Quality Vs Cost Curve
The notion that cost goes up with quality is often depicted using a quality vs cost curve, also known as a cost-quality tradeoff curve or a cost-performance curve. The shape of the curve can vary depending on the specific industry, product, or service being considered. In some cases, the curve may show a steep incline, indicating that a significant increase in cost is necessary to achieve even a small improvement in quality. In other cases, the curve may be more gradual, suggesting that incremental improvements in quality can be achieved at relatively lower cost increases.
Let me elaborate on the modern quality-cost equation. Manufacturing quality can be improved primarily through three approaches.
100% quality inspection
1st, and the most rudimentary approach to quality, typically, we manufacture a batch, then do a 100% inspection. The sorted out poor quality material is either reject or reworked. This approach, obviously, increase cost.
Periodic sampling inspection
2nd, and a bit more refined approach is to put in place a periodic, on-line sampling inspection system (manual or automated). When a poor-quality sample is detected, 100% inspection is done on the production of the preceding time window, the process is interrupted, adjusted and re-started. While this approach reduces the slope of the curve, it still increases cost. Plus, productivity is impacted due to frequent over adjustments & interruptions to achieve quality goals.
Real-time Statistical Process Control (SPC)
3rd, and the modern scientific approach is to use a real-time / online statistical process control software (like Zometric SPC & process capability Software). This software can analyse “trends” in real-time, predict and alert that something is “going to go wrong”. Not just that, it can also hint at possible causes depending on statistical pattern (or rules), thereby helping reduce down-time and improve productivity. This approach simultaneously helps improve quality, reduce cost of inspection/rejection/rework, and improve delivery/productivity by preventing guesswork based over adjustment and interruptions.
Sounds like Magic?
Yes, it is, until you see it implemented in your or your supplier’s shop floor. Our manufacturing clients are already benefiting. Why shouldn’t you benefit too? Contact us for a free consultation.