40 % Repeat Complaints: How an Automotive Tier 2 Supplier Stopped Closing 8Ds on Paper

Quality · 3 min read · 19.08.2026

Client

An automotive Tier 2 supplier of welded assemblies. 320 employees, three-shift operation, several assembly families for two customers. The company is presented anonymously — this is a composite case study compiled from multiple projects we have delivered in the automotive segment.

One welding line accounted for the largest volume. Both capacity and staffing had long been stretched to the limit, and with three shifts this showed up mainly at shift handovers. Certification and the production regulations were in order. The problem lay elsewhere: in how defects were actually being resolved.

Challenge

Customer complaints from the weld shop had been rising for three consecutive quarters, from 12 PPM to 31 PPM. The OEM customer responded with a notice of threatened escalation to CS2 (controlled shipping level 2). In practice, this would have meant sorting every shipment at the supplier's own expense and expecting frequent audits right in the weld shop. The supplier's rating for future contract awards would have suffered as well.

Worse than the numbers was the fact that the internal system was not working. 8D reports were being closed as a formality: the cause was described, a corrective action was declared, the report was closed. The same defects returned within 8 weeks, and repeats accounted for 40 percent of complaints. Meanwhile, the quality staff spent most of their time rewriting reports rather than working on the shop floor.

Approach

1. Analysis of 12 months of complaints. Together with the quality team, we reviewed all customer complaints and closed 8D reports from the past year. We sorted them by defect type, line and shift. A Pareto analysis showed that three defect types from a single line accounted for more than 60 percent of complaints — and that the causes lay in the process setup, not in insufficient inspection.
2. 8D training on real cases. The two-day training for quality staff, process engineers and foremen did not run on textbook examples. The teams worked on their own open complaints. They learned to distinguish the symptom from the root cause and to build the 5-Why analysis on evidence rather than assumptions. Tasks and deadlines were assigned during the training itself.
3. A root cause verification gate. We introduced a rule: an 8D cannot be closed until the team demonstrates the link between the eliminated cause and the observed defect. We added mandatory fields Cause Verification and Effectiveness Verification to the form. Closure was only confirmed by the quality manager once evidence had been submitted.
4. Effectiveness tracking in series production. Each corrective action was monitored by the foreman of the responsible shift for four to eight weeks using daily data. If the symptom reappeared, the report was reopened with the same team and the original cause — with no option to rewrite it. Statuses were posted on the line's board every day.
5. Monthly review with management. Half an hour, one sheet: PPM, share of repeat defects, open 8Ds. Deviations were addressed, not presentations.

Results

The first shift came after two months — fewer new complaints were recorded than in any month of the previous year. The time to close an 8D lengthened by a few days, but the reports stopped falling apart once a defect returned. After six months:

• Customer complaints fell from 31 PPM to fewer than 10 PPM.
• The share of repeat defects dropped from 40 % to less than 10 %.
• The planned escalation to CS2 was withdrawn following an audit at the OEM customer.

The company invested in neither new welding machines nor additional inspectors. The difference was not made by more inspection, but by discipline in verifying causes. Six months after the project ended, the system was running without a single external intervention — the review is now led by the operations director, 8Ds are coordinated by the quality manager, and the foremen consider effectiveness tracking a routine part of the shift.

Repeat complaints and 8D reports closed as a formality are not an isolated phenomenon. We address them within quality and cost reduction projects — you can find an overview on our services page.

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