So, found out the hard way that you can’t apply heat to neodymium magnets. Had 16 magnets to press into a print (tool holder). Thought since the soldering pen I use for inserting threaded nuts into prints works so well, I would use it for this too. And it did work well, but now all the magnets are not magnets any more. Yup, heat will demagnetize them. Part is useless, so had to trash it. Found out something new, but wish I had heard about this beforehand.
The way I’ve embedded magnets in prints in the past was to:
- Design a magnet-shaped (plus like 0.2mm of clearance) cavity into the print, but leave it completely “closed off” to where it’s “inside” the print.
- But only “closed off” by like 2 or 3 layers (I was printing at 0.2mm layer height for this particular print).
- Use “pause at layer” functionality in my slicer (I used Cura at the time) to pause just before the first layer that would “close off” that cavity.
- Start the print and when it pauses, drop the magnet into the cavity.
Yes, I was a bit nervous about the magnet potentially jumping up and sticking to some ferromagnetic metal that’s part of the print head, but that didn’t happen in my case. YMMV, I guess.
I guess theoretically it could also be the case that the heat from printing could weaken the magnet, but again, that wasn’t an issue in my case.
Just to elaborate on what my project was, I had a freely-spinning part that I wanted to be able to fix in place or unfix. I fashioned a “stop” that when engaged would fix the freely-spinning part in place. The way it works is that the stop can move freely up and down. Putting it in the “down” position fixes the freely-spinning part in place and gravity keeps it engaged. But to disengage it, you slide it straight up. At the top of the “track” in which it slides is where I put the magnet. I used the same technique as described above to embed a little stack of about four staples into the stop itself. So, by sliding the stop to the top of the track, the magnet attracts the staples, keeping the stop disengaged until you pull it back down again to where gravity will keep it engaged until you move it back up.
If you do this, make really good notes and markings on the polarity of your magnets.
The number of times I have tried this, to end up with two mating parts that repel each other.
Alternatively, just print recesses and glue them in afterwards.
I just stack the magnets first to get them all in the same polarity, and insert them, using the stack to push it into the hole, with a press fit they won’t jump out
I’ve used a lot of 12x3mm and smaller magnets without them jumping up and attaching to the print head but I did have it happen with larger 40x10x3 rectangular magnets. It ruined the print and caused a huge clog, but I came up with another way to embed magnets because of it.
I designed a long 10x3 tunnel into the print, printed the object without pause, then slid the magnets into the tunnel. I printed a couple spacers to go between the magnets to place them how I wanted them and I printed a plug to glue into the opening of the tunnel. The plug was a second color so it stood out and made a little accent.
I haven’t done it yet but I thought it would be cool to add a little decorative design to the original object to be printed in a second color and make the tunnel plug the same second color and hide it in the decorative design.
My magnets pull towards the printbed when i put them in.
But i also only cover them with a single .2 layer so they keep their strength.
Of course, if they’re on the bottom of the print.
Heat destroys magnetism.
Lesson learned, I guess 🙂 here’s some more:
At what temperature a material loses its permanent magnetic properties is called the Curie temperature. For Neodymium magnets this temperature is around 310–400°C (ca. 590–752°F). So if the heat is below that, you’re mostly safe.
Maybe look into how to design/modify a part and how you can pause your print a at a specific layer height so you can just drop in the magnets (use a drop of super glue to they won’t attach to the hot-end or make a test print with various diameters to find out the perfect width for press-fitting the magnets in) and then continue the print.
This also results in nicer looking prints because the magnets are invisible. Depending on thickness above the magnets and strength of the magnets the result might be less strong, so ideally there are only very few layers of material covering the magnets.
This is a very straightforward and in-depth video on how to do this in a good way:
They lose their coercivity far sooner. The higher the magnetization, the more sensitive it is. So N52 is more temperature sensitive than N45 (but both start to suffer around 80 °C). You also get alloys that are more tolerant and get specifications like 44H that can be used up to 120 °C or 35SH up to 150 °C.
So how do the magnetic build plates work? Some materials need high bed temps. 80C for nylon.
different types of magnet have different temps they demagnetize at
