Frequently Asked Question
Process selection balances material, geometry, required tolerance, surface condition, production volume, lead time, equipment, risk, and total cost. Start with the functional requirements and eliminate processes that cannot achieve the critical characteristics.
| Decision factor | Question |
|---|---|
| Volume | Is the process economical for the expected annual quantity? |
| Geometry | Can the process create the required walls, radii, holes, and access? |
| Material | Are strength, ductility, thermal, and corrosion requirements compatible? |
| Quality | Can capability and inspection meet the specification? |
Choose the process only after identifying special characteristics and the evidence needed to release production.
Process-to-quality relationship
Manufacturing engineering connects material and geometry to process variables, variation mechanisms, inspection, and reaction. For How to Select a Manufacturing Process, identify the functional characteristic first, then identify which process variable changes it, how that variable is measured, and what control prevents an unacceptable result. Separate first-order estimates from qualified process limits and distinguish a containment action from a corrective action.
USL and LSL are specification limits, μ is process mean, and σ is within-process standard deviation. Capability is meaningful only after stability and measurement-system capability are established.
Worked example
For USL = 10.10 mm, LSL = 9.90 mm, μ = 10.02 mm, and σ = 0.02 mm, Cpk = min[(10.10−10.02)/0.06,(10.02−9.90)/0.06] = 1.33. Before accepting this result, verify gauge variation, stability, sampling window, material condition, tool identity, and reaction plan.
Engineering check: record process settings, traceability, inspection method, owner, and disposition route for nonconforming output.