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I have built a few parts that have printed 'pins' on them (2mm diameter 1.5 cm length). Due to the orientation that the build requires the pins have to have support material on them. (The part has to be printed with the pins parallel to the build plate for strength reasons and the orientation can't change).

The problems i'm having is that the surface of the pins are quite rough. The pins are designed to press-fit into a soft rubbery tube, and the pin surface roughness is cutting into the softer tube. The roughness is due to both the layer edges of the print, and that the support material leaving some 'burrs'. I'd like to smooth the outside of my pins with some type of post processing technique. Ideally I'd like to keep the pins as close to dimensionally accurate as possible, but I realize they won't be perfect.

The two methods I've considered are sanding the pins by hand and placing my part in an acetone vapor chamber for a while.

Sanding, I think, is the best option of the two so far but it's a bit tedious, and is quite difficult to do, due to the size of the pins, their location and my fingers are pretty big relative to the space I'm working in.

I don't like the idea of using acetone because the few times I've tried doing this in the past, my parts always came out warped or misshapen I think due to the relief of stresses. (or I did it wrong, both seem plausible).

If anyone has a third option (or more) I'd be glad to hear. Or if there is another approach altogether that I haven't considered that can be done on an FDM style printer that would also be appreciated.

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    $\begingroup$ My inclination would be to print a hole to receive a separately made pin of some material, metal, plastic, even wood. Not in the spirit of 3-D printing, I know, but probably more practical. $\endgroup$ – Mick Mar 20 '17 at 10:50
  • $\begingroup$ With sanding, you can always remove a little, check, repeat. With acetone approaches, it's very easy to go too far, too fast. $\endgroup$ – Davo Mar 20 '17 at 11:47
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    $\begingroup$ Would you consider printing triangular holes (so no support is required), then printing the pins vertically with triangular bases? If you are amenable to an assembly instead of a mono-block print, I can write out a full answer on this. $\endgroup$ – Hari Ganti Mar 20 '17 at 18:25
  • $\begingroup$ I'd ideally like to keep the part a single piece, but It could be an option to replace the pins with a different part. and turn the project into an assembly. I'd more than likely print the part lengthwise along the bed of the printer so that the loading of the pins wouldn't be along the separation layers of the print as the pins will be taking a fair bit of loading. $\endgroup$ – Diesel Mar 20 '17 at 20:44
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Your objective is quite a challenge, considering the limitations within which you have to operate. Small diameter of an appreciable length is daunting indeed.

I would consider to use a regulated heat source such as a soldering station, one with removable tips. After electing an appropriate tip to handle the dimensions, a hole drilled into the tip to accept the pin diameter and length would be the next step.

There would be consideration needed for the plastic material pushed ahead of the soldering tip, as well as angular stability while pushing the soldering iron onto the pins.

To improve these circumstances, a sharp edge ground at the end of the soldering iron tip would give a better shearing of the excess plastic.

The temperature control would be critical to prevent destruction of the pin within the tip and to provide optimum removal via the cutting end.

Directly related to the above, but without the heat would be the equivalent tool to be used in a rotary grinder such as a Dremel. The bore of the custom-made cutter would match the pin and the sharp cutting end could also have serrations such as those found on hole-saws. Low speeds and a steady hand are required!

If either of the above suggestions do not remove sufficient plastic roughness, one would make the pins of a larger diameter and ensure that excess is removed to specifications.

EDIT: Additional thoughts. Hobby stores and online equivalents will sell very small diameter tubing. It might be an easy matter to find 2 mm inside diameter tubing of brass or even stainless steel. A few passes on a piece of sandpaper while the tubing is chucked in an electric hand drill and you have a sharp cutting edge.

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  • $\begingroup$ It's looking like the soldering iron is going to be the best approach $\endgroup$ – Diesel Mar 31 '17 at 14:35

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