IR sensor and Clever3D PEI aluminium plate

Discussion in 'BigBox General Chat' started by Alex9779, Oct 11, 2016.

  1. Alex9779

    Alex9779 Moderator
    Staff Member

    Sep 4, 2015
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    So as promised here are my findings:

    Up until now I had the Clever3D PEI aluminium plate in natural color which is some kind of silver and as described in some post spread across some other threads I had issues getting a consistent Z height after homing.
    Using a feeler gauge to measure the distance between nozzle and plate after homing showed that it varied.
    Some times I had 10 times the same values then 5 times greater, then 3 times smaller.
    I tried homing with different lighting conditions and settings and I can tell so far that my LED lighting, external lighting, bed temperature have no influence on this. I didn't believe it really before but now I am confident that it is that way.
    With this plate the IR is totally dependent on the surface but has issues with that color it seems.

    So now I have a black Clever3D PEI aluminium plate available and did the same tests.
    I ran the same firmware and settings.
    And so far I can confirm that color matters!
    After roughly about 50 homing sequences I always get the same distance of the nozzle to the bed.

    That is with the IR sensor that came with the BB.

    Regarding the findings of @fpex who had problems with his blue sheet and better results with the red one I have no real explanation but I think I has something to do with the emission spectrum of those colors. Maybe blue absorbs too much of the infra red of the sensor.
    Jari and mike01hu like this.
  2. Mark Curry

    Mark Curry Well-Known Member

    Jan 17, 2016
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    Very glad to hear this Alex, I will now consider buying a PEI plate. I will not give up on my IR sensor especially with the Duet, it is rock solid and much more tactile on the Duet browser interface.
  3. Ualdayan

    Ualdayan Member

    Dec 21, 2015
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    Does anybody know of a US seller that does PEI aluminum beds? The $60 price for the bed seems completely fair, but then the shipping from Clever3D to the US is another $50 - that seems a bit out there (the entire Bigbox kit was 52 pounds, or about $60-70.)
  4. dc42

    dc42 Well-Known Member

    Aug 16, 2016
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    I designed the IR sensor to work using the weak reflection from a glass surface, and also to work with BuildTak, which was only available in dark grey at the time. The ADC in the attiny microcontroller has only 10 bits resolution, so it was not possible to accommodate highly reflective surfaces as well. I suspect that the silver plate you tried was simply too reflective.

    Later versions of the sensor firmware tolerate somewhat higher reflectivity. They also flash the LED rapidly when the reflected light is too bright, so that you can tell there is a problem. If anyone wants their sensor reprogrammed with latest firmware then I can do it for a nominal charge.

    However, using a matt black plate with a thin PEI coating on top is an ideal solution. I have tested the black Clever3D plate too and I can confirm that it works well.

    I use the IR sensor on both my (non-bigbox) printers. One has a 3mm glass bed with black-painted aluminium underneath. The other is topped by thin PEI sheet bought on Amazon, painted black on the underside before being stuck on top of a 4mm glass plate using heat resistant adhesive sheet.
    Alex9779 likes this.
  5. Miasmictruth

    Miasmictruth Well-Known Member

    Sep 4, 2015
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    I use a bed coating on the glass that is not very reflective at all.

    I only mention it because I have had 0 issues with my z it's rock solid and have used this coating since my first print.

    So I guess my point is that it does indeed seem to work well with non or low reflective surfaces at least for me.
  6. Tom De Bie

    Tom De Bie Well-Known Member

    May 7, 2016
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    Is the new firmware somewhere available?
  7. lance

    lance Well-Known Member

    Nov 25, 2015
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