Fused Deposition Modeling (FDM) is one of the most commonly used 3D Printing technologies. FDM is colloquially often wrongly referred to as Fused Filament Fabrication (FFF) which is basically a desktop version of FDM technology. Know more about the difference between FDM and FFF. For the purpose of this article, and to uncover the details of this technology, we will address FFF technology as FDM itself, since the process is more or less similar. Just like in case of any other 3D Printing technology, an object in FDM, too, is created layer by layer. The only difference is in process methodology. Usually the materials used in FDM 3D Printing are thermoplastic polymers and are available in filament form.
Let us probe into how the FDM 3D Printing process actually works. Firstly, the thermoplastic filament is convoluted around the spool. This spool is then inserted into the printer such that the filament is ministered to the extrusion surface. The nozzle, upon reaching the required temperature facilitates the melting of filament inside it. Due to the flexible movement of the extrusion head in all the three directions, the melted material after getting extruded can be easily deposited in selected locations in the form of layered structure. In these locations, the deposited melted material cools and simultaneously solidifies. With the completion of each layer, the platform cascades and there is deposition of another layer. This FDM 3D Printing process continues in a loop until the entire object is manufactured completely.
Watch this video below explaining the FDM process in detail. (Video Courtesy: Stratasys)
As amazing as this FDM 3D Printing process is, the FDM 3D printers are also quite flexible. Most of the FDM 3D printers allow various modifications, change in printing parameters, variations in temperature of the nozzle or the platform, the build pace, layering heights, and changes in the speed of the installed cooling fan. The build size and the layer height are two of the most important factors for any FDM 3D Printing job.
The build size of most of the desktop FDM 3D printers is about 200 X 200 X 200 mm. On the other hand, the FDM 3D printers suitable for industrial use are usually as big as 1000 X 1000 X 1000 mm. If one aims at reducing the cost and also aesthetics for using a desktop FDM 3D printer, they can dissect the relatively smaller parts of a bigger model and then assemble them to get the desired FDM 3D Printing system.
Moving onto the appropriate layer heights, FDM 3D printers have a variation of the layer thickness from 50 to 400 µm. The fine the layer thickness, the better the surface quality and vice-versa. Know more about layer thickness and how it affects the quality of your part. An average layer thickness of 200 µm is usually incorporated in various FDM 3D Printing systems.
With the use of FDM technology, one has to be vigilant about the temperature of the FDM 3D Printing system. Warping is a situation which occurs when there is occurrence of internal stresses between layers. The variation in solidification of various parts due to uneven cooling speed leads to temperature difference in sections of the print. This leads to development of internal stresses due to differential cooling, which leads to warping. Making use of some adhesive materials in between the printing parts and the platform will also lessen the chances of warping.
The effective adhesion system in FDM 3D printing process is mandatory. When the molten thermoplastic FDM 3D Printing material is subjected to extrusion through the nozzle, it sticks to the previous layer. With application of temperature and pressure, the surface of each layer melts and gets bonded to the next layer. Since the strength of bond between the layers is comparatively lower than that of the material’s base strength, FDM part orientations should be meticulously checked for. Usually the strength of the FDM parts in the Z-axis is lower than the same in X-Y plane.
With FDM 3D Printing process, overhanging surfaces above a certain angle can be produced only with the help of support structures since the deposition of molten thermoplastic material cannot be done in thin air. The parts generated with FDM are usually not solid which, in fact, saves the printing time and the amount of material required. The perimeter of the parts is etched with shells and the interior is constituted with a low-density material called infill. The thickness of the shell and infill highly affect the overall strength of the FDM parts.
Acrylonitrile Butadiene Styrene (ABS) and Poly Lactic Acid (PLA) are the commonly used materials in FDM 3D Printing technology. Due to its ability to generate prototypes at a faster rate and at lower costs, FDM finds wide acceptability in the market.