Process Capability(工程能力).pptVIP

How to perform a PCS 4. Performing the PCS 5) Process Capability Measurement- Method Ⅱ Use of the Range to estimate σc The difference in the measurement between each pair gives a value called Range (R). Calculate the average Range (R ) of the 50 pairs. Estimate the standard deviation of the process’s capability(σc) as: R R σc = ― = d? 1.128 How to perform a PCS 4. Performing the PCS 5) Process Capability Measurement- Method Ⅱ Use of the Range to estimate σc Assure that each R collected was in control. Do this by calculating and upper control limit on the individual R’s by UCL =D?R = 3.268R If any range value is greater than 3.268R, discard this value, re calculate R and repeat procedure. How to perform a PCS 4. Performing the PCS 5) Process Capability Measurement- Method Ⅱ x and σh Obtain the average( x ) and the standard deviation( σh) of the process’s history by using all the individual measurements and calculating the average and the standard deviation in the conventional manner. How to perform a PCS 4. Performing the PCS 5) Process Capability Measurement- Method Ⅱ σh - Calculation S = √ ∑ ( x – x)2 or S = √ n ∑(x2) – (∑x)2 n – 1 n (n – 1) S: sample standard deviation ∑: sum of x: observed values x: arithmetic mean n: number of observations How to interpret a PCS 1. Drawing Conclusions 1) Interpreting the results of a PCS Process Capability ( ) x ( ) current capability x ± 3 σc x ± 3 σh typical history Product A Requirement Capable B most likely capital $