SPC

Watching the process

A control chart plots a measurement over time against limits set by the process itself. Move the process and add a special cause to see what the chart shows.

SPC separates normal noise (common cause) from something that changed (special cause).

CAPABILITY

Cp and Cpk

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C_p = (USL − LSL) / 6σ How narrow the spread is compared with the spec window

C_pk = min(USL − μ, μ − LSL) / 3σ Also penalizes a process that isn't centred

1.0 Barely capable: some parts will fall outside spec

1.33 A common minimum target

1.67 Typical for critical or automotive parts

Cpk answers one question: how comfortably does this process fit inside its spec?

ROOT-CAUSE TOOLS

From symptom to cause

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Pareto chart Scrap causes sorted largest first: attack the biggest bar

Fishbone Possible causes under Man, Machine, Method, Material, Measurement and Mother Nature

5 Whys Keep asking why until you reach a cause you can fix

8D Eight disciplines: a team problem-solving report many customers require

FMEA Score each failure mode for severity, occurrence and detection; fix the riskiest first

The tools are simple; the discipline is using them on data instead of hunches.

GAME

Fix a yield problem

Hipot failures have jumped on one line. Put the problem-solving steps in order.

Contain first, find the cause with data, fix it, prove it with SPC, then lock it in.

VALIDATION AND STANDARDS

Proving it, and writing it down

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IQ Installation qualification: installed right, calibrated, documented

OQ Operational qualification: works across its whole operating range

PQ Performance qualification: makes good parts consistently in production

ISO 9001 Quality management: documented processes, records, calibration, CAPA, audits

AS9100 ISO 9001 plus aerospace and defence extras like traceability and first-article inspection

"Say what you do, do what you say, prove it with records, and keep improving."

UNIT 11 STUDY COMPLETE

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Ready for the Fab Challenge?

You've used SPC and Cpk, walked through root-cause tools, and seen how equipment and quality systems are validated.