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FDM – Fused Deposition Modeling

Fused Deposition Modeling (FDM) is a 3D printing technology that extrudes molten thermoplastic filament layer by layer; it is the fastest and most economical route to concept and functional prototypes in a wide range of materials and colours.

FDM – Fused Deposition Modeling

What Fused Deposition Modeling is

FDM (Fused Deposition Modeling) — also called FFF (Fused Filament Fabrication) when the registered Stratasys trademark is to be avoided — is the most widespread 3D printing technology. The principle is simple: a thermoplastic filament is pushed, melted and deposited layer upon layer to build the object from the bottom up.

The heart of the system is the extruder. A motor pushes the filament — typically PLA, PETG, ABS, ASA or TPU — through a hotend that takes it above its melting temperature (around 200 °C for PLA, 240–260 °C for ABS and ASA). The molten material exits a calibrated nozzle, usually 0.4 mm, and is laid onto a build plate that is often heated to improve adhesion and avoid warping. The head moves on the XY axes to draw the perimeter and infill of each layer; a step on the Z axis (the layer, typically 0.1–0.3 mm) prepares the next level, and each new layer partly fuses with the one below, creating the structural bond.

Why choose it

FDM is chosen when speed, low cost and breadth of material choice matter more than a flawless finish. It is the most economical process, handles technical and functional materials — including carbon- and glass-fibre fills and flexible filaments — and needs none of the resin-and-alcohol post-processing typical of SLA and DLP.

The trade-off is resolution and mechanical behaviour. Layer lines stay visible and the finish is rougher than with resin technologies. Above all, the part is anisotropic: much stronger in the XY plane than along Z, because inter-layer adhesion is weaker than continuous material — so print orientation determines where the part will fail under load. You also have to consider the warping of high-temperature materials such as ABS and ASA — which contract as they cool and tend to lift at the corners, which is why they often require an enclosed chamber, whereas PLA suffers little — and the need for supports on overhangs beyond ~45°.

Typical applications

FDM is the fastest, most economical route to concept and functional prototypes. Typical cases are form-and-fit models, functional prototypes to be tested mechanically, brackets, jigs and production fixtures, large parts where other technologies would cost too much, and components in technical materials (flexible or filled) that are not easily produced in resin. In general, any context where cost, speed and material versatility matter more than a fine finish.

Printable materials

ABS
ABSAcrylonitrile-butadiene-styrene (ABS) is a common thermoplastic polymer used to make light, rigid objects and as a housing for electrical and electronic assemblies. ABS is a copolymer of styrene polymerised with acrylonitrile in the presence of polybutadiene, so it can be defined as a terpolymer.
ULTEM
ULTEMPolyetherimide is a high-performance amorphous engineering polymer introduced in 1982, commercially available under the ULTEM trade name. The stability of its imide bonds gives the material high heat resistance, resistance to deformation and high rigidity, while the bond between the phenyl rings provides the chain flexibility needed for good melt processability. It has good electrical insulation properties that are stable across a wide range of temperatures and frequencies.

FAQ

What is FDM best suited for?

For low-cost concept and functional prototypes, jigs and fixtures, when especially fine surface finishes are not required.

Which materials can be printed with FDM?

The most common are PLA (easy, for rapid prototypes), PETG (tough and durable), ABS and ASA (technical, resistant to heat and UV) and TPU (flexible). There are also filaments filled with carbon or glass fibre for greater rigidity.

Why are the layer lines visible?

They are a direct consequence of layer-by-layer deposition: each layer is typically 0.1–0.3 mm thick and leaves a visible line. They are reduced by using thinner layers and eliminated entirely with post-processing such as sanding and painting.

Are FDM parts strong?

Yes, they are suitable for functional uses, but they are anisotropic: stronger in the XY plane than along the Z axis, because inter-layer adhesion is weaker than solid material. Print orientation should therefore be chosen according to the loads the part will have to bear.

Are support structures needed?

Yes, for overhangs beyond ~45°, because the molten material needs something to rest on. With dual-material extruders you can use soluble supports (PVA, HIPS) that are removed without leaving marks.

What is warping and how is it reduced?

It is the lifting of the corners caused by thermal shrinkage during cooling, typical of high-temperature materials such as ABS and ASA. It is contained with a heated bed, an enclosed chamber and good bed adhesion; PLA suffers from it very little.

FDM or resin (SLA/DLP)?

It depends on the goal: FDM is cheaper, handles technical and functional materials and needs no resin-and-alcohol post-processing, but has a rougher finish; resin technologies give smooth surfaces and fine detail, at the expense of cost and mechanical strength.

Last updated: 10/06/2026