as an example,through quality management tools and six sigma method to study the process quality optimization and improvement.Firstly view the chart of First Passs Yield of product A,and the chart was included welding&assembly process and its two main parts(uppler and lower)of injection process,their actual data was lower than their target 99.5%,and then use the Pareto Chart to find out the main problem with 80%failure of their each process:barcode error happened to welding&assembly process,air bubble appearing of upper part and warping deformation of welding surface of lower part in their injection process.For the above three failures,the tools and method was used to analysis and find the failure cause by fault tree(FTA),process failure modes and effects analysis(PFMEA),fishbone diagram and causal matrix(C&E),Design of Experiments(DOE)respectively.The detailed research contents and conclusions are as follows:(1)Barcode error happened to welding&assembly process:The failure tree(FTA)was used to analyze the main potential failure causes of barcode error.These failure causes were input to PFMEA for re-evaluation and analysis.According to the detection degree of PFMEA standard,using "source detection" of level 3 was prioritized:barcode automatic identification device.At the same time also take other management action plan,and finally 100%compliance of the barcode is ensured to delivery into production line without any rework and scrap.(2)Air bubbles appearing of upper part in injection process:Check equipment,injection molding process,material and mold from these four area by fishbone diagram to find potential failure causes,and then defined 3 failure modes(y)according to the location of air bubbles,to identify 80%potential failure cause with main factors through cause matrix(C&E),and then implement corrective action plan.In the end,the defective products were significantly controlled,and the process stability and FPY were improved.(3)Warping deformation of welding surface of lower part in injection process:Use fishbone diagram to analysis and find seven process parameters in injection process,and then identified the three significant factors by DOE,they were cooling time,injection pressure and holding time.And find the best process matching parameters with DOE,and finally the warping deformation was controlled within size range,and also to meet customer’s CPK requirement of key dimensions.At the same time,in order to ensure the continuous stability of the process,using layered audit(CQI-8),process audit(VDA6.3)and molding system assessment(CQI-23)to continuously strengthen manufacturing process control and pursue continuous improvement,they provide the most powerful assurance.M company has successfully applied quality management tools and Six Sigma method,We hope that they can apply to other production lines and products by sharing this successful experience,and also it can be learned to other enterprises in the same industry.