Build Chamber Volume
The spectrum of FDM machines is wide ranging from small, lowcost machines to larger, more expensive machines that are adaptable and highly sophisticated. The FDM Fortus 400mc has a build chamber volume measuring 406/355/406 mm (x/y/z in mm) .
Build Time and Build-up Rate
The build time heavily depends on the amount of material in the part, the support material volume and build-up rate. The build-up rate is a function of layer thickness, road width and nozzle diameter.
In general, manufacturers indicate the build time to be 25-70% higher than for Stereolithography and Laser Sintering processes. Using Ultem 9085 with a T16 nozzle, 61 cm3/h can be produced.
Surface Quality and Accuracy
The surface quality is a function of the road width and layer thickness. As the contours of the passes of the extrusion and the single layers are still visible at the top, the bottom and the walls, FDM parts have the highest roughness. For instance, parts fabricated using 0.127 mm layers show a roughness of Ra = 12-14 µm. At a maximum part length of 127 mm, all available machines and materials are set to reach a precision of ±0,127 mm. For bigger parts the accuracy is set to be 0.1% (but at least 0.1 mm). According to the manufacturers’ specifications, the accuracy varies depending on the machine: for instance from to 0.37% to 0.6%. The accuracy of the FDM process is influenced by fewer variables in total than the accuracy of comparable processes, e.g. Laser Sintering.
Build Material: A wide spectrum of advanced materials, providing special properties are available for being processed by FDM. ABS (acrylonitrile butadiene styrene) is the most used material; nearly 90% of all FDM prototypes are made of this material. Derivatives of the ABS, e.g. ABSplus and ABSi, are significantly stronger, translucent and available in different colors. These materials are widely used for medical and automotive applications. Polycarbonates (PC, PC-ISO) are applicable under greater forces and loads than ABS. New, high-performance polymer Ultem 9085 and Ultem 1010 (PEI) are characterized by high heat and chemical resistance, and are more solid and stiffer. In general, parts produced by FDM are applicable at high heat, in caustic chemicals, sterilization and under intense mechanical stresses.
Support Material: The so called break away support structures (BASS) and the water-soluble support structures (Water Works) are applied as support material that can be broken off or dissolved in water, respectively. As mechanical removal becomes obsolete using Water Works, it is especially suitable for small parts or for parts with regions that are difficult to access.