Question

For a key joint, a precision machining process has a lower specification limit of a width of 0.99 mm and an upper specification limit of 1.01 mm. The standard deviation is 0.005 mm and the mean is 1 mm.

(a) What is the process capability index for the bottle filling process? (Round the answer to 3 decimal places.)

(b) The company now wants to reduce its defect probability and operate a “six sigma process.” To what level would they have to reduce the standard deviation in the process to meet this target? (Round the answer to 5 decimal places.)

Answer 1

Process capacity index is nothing but the statistical measure of process capacity to identify whether output is produced within customer's specification limits. The standard Cpk level is 2.0 for the six sigma process.

Process capacity is the number of times the process fits into the tolerance width. So, higher the value of Cp, the better the process.