Gottapu Mohan Rao

Mr Ramesh rised good point on acceptance level. Customer wants zero defect products. Selecting sample plan based on AQL means, supplier or inspector who is accepting the material based on sample plan is 95% confidence the accepted lot of material have rejected material which is lessthan the % of AQL. It means the accepted material is not zero defect. The only one way to confirm the zero defect is 100% inspection. But it is not possible practically to inspect 100% in all products / components at final inspection of supplier or inward inspection of customer. So, Customer and supplier should have common agrement on AQL level. Marketing people may be not accepts this but fact.

Hai all Impact of the tolerance setting definitely effects on product cost Also getting six sigma levels with tight tolerance too difficult - no doubt. But, Designer can identify must be qualities and AQ and circulate to manufacturing. No problem for critical parameters, he can fix tight tolerances as per requirement . For non critical parameters how can fix the tolerance ? Tight tolerance is a subjective. Tolerance tight or widen depends on selected process and process capability not depends on product. Designer calculates parameters & tolerances based on product functional requirement. Not on process capabilities. So, By default, Some times designers give narrow tolerance. If the designer is the responsible for the process cost, Quality cost and product cost, they will estimate tolerances rightly and release the product. Right design with right process selection definitely gives good sigma level output. Thanks & Rds