another IR sensor anecdote

Discussion in 'Calibration, Help, and Troubleshooting' started by R Design, Oct 2, 2016.

  1. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    My printer has been stable for weeks.

    Suddenly the first layer was WAY too close. Systematically.

    I knew previous print had come of easily and hadn't moved the bed.

    So first check was that the IR sensor was not catching on the dump bucket and being moved around. Not at all.

    Tried starting several prints to no avail.

    Then decided that perhaps the bed was a little grimy around the place where the sensor does the homing.

    Cleaned that patch of the bed.

    Then suddenly prints were starting WAY too FAR AWAY!! Little tubes of toothpaste. Hmm. So it did have something to do with the homing area?

    However still couldn't start a print and, having no desire to completely redo mesh levelling, tried putting down a milky thin layer of glue in the homing area.

    Restarted a print and first layer now 100% perfect just as it has been these past weeks.

    Is there a lesson in there somewhere?

    Have made a fool of myself before trying to explain what the IR sensor is thinking. So now will leave that to others.

    Would just like to add though that one of the many marvellous things about the sock is that you can stop and start prints willy nilly without having to keep checking to see what has oozed out of the nozzle and is now burning off on the heater block!
     
  2. fpex

    fpex Well-Known Member

    Joined:
    Oct 18, 2015
    Messages:
    621
    Likes Received:
    58
    Eheheh, net time this happens and it will ... I have already a piece f white paper under Kapton in the corner where I will foce homing. This is rather reliable and I rarely (as never) print there.
     
  3. elmoret

    elmoret Administrator

    Joined:
    Mar 1, 2014
    Messages:
    586
    Likes Received:
    91
    Yes, the lesson is that changing the coating on the surface of the bed affects its optical properties, and therefore the IR sensor's readings.
     
  4. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    It's beginning to seem that way.

    Which implies, I think, that one needs to find a way of maintaining a constant bed surface at the homing point. From the time one does the initial calibration, through all subsequent prints.

    The only way I can think to do that is to try to figure out the exact spot, and then keep it perfectly clean (no glue). Even when printing all around there (which is not that frequently).

    Anyone have any suggestions for the original BB glass bed? @fpex are you using glass or aluminium? I guess it makes no difference.
     
  5. Jean VISCONTE

    Jean VISCONTE Member

    Joined:
    May 15, 2016
    Messages:
    17
    Likes Received:
    6
    Using aluminium bed recently, I found 2mm difference in setup.
    When using glass, I use a special spray , Dimafix, for holding ABS and it fits perfectly, I have just to cover then 150,100 point with a tiny piece of paper when spraying for keeping the area perfectly clean.
     
  6. fpex

    fpex Well-Known Member

    Joined:
    Oct 18, 2015
    Messages:
    621
    Likes Received:
    58
    I personally hate thes IR sensors. I have two printers with it and sometimes they decided to awok resulting in recalibration everything.
     
  7. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    The induction probe on the Original Prusa Mk2 looks nice (not too big & they've programmed auto-mesh). How did they modify the PCB bed so as to be able to use induction with it?
     
  8. richgain

    richgain Well-Known Member

    Joined:
    Dec 18, 2015
    Messages:
    71
    Likes Received:
    33
  9. Falc.be

    Falc.be Well-Known Member

    Joined:
    Sep 4, 2015
    Messages:
    243
    Likes Received:
    38
    I am installing that as soon as possible, i can use those mounting points for a fan
     
  10. R Design

    R Design Well-Known Member

    Joined:
    Oct 7, 2015
    Messages:
    918
    Likes Received:
    183
    The sensor on the bed solution fits with the idea of having a constant reflective surface.

    The reason some of us are hanging onto the old system is the promise of automatic mesh levelling coming very soon.

    However by the sounds of things one will have to maintain a very constant optical surface across the bed for that to work!
     
  11. Alex9779

    Alex9779 Moderator
    Staff Member

    Joined:
    Sep 4, 2015
    Messages:
    2,405
    Likes Received:
    731
    When I will get home so hope to have black PEI plates available. Also I ordered an IR Sensor with my Duet Wifi and it is a newer version than I have from my BB. Smaller diodes and I read the firmware was also changed. I will do some testing and report.
    I have very good results with the PEI plate regarding adhesion. I didn't use any coating yet so there is nothing to clean after a print to get the same surface as before...
     
    K3LAG likes this.

Share This Page