Z-Axis bed offset and dual commissioning

Discussion in 'Calibration, Help, and Troubleshooting' started by Brian Dowling, May 7, 2016.

  1. Brian Dowling

    Brian Dowling Active Member

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    Ok, first, I looked all over for these details, but have not seen these questions answered specifically. Hope I did not miss it. Feels so close here to first print. ...

    So my dual is up and running. I had one issue where the Y axis was running the wrong direction. Not sure why, the pins looked right in that one. But i just flipped the cable and proceeded to home.

    After setting the IR sensor once I then leveled/trammed the bed manually to start. Then did the Prepare > Bed Level just to be sure. Finally i set IR height a second time with the belt spacer to be sure bed adjustments didn't throw it off.

    Problem I think I have now I is the z-axis offset right after homing. After the calibrating ir height steps in commissioning docs, the dual says to home and then kinda just stops leave you hanging wondering how to know if it is right. I know this is the experimental version but there has to be shared wisdom across the community on this, So...

    1) how high should the nozzle be above the bed after home? Mine is ~0.88 millimeters.

    2) I see no z-offset setting in the firmware for the dual like the single instructions suggest. I take it this is how the factory fw is and I think I saw mentioned it was available in one of @Alex9779 builds to get that capability? I think I need to get Octoprint fw upgrades working first because I'm not going to open the bottom just to access the USB port. ;)

    3) Part of the Z setting requires moving the Z manually, which obviously points out if you do one side even slightly off you bed is no longer level, same happens if one side miss a step. Is there some experience out there for dealing with this.

    Overall all my axis seem to be running smoothly. The steppers seem to get hung up at the near bottom of the Z. I need to recheck the alignment I think. Y does seem to make some loud noise in the + direction. Not sure why.

    Thanks,
    Brian
     
    #1 Brian Dowling, May 7, 2016
    Last edited: May 8, 2016
  2. Kick2box

    Kick2box Well-Known Member

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  3. Brian Dowling

    Brian Dowling Active Member

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    But then i should see 4mm as the Z offset on the lcd, correct? I see zero and cannot move the z axis any closer to the bed than its home zero position, at least via motion controls.

    Also trying to understand why there needs to be no software offset to acurately adjust the IR sense of zero. The 2.5mm belt adjustment is just to set the thing higher than the nozzles. Even the docs for the sensor state they ship within a range of trigger sensitivity (https://miscsolutions.wordpress.com/mini-height-sensor-board/ ). Others have had head crashing issues with this sensor. Maybe different reasons, but still. The single has the offset setting??

    To start anew should i load failsafe and redo?
     
    #3 Brian Dowling, May 7, 2016
    Last edited: May 7, 2016
  4. Brian Dowling

    Brian Dowling Active Member

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    Is there a part of our commissioning that does this behind the scene, I'm not sure where or how it would know, that the heads are on the bed unless in the mesh leveling?

    To calibrate the sensor for bed probing, apply 12V power to your printer, home X and Y, then position the head over the centre of the bed. With the nozzle at operating temperature, lower the head so that it is just touching the bed or just gripping a sheet of paper. Send G92 Z0 to define that position as Z=0. Remove the paper and raise the head in small steps until the LED illuminates, and continue raising the head until it goes out again. Now lower the head in 0.05mm or smaller steps until the LED illuminates again. Read off the Z height (e.g. by sending command M114 to your printer) and use that value as the Z probe trigger height in your firmware configuration.​

    Note: after turning your printer on, do not perform any operation that uses the sensor for 5 seconds, until the LED has done its 2 flashes.​
     
  5. Kick2box

    Kick2box Well-Known Member

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    Just put the nozzle to the bed and adjust the sensor with the belt. if the later trigger point is far off, you could change the sensor position slightly. The rest is done with mesh leveling. The procedure you describe above is required for auto bed leveling only.
     
  6. Miasmictruth

    Miasmictruth Well-Known Member

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    With the dual you have to go through the mesh leveling procedure.

    http://wiki.e3d-online.com/wiki/Printer_Commissioning
    Look under mesh leveling

    you get to it from the LCD Via the Prepare menu, select Level Bed.

    one things I do differently is instead of the paper method I carefully lower the nozzle until the light disappears between the nozzle and the bed, if your having trouble lower the lights in the room and shine a light on the back acrylic.

    at the end before printing make sure you do the following: From the Control menu select Store memory.


    If your able to use my method you will get a perfect level, its much more repeatable then the paper method. one thing to note, watch both nozzles, if you haven't leveled the bed with the stand offs it could be at a slight angle, or if you nozzles are not perfectly aligned in Z one could be touching and not the other which will cause issues if your looking at the higher nozzle you will grind the other into the bed.


    To level the bed with standoffs, ideally get a dial indicator (15 bucks off amazon) secure it do the print head so that the probe is at least 1cm below the nozzles. raise the bed until the indicator is in the middle of its range. Then using the stand offs raise/lower each corner until you get to a point that when you move the head to each corner you get little to no movement on the needle. Make sure what you re tighten the top nut as it likes to loosen sometimes when making adjustments. Also make sure you over tighten or loosen any of the standoffs.

