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+---
+title: "Pre-fabrication validation checklist"
+task: ""
+lineage_type: import
+upstream_source: https://github.com/K-Dense-AI/scientific-agent-skills/blob/b2a92ba0/skills/lab-hardware-cad/references/validation.md
+upstream_sha: b2a92ba0
+imported_at: 2026-08-14
+prompt_class: unknown
+upstream_changes: accepted
+author: upstream
+validated: false
+---
+
+# Pre-fabrication validation checklist
+
+Work through this before telling a user a part is ready to fabricate. Each item names the failure
+it catches, because a checklist without consequences gets skipped.
+
+## 1. Provenance
+
+- [ ] The STEP was produced by `gen.py` from the current model source.
+      *Catches: a stale artifact that no longer matches the code you just edited.*
+- [ ] A `*.manifest.json` exists alongside it, and its `source.sha256` matches the model file.
+      *Catches: silently editing an exported STEP, which makes the design unreproducible.*
+- [ ] The manifest's `interfaces` block is non-empty and its values are the ones the model
+      computed after any `--param` override.
+      *Catches: a static `INTERFACES` list frozen at import, recording pre-override numbers.*
+- [ ] Every parameter in the model is named with units.
+      *Catches: the bare `12.7` nobody can later identify as half an inch.*
+
+```bash
+python scripts/gen.py part_model.py --outdir out/
+```
+
+## 2. Geometry is sound
+
+- [ ] `is_valid` is true.
+      *Catches: self-intersecting or non-manifold solids that slicers and CAM silently mangle.*
+- [ ] `solid_count` is what you expect — usually 1.
+      *Catches: a boolean that failed and left two disjoint lumps, or a feature floating free of
+      the body.*
+- [ ] Volume is plausible for the part's size and wall thickness.
+      *Catches: a cavity modelled solid, or a subtract that did nothing.*
+
+```bash
+python scripts/check.py facts out/part.step
+```
+
+## 3. Interfaces
+
+- [ ] Every interface dimension has a written source: a standard ID, a vendor drawing, or a user
+      measurement. **None came from memory.**
+      *Catches: the single most expensive failure mode in this skill.*
+- [ ] Every interface covered by a standard is declared in the model's `interfaces()` and passes
+      `check.py interfaces`.
+      *Catches: an interface nobody checked because the outer bounding box could not see it.*
+- [ ] Features that receive a standardised component use `intent: "envelope"`.
+      *Catches: a pocket sized to nominal, which fits only the smaller half of conforming parts.*
+- [ ] Any standard entry marked `verified: false` was confirmed against the primary document, or
+      the user was told it is unconfirmed.
+      *Catches: propagating a derived number as if it were read from the standard.*
+- [ ] Metric vs imperial is confirmed where both exist, and no expression mixes them.
+      *Catches: the 25.0 vs 25.4 mm grid error, which accumulates to 1.6 mm over four holes.*
+- [ ] Interfaces not covered by any bundled standard — a vendor drawing, a measurement — were
+      reported to the user as unchecked, with the number and its source.
+      *Catches: a silent gap where the automatic check simply had nothing to say.*
+
+```bash
+python scripts/check.py interfaces out/part.manifest.json
+
+# one dimension by hand, when it is not declared in the model
+python scripts/check.py fit --standard <id> --intent envelope --clearance <mm> --value <dim>=<mm>
+```
+
+## 4. Fits and assembly
+
+- [ ] Every mating dimension has a deliberate clearance chosen for the process.
+      *Catches: nominal-to-nominal fits, which do not assemble.*
+- [ ] Multi-part assemblies were checked for interference.
+      *Catches: parts that overlap in CAD and therefore cannot exist together.*
+- [ ] Rigid multi-hole mounting patterns have at least one slot.
+      *Catches: a four-hole bolt pattern binding on accumulated tolerance.*
+
+```bash
+python scripts/check.py clearance out/a.step out/b.step --min 0.3
+```
+
+## 5. Manufacturability
+
+- [ ] Minimum wall and feature sizes are within the chosen process (`fabrication-limits.md`).
+- [ ] Print or machining orientation is stated, and load runs along layers, not across them.
+- [ ] Threads use inserts or captive nuts rather than printed threads, unless coarse.
+- [ ] Enclosed cavities have a drain path for resin, and support-free access where possible.
+- [ ] Milled internal corners have relief for the tool radius.
+
+## 6. Material
+
+- [ ] Material is compatible with the **cleaning agent**, not only the sample.
+      *Catches: acrylic crazing on 70% ethanol; PLA distorting in an autoclave.*
+- [ ] Sterilisation method is stated and the material actually survives it.
+- [ ] Anything contacting cells, tissue, or animals has a justified material, or contact is
+      designed out.
+      *Catches: assuming a printed resin part is cell-safe.*
+- [ ] Optical requirements — autofluorescence, scatter, transmission — are addressed if the part is
+      near a beam or a detector.
+
+## 7. Visual review — mandatory
+
+- [ ] A snapshot was rendered **and read** after the most recent generation.
+- [ ] Confirmed in the image: features on the intended faces; correct mold/chip polarity; every
+      port, bore, and boss present, inside the body, and passing through; nothing consumed by a
+      fillet; clear apertures unobstructed.
+
+```bash
+python scripts/snapshot.py out/part.step --out out/part.png
+```
+
+**This step is never waived by the numeric checks passing.** `is_valid: true` with a correct
+bounding box is fully consistent with a pocket cut on the wrong face or an inverted mold. Those
+errors are obvious in the picture and invisible in the numbers.
+
+## 8. Report
+
+Give the user, explicitly:
+
+1. Process and material, and why.
+2. Every interface dimension with its source and tolerance.
+3. Clearances chosen, and the fit class they came from.
+4. What the snapshot showed — described, not merely "a snapshot was generated".
+5. Every check that did not pass, and every dimension you could not verify.
+6. A recommendation to print a test coupon of the critical interface before committing to the full
+   part, whenever the design depends on a fit.
+
+State the unverified items plainly. A part list with one honest "this dimension needs
+confirmation" is far more useful than a confident one that is silently wrong.