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Newsletter 2006 issue 3 |
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Dubious Defects
The Lean Manufacturing Consortium (LMC) contends that the true cost of poor quality is usually underestimated. Defects can involve wasted labor, machine hours and time delays, but often only the cost of wasted raw materials is accounted for. To illustrate its point, LMC calculated the defect cost of a bent flange in window manufacturing—$135 in lost raw materials grew to $2,673 when hidden costs were included.
Finding the root cause of defects and tracking defect data over time can make operations more effective and profitable.
Understanding
Comparing your situation to how a process should work can offer clues to sources of defects. A fiberglass fabricator was having trouble getting OEM specified low-HAP (hazardous air pollutants) resins to work at his facility. After repeated failures, the owner probed the OEM about how it was able to get the resin to work. He learned that the OEM was adding solvent (the HAPs) to make it flow better!
Analysis
Many shops don’t have the process scale or mathematical training for applying the statistical analysis of Six Sigma. But with good data collection, you can identify weaknesses in your operations, from inadequate personnel training to poor-quality incoming materials. Keep a record of defects, recording type of defect and associated costs.
An Aberdeen Group study found that manufacturers who monitored DPMOs (defects per million opportunities) produced the best results (99.9 percent good quality), better than those that measured percentage of defects (94 to 96 percent good quality), rolled throughput or first-pass yield.
Whether you’re trying to eliminate micro solder balls on circuit board assemblies, poor thermoplastic butt-weld integrity or gas porosity in castings, tracking defects can help you pinpoint—and prevent—their causes.
What Do Defects Really Cost? This Lean Manufacturing Consortium document traces a simple defect through the manufacturing process at a window plant. At each point, the costs of wasted time and material are calculated.
The Lean Six Sigma Benchmark Report Aberdeen Group study on companies practicing Six Sigma.
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