Project Background
One of the key products of an energy company had a rolled throughput yield of 92% .The cost of rework for this product was €111 per unit or €107,000 per year. A new cable power reliability product family was designed to replace the existing product in USA, Brazil & Europe but the rolled through put yield of the new product was only 71% damaging reputation and market penetration.
Problem
The RTY for the new product was 71%. Initial power up test failures were running at 21% costing €438,000 p.a. The Black Belt discovered excess variation in the connection fitting sequence during test setup giving rise to false failures – the company was failing good units. However, the Black Belt also discovered damaged or poor condition test cables. The company was unable to test using a small auxiliary transformer at test stage as wires were not connectable, wires were incorrectly fitted and crystals were blowing on test due tolerance stack up on capacitor and resistors.
Solution
A cross functional team was set up of people involved with the design, parts procurement and production of the product. After mapping the process, noting the data capture points using extensive FMEA and process capability analysis the team modified the test software to guide operator through correct setup procedure. A TPM system was set up on test carts for test cables and computerised checking of cable condition. In-process testing was introduced for the small auxiliary transformer. The product was poka-yoked with re-designed wiring harness and connectors so they can only fit one way.
A new specification capacitor and resistor was fitted to the crystal circuit.
Business Benefits
RTY was increased from 71% to 80% by reducing initial power up test failures. Failure costs were reduced by €135,000. Design changes at a supplier were needed and a second successful Six Sigma project was set up to address supplier related yield issues.
