But, the Beacon 3D along with mesh leveling and selective leveling area are my favorite recent innovations in 3D printing.
Vorons also have a nozzle probing design: https://github.com/VoronDesign/Voron-Tap
With a BLTouch, you need to adjust the z-offset, because the nozzle tip and the BLTouch trigger height are not the same. Once that is calibrated, it should continue to work fine as long as the sensor is working properly.
I think it mainly comes down to the accuracy of the sensor. If your sensor gives you a +-0.03mm reading when probing the same spot, then you will have high and low spots in your bed mesh that you can't correct with z-offset.
This could explain your issues with the BLTouch you mentioned in another thread here. I have various brands of knockoff BLTouch sensors, and the worst one had a +-0.02mm range when measuring points, which made it impossible to get a good bed mesh. The one I replaced it with had about a +-0.005mm accuracy, which fixed my issues with the low and high spots.
The pressure sensor on the hottend is superior to any other method, because it has much better resolution (though maybe not better than the Beacon), and it can adjust to print conditions in real time, which no other start-of-print sensor can do.
EDIT: I'm not sure, this article says it can detect spaghetti just from the pressure difference, for example:
https://all3dp.com/1/nextruder-prusa-xl-deep-dive/
It also hints at detection of the height while printing.
They currently only use the load cells for bed leveling: https://www.youtube.com/watch?v=F7ETSVu04ao&t=940s
I could be wrong, but I would expect that the load cell readings would be far too noisy in order to determine the height of the nozzle while printing. Even if they were accurate, different materials would also behave differently due to different viscosities.
I do have two BLTouch printers and lots of Prusas with the PINDA inductive sensor. What excites me about direct nozzle force sensing is that it eliminates the need to calibrate z height offset between the sensor and the nozzle. I don’t know if Bambu’s bed sensor is as good as Prusa’s nozzle sensor but anything that eliminates the mechanical stack up between nozzle and sensor is an improvement IMO.
Though I do realize much of my gripes come from the fact that the PINDA mount on the Prusa Mk3s is kinda weak and I’ve had several fail, requiring an annoying service job.
It’s accurate to single digit micrometers (yes, actually).
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.
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.
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.
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.
Hmm, from this I understood that a sheet magnet will ruin Beacon.
I don't have a magnet that's coated in PEI, I have a magnet sheet on the bottom (stuck to the big bed plate), and, on top of that, a thin steel plate (the one you bend to pop the print off) coated with PEI on each side (smooth/rough PEI). If the magnet sheet under the steel plate doesn't mess with Beacon, I'm going to buy a Beacon right now.
https://docs.beacon3d.com/faq/
What you’re describing is the ideal material stack up for beacon. Only thing you may need to do is load a different nozzle offset for the smooth vs rough side, since the thickness of the PEI is probably not the same.
> Magnetized rubber sheets have a high number of poles, and result in no detectable artifacts.
Which kind of sounds like what I want, but doesn't actually say "you'll be fine if you have a magnetized rubber sheet", "no detectable artifacts" might very well mean "the sensor doesn't detect your bed".
Thanks for the clarification, this sounds great.
You can also join one of the many discord servers (Rat Rig probably has one) and ask there for details