cpk讲义（CPK handouts）.docVIP

cpk讲义（CPK handouts） Cpk - process capability index CPK=, Min[(USL-, Mu), /3s, (Mu - LSL) /3s] Talking about Cpk application 1., Cpk is defined as process capability index, which is a quantitative response of a project or process level, and also a kind of index of Engineering evaluation. 2., the two parameters that are closely related to Cpk: Ca, Cp. Ca: process accuracy. Cp: process precision. 3. Cpk, Ca, Cp three: Cpk = Cp * (1 - Ca), Cpk Ca and Cp neutralization reaction of the two, Ca reaction is position (central tendency), the reaction of Cp is the dispersion relations (discrete trend) 4. when selecting process stations not to use Cpk for control, the primary consideration should be cost considerations, as well as the impact of their quality characteristics on the post process. 5. calculation of sampled data should be at least 20~25 group data, the square has a certain representation. 6., in addition to the collection of sampling data, Cpk should also be aware of the quality specifications of the upper and lower limits (USL, LSL) before they can successfully calculate their value. 7. first of all available Excel of the STDEV function automatically calculates the standard deviation of the sampled data, then calculate (a) (T), and the tolerances for the target value (U). Specification tolerance = upper specification limit - specification limit; SPECIFICATION (center = upper specification limit + specification limit) /2; 8. according to the formula: the accuracy of the process is calculated: Ca value 9. according to formula: Cp =, calculate the process density: Cp value 10. according to formula: Cpk=Cp, calculate process capability index: Cpk value 11. Cpk rating criteria: (accordingly, the standard can be used to calculate the process capability index) A++ Cpk more than 2 excellent can be considered to reduce the cost of A+ 2 Cpk 1.67 and shall keep the A good 1.67, Cpk = 1.33, good ability in stable state, but should try to upgrade to A + level B 1.33 Cpk 1