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Fused deposition modelling builds a product up in thin layers of thermoplastic wire-like filaments. According to the proponents: ".... there's no need for messy liquid photopolymers, no powders, no lasers. An FDM machine enables full desktop operation and is fully suitable for use in an office environment."
The process starts from a 3D geometric CAD model, which is computer-sliced into horizontal layers. In the machine, molten thermoplastic material (ABS) or wax is extruded through a fine nozzle. The extrusion head with its nozzle is governed in x- and y-direction by the computer in accordance with the 3D model's slices, to produce the required cross section.
A second nozzle at the same time creates a supporting structure as required, e.g., to allow the formation of overhanging edges. When the model is finished, the supporting structure is easily removed. The layers are built on a horizontal table, which is lowered step by step as each layer is added.
Layer thickness depends on the nozzle orifice, the feed rate of the material and the speed of the extrusion head. It ranges typically from 0.18 mm to 0.26 mm/s. Large(r)-sized models are assembled from separate parts. It is easy to use different colours for these parts.
The mechanical properties of models made by FDM are comparable with those of injection moulded parts. FDM parts can be functionally tested, before any capital outlay for the construction of injection moulds becomes necessary.
Maintaining the molten material at precisely the right temperature (within 0.5° C above the solidification point of about 272° C) is fundamental to the FDM process. Only then, the material solidifies quickly enough upon extrusion to generate usable wires, while still bonding to the previous layer through thermal fusion.When using a polyester material (FDM Genisys Xs) a temperature of 165° C is chosen.
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