Rebuilding a Plating Line: From 10% to 85% FPY in Four Months
The Problem
When I inherited the nickel/chrome electroplating program, the line was running at approximately 10% first pass yield. Nearly nine in ten parts were failing visual or dimensional inspection. The team had normalized this—rework cycles had become standard operating procedure, and no one had formally mapped what was causing the failures.
Define & Measure
We started by building a defect taxonomy. Over three weeks, every rejected part was logged with defect type, location on part, bath position, operator, shift, and process date. The data revealed something unexpected: defects weren’t random. They clustered in specific rack positions and correlated strongly with bath chemistry drift on the overnight shift.
| Defect Type | Frequency | % of Rejects | Root Cause |
|---|---|---|---|
| Pitting / Nodules | 312 | 41.2% | Bath chemistry / organics |
| Adhesion Failure | 198 | 26.2% | Pre-treatment inadequate |
| Thickness Out-of-Spec | 147 | 19.4% | Current density / rack position |
| Burn / Roughness | 100 | 13.2% | Current density at rack edges |
Analyze & Improve
The pitting and nodule failures pointed directly to organic contamination in the nickel bath. We implemented carbon treatment on a fixed schedule, added real-time pH and temperature monitoring, and set hard limits on when the bath could run without a chemistry verification. The adhesion failures required a complete overhaul of the pre-treatment sequence—adding an ultrasonic cleaning stage and revising the activation dwell time specification.
The rack redesign was the final unlock. Edge-position parts were systematically burning due to current density spikes at rack extremities. We added edge shielding, redesigned the rack geometry, and implemented SPC controls on critical bath parameters before the line ran each shift.
Results
By month four, FPY had reached 85.3% and held. The improvement translated directly to reduced rework labor, less materials waste, and the elimination of a secondary inspection station.
| Month | FPY | Pitting Rate | Adhesion Fail | Key Intervention |
|---|---|---|---|---|
| Baseline | 10.2% | 41.2% | 26.2% | — |
| Month 1 | 28.4% | 22.1% | 26.0% | Carbon treatment schedule |
| Month 2 | 42.1% | 18.4% | 19.3% | Pre-treatment overhaul |
| Month 3 | 67.8% | 9.2% | 8.1% | Rack redesign + edge shielding |
| Month 4 | 85.3% | 4.1% | 3.8% | SPC controls live |