Question 1

What is FDM 3D printing?

Accepted Answer

FDM (fused deposition modeling), also called FFF, builds a part by extruding molten thermoplastic filament layer by layer. It is the most common and lowest-cost 3D printing process, good for prototypes, jigs and fixtures, and rugged functional parts.

Question 2

What materials does FDM use?

Accepted Answer

Common FDM materials include PLA for cheap concept models, ABS and ASA for tough housings, PETG for chemical resistance, nylon for wear parts and living hinges, polycarbonate for heat and strength, TPU for flexible parts, and carbon-fiber nylon for stiff structural parts.

Question 3

What tolerance can FDM hold?

Accepted Answer

Typical FDM tolerance is about +/- 0.5% of the dimension, with a minimum of roughly +/- 0.5 mm. It is the loosest of the common additive processes; for tighter tolerances consider SLS, resin, or machining.

Question 4

FDM vs SLS: which should I use?

Accepted Answer

Use FDM for the lowest cost, large parts, and quick iterations. Use SLS when you need stronger, near-isotropic parts, complex geometry with no supports, or small production batches. SLS parts are more uniform; FDM is cheaper.

Question 5

How strong are FDM parts?

Accepted Answer

FDM parts are strong along the layers but weaker between them (the Z direction), so orientation matters. Engineering filaments like nylon, polycarbonate, and carbon-fiber blends give functional strength; design and orient the part for the load path.

Design rule	Typical spec	Why
Typical tolerance	+/- 0.5% (min +/- 0.5 mm)	Layer-based; tighter with a tuned machine.
Min wall thickness	0.8 to 1.0 mm	At least two perimeter passes for a solid wall.
Min feature size	~2x nozzle (0.8 mm)	Below the nozzle width, detail is lost.
Max unsupported overhang	<= 45 deg from vertical	Steeper overhangs need support material that leaves marks.
Layer / Z strength	weaker between layers	Orient the part so loads run along layers, not across them.
Clearance for fits	0.3 to 0.5 mm	Tighter gaps fuse mating parts together.

Process	Best for	Typical volume	Choose it over FDM 3D Printing when
SLS	Stronger, complex parts, no supports	Low-volume production	You need near-isotropic strength or complex geometry FDM cannot support.
SLA / Resin	Fine detail, smooth cosmetic finish	Prototype	You need crisp detail or a smooth surface FDM layer lines cannot give.
CNC Machining	Tight tolerance, engineering materials	Prototype to production	You need tight tolerances or full engineering-grade material properties.
Injection Molding	High-volume identical plastic parts	1,000+	You are past a few hundred parts and can amortize a mold.

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