Reducing Recurring Defects from 40%: How an Automotive Supplier Stopped OEM Complaints

Quality · 3 min read · 12.08.2026

Client

The client is a medium-sized automotive supply company (a Tier-2 supplier of welded assemblies). The plant operates a continuous three-shift operation and employs 320 people. Although the company was profitable, the pressure from OEM manufacturers regarding quality was growing. The initiator of the changes was the Quality Director. He was looking for an external partner to change the process setup to stop the impending loss of a key contract.

This text is an anonymized composite case study. It reflects our experiences from multiple projects in this segment. The goal is to protect our partners' trade secrets and demonstrate working solutions.

Challenge

The number of customer complaints from the welding shop had been growing for three consecutive quarters. The PPM rate increased from 12 to 31. The OEM customer sent an official warning with the threat of escalation to CS2 (Controlled Shipping 2) status. This would mean mandatory 100% inspection of parts by an external company at the supplier's expense.

Another issue was the internal illusion of resolution. Teams were closing 8D reports formally just to satisfy administrative requirements. The documentation contained generic conclusions like “operator error” without in-depth analysis. The same defects were returning to production within as little as eight weeks. The rate of recurring defects exceeded 40 percent.

Approach

Instead of generating more paperwork, we went to the line. We proceeded in four steps:

1. Shop floor audit. We started in production. We observed the welding process, measured real machine parameters, and monitored operators across all three shifts. We identified critical points with deviations from the standard.
2. 8D methodology reset. We facilitated workshops for supervisors and quality staff. Instead of filling out forms, we trained the 5 Whys technique directly on actual defective parts. The goal was to find the systemic root cause, not to blame the operator.
3. Verification of corrective actions. We stopped accepting desk-based solutions. We tested every proposed action on the welding lines with measurable targets. We tracked the real impact of parameter adjustments on the number of defective welds.
4. Implementation of new standards. We translated verified procedures into clear work instructions. We introduced daily short meetings at the line. Operators were given the mandate to stop production upon detecting an anomaly, even before a complaint arises.

Results

The change in approach stabilized the process. The quality team stopped being just a department handling complaints and became a partner to production.

• Customer complaints dropped from 31 PPM to less than 10 PPM within the first six months.
• The rate of recurring defects in the welding shop was reduced from 40% to less than 10%.
• Following a verification audit, the OEM customer completely lifted the CS2 escalation status.

The company avoided the costs of external sorting inspection. Machine capacities were freed up because we stopped manufacturing and scrapping hundreds of defective parts. Corrective 8D reports now serve as an internal knowledge database for new technological challenges.

Solving the crisis was the first step towards stabilizing the company. The next logical step is the systematic elimination of waste. Take a look at our approach to cost reduction.

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