3D Printing and Additive Manufacturing in PCBA

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Contrary to popular belief, 3D printing and additive manufacturing are not the same thing; however, they can be used interchangeably for the sake of ease. According to ASTM F2792-12a “Standard Terminologies for Additive Manufacturing Technologies,” 3D printing is “the fabrication of objects through the deposition of a material using a print head, nozzle, or other printer technology.”

The process starts with a 3D model drawing that is done on any standard CAD software. This 3D model file is then converted into a stereolithography file format by either the native program or a third-party file converter. Some printers have this file conversion capability as part of their software suite for their printers. The file is then converted into GCode or a language that the printer can understand, essentially creating the file into cross sectional slices of the part. This step is commonly known as “slicing.”

Once the slicing of the drawing has been done the printer is ready to start the print. For nearly all 3D printers, the above process is the same, with the printing process itself being the main differentiator. In a fused filament fabrication printer, once the 3D drawing is sliced, the printer can begin printing. The main components of the printer are, the print bed, the extruder, the hot-end, and the material. Material for this technology usually comes in a wire form on a spool. This wire filament is fed into the extruder, the extruder uses torque and pinch to control the speed of the filament being fed into the hot-end. Once the filament is in the hot-end, it is melted using heat.

The melted material is forced out of the hot-end by the extruder that is pushing in more material from the top. The hot-end, usually made of aluminum, deposits the melted material onto the build plate in a designated pattern as dictated by the software. As the material is being deposited by the hot-end, the build plate is moving in a X-, Y- or Z-axis depending on the part requirements of what is being printed. In some printers the build plate will stay stationary 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 chamber 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 components 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 varying layer heights in the print. The even distribution 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.



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