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Thread: “Do it yourself” post processing?

  1. #1
    New Member
    Join Date
    Feb 2023

    “Do it yourself” post processing?

    I am developing a complicated product where most of the parts have to be 3D printed. The production version will mostly be made from PA12 printed using MJF as it is a bit stronger than PA12 SLS. These parts will be polished as part of the prototyping/production process. One part of the product is under a lot of bending stress and needs to be very stiff and strong. I have been prototyping this part on my Ultimaker S5 using PA12-CF. I have managed to push this beyond normal suggested guidelines and have been able to print it with a 0.15mm layer height and a 0.40mm print core. The problem is that it has a very rough finish, as is typical any time you add carbon fiber to a material. I have been thinking of trying to smooth this out during the prototyping / beta testing phase of the project using a rock tumbler and some type of polishing material such as ceramic. Before I invest in the equipment to try this, I wonder if anyone has tried smoothing 3D FDM prints using a rock tumbler. When the product goes into production, this will probably be made by SLS with PA12-CF powder and then polished normally, but this is very expensive to have done by a prototyping service when I am steal tweaking the design. By expensive, I mean that a single part that is about 120mm x 15mm x 7mm in rough dimensions will cost at least $50 each. One service quoted $96 for this single part!

    Thoughts on this idea?

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Bold Springs, GA
    Thoughts and comments after 2 minutes of thinking:

    For clarity “Print Core” = extruder nozzle diameter?

    So, PA12 is nylon and PA12-CF is a carbon reinforced nylon filament. Nylon is not reactive with most chemicals and vapor smoothing as used with ABS is not possible as I understand it.

    .15mm layer sounds impressive I do wonder what your yield is without nozzle clogging. Moreover your part print time requires patience.

    I’ve never heard of rock tumbling anything 3D printed with a polymer and my gut feel is that it will not work. However – try it and see what happens…

    Sanding is another option but it’s time consuming and results vary. A design that includes gussets or other stiffening/strengthening features may be a more practical approach. More print time less post processing for stress riser features.

    I do wonder is there’s coatings or paint like products that adhere to nylon and fill the irregularities between layers - thus reducing localized stresses.
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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