FDM (Fused Deposition Modelling) is an additive manufacturing technology that uses a thermoplastic extruded through a nozzle to build up a part layer by layer. The process begins with an STL file that is sliced into layers and then sent to the FDM machine. A plastic filament or metal wire unwinds & supplies material to the extrusion nozzle, typically being pushed by a worm drive. The nozzle is heated to melt the thermoplastic, which is then deposited on the build platform. The nozzle can be moved both horizontally and vertically, controlled by servos or stepper motors, and follows a tool path created by the software (similar to a CNC mill). The extruded material then cools soon after it is deposited – creating the solid part.
Some FDM parts will require a support structure, which can either be made from the same material as the part itself, or from a soluble material. Although FDM is capable of dealing with small, unsupported overhangs, there are restrictions of the angle of the overhang – this is where using the support materials can be very useful. Some machines are also capable of laying down different colours of the same part material.
Once the machine has finished building, the part can be removed and any support structures either removed by soaking in a water and detergent solution – in the case of soluble supports, or broken off by hand when using thermoplastic supports. The parts can then be finished by hand to improve the surface finish, milled, painting or electroplated to improve function.
There are a vast number of materials that can be used in an FDM machine, including ABS (Acrylonitrile Butadiene Styrene), PLA (Polylactic Acid), PC (Polycarbonate), PA (Polyamide) & rubber. These materials all have differing temperature & strength properties.
FDM has a wide number of uses, and is used across the motorsport, aerospace, automotive & manufacturing industries. FDM is also commonly used by engineers to build prototype parts that can withstand being fitted to assemblies, whilst remaining dimensionally accurate. Thermoplastics are quite resilient to heat, chemicals and mechanical stress – making FDM an ideal process for prototyping and small volume manufacture.
The drawbacks of FDM are that, in comparison to other 3d printing processes, the build times can be comparably longer, and hand finishing the parts to a high standard will take longer than a similar SLA or SLS part.