This paper addresses a systematic and scientific tolerance design method-six sigma tolerance design. First a specifically quantified goal is determined for tolerance design with an assembly case analysis to show how six sigma is designed into the product. The design and optimized flow is put forward. This method leads to a set of design principles and practices which are embodied in the thinking of concurrent engineering (CE). The philosophy underlying design for manufacturability (DFM) finds expression in CE. Six sigma tolerance design provides a way to achieve six sigma quality and beyond. It is the result of requirements for higher quality product at lower costs.

Continuous quality improvement is now the focus of research and application in quality engineering. To achieve continuous improvement, it's necessary to integrate quality tools and to plan, design and control the whole process of creating quality. Based on the extensive literature review and the philosophy of concurrent quality engineering, the paper analyzes the relationships among major quality tools such as QFD, FMEA, DOE and SPC and presents a basic model and structure for the integration of quality tools.

保持测量系统的稳定性是质量控制的重要内容之一。本文在分析了累计和控制图和传统休哈特控制图的基础上，指出了传统休哈特控制图的不足，提出将累计和控制图应用于测量系统稳定性的控制。理论研究和案例分析均表明，当测量系统引起的被测质量特征值的均值发生小幅度偏移时，用累计和控制图比休哈特控制图更有效。

本文在大量调研的基础上，对我国制造业质量管理现状进行了分析，剖析了当前我国制造业质量管理中的主要问题及其原因，提出了提高我国制造业质量管理水平的策略。对我国制造业质量管理水平的提高具有现实意义。

How to continuously improve product and process quality has been a focus of research in quality management. A company that is going to set up its CAQ or establish an effective quality system should make sure that the CAQ or quality system will lead to continuous quality improvement so as to meet customer's growing demand for quality. Based on Juran's quality loop philosophy, the paper presents how to utilize continuous quality improvement tools in product design and manufacturing. It addresses the application of QFD and design of experiment to optimize product/process design and how to integrate quality tools. Based on the philosophy of concurrent quality engineering and successful experience of some world class businesses, the paper presents a continuous quality improvement flowchart and puts forward to the strategies to implement continuous quality improvement.