非对称偏差下质量特性值分布评价

Evaluation on distribution of measured characteristic with asymmetric tolerances

传统的统计过程控制以公差中心为基准研究质量问题,对基本尺寸未给予足够重视,导致公差为非对称偏差时产品质量测度方法缺乏完善性.对此,以基本尺寸为基准,对非对称偏差下基于正态分布和切段正态分布假设的产品质量水平进行了分析,运用Taguchi质量损失函数对两类分布下产品价值的期望进行比较.结果表明,质量特性值服从切段正态分布的产品质量水平较优,产品价值的期望较高.

The quality of a process or product was studied based on the center of the specification interval in the conventional SPC but on target value, which led to inadequate measure of the quality under the condition of asymmetrical tolerances. In terms of this problem, the quality of a process or product was analyzed based on target value when the process was characterized by normal distribution or piecewise normal distribution. Taguchi quality loss function was applied to describe product value. To compare the process-and product-quality for the measured characteristic with the above two distributions, the expected value of product value was given. Results demonstrate that the quality of a process or product for the measured characteristic with piecewise normal distribution is better than that with normal distribution.