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Process Capability - Coggle Diagram
Process Capability
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Process Capability Index
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A capable process is not necessarily in the center of the specification, but it falls within the specification limit at both extremes
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Acceptance Sampling
Take samples at random from a lot (shipment) of items
- Inspect each of the items in the sample
- Decide whether to reject the whole lot based on the inspection results
- Only screens lots; does not drive quality improvement
Rejected lots can be:
- Returned to the supplier
- Culler for defectives (100% inspection)
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AQL and LTPD
Acceptable Quality Level (AQL)
- Poorest level of quality we are willing to accept
Lot Tolerance Percent Defective (LTPD)
- Quality level we consider bad
- Consumer (buyer) does not want to accept lots with more defects than LTPD
Average Outgoing Quality
AOQ = (Pd)(Pa)(N - n) / N
where
Pd = true percent defective of the lot
Pa = probability of accepting the lot
N = number of items in the lot
n = number of items in the sample
- If a sampling plan replaces all defectives
-If we know the incoming percent defective for the lot
The maximum AOQ is the highest percent defective or the lowest average quality and is called the average outgoing quality level (AOQL)
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Automated Inspection
- Modern technologies allow virtually 100% inspection at minimal costs
- Not suitable for all situations
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