FDM 3D printing

FDM 3D printing (fused deposition modeling), also known as FFF (fused filament fabrication), is the most widespread 3D printing technology. A plastic filament is melted in a nozzle and deposited layer by layer onto a build plate, gradually building up a physical object. Both names describe the same process; FFF came into use as a generic term because FDM was originally a trademark.

The main advantages of FDM printing are availability, speed and a wide choice of materials. For prototyping, the most common are PLA (inexpensive and easy to print, industrially compostable), PETG (better toughness, suitable for functional parts), ABS and ASA (higher heat resistance, with ASA also resisting UV radiation), nylon (toughness) and TPU (flexible parts).

The accuracy of FDM printing typically ranges from ±0.2 to 0.5 mm, depending on the printer, material, part size and print orientation. For prototypes that check form and fit, this accuracy is usually sufficient. For parts with critical tolerances, SLA printing or CNC machining is a better choice.

The limitations of FDM printing are anisotropic mechanical properties (parts are weakest in the direction perpendicular to the layers), visible layer lines on the surface and the need for supports under overhangs. Surface finishing (sanding, filling, painting) can improve the appearance considerably.

FDM printing is a good choice for the first physical check of form and fit, for larger parts where other technologies would be expensive, and for simple functional parts without high accuracy requirements: brackets, covers, jigs and fixtures, templates, gauges or electronics enclosures.

Thanks to the low cost per part, it also suits fast iterations, where several variants are tried within a few days. With engineering materials (PETG, ASA, fiber-reinforced nylon), you can also print parts for limited end use.

The most common mistake is the wrong orientation of the part on the build plate. A load acting perpendicular to the layers can split the part along a layer line even at low force. Tell your supplier how the part will be loaded, or specify the orientation yourself.

Allow for dimensional deviation and shrinkage, especially with ABS and nylon and with large flat parts, which can warp. Holes for pins and bearings usually come out undersized and are best drilled or reamed to size. In your request for quote, ask about the material, layer height, infill, number of perimeters (walls) and whether support removal is included in the price.