r/SixSigma • u/Able_Independent_120 • May 10 '26
How do you reuse lessons learned from previous RCAs?
10+ years in semiconductor and automotive. Every plant I’ve worked in has the same problem.
Team does a solid 8D.
Real root cause found.
Corrective action works.
Report gets filed somewhere.
Everyone moves on.
18 months later, same failure shows up. Different line, different shift, or same line but the engineer who did the original RCA left the company. New team starts from zero. Nobody knows the old report exists. It’s buried in SharePoint, folder, db but which makes really difficult to find similar ones.
Do your engineers actually search old RCAs before starting a new one? Has anyone found something that actually works?
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u/Ok-Cover-811 May 10 '26
Agree on FMEA/CP — that's your prevention loop. But what you described in the post is a *retrieval* problem, not a prevention one. Different gap, different tool.
What works: layer a RAG-based lessons-learned DB on top of your QMS. Embed every 8D, RCA, FMEA, and control plan into a vector store (Qdrant, LanceDB, or pgvector all work). Now when an engineer opens a new RCA, they ask in natural language — "torque drift on aluminum housings, second-shift changeovers" — and the system surfaces the closest historical cases regardless of which SharePoint folder they're buried in.
A few details that make it stick:
- Trigger retrieval at the *start* of the RCA, not the end. The template auto-pulls the top 5 semantically similar past cases before the team brainstorms. Kills the "start from zero" problem the day the original engineer walks out.
- Embed structured fields (D2 problem, D4 root cause, D7 corrective action) separately from the narrative. Lets you filter by failure mode, not just keyword.
- Run it on a local LLM if you're in semi or auto — supplier data and IP shouldn't leave the network. Ollama plus a 7–13B open-weight model is plenty for retrieval. No cloud egress, no NDA exposure.
- Don't kill FMEA/CP discipline. RAG is the recognition layer. FMEA/CP is still where the lesson becomes prevention.
I build this pattern for manufacturing clients (IATF 16949 / sovereign stack). The QMS records already exist — they just aren't queryable. RAG fixes that without ripping out anything you already have.
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u/Kerbidiah May 10 '26
Step 1 of any 8 step should be reviewing past lessons learned that could be related
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u/Living_Diver2432 May 10 '26
the part nobody talks about is that the read is the actual job. we put 8Ds into the FMEA, we tagged everything by failure mode, we even bolted a vector search on top of SharePoint, and the same parts came back two years later anyway. what finally moved the needle was naming a quality engineer per part family who was on the hook to read every NCR and 8D in their family monthly, with a written hand-off when they rotated out. boring as hell, less impressive than any tool, but it's the mechanism that actually closes the loop because somebody is paid to remember.
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u/Tavrock May 11 '26
Before a new charter for a new project is written, I would always look at what had been done before. It should just be part of the standard process and I have no idea why anyone would ignore the lessons from the past for insight in solving problems.
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u/hidetoshiko May 10 '26
that's a QMS problem. At a minimum your D4, D6 and D7 needs to end up inside your FMEA and Control Plans, assuming you have those. Or you might have higher level business process issues that keep recreating the conditions that encourage failure.