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auto bed levling idea! need help.

Posted by tintinz 
auto bed levling idea! need help.
December 28, 2013 03:37PM
Hey. i have an reprap prusa Air. and want to add auto bed levling without a switch on the extruder.

my hotend are E3D hotend

so my hotend are total in metal.

my idea are to use the 3:th termostatis port in ramps 1.4 to detect 0 resistans between hotend and a folie on the bed.
So set a clamb on the hot end and a folie bit and plase the folie on the bed. when the hotend touch the bed it get like 0 resistance and know its touch the bed.

Good Idea ?
Re: auto bed levling idea! need help.
December 28, 2013 08:32PM
It's been discussed before. It's feasible but most likely not high reliability. The most likely issue is if there is any plastic residue on the tip it will not make good electrical contact.
Re: auto bed levling idea! need help.
January 04, 2014 09:06PM
It's also been found that repeatedly running your hotend into a piece of metal wears down the extruder and nozzle. The best way I've found is the use of a z probe or a momentary switch.

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Re: auto bed levling idea! need help.
January 05, 2014 09:38AM
Unfortunately, I don't think using the nozzle as a contact sensor would be reliable.

For a contact sensor, I would use a servo with a simple push switch, or maybe a dial type mechanism, with a lever connected to a position sensor, perhaps a potentiometer or Hall type device. The sensor tip would need to be lowered into place for sensing, then moved out of the way during printing.

A non-contact method would be ideal, as that would not require any moving parts, as it can be mounted above the nozzle tip.

The Ormerod uses an photo-sensor which shows promise, one problem with IR sensors is dealing with different ambient conditions. I think that can be fixed with a bit of electronics. It needs reflective tape on the bed, so senses at the four corners.

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Re: auto bed levling idea! need help.
January 28, 2014 10:20AM
I have a omron spy402 ir proximity sensor which is very very cool, it uses modulated IR to eliminate the effects of ambient IR from sunlight or the hotend or bed itself. Its seems to be very very accurate. Im running it up at the moment as a non contact bed leveling probe.
Re: auto bed levling idea! need help.
January 30, 2014 02:51PM
That IR proximity sensor sounds very good indeed, I wonder why this isn't more common?

A cheaper alternative may be to use one of those cheapie hc-sr04 ultrasonic modules. I've played about with them in the past and they seem to work quite well.

Maybe I'll give it a go in the future!

Re: auto bed levling idea! need help.
February 07, 2014 01:57PM
Hi, I've already try to use the hotend tip as a contact with an aluminum platform and didnĀ“t go well, For some reason it seems the diferent metals, in my case stainless steel (nozzle) and aluminum (platform) can't conduct the amount of electrons necesary to close the circuit, You'll need a larger point of contact to make this possible.
I got a video of the prototype I'll be uploading pretty soon.
It needs a few tweeks yet, but... that's the idea of a prototype

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