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一、控制图的概念1、控制图——是对过程/工序的质量特性值进行测定、记录、评估,从而分析和判断过程/工序是否处于控制状态的一种使用的带有控制界线的并按时间顺序进行描点的图。2、控制图原理——“±3σ”原理当生产过程/工序处于控制状态(即只有正常波动的稳定状态)时,产品总体的质量特性值数据的分布一般服从正态分布规律。从正态分布的性质可知,产品质量特性值落在μ±3σ范围内的概率为99.73%,落在μ±3σ范围之外的概率为0.27%;而超出一侧,即落在大于μ+3σ或
First, the concept of control charts 1, the control chart - is the process / process quality characteristics of the value measured, recorded, evaluated to analyze and determine the process / process is in control of the use of a controlled boundary and Chronological order of the plot. 2. Principle of Control Chart - “± 3σ” Principle When the production process / process is under control (that is, only the stable state with normal fluctuation), the distribution of the overall quality characteristic value data of the product generally obeys the normal distribution law. From the nature of the normal distribution, the probability of the product quality characteristic falling within the range of μ ± 3σ is 99.73% and the probability falling outside the range of μ ± 3σ is 0.27%; while exceeding one side, ie, falling below the range of μ + 3σ or