Cpk vs ppk 1.335/30/2023 ![]() What is the difference between Cp, Cpk and Ppk?Ĭp and Cpk are used for short term studies. ![]() A process that is running at six standard deviations or six-sigma has a process capability of 2.0 and a defect rate of only 3 defects per million units produced. So a process that is running at 3 standard deviations has a process capability of 1.0 and a defect rate of 67,000 per million units produced. When the process is centered to the specs and the process isn’t shifting all over the place, then Cp, Cpk and Ppk will all be very close numbers and each standard deviation represents 0.33 Cp, Cpk and Ppk.Īt a high-level each standard deviation represents 0.33 in your process capability model. If a process is centered and there are no shifts or drifts in the process due to assignable causes, then there is an easy connection between standard deviation and each of the three process capability measures. Each of these measures are related to standard deviation so if you understand how process variation is measured using the standard deviation then you can easily understand the three main measurements used in process capability studies. The three main measurements used in a process capability study are Cp. Measuring and understanding process variation is the first step in process improvement. Processes variation is a fact of life in a plant. Understanding process capability is essential for factory leaders at all levels.
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