Re: Nozzle touch auto bed leveling

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frankvdh
This method relies on measuring the resistance between nozzle and a metal bed... when it's zero, the nozzle is touching. If your printer has a metal structure, the nozzle may already be electrically connected to the bed, so it will always read zero.

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frankvdh
Obviously you can't use this if you print onto glass or tape, which is exactly what most people do.I don't know of any people printing directly onto the aluminium bed.

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frankvdh
Unless you use some electronics (it could just be a couple of resistors, or maybe a transistor) at the controller board, you'll need to run 5V (or 3.3V, depending on the type of controller board) to the nozzle. If a short circuit occurs from your 12V heater supply to 5V sensor input, you will probably destroy that input on the controller, and may destroy the entire controller board.

If there's some filament stuck on the nozzle then the nozzle (especially if it is cold) will never touch the bed and trying to set the height or auto-level will drive the hotend into the bed, probably damaging the printer.

Personally, I think that this is worse than nothing; at least if there's no sensor, you know to manually set the nozzle height, and NOT to use the home or auto-level commands. And there's nothing to damage your printer.