Magnets in 3D Prints: How to ruin your printer edition

Comments · 432

• JJ

  @JJFX- · 3 months ago (edited)

  Many people often confuse a magnet&apos;s Curie temperature with heat resistance. While the Curie temp (point it will completely demagnetize) of sintered neodymium exceeds 300C, standard grades (N35, N42, etc.) have a maximum rating of about 80C where irreversible flux damage starts to occur. Higher grades (e.g N42M, N42H, N42SH) have additives that can increase their coercivity and temp rating to about 100-150C. Specialty grades can push upwards of 200C but beyond that something like Samarium-Cobalt is needed.<br><br>However that&apos;s for single magnets in an open state. You can partially increase resistance to flux damage by just fixing it to a material like steel to close the magnetic circuit. That can potentially allow even standard grades to exceed 100C before significant damage occurs but you still can&apos;t take a soldering iron to it.<br><br>Also the reason cheap 3D printer bed magnets aren&apos;t notably damaged at 100C+ (as many claimed they would over the years) is because they&apos;re made from ferrite particles that are more resistant to this than neodymium and it&apos;s constantly in a closed state against a piece of steel. The main concern are the binders, adhesives or certain bed surfaces degrading but even many cheap ones still hold up to 100-105C reasonably well.

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• ST

  @Stray-Signals · 3 months ago

  I ran a 3d printing shop for a couple years, printing a variety of toys and novelty items using a small fleet of Ender 3 like printers. I have a few designs that use magnets and I always preferred embedding over other solutions. This was important for toy design to avoid the risk of a dislodged magnet becoming a choking hazard for kids.

  174

• JO

  @johnvandenbos1673 · 3 months ago

  What I have done when inserting magnets during printing is, put super glue first, then the magnet. Let it dry for a couple of seconds, then continue the print. Now they will not pop out to the nozzle as they are stuck due to the glue.

  208

• JL

  @jlitwiller · 3 months ago

  &quot;Don&apos;t try to heat-set magnets.&quot;<br><br>Yeah, I learned that one the hard way.

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• TH

  @thebeluvdtrex · 3 months ago

  Im glad im not the only one checking the polarity forgetting which side and checking again multiple times 😂

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• PO

  @poptartmcjelly7054 · 3 months ago

  <a href="https://www.youtube.com/watch?v=xTfytJBLEn4&amp;t=200">3:20</a> you can also add a small lip just above the magnet hole because most magents have rounded corners and will happily snap into place without having a perfect size hole and will still be flush with the surface.

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• CR

  @CrabtreeCAD · 3 months ago

  In my experience, a press fit in a circular counterbore works just fine. The seam that forms from printing the counterbore kind of acts like a rib anyway

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• RP

  @rpiian · 3 months ago

  I designed the Centauri Carbon SM-33 magnetic cover. I found that the magnets, while printing ASA, had the potential to REVERSE POLARITY. Which is extremely problematic when you want to keep your tool head cover attached during printing. While incredibly annoying, as it completely scraps the cover, I also found it interesting and did not know this was a thing initially. Magnets surprise me in so many ways 😄

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• RF

  @RFC3514 · 3 months ago (edited)

  <a href="https://www.youtube.com/watch?v=xTfytJBLEn4&amp;t=346">5:46</a> - Actually, it&apos;s generally a good idea to leave a small gap above the magnet (meaning, have it about 0.5 mm below the surface of the part), so the magnets don&apos;t smack into each other when the parts attach. I wouldn&apos;t add a lip, though (that&apos;ll generally lead to a gap between the parts themselves), I&apos;d just make the hole slightly deeper than the magnet.<br><br>And always glue them (I use epoxy). PLA &quot;relaxes&quot; with time (as do some other plastics), and a simple friction fit will become weaker with time, to the point that the magnet on one side will eventually pull the other one out.

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• JU

  @justinmorgan7851 · 3 months ago

  “Now all I know about magnets is this: Give me a glass of water, let me drop it on the magnets, that&apos;s the end of the magnets.”

  5

• TH

  @theaninova · 3 months ago

  Friction fit: remember, PLA has creep. Friction fit also works only until your environment is warm enough for heat expansion to release your magnet. My Stealchanger carriage had its magents solid/never coming out with just friction fit, until I started printing ABS for an hour, after which they started to just fall out.

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• JA

  @James_D_S · 3 months ago

  Totally have a brief case full of printer parts too

  7