Measure Capability Analysis Dedy Sugiarto 1 Capability Analysis

Measure : Capability Analysis Dedy Sugiarto 1

Capability Analysis (The Concept) v Process capability examines: – The variability in process characteristics. – Whether the process is capable of producing products which conform to specifications. v Process capability studies distinguish between conformance to control limits and conformance to specification limits (also called tolerance limits). 2

Capability Analysis (The Concept) v If the process mean is in control then virtually all points will remain within control limits. v Staying within control limits does not necessarily mean that specification limits are satisfied. v Specification limits usually dictated by customers. 3

Capability Analysis (The Indices) • Cp < 1 (Process is unsatisfactory). Potential Capability Index • 1 < Cp < 1, 33 (Process is of medium relative capability). • Cp > 1, 33 (Process show high relative capability). • This index show well a process is able to meet specifications. • The higher the value of the index mean the more capable is the process. 4

Capability Analysis (The Indices) • If Cp = Cpk (Process is centered at the midpoint of the specifications). Actual Capability Index • Cpk < Cp (Process is offcenter). This index takes process centering into account! 5

Capability Analysis (The Conclusion) v The message from process capability studies: – First reduce the variation in the process. – Then shift the mean of the process towards the target. 6