Lesson 12 Key Concepts by milky shakee

PROCESS CAPABILITY ANALYSIS

milkyshakeezz — 2023-08-12 02:31:55 UTC

milkyshakeezz — 2023-08-12 02:34:32 UTC

A process that is able to produce output that meets specifications.
Almost 100% of the output from the process is within specifications.
If process is in control but fails to meet specification requirements --> Process needs to be improved or re-designed.

milkyshakeezz — 2023-08-12 02:36:32 UTC

Shift mean to the center

milkyshakeezz — 2023-08-12 02:37:02 UTC

Reduce the variation [StDev] of the process

milkyshakeezz — 2023-08-12 02:39:15 UTC

Statistical measurement of a process's ability to produce parts within customer's specification limits on a consistent basis.
Measured by capability indices such as Cp, Cpk, Pp, Ppk.

milkyshakeezz — 2023-08-12 02:43:39 UTC

milkyshakeezz — 2023-08-12 02:46:45 UTC

Refers to the consistency of the process with respect to important process characteristics.
If consistent over time, process is stable.

milkyshakeezz — 2023-08-12 02:48:02 UTC

milkyshakeezz — 2023-08-12 02:50:08 UTC

Process capability index is a statistical measure of process capability.
Process capability indices measure how much "natural variation" a process experiences relative to its specification limits.

milkyshakeezz — 2023-08-12 02:52:39 UTC

milkyshakeezz — 2023-08-12 02:57:52 UTC

milkyshakeezz — 2023-08-12 03:00:31 UTC

Cp or Pp index compares the allowable spread [USL-LSL] against the process spread [6 sigma].
However, they fail to take into account if the process is centered between the specification limits.

milkyshakeezz — 2023-08-12 03:01:08 UTC

milkyshakeezz — 2023-08-12 03:06:50 UTC

There are chances that data points lie between the specification limits but are far from the target.
Necessary to calculate how far off the target is.
Cpk and Ppk account of the centering of the process -- Indicate shifting or closeness of process average from the target or mean value.

milkyshakeezz — 2023-08-12 03:07:46 UTC

milkyshakeezz — 2023-08-12 03:10:40 UTC

milkyshakeezz — 2023-08-12 03:13:15 UTC

milkyshakeezz — 2023-08-12 03:16:01 UTC

Cp and Pp will always be greater than Cpk and Ppk, respectively.
Cpk > 1: Process will mostly produce output that is within the specification limit, larger Cpk is, the better.
Cpk < 1: Process will produce output that is outside the customer specification limits.