Machine Design #103: Surface Roughness by Function — Not Every Surface Must Be Shiny
MINATA turns the Vietnamese source into an evidence-led guide. functional surface roughness must preserve function, manufacturability, inspectability, cost, and serviceability when the boundary changes.
Function before a number
Write the input, expected result, acceptance limit, failure symptom, and measurement method before choosing a geometric value, roughness, or fit. Assign an owner to every value and change.
Core checks
- Function: contact, seal, friction, or appearance: record value, source, method, owner, and pass/fail evidence.
- Roughness parameter and measurement direction: record value, source, method, owner, and pass/fail evidence.
- Material, tool, feed, and process capability: record value, source, method, owner, and pass/fail evidence.
- Coating, burr, lay, and edge condition: record value, source, method, owner, and pass/fail evidence.
- Measurement instrument, cutoff, and uncertainty: record value, source, method, owner, and pass/fail evidence.
- Supplier, cost, and acceptance evidence: record value, source, method, owner, and pass/fail evidence.
| Failure mode | Symptom | Verification |
|---|
| Function not defined | Over-tight or weak geometry | Rebuild the functional stack |
| Datum not real | Inspection and assembly disagree | Try the real fixture |
| Documents out of sync | Correct value, wrong revision | Baseline every reference |
1. Review pass: function and load path
Review function and load path for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
2. Review pass: datums and relationships
Review datums and relationships for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
3. Review pass: process capability
Review process capability for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
4. Review pass: assembly and adjustment
Review assembly and adjustment for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
5. Review pass: inspection and uncertainty
Review inspection and uncertainty for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
6. Review pass: failure and recovery
Review failure and recovery for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
7. Review pass: supplier and acceptance
Review supplier and acceptance for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
8. Review pass: revision and change
Review revision and change for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
9. Review pass: cost and trade-off
Review cost and trade-off for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
10. Review pass: safety and misuse
Review safety and misuse for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
11. Review pass: data and audit
Review data and audit for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
12. Review pass: training
Review training for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
13. Review pass: field feedback
Review field feedback for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
14. Review pass: final release
Review final release for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
15. Review pass: function and load path
Review function and load path for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
16. Review pass: datums and relationships
Review datums and relationships for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
17. Review pass: process capability
Review process capability for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
18. Review pass: assembly and adjustment
Review assembly and adjustment for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
19. Review pass: inspection and uncertainty
Review inspection and uncertainty for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
20. Review pass: failure and recovery
Review failure and recovery for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
21. Review pass: supplier and acceptance
Review supplier and acceptance for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
22. Review pass: revision and change
Review revision and change for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
23. Review pass: cost and trade-off
Review cost and trade-off for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
24. Review pass: safety and misuse
Review safety and misuse for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
25. Review pass: data and audit
Review data and audit for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
26. Review pass: training
Review training for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
27. Review pass: field feedback
Review field feedback for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
28. Review pass: final release
Review final release for the functional surface roughness. The key risk is contact, seal, friction, coating, measurement direction, and process cost. Define lower and upper boundaries, the simultaneous worst case, evidence source, owner, and change trigger. Confirm model, drawing, BOM, material, process, inspection, and work instruction use the same revision. Test normal operation, variation, wrong input, interruption, and a controlled fault. Record actual value, unit, condition, instrument or log, sample or serial, pass/fail, and next action.
MINATA release checklist
- [ ] Function, boundary, and failure symptom are written.
- [ ] Datums, ownership, process, and mistake-proofing are clear.
- [ ] Six topic checks have evidence and pass/fail limits.
- [ ] Manufacturing, assembly, inspection, and maintenance were tried.
- [ ] Revision, supplier, material, and configuration records agree.
Good engineering is an explicit chain that survives manufacture, operation, maintenance, and change. For functional surface roughness, evidence that geometry and function remain reliable is the MINATA standard.
Public references
- MINATA Q-up design practice and internal review checklist.
- Applicable geometric, material, surface, or quality standard selected by the project owner.
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