Research On Production Process Quality Improvement Of Company M Based On SPC/DOE

Rework,as a key element affecting quality cost,has always been one of the critical process quality issues to be controlled,especially in the auto parts industry which is dominated by the production model of multi-variety and small-batch.At the moment for the peculiarity of many production shift and small production number,under the circumstance that applying traditional quality management methods has little effect,employing high-precision measuring equipment as a post inspection measure is one of the main quality management methods.However,this can only ensure that the non-conforming products do not flow to customers,only provide a determination whether the product is qualified.Very little effect is produced on the control and improvement of process itself,especially for rework problem which has high demand on process capability of each process.Therefore,the rework problem solving should be still focused on the usage of quality management methods which suitable for production model of multi-variety and small-batch,and be solved by controlling and improving the stability of all processes.Based on the analysis of a project in Company M,this dissertation concludes that the main reason leading to rework is the instability of the previous processes,and further analyzes that this is caused by failing to effectively monitor the process at the development stage,insufficient process monitoring capability in mass production stage and complex parameter setting in the case of multiple quality objectives.According to the various features and circumstances of these problems,referring to numerous suitable methods and theories,the following methods can be used to improve this rework problem.Firstly,the Q chart would be used to effectively monitor the process in the development stage in case of little data could be used.Secondly,the Exponentially Weighted Moving-Average chart(EWMA chart)would be used to sensitively monitor the process in the mass production stage affecting by the production model of multi-variety and small-batch in case of frequent change of production schedule.Thirdly,the Design of Experiment(DOE)would be used to seek the region of optimal parameter for the area with multiple quality requirements in case of only a few tests could be carried.Through verification results after improvement,the stability of the process has been significantly improved,therefore the rework problem must be contained.According to the research and analysis of this dissertation,the comprehensive application of quality management tools(Q chart,EWMA chart and DOE methods)can not only improve the rework problem of Company M,but also effectively enhance the process management capability towards other projects.The result of this dissertation has reference value to the quality improvement of other similar manufacturing enterprises.