Quality9 min read
Sampling plans: AQL, zero acceptance and the risk in between
How attribute sampling plans work, what an AQL promises and why a zero acceptance plan moves the risk instead of removing it.
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Topic hub
Quality and inspection
Quality is a set of decisions made before the first part is measured. These guides cover general tolerances, GD&T, first article inspection, PPAP and the records a buyer should expect with a production shipment.
Guides in this topic, page 2
Quality10 min read
Tolerance stack-up analysis: worst case and statistical
How to build a dimension chain, calculate the worst case, apply the statistical method and decide which answer the assembly needs.
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Quality8 min read
Traceability and lot control: from raw material to shipment
How to define a lot, keep the identifiers readable through every process and prove the chain in both directions before a customer asks.
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Quality10 min read
Vision systems and optical inspection: speed, limits and false calls
A camera does not inspect a part; a camera, a lens, a light and a fixture do. How to set up optical inspection that finds real defects without drowning the line in false calls.
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Quality8 min read
Change control for drawings and processes: revisions, approvals and cut-in
A practical route from change request to first new part, including the impact checks and the stock decisions most programmes leave until too late.
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Quality8 min read
Cpk and Ppk: what buyers should ask for
Two capability indices, two standard deviations and two different questions about whether a process can hold a tolerance.
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Quality10 min read
Measurement uncertainty: why a pass may still be a fail
Every reading carries a margin. How to build a small uncertainty budget, apply a decision rule and stop arguing about a result that sits on the limit.
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Quality9 min read
Profile tolerance: surface and line, and how to use them well
One control for form, orientation and location, plus the difference between a surface zone and a line zone and where each one earns its cost.
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Quality9 min read
MSA and gauge R&R: how to tell whether a measurement can be trusted
The studies behind a measurement system, the numbers a gauge R&R produces and how to read them before a tolerance decision.
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Quality9 min read
Non-conformance reports and 8D: containment, cause and closure
The fields that make an NCR usable, the containment that protects the customer, and the eight disciplines that stop the same defect returning.
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Quality9 min read
Position tolerance and bonus tolerance, with a worked hole example
How a position zone is built, when bonus tolerance applies, and why the M modifier is not a licence to ignore the worst case.
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Quality10 min read
SPC for custom parts: control charts in low-volume production
Control charts were built for long runs. Here is how to use them on fifty-piece lots without inventing limits or overreacting to noise.
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