Question

Calculating process sigma for multiple steps: Opportunity-based method and Throughtput method .Explain them on the example.

Answer 1

Opportunity based method can be said as the defect per opportunity (DPO) which have 5 steps of calculating process sigma:-

DPO calculation – Step 1

determine the total number of units to be sampled.

DPO calculation – Step 2

determine the number of defect opportunities per unit.

DPO calculation – Step 3

determine the total number of defect opportunities ONLY for the sample size under consideration.

DPO calculation – Step 4

count the defective opportunities within the sample group.

DPO calculation – Step 5

divide the total number of defects by the total opportunities only for the sample size under consideration.

DPO:- It is the ratio of the number of defects in a sample to the total number of defect opportunities.

Throughput method:- This approach called Enhanced Rolled Throughput Yield (ERTY), unlike other methods, pays particular attention to such factors as the difference between scrap and rework cycles, the cost of scrap and rework and the sequence of stages.

● Throughput yield is calculated by multiplying yields of each process step. It is first necessary to calculate the yield of each process step. We can estimate the yield of a process step by dividing units accepted by the number of units produced for that step.

Moreover, the this approach is able to cover all other methods.

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