Study On Brazing Quality Improvement Of Heat Exchanger In M Company

The quality of the heat exchanger which as the core components of gas water heaters directly affects the production of hot water capacity and the cost of the whole machine.The quality of the heat exchanger is largely dependent on the brazing process.Currently,M company's brazing quality management methods stay in the inspection phase,and process standards are formulated to rely on empirical data.So process control ability is weakness,brazing defect rate as high as 8.41%.In order to effectively improve the quality problem,M company uses Six Sigma management tools and ideas,gradually select the key factors affecting the brazing by the data statistics and analysis.And then improve and optimize the level of the factor finally,to achieve the purpose of reducing the brazing defect rate.In this paper,the heat exchanger brazing quality improvement and optimization process are described in detail in three parts.The concrete analysis and improvement are as follows:The first part focuses on the status of quality problems,there is a large number of mass fluctuations and many abnormal points from the from the P-value control chart,so we need to stabilize manufacturing processes,and then carry out the improvement and optimization.The second part explains the reasons for the volatility,the key factor analysis and the key factor improvement.The process analyzes the source of abnormal fluctuations from two aspects: On the one hand from the measurement system analysis.By analyzing the variability and reproducibility variation of the measurement system,the main source of measurement variation was found,and the variation of the measurement system was reduced from 55.8% to 10%.Another hand is the process capability analysis.By analyzing all the processing capacity of the process,nozzle lack of process capability,is the main source of processing fluctuations.The clamping force,die size,die finish can effectively improve the process capability of nozzle process by IPO analysis and C & E matrix analysis.Using the hypothesis test method,it is verified that the above three factors can improve the processing capacity of the nozzle process.After processing capacity to meet the requirements of all key processes,the brazing defect rate decreased from 5.58% to 0.99%,also,brazing quality fluctuations significantly reduced.The third part describes the key factors to optimize and control.The optimal gap level is determined by comparing the yield,process feasibility,and economy of different gaps.Optimization of the cleaning process Based on the hypothesis test,the analysis of the two levels of non-performing rate of whether there is a significant difference.The analysis of low free alkalinity had no significant difference in the rate of nonunion,so reduce the amount of cleaning agent can achieve the purpose of cleaning process optimization.The temperature is optimized by DOE,we found 2,3,4 heating zone is a significant response area,then use the minitab factor optimizer to find the non-performing rate at 99.9% of the temperature,verify that the factor level is valid and reliable by actual production.Finally,keep the results of the improvement before standardization,training staff about standard content and Establish SPC monitoring mechanism,So that the improvement effect can be maintained.