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Thread: Do it yourself post processing?

  1. #1
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    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
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    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.

  3. #3
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    I pondered for more than just two minutes... hehe... Could you please tell me what diameter of nozzle is being referred to? It seems to me that with larger nozzle diameters, there's less clogging.

  4. #4
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    In my case, sanding helped improve.

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