[Kirby64]

Yes, I have one and it works exceptionally well. The only caveat is that it’s measuring the metal surface directly and not the actual physical surface (such as PEI), so you need to load different offsets if you swap between different material surfaces such as textured PEI, flat PEI or bare steel.

[stavros]

Oh, how does it do it? I thought it used light/laser to measure, if it's measuring the metal it might not be very accurate with my two layers of magnet and PEI sheet on top...

[Kirby64]

It generates a field using the coil measures the eddy currents in the material directly below it. As long as you have a spring steel sheet and don’t have those large discrete magnets (either lots of tiny round magnets or the sheet magnets) it works just fine.

It’s accurate to single digit micrometers (yes, actually).

[stavros]

Wow, that's impressive. Aren't most buildplates made of aluminium, though? Also I always worry that the PEI sheet over the plate will introduce inconsistencies, let alone that mine has an extra layer of magnet sheet on it (and, as you said, the magnet even makes the detection not work).

However, it seems very doable to have a Beacon for the bed scanning, and a BLTouch for getting the physical distance over the sheet plate.

[Kirby64]

Most PEI sheets are quite uniform so you don’t really have issues with that. As long as they’re applied to the build plate without bubbles they’re generally as flat as the plate surface.

Also, no, almost no build plates are aluminum. Modern printers usually use a silicone heater bonded to an aluminum frame, which either has magnets embedded in it or a sheet magnet applied on top of it, then a spring steel plate with some sort of PEI on top is what you print on. That’s what Prusa and Bambu use, for instance.

I don’t know why you’d want to use BLtouch to get the physical distance, since you calibrate the physical distance when calibrating the beacon sensor itself. Not a problem unless you frequently swap between materials of different thicknesses.

[stavros]

> Also, no, almost no build plates are aluminum.

Ah, I must be misremembering, thank you.

> Not a problem unless you frequently swap between materials of different thicknesses.

Yep, exactly, I have a PEI sheet (with a magnet) and it has a smooth and a rough surface, and I end up swapping between them sometimes. I guess it doesn't really make any difference, since they're both the same height (as they're two sides of the same sheet), but, as you say, my magnet sheet ruins the Beacon homing anyway.

[Kirby64]

Explicitly a magnet sheet does NOT ruin Beacon and is the preferred magnet type for sticking down build surfaces. The only problematic magnets are point magnets that are very strong, as the magnet field can penetrate the surface of the material being scanned and impact the readings (but only at that point).

It sounds like what you're describing is sheet magnet that is coated in PEI, but I highly highly doubt that is what you have. The magnet is attached to the frame, not the material that you print directly on.