1. Got a question or need help troubleshooting? Post to the troubleshooting forum or Search the forums!

IR sensor and bed leveling issues

Discussion in 'Troubleshooting' started by f_d, May 18, 2020.

  1. f_d

    f_d New Member

    Joined:
    May 22, 2014
    Messages:
    3
    Likes Received:
    0
    I've had my C2 for quite a while now and have only done a handful of prints on it because beyond the first few prints, I could never get the bed leveling to work right, and I've continued to use my old R1 Kickstarter instead (yes, I was an original supporter, so maybe that earns me some extra troubleshooting points?).

    Anyways, I haven't used the C2 for quite a while, but since I've got a lot of spare time these days, I thought I might try getting this thing debugged. So first off, my C2 bed is not level and not flat, so obviously this makes having a functional bed level system pretty critical. I've been thinking about the sequence of events that led up to the leveling system not working right and all the steps I've attempted since and what I think I've isolated the problem: The stupid IR sensor is not accurate (repeatable) and is also color sensitive, and it has too big a Y offset to compensate for the warp in the plastic printbed.

    I think my troubles started when I ran out of the black painter's tape squares and switched to blue painter's tape strips instead.. I could not get good first layers even tweaking the Z-offset values. Thinking back, I'm pretty sure that's when the issues began.. Initially I attributed the issue to just bad PLA and continued to print ABS instead on the black BuildTak surface (that stuff is F-ing amazing- ABS sticks better unheated on BuildTak than on my R1's heated bed) until one print stuck too well and removal ripped a chunk out of the surface. My local 3d printer supply didn't have BuildTak, but had another brand LockBuild, which was the same stuff, only in orange instead of black (orange is the new black?). And I think this is when the bed leveling just stopped working for me altogether..

    The symptoms of the malfunctioning bed level with blue tape was that it got close, but left a slight tilt in the bed so that one side of the bed resulted in extruder clicking (too close) and the other side resulted in the extrusion not sticking or in the worst case, extruding in air, causing a mess. Adjusting the Z-offset with the Wizard didn't work as the stupid printer seemed to just compensate and cancel out or ignore whatever the offset value was.. I could print small items if I wss careful to place them in a location where the bed level was close enough for a good first layer, but bigger items would not work as I couldn't get a complete first layer.

    I read these forums and noted the ambient light compensation, which led me to investigate some more. Turning off the LED bed lights and room lights helped, but the bed level was still very surface and color dependent- darker colors in general worked better, but I could never find anything that completely "fixed" the issue..

    I also experimented with firmware: I got the official Robo firmware off Github and turned on UBL and manually ran the G29 commands and it confirmed that the bed was warped and that repeatability was an issue (mesh values showed deformations and that multiple probings resulted in slightly different values each time- the centre of the bed towards the right rear was most consistent); buit also pointed out that the Y-offset in the sensor was also another issue: the front of the bed was empty points. Which explained another symptom I never previously attributed to the leveling system: the priming strip it printed at the very front of the bed was always too close to the bed and clicked the extruder). I could get a pretty close to level bed by altering the UBL mesh parameters to do a 9x9 mesh and several G29 P3 commands to fill in the missing data, but while it was now level, the Z-offset could not be adjusted at all: using the Wizard resulted in a bunch of lines of plastic of pretty much all the same consistent thickness (ie, I think it properly compensated for the warp) but that didn't quite stick to the bed (ie I needed a smaller Z-offset). Problem is however that adjusting the Z-offset value in the Wizard doesn't do anything: whatever value is set, the test just prints exactly the same thickness of extrusion.. As I noted previously, it's as if the printer is either ignoring the value or compensating for it.. I can get a level bed now, but I still can't print because the offset is too high and nothing sticks..

    Can anyone think of what might be going on based on these symptoms? The only thing that I can think of is that IR sensor- I'm ready to rip that stupid sensor out of the machine and stick in a BLTouch or something else.. On my R1, since I've upgraded to Marlin 1.19 and have put a display on it, I can babystep on the fly if the offset isn't quite right, but since the C2 is running through an R-Pi with Footprint, there's no way I can do that..
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    22,232
    Likes Received:
    7,143
    I manually level mine. I do this with strips of tape that cover the points where the magnetic posts lock on.
    I do a one-layer test print and use that repeatedly to adjust the corners until it is as level as it can get.

    From there you can still use autoleveling if you want to get it somewhat better.

    My suggestion (more so given the small bed size) is you take that approach, Manually level it.

    The later revs of the firmware will break the autoleveling by storing a non-negative Z offset. Check yours (look at it under EEPROM settings in the LCD screens) and make sure it is negative...
     
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    22,232
    Likes Received:
    7,143
    P.S. you can still upgrade marlin -- just do it via the Pi... SSH to the Pi and make sure VNC is running and then VNC to the desktop and run the Arduino Compiler on the Rasperry Pi to upload whichever version of Marlin you want. Just make sure your CONFIGURATION.H as all the details right for the C2.
     
  4. tkoco

    tkoco - -.- --- -.-. ---
    Staff Member

    Joined:
    May 7, 2018
    Messages:
    580
    Likes Received:
    223
    With the print bed being removable and due to the inherent warp of the bed: I suggest before you manually level the bed to mark the front edge of the bed.

    Assuming that you don't cover the posts with tape, apply a dry lubricant to the 4 posts of the aluminum print platform. The magnetic pull ( between the print bed and the posts which it sits on ) can cause excessive friction - similar to the friction which a refrigerator magnet exerts when you stick it to the vertical side of the refrigerator. With lubricant on the posts, the print bed will settle to the proper position when you seat it.
     

Share This Page