Engineering thermoplastics. Large parts. Aerospace rated.

FDM advantages: Ultem 9085 (aerospace FST) not available in other 3D processes. PEEK capability. Larger build volume. Engineering ABS/PC with production-like properties. Mechanical anisotropy (can tune strength direction). SLS advantages: better surface finish, no support structures, better for smaller parts, faster cycle per part in batch production. For aerospace with material specs, FDM. For consumer electronics and general prototypes, SLS/MJF.

FDM produces visible layer lines — characteristic "ridged" appearance. Not suitable for fine cosmetic applications without post-processing. Smoothing options: vapor smoothing (acetone for ABS, specific solvents for other materials), sanding and painting, chemical smoothing. For engineering prototypes and functional parts, layer lines cosmetic issue only. For end-use products requiring smooth finish, consider MJF or SLA.

FDM: ±0.2-0.5 mm typical on critical features. Larger parts have more thermal distortion — bigger parts, worse accuracy. For tolerance-critical features, post-machining brings specific dimensions to CNC tolerance. For aerospace parts with dimensional requirements, CNC post-processing standard after FDM.

Ultem 9085: FAA-certified material for aircraft interior per FAR 25.853. FST (flame, smoke, toxicity) compliance. Mechanical properties sufficient for non-structural aircraft interior — cabin parts, overhead storage hardware, interior trim. Standard 3D printing aerospace workflow: print → inspect → qualify per customer specification. Aerospace customers using FDM Ultem for production interior parts — validated process.

PEEK FDM requires specialized high-temperature printers — 400+ °C nozzle, 200+ °C chamber, 160+ °C bed. Few machines capable. Limited service providers. PEEK parts have property anisotropy — typically 70-90% of injection-molded PEEK properties. For PEEK prototypes: FDM is fastest. For production PEEK, CNC machining from extruded rod typically better mechanical properties.

FDM cost: comparable or slightly higher than SLS/MJF for similar-sized nylon parts. Engineering materials (Ultem, PEEK) significantly more expensive — Ultem 9085 parts 3-5× PA12 nylon parts. Large parts: FDM most economical (handles sizes other processes cannot). For standard functional prototypes in nylon, SLS/MJF cheaper. For specialty engineering thermoplastics or large parts, FDM is the right process.