What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?  

Re: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

I am using epoxy-glue for the job. Super-glue might be a bad idea, since most of CA glues melt above 80°C.

Re: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Loctite red. I re-did all my magnets with it. Quick, easy, and they've been holding strong for months. Just a smear on one side of the magnet. Hold it in place for 30 seconds. Done.

Re: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Same issue here, did some long prints with ABS and 4 magnets popped out, 2 of which collided with each other mid-air and broke in 2 which changed the polarity.

Found this place which seems to be an exact replacement:
https://www.umagnets.com/p/20mmx6mmx2mm-thick-neodymium-block-magnet-n35-thin-magnets-super-strong-rectangular-rare-earth-flat-magnets-20-x-6-x-2mm/?attribute_pa_pack-of=pack-of-20

Not a bad price.

My searching for an adhesive lead me at first to tailpipe sealant as it's rated upwards to 1000c, but going to try some Sugru first as it is rated upwards to 380c which the bed would never reach in the first place. Sugru also seems much easier to remove & replace in the event the magnet weakens.

Re: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

I had five magnets come off., none of them had glue rests on them. That indicates that the glue did not stick to the magnets. I have been working with neodymium magnets for several years now and in my experience they will only stick when you properly sand the surface of the magnet. Nothing will stick to a smooth surface, the glue requires a rough surface. I used a small screwdriver to get all of them off, sanded them and glued them back on using Gorilla Weld ($6 at Home Depot). This glue can take temperatures up to 300F (150C). I hope I will be fine now.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

I am having the same problem.

I glued a cople with contact glue some weeks ago and they didn't moved again.

I wrote today to support because it cotinue happening (more magnets fell down and some broke) and they suggested me to glue them with epoxy glue. They will also send me some magnets to replace the broken ones.

Probably I will unmount the bed and glue all magnets again.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

What ever magnet you get to replace your missing and broken ones should be high temperature resistant. AFAIK, most general purpose Nb magnets will loose their magnetism when heated up. Prusa specifically says in their advertising that they use high temperature resistant magnets.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Anyone try JB weld?  It will take 500 F or 260C sustained.  

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Interesting thread.

All of the problem cases seem to involve bed temperatures of at least 100C. That the working limit of Prusa glue?

I hope Prusa is monitoring this. Using a higher temp glue at the factory is a really cheap solution.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

I research this topic a lot in the past.  I clue aluminum motor retainers on rockets.  The aluminum tops out at about 240-250 C.  I can yell you I that  JB Weld easily holds for years.  I have never had it fail even with an errant ballistic recovery.  

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Just found several of my magnets loose or having fallen off (two stuck to the rails) probably a result of 7 weeks of 24 hour PETG faceshield printing.  I'll try epoxy.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Posted by: @anthony-e7

Same issue here, did some long prints with ABS and 4 magnets popped out, 2 of which collided with each other mid-air and broke in 2 which changed the polarity.

Found this place which seems to be an exact replacement:
https://www.umagnets.com/p/20mmx6mmx2mm-thick-neodymium-block-magnet-n35-thin-magnets-super-strong-rectangular-rare-earth-flat-magnets-20-x-6-x-2mm/?attribute_pa_pack-of=pack-of-20

Not a bad price.

My searching for an adhesive lead me at first to tailpipe sealant as it's rated upwards to 1000c, but going to try some Sugru first as it is rated upwards to 380c which the bed would never reach in the first place. Sugru also seems much easier to remove & replace in the event the magnet weakens.

Even though this is a 2019 thread, I need to comment on this. That magnet linked is rated up to 80° Celsius and most likely will not work properly. There is high temp magnets für applications like this that will suit better.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@alex_sc

I suggest JB weld.  You will never get your bed warm enough to weaken it.  I use it to attach aluminum rocket engine retainers on high power rocket motor blocks.  They get to 260-280C without a problem.  

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Posted by: @charles-h13

@alex_sc

I suggest JB weld.  You will never get your bed warm enough to weaken it.  I use it to attach aluminum rocket engine retainers on high power rocket motor blocks.  They get to 260-280C without a problem.  

You did not read my post. I did not ask for glue but gave an advice regarding the magnet suggested above.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@alex_sc

Yes, I can read and did read your post.  Did read the purpose of the thread?  There is no reason to be hostile or confrontational.  I am recommending this over the muffler repair product in the post you quoted.  The reason I suggest JB weld over the muffler product is it gives a stronger bond.

If magnets are what you want, I would order 2mm x 6mm x 20mm magnets from AliExpress.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@charles-h13

This was not meant to be hostile, just to be clear that this was not the point of my post, since you directly adressed me. I am aware of JB Weld, you mentioned it two posts above mine, in direct reply to mine and in your last. Problem is, all my magnets are still in place and there is no JB Weld in Germany  😜 

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Posted by: @david-f42

I have two magnets that have fallen out from the bottom of the heat bed. My first thought was to superglue them back into position, but my second thought was that I'm not sure how well that would holdup to heat. So, what kind of glue should I use?

I used this one: https://www.k2-global.com/de/products/k2-black-silicone-350c-85-g

I replaced the magnets with neodymium type 45uh 20x6x2mm.

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@alex_sc

no problem.  I did no know your location.  A couple of colleagues use JB weld in Germany.  Not sure how they get it.   

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@charles-h13

no problem: https://www.amazon.de/JB-Weld

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

Posted by: @robert-rmm200

Interesting thread.

All of the problem cases seem to involve bed temperatures of at least 100C. That the working limit of Prusa glue?

Alas, I never heat the bed above 90 degrees (printing PET) and I had two magnets fall out of my Mk3S yesterday.

I never let the metal plate snap in place but always lowered it gradually and carefully. Just looks like the glue Prusa used to hold the magnets in place isn't up to par. I'll have to see where I can find the correct heat insensitive epoxy or glue in the Netherlands...

RE: What kind of glue to use for re-attaching magnets that had fallen out of the heat bed?

@wilko

Maybe you try this product: https://www.amazon.de/gp/product/B00GFACVWO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I use it very often on the printer for heat resistant applications. I print PEEK at bed temperatures of 140 to 150 degrees C. and I have not lost a magnet yet.