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I have an SLA printed part I want to put a brass threaded insert in using a soldering iron. The insert is slightly larger than the hole so I would assume the edge will melt and re-freeze around the teeth. Are there any issues with melting SLA or this idea in general?

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    $\begingroup$ Why not go with a press-fit, plus a couple drops of epoxy if so inclined? $\endgroup$ – Carl Witthoft Oct 17 '18 at 14:49
  • $\begingroup$ @CarlWitthoft it's a thin thru hole unfortunately, and when I modified the design (this is an assembly not a single part) I can no longer access the back face to put a nut on, hence the idea of making it threaded. $\endgroup$ – Crazymoomin Oct 17 '18 at 15:26
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The plastic used in SLA printing is what is known as a thermoset plastic, as opposed to the thermoplastic plastics used in FDM printing. What this means, is that it can not be melted. The reaction that hardens SLA materials is irreversible. If you heat up the plastic it won't melt, it will just burn (if it gets hot enough). What you're planning is a bad idea, and it won't work.

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  • $\begingroup$ OK, that's that idea out of the window, but thanks for the advice. I don't think there are any good alternatives for putting an insert in sadly, looks like I'll have to put the mount somewhere else (it's an old model and I really don't want to reprint it). $\endgroup$ – Crazymoomin Oct 17 '18 at 14:17
  • $\begingroup$ Well, there's an indirect solution: print the part with an oversize hole with a deliberately rough boundary . Then line the hole with some fresh plastic, insert the metal part, and heat to melt& fuse the new material into both the metal part and the boundary. Seems like a lot of work to me. $\endgroup$ – Carl Witthoft Oct 17 '18 at 14:48
  • $\begingroup$ @CarlWitthoft indeed. Thankfully there are other non-SLA parts in the assembly I can reprint more easily, it's just more awkward to mount the sensor there. But it looks like that's the best option. $\endgroup$ – Crazymoomin Oct 17 '18 at 15:28
  • $\begingroup$ Another approach would be to do as Carl suggests, but apply the liquid resin to the inside of the insert. If the resin is daylight cure or UV cure, placing the insert area in the sun should fuse the insert in place. $\endgroup$ – fred_dot_u Oct 18 '18 at 0:07
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There is an alternative. Use screw to expand inserts before final curing. After washing, but before curing, place the threaded insert into the hole. Use a screw to expand it into the hole walls. Curing will then 'fix' the insert into the hole. Hope this late advise is usable. TC Carr

https://www.mcmaster.com/screw-to-expand-inserts/

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Is it possible to make the hole larger, put the brass insert with a pre-installed screw inside the hole, fill the area with resin and cure with UV lamp?

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    $\begingroup$ Hi and welcome to 3DP! Unfortunately, your answer does not answer the question. Without wishing to sound harsh, StackExchange is a Q&A site, and not a forum of threaded messages. The reason for this is to aid the search for answers to issues, and provide it in a structured Q&A way. I know that this might seem a pain, but can you repost your question using the Ask Question link at the top of the page? When you repost your new question, please feel free to refer back to this original question using the URL, seeing as it is the reason why you posted in the first place. Thanks! $\endgroup$ – 0scar Jun 10 at 9:37

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