The Research On Improving The Qualified Rate Of Finish Boring Valve Guide And Seat Ring In ZQ Company

The cylinder head is one of the important parts of the engine, and finish boring valve guide and seat ring is the key process to manufacture the cylinder cover. The machining accuracy has a significant effect on the power and performance of diesel engine. When the engine works, the valve open and close periodically and constantly, make reciprocating motion and repeated shocks seat in the valve guide, so the valve, valve guide and seat ring is one of the most severe conditions of friction in the engine. At the same time, the seat must withstand the periodical heat load and mechanical load, which requires the valve seat conical surface has high sealing performance, otherwise it will lead to reduction of engine power.At present, the qualified rate of finish boring valve guide and seat ring in ZQ company is about95%, after many times of repair the qualified rate is about97%. As a resulting, milling seat groove, pulling the seat, press out the valve guide, repressing valve guide and seat ring, second finish boring, the abandonment of finished products valve guide and seat ring, it’s not only a waste of human source but also caused losses on scrapping parts and cylinder head. This paper researches on the qualified rate of finish boring valve guide and seat ring. Some processing technology at home and abroad about finish boring valve guide and seat ring are analyzed and compared, and find out the factors influencing the machining accuracy before the guide hole and the valve seat hole. Based on the actual cylinder head machining line through the investigation and analysis in this paper, using a variety of tools for quality management, starting from the cutting tools, tooling, gages, management and front process, finally finds out the finishing guide hole verticality deviation has a significant impact on the seat machining; the parallelism of milling surface and bottom has a significant impact on seat jumping overproof.The significance of this thesis lies in the basic research of various quality management tools, integration of theory with practice, this thesis improves the qualified rate of finish boring valve guide and seat ring, reduce the repairing cost and scrap.This paper introduces the whole process of improving the qualified rate of finish boring valve guide and seat ring, follow the scientific, practical and operational principle, on how to apply the various quality management tools to improve the quality of the products and research. Based on the theory of numerous quality management tools and methods, using the classical DMAIC flow, problem definition, measurement, analysis and solve the problems, and finally control problems.In the structure of the paper, the systematic and the level combine together. In the process of analysis, the qualitative and the quantitative combine together. In the theory and method, choice of comprehensive utilization of various quality management methods, including statistical process control, project management, six sigma, and strive through the organic combination of various quality management theory to solve practical problems.