Fused Deposition Modeling (FDM)

Fused Deposition Modeling builds plastic parts layer by layer from filament, offering low-cost prototyping and functional parts with visible layer lines and moderate accuracy.

Overview

Fused Deposition Modeling (FDM), also called fused filament fabrication (FFF), extrudes heated thermoplastic filament through a nozzle to build parts layer by layer. It handles simple to moderately complex geometries, internal channels, and snap features, but always with visible layer lines and anisotropic properties.

Use FDM for fast, low-cost prototypes, fixtures, and functional parts when you do not need cosmetic surfaces or very tight tolerances. It excels at larger parts, robust engineering plastics, and quick design iterations. Tradeoffs include weaker strength in the Z-direction, limited fine detail, support-scarring on overhangs, and post-processing to achieve tight fits or smooth finishes. For many engineering uses, it’s the most economical way to prove form, fit, and basic function before committing to more precise or cosmetic processes.

Common Materials

  • PLA
  • ABS
  • PETG
  • Nylon (PA12)
  • Polycarbonate (PC)
  • TPU

Tolerances

±0.010–0.020"

Applications

  • Assembly jigs and fixtures
  • Functional prototypes for fit and basic load testing
  • Equipment brackets and mounting hardware
  • Custom sensor and electronics enclosures
  • Ducts, manifolds, and cable routing hardware
  • Soft jaws and tooling aids

When to Choose Fused Deposition Modeling (FDM)

Choose FDM when you need fast, inexpensive plastic parts for prototyping, fixtures, or low-volume end-use with moderate accuracy and visible layer lines. It suits larger parts, robust geometries, and engineering thermoplastics where strength and cost matter more than fine detail or cosmetic finish.

vs Stereolithography (SLA)

Pick FDM over SLA when you need tougher, less brittle parts from common engineering plastics like ABS, PETG, or nylon, and can accept visible layer lines. FDM is usually cheaper for larger, less detailed parts, fixtures, and rough functional prototypes where ultimate surface finish is not critical.

vs Selective Laser Sintering (SLS)

Choose FDM instead of SLS when budget is tight and part size is large, and you can live with supports and slightly lower feature resolution. FDM is usually more economical for one-off prototypes, basic jigs, and fixtures where powder-free internal cavities and lower material cost are more important than isotropic strength.

vs Multi Jet Fusion (MJF)

Select FDM over MJF when you need very low part cost per piece, do not require fine text or small features, and want access to a wider range of filament materials. FDM makes sense for quick design iterations and shop-floor tooling where cosmetic uniformity and batch consistency are less critical.

vs Digital Light Processing (DLP)

Use FDM instead of DLP when mechanical robustness, impact resistance, and heat performance matter more than ultra-fine detail and smooth surfaces. FDM suits functional brackets, fixtures, and housings that see real loads, where DLP’s brittle resins and smaller build volumes can be limiting.

vs PolyJet

Prefer FDM over PolyJet when you value material toughness, lower cost, and larger build volumes over multi-material or soft-touch cosmetic prototypes. FDM is better for hard-use tooling, end-of-arm tooling, and shop aids that must survive rough handling and elevated temperatures.

Design Considerations

  • Use a minimum wall thickness of 1.2–1.5 mm for structural walls and increase thickness for tall or slender features to reduce warping and breakage
  • Limit unsupported overhangs to 45° from vertical or add self-supporting chamfers and gussets to minimize support material and cleanup
  • Orient critical load paths and snap fits in the XY plane to maximize strength; avoid relying on Z-direction strength for highly loaded features
  • Design holes slightly undersized and allow for drilling or reaming if you need tight fits or accurate pins and fasteners
  • Break very large flat surfaces with ribs, lightening pockets, or slight contours to reduce warping and improve dimensional stability
  • Call out realistic tolerances only on critical features and allow clearance on mating parts to accommodate FDM variability and surface roughness