Research On Quality Improvement Of The Carriage In Limited Quantities Based On Six Sigma Management

Six Sigma management method, one important method in the management quality, is aimed at improving the business process and customer satisfaction. Six Sigma management, referred to problem definition, possible factor measurement, ascertainment of factor measurement, improvement of factors and control, is widely applied to improve the management quality. This thesis is based on the Six Sigma management to improve one kind of stage which was produced in our company and to find the necessity of the quality control. Because welding is the most important part in the craft process for the stage, the factors on the welding were analyzed mainly. Finally, the quality of stage was apparently improved by optimizing the welding parameters.In defining process, by means of ensuring the welding problem produced during manufacturing the stage, analyzing the customer demand and the neccesity of improvement, it was indicated that the improvement of the stage is neccesary. And the reason was as following:1) the production improvement was closely related to the customer demand; 2) the production improvement can make the cost decline and make the profits raise. In measuring process, firstly we painted the welding flow diagram, subsequently nine factors was obtained by Pareto and FMEA methor based on the present production, and finally four main factors was decided by excluding three under-controlling factors, utilizing twin-poisson analyze on the welding parameter and analysis of regression on the groove. The main factors were welding electricity, gas flow rate, welding voltage and groove. In improving process, we obtained the optimum best parameters of the four factors above by using center composite designing calculation, parameter surface diagram and so on. In controlling process, we confirmed the best design by analizing the capacity of optimizing parameter and predicting the ability of controll on the process.Through the implementation of Six Sigma, penetrate Six Sigma management philosophy into the whole quality improvement process, the suitable parameters for the welding process of the stage is obtained, as a result, the quality of stage is improved apparently. The defect rate of stage is declined from 1.6 to 0.4, and the one-off acceptance and qualification ratio is improved from 10% to 60%, finally the quality cost decreased by 185 million RMB. Furthermore, because of the success of project, we find a new way to improve the manufacture quality for the company.