How FDM 3D printing works

What is FDM 3D printing?

FDM printing, also called FFF (Fused Filament Fabrication), is an additive manufacturing process. Traditional machining removes material from a block; 3D printing does the opposite and adds material layer by layer to build an object in three dimensions.

The principle is simple: a plastic filament is melted in a heated nozzle and laid down precisely on a build plate, one layer after another, until the object is complete. Think of a very precise, computer-controlled glue gun.

The technology was invented in the 1980s by Scott Crump, founder of Stratasys, and became widely available in the 2010s thanks to open-source printers such as the RepRap. Today, professional FDM printers reach accuracies of 0.05 mm and can handle many technical materials.

The FDM printing process step by step

1. 1

   Preparing the 3D file

   Everything starts with a 3D model. You supply your file (STL, OBJ, STEP or 3MF) or our CAD service creates it for you. The model goes into slicing software, the slicer, which cuts it into hundreds or even thousands of thin horizontal layers. The slicer also works out the exact path the nozzle will follow on each layer, the travel speed, the internal infill and the supports needed. The result is a G-code file: the precise instructions the printer will carry out.

2. 2

   Heating and calibration

   The printer heats two things. The nozzle rises to the melting temperature of the material: around 200 °C for PLA, 230 °C for PETG and 220 °C for TPU. The heated bed settles at 50-80 °C so the first layer sticks properly. This takes a few minutes. Professional printers also level the bed automatically (auto-levelling) so the gap between nozzle and bed is even across the whole surface.

3. 3

   Extruding the filament

   Extrusion is the heart of FDM. A motor pushes the plastic filament (1.75 mm in diameter, from a spool) into the hot nozzle. The plastic melts on contact with the heater block and comes out through a fine opening, 0.4 mm as standard. The molten filament is laid in a continuous bead, a little like toothpaste from a tube but placed to a tenth of a millimetre. A cooling fan sets the plastic straight away so it keeps its shape.

4. 4

   Building layer by layer

   The nozzle moves in X and Y to draw each layer. When a layer is finished, the bed drops (or the nozzle rises) by one layer height, typically 0.2 mm, and the next layer begins, hundreds of times over. Hollow areas are filled with an infill pattern (gyroid, grid, honeycomb) whose density sets the strength and weight. Overhangs beyond 45° need temporary supports, printed in the same material and removed afterwards.

5. 5

   Finishing and post-processing

   Once printing is done, the part cools on the bed and is removed. Supports come off by hand or with tools. Depending on the finish wanted, the part can then be sanded, primed and painted. Layer lines are inherent to FDM: progressive sanding (120, then 400, then 800 grit) followed by primer gives a smooth surface ready for paint, the usual route for cosplay props and figurines.

Key FDM print settings

Print quality depends on many settings, which we adjust to your project and the material.

Advantages and limits of FDM printing

Advantages. An affordable cost, with inexpensive materials and machines. A wide choice of materials: PLA, PETG, TPU, ABS, nylon and more. Functional parts with real mechanical strength. Large build volumes. Speed: a prototype in a few hours. Personalisation, since every part can be different. And little waste, because material is only added where it's needed.

Limits. Layer lines are visible, so the surface isn't smooth straight off the printer. Parts are anisotropic: weaker between layers than within a layer. Overhangs beyond 45° need supports. Resolution is lower than resin (SLA) printing, which our FDM vs SLA guide compares in detail. A smooth finish requires sanding. And only thermoplastics can be printed: no metal.

How we print FDM parts at Toulouse3DPrint

We print on professional FDM printers with automatic bed levelling and an enclosed build chamber to keep the temperature under control, and we keep an eye on every print as it runs.

We work with the three main FDM materials, PLA, PETG and TPU, and recommend the one that best suits your project. Our settings are tuned for each material and each type of part, from a small replacement part to a complex cosplay project.

Want to try FDM printing? Upload your 3D file on our order page for an instant quote. Your part is made in Toulouse: collect it at the workshop or have it delivered anywhere in France by Mondial Relay or Colissimo. We also ship abroad; contact us for the shipping cost, in English if you prefer.

Frequently asked questions

What is the difference between FDM and FFF?

None in practice. FDM (Fused Deposition Modelling) and FFF (Fused Filament Fabrication) are two names for the same process: a plastic filament melted in a nozzle and laid down layer by layer.

Which layer height should I choose?

0.2 mm suits most parts and is a good balance between quality and speed. 0.1 mm gives finer detail but takes much longer; 0.3 mm prints faster with more visible layers.

Does a 3D printed part have to be solid to be strong?

No. Strength comes from the infill and the walls: around 20% infill for decorative objects, 40-60% for functional parts, and 3-4 walls for mechanical parts. 100% infill is only for maximum strength.

Why are there lines on an FDM print?

They are the layers themselves, typically 0.2 mm high. They are inherent to FDM and disappear with progressive sanding and a coat of primer before painting.

Can FDM print metal?

No. FDM only prints thermoplastics such as PLA, PETG and TPU. At Toulouse3DPrint we print in PLA, PETG and TPU.