dc42 Hot End Sensor problem

I have a strange problem with the DC42 Hot Sensor board. I was using a coated alluminum plate in my Ormerod and all was working perfect. Now I replaced the alluminum plate with the original glass and kepton, without the rectangular reflecting paper on the corners, as adviced, but the red led on the sensor board doesn't light up any more! This happens only if I put the glass in contact with the plate alluminum heater. If I put the glass under the sensor but away ( i.e. 1 or 2 cm upper) form the alluminum, the sensor board is working normally and the red trigger led goes on and off depending from the distance. I cannot understand what's the problem!
Please help! :-)

Edited 2 time(s). Last edit at 10/14/2014 01:40PM by smoothboy.

Hi smoothboy, which version of the board do you have, the IR+ultrasonic one or the differential IR one? I'm not in the office right now so I can't check my records.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks, I do have the differential IR board (vers 2).

Thanks. Please ensure that the board is mounted so that it is perpendicular to both the X and Y axes, and check that the IR emitters and photo transistor have not become bent (see photo at [miscsolutions.files.wordpress.com] and check the orientations of Q2, D5 and D6). Then measure the trigger height of the edge of the board above the glass without the aluminium below it, or with some black paper between the glass and the aluminium. I'm wondering whether you have a board with an abnormally low trigger height, which would make it overly sensitive to reflections from objects underneath the glass

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes the diodes are perfectly perpendcular to the board as in the photo. The height in the case of a glass + kapton surface with a black surface underneath it is 2.60 mm. I cannot get the led on, if the glass is directly in contact with the alluminum heater. With my coated alluminum plate I got the led on, with a distance of 3.00 mm
Thank you.

Smoothboy, those symptoms look odd and I'd be happy to send you a replacement board. I've done some more tests, and I find that having aluminium under the glass plate causes a negligible shift in the trigger height when the glass is covered with Kapton, and only a small decrease in trigger height when the glass is not covered with Kapton.

Before I send a new board, please check whether the XY position of the print head makes a difference to whether you can get the board to trigger or not, when the aluminium plate is under the bed. If the problem occurs at only one place or a few places, then it could be that there is a scratch on the aluminium at that point that just happens to cause a strong reflection from the far LED right into the phototransistor.

Also, can you confirm that the 2.6 and 3.0mm figures are the height of the board edge above the print surface? Or are they the nozzle heights?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you for your support.
Unfortunately there is no place on the bed (with the glas or glass + kepton) where I can get the trigger, neither when the nozzle is in touch with the surface. I didn't noticed this before, because I always used the alluminum coated plate, and I got the trigger easily ad a distance of abt 3 mm from the edge of the sensor board.
If I put a black surface underneath the glass, I can get the board triggering just before the nozzle can touch the surface, (a paper foil goes easly under the nozzle and still not drags).
The board is marked 2,75 mm by hand.
Hope this could be of some help.
Many thanks.

Rick.

Rick, how high is the edge of the board above the tip of the nozzle? To measure it, I suggest you lower the nozzle until it is just touching the bed, send G92 Z0, then raise the nozzle using the web interface or Pronterface until you can just fit the shank of a (for example) 3mm drill between the bed and the edge of the board. Then the height of the board above the nozzle is 3mm (or whatever the size of the drill is) less the height of the nozzle as read from the web interface or Pronterface.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I find 2.9

Edited 1 time(s). Last edit at 10/15/2014 08:00AM by smoothboy.

Thanks for measuring that, it explains why you are having difficulties. The board should be mounted so that its lower edge is between 1mm and 2mm above the tip of the nozzle. This ensures that the board will be low enough to trigger before the nozzle touches the bed. For example, if the edge of your board were at the maximum recommended height of 2.0mm above the tip of the nozzle, then the 2.75 mm +/- 0.25mm trigger height that I measured when testing your board will correspond to at least 0.5mm nozzle height above the bed.

So I think you will need to reprint the fan duct to lower the board mounting holes by at least 1mm. I already changed the design of the modified fan duct (not the one-piece version) 10 days ago to lower the board by 0.7mm because someone else had a similar problem, but 0.7mm is not quite enough for your machine. If you are familiar with OpenScad then you can change the design yourself, the file is [github.com]. If not, let me know which fan duct design you are using, then I will make the change and generate a new STL file for you.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you so much. I'm not familiar with OpenScad. If you are so kind to generate the STL it would be great! Many thanks again.

Rick.

Are you using the modified version of the heatsink duct with the original fan duct, or are you using Matt's one-piece duct?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The modified version with original fan duct. Thank you.

I've put that STL file at [github.com]. It places the board 0.5mm lower than in my revised (as of 10 days ago) design at [github.com]. That in turn places the board 0.7mm lower than in my original design, which I presume is the one you used.

I think this should sort out the problem, but please let me know either way.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thank you I'll print it out asap and keep you informed
Rick.

YES !!! That was the problem. With new printed part now the sensor is working like a charm! I'm printing on glass + kepton now perfectly!
Thank you for your invaluable support.

Rick.

Thanks for letting us know!

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].