Heat Insert Technique?
Posted: Wed Aug 05, 2020 2:55 am
I have a project that requires a housing for a small battery powered circuit. I want to use threaded brass inserts for the cover screws so the threads will hold up for multiple battery changes. The eventual goal is to make a couple dozen of the things.
After some research, I ordered inserts, a soldering iron & special tip from McMaster Carr:
https://www.mcmaster.com/heat-inserts
I have a Dremel drill press, and printed an adapter to hold the iron from Thingiverse: https://www.thingiverse.com/thing:3937099
I experimented with dimensions for the printed "boss" the inserts go into, and I'm getting the right hole size. I've done a few tests, and although it's working, and the inserts appear to be nice & solid, there are a couple of issues I'm seeing:
1) Even with a bevel at the top, the molten plastic oozes out around the insert, leaving a significant raised ridge. This is with the top of the insert ~ flush with the top of the boss. The ridge has to be trimmed off with an Xacto knife at this point, which will be a pain in the neck in "production".
2) Once I have the insert level with the top of the boss, when I lift up the iron, the insert wants to rise up out of the hole, and I have to push it back down a 2nd or 3rd time. It's like it's being pushed out by the continuing expansion of the plastic. The inserts are tapered, so sideways expanding plastic may tend to lift them. The threaded hole goes all the way through the insert, and the hole they go into extends a good ways below the insert, so I don't think they are being lifted by pressure from below.
I'm using eSun PLA+ which prints ate ~ 210C. The soldering iron is a cheap Weller 40W iron with no temperature control. It's advertised as going to well over twice that. My suspicion is that the tip is WAY too hot. I have an old Variac that I can use to turn it down, and I'll try that next.
In the meantime, I figured I'd see if there were any tricks or advice from the forum that could help shorten the learning curve.
Thanks!
After some research, I ordered inserts, a soldering iron & special tip from McMaster Carr:
https://www.mcmaster.com/heat-inserts
I have a Dremel drill press, and printed an adapter to hold the iron from Thingiverse: https://www.thingiverse.com/thing:3937099
I experimented with dimensions for the printed "boss" the inserts go into, and I'm getting the right hole size. I've done a few tests, and although it's working, and the inserts appear to be nice & solid, there are a couple of issues I'm seeing:
1) Even with a bevel at the top, the molten plastic oozes out around the insert, leaving a significant raised ridge. This is with the top of the insert ~ flush with the top of the boss. The ridge has to be trimmed off with an Xacto knife at this point, which will be a pain in the neck in "production".
2) Once I have the insert level with the top of the boss, when I lift up the iron, the insert wants to rise up out of the hole, and I have to push it back down a 2nd or 3rd time. It's like it's being pushed out by the continuing expansion of the plastic. The inserts are tapered, so sideways expanding plastic may tend to lift them. The threaded hole goes all the way through the insert, and the hole they go into extends a good ways below the insert, so I don't think they are being lifted by pressure from below.
I'm using eSun PLA+ which prints ate ~ 210C. The soldering iron is a cheap Weller 40W iron with no temperature control. It's advertised as going to well over twice that. My suspicion is that the tip is WAY too hot. I have an old Variac that I can use to turn it down, and I'll try that next.
In the meantime, I figured I'd see if there were any tricks or advice from the forum that could help shorten the learning curve.
Thanks!