Information needed on leveling sensor technologies.

I am looking for information on what technology various commercial 3D printers use for sensing the bed level, particularly the most common desktop printers. Of most use would be pointers to documentation from the manufacturers that divulges what they use, be it inductive, capacitative, microswitch etc..

The reason that I need this is that we (myself and DjDemonD) have submited an article to an open access journal (MDPI Inventions) and it is currently undergoing peer review. One of the reviewers has requested that the article should include evidence that piezoelectric discs are not a common existing technology on 3D printers: It seems best to list what is used along with urls or pointers to the information - personal knowledge is helpful as it may allow me to find citable data even though it but can't itself be cited.

This information will of course also be entered into the RepRap Wiki, possibly also useful would be information on kits of parts for retro-fit kits to enable automatic bed leveling.

We have about 5 days to get the revised manuscript together so it is a little bit urgent.

Thanks for any info you can give.

Well, to be honest I can't think of another commercially available piezo sensor kit. I haven't heard of too many hobby hacks using one either, so it's definitely uncommon from my point of view. That being said, I quite like it since it's a sensor with zero XY offset from the nozzle and doesn't require tuning to get it to trigger at the proper z height. I can't think of a big name printer that uses this method.

You could try referencing what other high end manufacturers use. Prusa uses an inductive sensor, ultimaker an IR sensor, aleph objects use a contact sensor with the corners of the bed, ditto for zortrax. Printrbot used capacitive sensors, I think they moved to inductive but I'm not sure. All of this should be available from the source files which you can link to or at the very least a feature or spec sheet. Anecdotally, I seem to hear and see much more about inductive sensors than any other type. Most chinese kits that include autolevel seem to use an inductive sensor or occasionally a BL touch.

Hi Trakyan,
Thanks for your input, I am fighting a losing battle against the fact that most manufacturers publish only that they have auto-leveling without saying anything about the technology - other than that they all claim to use the best method

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Trakyan

Well, to be honest I can't think of another commercially available piezo sensor kit. I haven't heard of too many hobby hacks using one either, so it's definitely uncommon from my point of view. That being said, I quite like it since it's a sensor with zero XY offset from the nozzle and doesn't require tuning to get it to trigger at the proper z height. I can't think of a big name printer that uses this method.

The only other piezoelectric kit is in Brazil and was designed by ECJ a regular contributor to this forum. There are also two Chinese companies selling copies of Moriquendi's circuit in the most blatant plagarism I have come across.

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You could try referencing what other high end manufacturers use. Prusa uses an inductive sensor, ultimaker an IR sensor, aleph objects use a contact sensor with the corners of the bed, ditto for zortrax. Printrbot used capacitive sensors, I think they moved to inductive but I'm not sure. All of this should be available from the source files which you can link to or at the very least a feature or spec sheet. Anecdotally, I seem to hear and see much more about inductive sensors than any other type. Most chinese kits that include autolevel seem to use an inductive sensor or occasionally a BL touch.

It is pointers to the spec sheets that I most want - the old fashioned full spec sheet with document numbers and dates etc. would be really really good but not even HP seem to do that sort of thing anymore.

Those I have found so far include:-

• The Prusa i3 used an inductive probe called the PINDA.
• The Lulzbot Mini and TAZ 6 both use conductive 'washers' on the corners of the build plate and electrical contact with the nozzle.
• The UP! Plus 2 3D uses a microswitch mounted to a carrier which has to be manually connected to the nozzle. This gets the out of level data but I think the actual nozzle height is got by driving the by driving the nozzle down in the centre of the plate until it stalls and then going up to the upper Z limit switch while counting the steps to do so (I haven't been able to confirm this but it seems to be what is happening)
• The Ultimaker 3 uses a cleaver capacitive nozzle contact sensor which measures the capacitance from the nozzle to the plate as the nozzle approaches the plate. This increases until the nozzle makes contact - the point where the capacitance stops going up marks the contact. (This is really cleaver but sensitive to anything else effecting the capacitance - touching the plate etc..)
• The Fusion3 F400-S uses DC42s optical proximity detector.

Even with the above it is a fight to use anything on the sales site as a citable reference.
I had forgotten about the Printrbot and have just looked it up but so far I haven't been able to confirm from hhe online literature if it is capacitve or inductive.

I have found a fairly inconclusive reference that indicated that several of the major industrial FDM printers use piezo sensors but not even if they are for the print bed or which models.

So any more info that anybody can give will be gratefully recieved.

Mike

I recall a video done by Tom saying the printrbots he used had a capacitive sensor.

And you're right, to be honest I had a quick look for some sources when I was writing up my last post and couldn't find much if any information beyond "we have bed leveling". You could try some video interviews/reviews since they often mention exactly what type of sensor the machine uses. Tom in particular usually goes into sufficient detail, but I don't know if that is cite-able.

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leadinglights
There are also two Chinese companies selling copies of Moriquendi's circuit in the most blatant plagarism I have come across.

You developed the circuit, I just put it on a PCB and manufactured it.

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

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Moriquendi
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You developed the circuit, I just put it on a PCB and manufactured it.

Idris

You give yourself too little credit, I just plugged together several standard circuits and trimmed them up to respond to the signals I saw on my test rig. By turning my circuit into one that could be made and trimmed you did as much - we even used the same application note from Texas [forums.reprap.org]

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Trakyan
I recall a video done by Tom saying the printrbots he used had a capacitive sensor.

And you're right, to be honest I had a quick look for some sources when I was writing up my last post and couldn't find much if any information beyond "we have bed leveling". You could try some video interviews/reviews since they often mention exactly what type of sensor the machine uses. Tom in particular usually goes into sufficient detail, but I don't know if that is cite-able.

It gets worse than "we have bed leveling" as some simply state that they are auto calibrated from the first layer up. Even "open source" often means "you can adjust some parameters". I suspect I could get better specifications from at least some manufacturers but only by writing to each of them and being grateful for any crumbs of transparency that any of them show - time does not permit that as I only have a couple of days before re-submitting.

Mike

Sorry I couldn't be of much help, I've been really busy (and continue to be until Wednesday)