A) A Cpk index value of 1 is the highest possible. Capability analysis uses measures like Cp, Cpk, Pp, Ppk to determine the process capability. The Cp & Cpk calculation is based on the process mean & range and has nothing to do with how many points are in or out of spec. Uploaded by: jayewilson93 Top Answer b . c. The Cpk index can only be used when the process centerline is also the specification centerline. In actual practice, this shouldn't happen very often. Also, the further the mean moves away from the middle of the specification limits, the more different Cp and Cpk become. PDF Making Sense of Accuracy, Repeatability and Specification ... 6205-2RSH/VA947 - Deep groove ball bearings | SKF d. Positive values of the Cpk index are good; negative values are bad. The Six Sigma approach is a data-driven approach to problem-solving. D. Positive values of the Cpk index are good; negative values are bad. Specifications or requirements are the . SUPPLEMENT 6: STATISTICAL PROCESS CONTROL Flashcards | Quizlet This mean is about 5 units higher than the midpoint of the specification limits. specification limits then the difference between the Upper specification (U) and Lower specification (L) should be larger than 6σ. Cpk is calculated using the specification limits, standard deviation or sigma, and the mean value. 8. If the Cpk index exceeds 1 a. the AQL must be smaller than the LTPD ISDS Exam 2 Chapter S6 Flashcards | Quizlet Difference between Cp, Cpk and Pp, Ppk [Potential] Process Capability Analysis (Cp, Cpk): A process capability study uses data from a sample to PREDICT the ability of a manufacturing process to produce parts conforming to specifications. Answer the following questions for these characteristics. Therefore, the within and overall standard deviations are similar, which means Cpk and Ppk are similar, too (at 1.13 and 1.07, respectively). The STC will meet annually in April to determine the ST schedule for the following year. A high Cpk index means, then, that you have a good process with a small spread in relation to the tolerance width, and also that it is well centred within that width. Only infinitely large sample size can give us 100% confidence that our measurement coincide with the true value. A: Shift the mean to center the process between the specs, without increasing the variation. Cpk is the minimum of: (57-48)/4.5 = 2, and (60-57)/4.5 = 0.67 So Cpk is 0.67, indicating that a small percentage of the process output is defective (about 2.3&percnt;). Cpk is the minimum of Cpu and Cpl. size sample Cpk [0126QZ] For these process data, Cpk is 1.09. The CPK data for a weekly sample of 30 in each of the first six is 1.65, 1.58, 1.67. PPM data can be used to indicate areas variation requiring attention. How to Improve Cpk - Minitab A larger standard deviation indicates that a data set has a wider spread around its mean. If Cpk is equal to Cp, the process is set to produce exactly in the middle of the tolerance range (see Fig. Assume that the quality. DPU = number of defects / number of units DPU = 200/1000 = 0.2 DPU = 20% Defects per Million Opportunities (DPMO) DPMO is based on DPO, but in real-world manufacturing type numbers. The Cpk value should be between 1 and 3. Control charts are SPC tools used to plot process output characteristics for both variable and attribute data to show whether a sample falls within the normal range of variation: X-bar, R, P, and C-charts. The Cp & Cpk calculation is based on the process mean & range and has nothing to do with how many points are in or out of spec. The larger the Cpk, the more units meet specifications. The Cpk index can only be used when the process centerline is also the specification centerline. When performing the USP General Chapter <788> Particulate Matter in Injections test for a large volume parenteral (LVP), is it acceptable to take the average among the units tested to determine . Standard shell sizes from 3 inches through 31 inches in diameter; with custom designs up to 60 inches in diameter. Explanation: A process with Cpk of 2.0 (+/- 6 sigma capability), i.e., the process mean is 6 sigma away from the nearest specification can be expected to have no more than 0.002 nonconforming parts per million. The manager is asked to provide CPK data for a specific parameter that is shown to be in control and predictable. The larger the Cpk, the more units meet specifications. Because Cpk less than 1.33, the potential capability of the process does not meet requirements. The larger Cpk is, the less likely it is that any item will be outside the specification limits. 3. e. None of the above is true. The current specifications on the tubing are 0.1340+0.001 inches. D. Positive values of the C pkindex are good; negative values are bad. Without reducing variability, the Cpk could be improved to a maximum 1.33, the Cp value, by centering the process. If Cpk is lower than your benchmark, consider ways to improve your process, such as reducing its variation or shifting its location. (6 Points) Control charts are to be kept on the thickness measurements for the process that produces steel tubing. b. C. The C pkindex can only be used when the process centerline is also the specification centerline. When the mean of the process is outside the customer specification limits the value of Cpk will be Negative Cp & Cpk when a process is stable and Pp & Ppk when a process is new, the way you calculate each are a bit different, too. A high Cpk index means, then, that you have a good process with a small spread in relation to the tolerance width, and also that it is well centred within that width. d. Positive values of the Cpk index are good b. 3. d. 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