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    The Best Way to Post-Process FDM 3D Prints, True or Not?
    03.18.2021 | Cherry Chen | News
    Researchers from Nantong Institute of Technology and Jiangsu Key Laboratory of 3D Printing Equipment and Application published a paper entitled "Research on Artificial Post-Processing Technology for FDM Formed Parts", regarding manual post-processing on 3D printed parts made by FDM technology, which is of low accuracy with stair steps on.

    Due to the "stair-stepping effect", the 3D printed parts have rough surface, noticeable stripes, the surface quality is so poor that it can't meet customer's requirements. Therefore, post-processing is a very important step. This paper mainly studies and summarizes the manual post-processing technology of FDM printed parts, and provides a specific implementation method of post-processing, which provides references for post-processing and other forming processes of FDM 3D printed parts.


    To "further improve the surface quality and strength of the 3D printed model", the post-processing is usually of a necessity. Here are some of the common methods of post-processing FDM molded parts as follows:
    Organic solvent chemical treatment;
    Heat treatment;
    Mechanical treatment with a grinder;
    Surface coating treatment

    Researchers responsible for this paper pay their attention on a manual post-processing process that requires several projects to work properly, such as airbrush pumps with gas tanks, coloring pens and tool kits, gloves, masks, and water-diluting solvents in solvent bottles, fast-drying small filling soil, 80-3000 mesh sandpaper, detergent, trowel, scraper, etc.

    They used PLA filament and a 3D printer to create a vase model for post-treatment as an example. After the vases were printed, they removed the plate with the model from the printer.


    To clean up the rough surface, the researchers pointed out that users can polish the 3D printed model with low mesh sandpaper. To prolong the life of the sandpaper and smooth the surface of the model, the model and the low mesh sandpaper need to be submersed in water and fined sand along with the model texture.

    They then continued to use a technique called quick-drying small fillers, which added a small amount of filler to the gaps in the model; then, evenly spread the filler with a hard scraper.

    The researchers mentioned: “After filling the soil to harden, wait 30 seconds and use 1200-1500 mesh sandpaper, as shown in Figure 5. If there are still small grooves, repeat the above steps. Fill the soil in a large area. Only when there is no groove, and it feels smooth, users can proceed to the next step."

    The next step is to spray the soil that can be filled with water. First, rinse the surface of the model with water, then fill the soil with a watering can, then wipe the model with non-woven fabric and spray it in the "ventilated position", keep the nozzle at about 20 cm, and spray it quickly and evenly 1 to 3 times.

    The research team explained: "In general, choose grey watering can water to fill the soil because the gray color is neutral."

    After spraying the water and filling the soil, it is air-dried. Then, before entering the coloring stage, 2000-3000 high-mesh sandpaper was applied in one direction for "slight grinding".

    3D printed, polished and processed models should be cleaned and dried before applying pigment. Users can use the spray gun to add a base color or cover the color of most areas of the model. Users need to spray with a 1:2 ratio of thinner and pigment, and you should be able to adjust the amount of gas injected during spraying.

    Researchers also 
    stated that users can use brushes of different thickness and size to draw details, or use a pen to paint on a detailed part of the graphic, or cover it with a different width of the cover tape, and then spray the spray gun to paint.”

    Once the paint and spray paint is completely dry, you can apply a protective paint evenly over the model. The research team used B603 water-based matting agent for 3D printed vases.


    The team also shared some precautions for smoothing the post-processing process, such as using software to reduce the amount of unnecessary support structures, applying a thin layer of glue to the plate to prevent deformation, and the importance of observing the model while printing.

    They point out that the "difficulty" of post-processing methods and the method itself may vary from one 3D printing technology – the method for FDM does not necessarily apply to SLAs, and so on.
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