Anyone using SmCo magnets for their build plates?

  • We just got a nice CNC router at our makerspace, so once I've got some hours on it cutting various natural and artificial polymers, I'm stoked to try making a bespoke heated bed from some tooling plate!

    Given that there is some reasonably likely future where I build a printer capable of melting PEI, I thought it might be nifty to use Samarium Cobalt magnets instead of NdFeB. Curious to see if anyone here's done that before?

    Eyeballing temperature charts it looks like there's no real justification for it, but I picked up a set at a reasonable price so thought I might have a go at it anyway.

  • @whopping-pochard said in Anyone using SmCo magnets for their build plates?:

    ..............Eyeballing temperature charts it looks like there's no real justification for it, ..............

    Not unless you want to run the bed at >300 deg C or so 🙂 Buy hey, if you've already got some why not?

  • I don't know of many bothering to do their own magnetic bases, but now I want to swap my neodymium endstop magnets to some of these... mostly for pointless self-satisfaction despite the fact that temperature changes in the frame would drive me to do a bed cal regardless of how stable my endstops behaved over time...

  • I opted for N35UH, allegedly good for 180C, and seems to hold at 110C, looked at the more exotic stuff, but was far too pricey.

  • Hi,

    most people who I've seen build printers with this kind of capabilities (myself not included, unfortunately - my high temperature print bed still uses paper clips), actually opt for vacuum tables. They seem to work well at elevated temperatures and give you a set of options for print surfaces (different polymer sheets, aluminium / glass plates, etc). You can use your mill for that, too 🙂

    best regards, Niklas

  • I have, just.

    300mm diameter plate, 32x 9mm diameter x 3mm thick magnets held in place by thermally conductive epoxy (MG chemicals 8329TFS). That's a nice slow (3 hour working life) tolerant epoxy. It needs to heat-cure, but I just stuck it in the oven set to 90C for a couple of hours.

    It hasn't actually had any use yet (on account of I haven't put the printer back together yet) though!

    The magnets I used have the same Ni plating that most Nd magnets come with, so I don't think there is any real difference in terms of what you do, except you need more and/or bigger SmCo magnets to get the same attractive force.

    Top face
    top face
    detail of top face

    Back / bottom face
    bottom face
    I over-filled the holes then sanded back to give a smooth face to mount the heater element to. I think this adhesive shrinks - the first time I did it I struck the wet adhesive flush, and after it was cured the adhesive surface was recessed.

  • @achrn said in Anyone using SmCo magnets for their build plates?:

    I think this adhesive shrinks

    I think that is common for all(?) epoxies. When filling large cavities it can be beneficial to it in smaller batches to avoid cracking due to shrinking (even if the exothermic reaction in itself isn't an issue).

  • @deckingman "Why not?" plays a large role in my decisionmaking process, despite the fact that the outcomes of my decisions frequently provide a good answer to the question!

  • @achrn Ooooh that looks fabulous! Thanks for the epoxy link, too!

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