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I recently decided to upgrade to auto bed-leveling using an inductive proximity sensor and an aluminum build plate on my Prusa i3. I also wanted to try to secure the build plate using neodymium magnets at 4 points, with the magnets being secured with bolts to the Y-carriage, and steel washers glued to the bottom of the aluminum build plate (since aluminum is not magnetic).

I would like to know if anybody has attempted this, and what the results were, as well as any issues incurred. My primary concern is a possible interference between the small magnetic field that is created by the magnet, and the sensor when probing the plate. I fear this question may sound a little open-ended, but I would just like to know if this could work. Please feel free to ask any follow up questions to details I may have missed. Thank you.

P.S. I would also like to note, in case there is any relevance, I do not plan on using a heated build plate, since I have a heated build chamber.

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  • $\begingroup$ My main concern would be the strength of the glue when the heated bed is on. When I use Elmer's glue on my abs models to hold them to the bed, it softens when the bed is heated. $\endgroup$ – Eric Johnson May 15 '16 at 1:18
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Good question. The magnets from the build plate will almost certainly interfere with your inductive sensor, the movement from the carriage will induce a current in the inductor as it approaches the magnet and may cause it to trigger. If you're looking for a mag build, I'd suggest looking at: http://www.3dprintermods.com/prestashop/index.php?id_product=9&controller=product

I'm just about to get into auto-leveling myself, with this particular build there are a few ways to get around the issue. If you plot your auto level to occur as far from the magnets as possible (x,y location wise), then you might be ok. Otherwise you might consider investigating optical and touch probes.

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You might use the magnets themselves or additional ones on top for the leveling process, as partly discussed in this thread:
http://forums.reprap.org/read.php?1,479795

A mechanical or piezo switch might also solve the issue for you with a lot less guesswork and trouble.

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