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74 SMT007 MAGAZINE I APRIL 2018 ary and the hot-end will move in a Cartesian plane to create the print. This process describes fused filament fabrication (FFF), which is one of the technologies that the company currently employs. Fused filament fabrication currently is used mainly for plastic materials. If metal printing is required, direct metal laser sintering is utilized to print metal parts. The process of creating a 3D model to be understood by Direct Metal Laser Sintering printers is as described above; however, the process of printing is vastly different. Metal printers are usually larger in footprint due to the high-quality components and the auxiliary processes required to ensure effective operation of the machine as well as quality of the print. The main components of a metal are the build plate, re-coater, laser and powder. Before a metal part is printed, the build cham- ber will fill up with an inert gas, usually argon. This is to ensure that no oxidation occurs during the process. The build plate where the powder is residing, and the re-coater blade will be leveled. This can be done manually, but most printers can be automatically calibrated to level before a print starts. After the compo- nents are leveled, the print can start. A laser will sinter the powder in the cross-sectional geometry of the part. Once the sintering for that level has finished, a re-coater blade that was located off to the side of the build area will move over the sintered layer and coat a new layer of powder on top. The layer of powder that is re-coated onto the sintered layer is very important to the integrity and quality of the print. If too much powder is re-coated, the layer below and the layer above may not be sintered together well by the laser. If there is too little powder, the laser might sinter already sintered powder, causing vary- ing layer heights in the print. The even distri- bution of powder and the correct amount of powder is a key area that currently affects how the powder is re-coated on top of itself. Layer by layer powder will be re-coated and sintered by the laser until the part is complete. Material jetting processes are very similar to the above. Resin is loaded into a printer, where it travels into a printhead, the printhead has several nozzles or resin dispensers (much like a two-dimensional inkjet printer). The resin is then extruded from the miniaturized nozzles onto a build platform in the two-dimensional cross section of the part. After, the layer is passed over with a UV light source or other light activation that cures the resin that was deposited. The printhead then deposits another layer on the previously cured layer, this is done repeatedly until the part is completed. Materials Evaluated There are several materials that are avail- able for 3D printing for various engineering uses. Various vendors offer over hundreds of different materials that are either specific to an application or to a specific desired char- acteristic. For this study, eight materials that are regularly used for engineering applications were evaluated and characterized to determine which can be used in PCB processes. Material identifying characteristic as well as the desig- nation is shown in Table 1. TESTS PERFORMED To properly characterize the materials that could be used for engineering applications, various tests were chosen and performed so that a decision tree could be created. The ulti- mate goal of the project is to be able to have a Table 1: List of materials evaluated for this study.

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