    If you don't have an indicator it can be done by raising the bed to the nozzle, you will probably want to start off with the stand offs almost fully tight then position the bed 1mm below the nozzle and slowly raise each corner until just before it touches the nozzle.
     
    #6 Miasmictruth, May 9, 2016
    Last edited: May 9, 2016
    Brian Dowling likes this.
  7. Brian Dowling

    Brian Dowling Active Member

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    @Miasmictruth -- all good advice. I saw mention of the reflection technique elsewhere and was going to try that as well.

    I think the Build manual really should be updated to make it clear that leveling is REQUIRED on the dual to calibrate the Z height and set the 4mm Z offset. I think Marlin firmware has this as zprobe_zoffset. I still don't seem to have a wiki account or I'd make some notes.

    My other mistake was my CompSci mindset was thinking somehow that "Bed Leveling" was just setting everything all relative to the Home detection of bed height. e.g. I was just setting the mesh offsets, so I think I initially used a thicker feeler gauge instead of paper because I thought it would be more accurate in setting this "level offset" -- not realizing I was suppose to be telling marlin where the bed was.

    I did end up re-doing the bed leveling and finally I saw the Z height after homing shows 4mm on LCD -- I think this is the Key, if you are not seeing this, you haven't properly done the bed level and saved settings.

    I think there is a slight fw bug here though; the LCD reports 4mm, but it is not physically 4mm off until you command it to move. This may have be a leftover from a retractable probe? Once you command any motion X,Y,Z it then it lowers the bed to 4mm (and it remains Z=4 on LCD).

    The other test is that I can use the Motion commands in the LCD to bring Z back to '0' and see the nozzles are just touching the bed as they should be.

    Thanks for the tips. Hopefully this thread helps others as well.

    Cheers,
    Brian
     
  8. mike01hu

    mike01hu Well-Known Member

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    Having completed my build and successfully powered up and proved all elements are active (one faulty stepper driver), I have run into difficulties with Z offset due to the fact that when doing auto-home the X and Y perform as expected but, because the IR sensor is off the bed, for Z-home it just crashes the bed into the nozzles. I think I am using the RC6 hybrid firmware from @Alex9779 but not sure without checking again. I suspect the feature that moves to X150,Y100 before Z home is not operative but I'm not sure where this lives in the code. Also, the Z offset menu item under the "Control" section on the LCD is not available. Feedback would be appreciated.
     
    #8 mike01hu, May 14, 2016
    Last edited: May 14, 2016
  9. Miasmictruth

    Miasmictruth Well-Known Member

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    First question is does your sensor light up red if you put something under it.

    Second how much higher is the sensor then the nozzles off the bed should be only the thickness of a belt
     
  10. mike01hu

    mike01hu Well-Known Member

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    Everything works as correctly other than the auto-home for the z-axis due to the IR being off the bed to the left. After 6 hours sleep I will now come at it with a fresh mind and load a later firmware version as well.
     
  11. corey

    corey Well-Known Member

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    Just finished my titan build, now looking or some firmware, keep me updated with that you do, having an hour break watching practice 3 F1
     
  12. Miasmictruth

    Miasmictruth Well-Known Member

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    The Z sensor is off the bed? Guessing you have a Titan or hybrid then your right you need new firmware check out @Alex9779 he has a firmware you meet all your big box needs.
     
  13. mike01hu

    mike01hu Well-Known Member

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    Yes, all OK now as the firmware that I had downloaded was not the latest. I updated and all OK, so now for calibration and action! :cool:
     
  14. Miasmictruth

    Miasmictruth Well-Known Member

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    Great :) your to the fun part now
     
  15. mike01hu

    mike01hu Well-Known Member

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    Make sure you get Alex's update from here. I am now happy that everything is as expected and I can get back to production!
     
    Steven Burns and Alex9779 like this.
  16. Alex9779

    Alex9779 Moderator
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    So @mike01hu all working now? I checked the configs again (yes of all branches...!) and they seem to be fine so no idea what firmware you had on your board where the head did not move to a safe Z home spot...
     
  17. corey

    corey Well-Known Member

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    Ales9779 firmware all installed and running fine first time... might have to do the mirror thing like Ales9779 as i can not seem to get Cura to print with extruda 1.... @Alex9779 beaning a fellow UM user also is there a way to tell Cura to use extruda 1 or am i going to have to mirror ?
     
  18. Alex9779

    Alex9779 Moderator
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    No idea. I did not use Cura for a long time...
     
  19. mike01hu

    mike01hu Well-Known Member

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    Yes Alex, I was mystified too until I realised that the download was not where I thought it was and I had picked an earlier one! o_O Thank you for your efforts.
     
  20. Pter

    Pter Member

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    What's the difference between the mbl en the abl firmware?
     

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