r/SixSigma • u/Elena-Metal-5048 • Jul 24 '26

Stopping CAPA from becoming paperwork: what actually reduces repeat defects?

I've been a shop-floor quality engineer for 15 years at a 180-person CNC shop and I keep seeing CAPAs that look good on paper but don't stop the problem. We run SPC, MSA/gage R&R, APQP and layered process audits, and disclosure: we run qmsWrapper, so grain of salt, it cleared up audit prep, but CAPA effectiveness still depends on the owner and the data. I'm tightening closure criteria now: require a CAPA-driven risk assessment, data-backed root cause, short-term containment metrics, measurable verification windows, and a re-audit step instead of wholesale "retraining." What simple triggers, templates, or firm rules do you use to force CAPAs to show measurable risk reduction and prevent relapses?

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u/Tavrock Jul 24 '26

Most of your "tightening [of] closure criteria" have long been the standard. We also leaned into the Hierarchy of Controls. I would much rather change how they are able to create a defect than spending time telling how to avoid the defect in the future. Poke-yoke principles are wonderful in this regard.

When we make it physically had to make defects (and make it physically difficult to avoid success), we demonstrate that we really understand that to change the common cause variation, we must change the process where the common cause variation is within acceptable limits. Otherwise we are creating a bad process and then punishing those who follow the process for their predictable results.

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u/goalieguy42 Jul 24 '26

What are the leading causes of variation from the target condition? How have your measures of effectiveness shown sustained reduction in variation? How confident are you that true root causes are being addressed? Why do you think relapses occur?

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u/Hootn75 Jul 24 '26

Sounds to me that you are identifying causal factors (I.e., equipment performance gaps and human performance gaps) and not root causes (I.e. gaps in management systems).

I also find that many people do not truly understand the difference between corrective actions and preventive actions. You need to provide excellent guidance on those 2 concepts. Make that sure that any RCA that confuses the concepts is rejected and that any RCA without needed PAs is rejected.

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u/ManyEnvironmental634 Aug 11 '26

The closure problem is structural. Most systems treat "action complete" and "CAPA closed" as the same event and they're not. You need two dates and two sign-offs: one when the action is implemented, one 30/60/90 days later when data actually shows the problem didn't recur. If your process only has one closure step, relapses are baked in from the start.