Part Features to Avoid
Thin walls, deep pockets, sharp corners, unsupported text — and the redesigns that fix them
Most quoting and manufacturing failures come from a short list of avoidable features: walls below the process minimum, deep narrow pockets, sharp internal corners, unsupported overhangs, tiny text, and zero-draft vertical faces in molding. Each has a simple redesign that preserves function while cutting cost and risk dramatically.
1. Walls, ribs and thickness
Avoid walls thinner than the process floor: CNC metal 0.8 mm, plastic 1.0 mm; printed 0.7–1.0 mm (process-dependent); molded 1.0–4.0 mm uniform. Thin walls vibrate (machining), warp (printing), or sink/fill poorly (molding). Fix: thicken, or add ribs/bosses to stiffen.
Avoid abrupt thickness changes — they create stress concentrations and differential cooling (sink marks in molding). Transition gradually or add a fillet.
2. Pockets, corners and depth
Deep narrow pockets force long tools that deflect: keep depth:width ≤ 4:1 for milling; beyond that, EDM or redesign. Internal corners should be filleted ≥ 0.5 mm (tool radius); sharp internal corners are simply unmachinable by round tools.
Undercuts in molding need side actions ($$$): rotate the feature into the pull direction or accept the tooling cost. Printing: overhangs beyond 45° need supports — orient or redesign the face.
3. Text, threads and small features
Text smaller than 0.5 mm depth is unreliable in machining and molding; use ≥ 0.8 mm or switch to laser marking. Threads below M1.6 break taps — use M2+ or insert hardware. Holes below 0.8 mm need EDM or laser drilling — resize or post-machine.
Features that invite failure: razor edges (break them), blind fine threads (through-hole or enlarge), unsupported long spans (rib them), and tight tolerances on cosmetic faces (loosen them).
4. The redesign-first habit
Before quoting, run the DFM checklist: walls, draft, radii, threads, tolerance, text, overhangs, depth ratios. The platform flags violations on upload with suggested fixes — most are 30-minute redesigns that cut cost 20–50%.
When a feature is genuinely required (thin wall for weight, sharp corner for function), say so: the quote and DFM notes will confirm the process cost, and you decide if it is worth it.
Quick reference
| Feature | Problem | Fix |
|---|---|---|
| Wall < 1 mm (plastic) | Warp, break, sink | Thicken or rib |
| Deep pocket > 4:1 | Tool deflection | EDM, or widen |
| Sharp internal corner | Unmachinable | Fillet ≥ 0.5 mm |
| Overhang > 45° (print) | Supports needed | Orient/redesign |
| Zero draft (mold) | Part sticks | Add 1–2° draft |
| Text < 0.5 mm | Unreadable | Enlarge or laser mark |
| Thread < M1.6 | Tap breakage | M2+ or insert |
Sources & references
- ISO 2768 / DIN 16742 — Feature limits
- Xometry Learning Center — Features to Avoid (public engineering reference)