---
name: "fdm-structural-review"
description: "Review load-bearing FDM/material-extrusion parts using process-specific evidence, printed orientation, walls and infill, anisotropy, creep, fatigue, environmental exposure, and coupon planning. Use when sizing a functional printed bracket, enclosure, boss, insert, snap-fit, beam, or lattice; when choosing walls versus sparse or solid infill; when interpreting PLA, PETG, ABS, ASA, nylon, or composite data; or when deciding whether effective properties, explicit lattice FEM, coupons, proof tests, or an engineer are required."
metadata:
  dev.v-san.skills: |-
    origin: "original (personal skill)"
    version: "0.1"
    changeDate: "2026-08-01"
    dependsOnSkills:
      - "mechanical-strength-review"
    requires:
      dependencies:
        - "Python 3.10\u002B for material-profile validation"
    sources:
      - "https://www.astm.org/f3489-23.html https://store.astm.org/f3529-21.html https://www.iso.org/standard/76909.html https://www.nist.gov/publications/estimations-effective-youngs-modulus-specimens-prepared-fused-filament-fabrication https://www.nist.gov/publications/mechanical-strength-welding-zones-produced-polymer-extrusion-additive-manufacturing https://doi.org/10.3390/app12042180 https://pmc.ncbi.nlm.nih.gov/articles/PMC9950821/\n"
---

# FDM Structural Review

Treat the sliced, printed structure as the engineering material. Do not substitute filament-family marketing values for part properties.

## Workflow

1. Use `mechanical-strength-review` to establish requirements, load cases, load path, failure modes, deformation limits, duration, cycles, temperature, environment, and consequence of failure.
2. Record the exact material, lot if available, printer, nozzle, temperatures, layer height, line width, wall count or wall thickness, top/bottom shells, infill pattern and density, build orientation, raster strategy, conditioning, and service state.
3. Run `scripts/validate_material_profile.py`. Treat its result as evidence readiness, never as a safety verdict.
4. Choose the structural idealization from [structural-method.md](references/structural-method.md): explicit walls with conservative infill treatment, calibrated effective material, homogenized lattice, or explicit lattice geometry.
5. Establish directional allowables from the hierarchy in [material-evidence.md](references/material-evidence.md). Require process-matched coupons when the load-bearing claim depends on uncertain layer welds, sparse infill, creep, fatigue, inserts, or snap-fit cycling.
6. Size geometry with explicit section properties and named allowables. Place material along the load path; add radii and local solid regions at load introduction, holes, bosses, and inserts.
7. Plan coupons and an assembly or proof test using the same printer, material, orientation, wall/infill rules, conditioning, and service-relevant load mode.
8. Report assumptions, process profile, material evidence, predicted modes, margins, uncertainty, and required validation separately.

## Non-negotiable rules

- Do not map `15% infill` to `15% modulus` or `15% strength`.
- Do not assume slicer percentage equals measured relative density.
- Do not call `100% infill` isotropic or equivalent to injection-molded stock.
- Do not invent universal PLA, PETG, gyroid, wall-count, or safety-factor values.
- Do not use a tensile coupon alone to claim creep, fatigue, insert pullout, impact, or snap-fit life.
- Require human engineering and qualification for serious safety or regulatory consequences.

## Resources

- [structural-method.md](references/structural-method.md) — walls, infill, gyroid, homogenization, and sizing workflow.
- [material-evidence.md](references/material-evidence.md) — evidence hierarchy and profile template.
- `scripts/validate_material_profile.py` — deterministic readiness and evidence-gap report.