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Solved Relative access observations/questions

Discussion in 'Troubleshooting' started by mjensen2k, May 25, 2016.

  1. mjensen2k

    mjensen2k New Member

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    Relative newbie (a month) but obsessed with understanding why/how things happen and getting the most out of my toys.

    R1+
    Hatchbox PLA
    Dual fans and ducts
    Buildtak surface
    Matter Control

    Observation: As others have said, the middle of the display wasn't the middle of the print bed. Ok, not a big deal on smaller prints.

    BUT, it also appeared to 'move' on me. I.e. it wasn't always the same offset. I'm not positive about this, as it was small, but it seemed to be a moving target. Again, not a big deal on smaller prints.

    While troubleshooting a Y-axis limitation (found to be a pinching ribbon cable) I found that my Y axis would show me inconsistent negative values in the low end. As I tried to stretch the limits of my print area and understand where on the print bed a print will actually land, I started to see this following:

    If I attempt to manually advance the Y (or X or Z) beyond their expected high stop with the software (advance via control settings). The Y number will continue to rise, though the head/bed cannot move. So say I have 252mm of Y travel. I can click on the Y and it will hit the end and the Y will continue to go up to 253, 254, 255... But the bed didn't move, of course. It cannot.

    Then when I back down, I will hit the home limit at something above 0. Say I 'thump thump' on the top end for 8x1mm clicks, I will hit the home at a 'coordinate' of +8mm. If I 'thump thump' at the bottom for now 10 x 1mm clicks, it will show me -2.

    I understand that this is all relative. But I wonder that if the Y is 'shifted' this way by say 5mm and the Y is shifted this way by -10mm, then what shows up on the Matter Control screen and what shows up on the bed will be different by 5 and -10mm respectively. Make sense?

    So If I 'thump thump' a couple of times, it messes with my 0s and then matter control and my printer are off from each other.

    I do have G28, homing, in my startup G code, but reading the g-code wiki, it seems to state that this simply moves to the limit switches. It's not clear to me if this relative coordinate is used in the calculation from the g-code of the print.

    A) thank you for reading
    B) does the above make any sense?
    C) when/how can I reset the 0s on each axis besides the sledgehammer approach listed above?
    D) does it even matter if the 'home' of Y or X is not at zero?
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    A) Any time.
    B) Yes, mostly :)
    C) Home ALL should reset all of the axis to zero. If it is NOT then your software is not working correctly.
    D) Home is zero. Unless your home switches are mechanically FUBAR. Home is where the switch is. Those are the only position indicator/feedback the Robo has.

    You can manually drive any axis beyond the limit for it. The size limits do not apply to manual control via software or LCD display.
    They will be ignored. The slicer has to be configured for the bed size and it will not let a sliced model go beyond the limits (most will simply not slice with a model too large error)
     
    #2 mark tomlinson, May 25, 2016
    Last edited: May 25, 2016
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    To elaborate, when you home an axis via the HOME command it will drive the printer until the HOME switch for each axis you homed has triggered. When that happens you are home.
     
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  4. mjensen2k

    mjensen2k New Member

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    Thanks! I think I get it, but I'm afraid I didn't get my whole question across perhaps?

    Press home - the printer moves the printer until each of the three axis hit their respective switches. Check.

    I guess my question is... if those switches (through my own fault) are at 0, -10, 0 because of the thump-thump stuff mentioned earlier... Does the firmware/Matter control talk and say "Hey, I just homed as you asked and BTW, this is where it appears to be?? You'd best shift everything by 10 so that you can use those 10mm..."

    Otherwise, the software wouldn't send something below 0 (akin to the z axis going negative) and hence not use those other 10mm.

    Thoughts?
     
  5. Geof

    Geof Volunteer Moderator
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    Wherever the switch says home is the new 0. If the software thinnks thats 10 mm instead of 0 you lose those 10 mm until the next home.

    I havnt had the issue but i suppose if you went full build plate hit home at 10mm instead of 0 your softwsre would try to print 10 mm off the playe because what was 10 is now 0
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep. The switches do not move so when they trigger that is zero.
    If the software is telling something else then it has a bug.

    Sent from my Xtreme Play Tab v2 using Tapatalk
     
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  7. mjensen2k

    mjensen2k New Member

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    Thanks everyone! When/if I get this big print successfully finished, I'll do a little more testing/investigating on how the software (Matter Control in this case) handles the Homing and the relative coordinates! This really doesn't much matter of course unless you are trying to print right to the edges (like I'm doing now). And then there are bigger problems like warping, etc.!
     
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  8. Geof

    Geof Volunteer Moderator
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    Using the full buold plate is a task. Your z offset must be perfect due to less heat on the edges of the bed than the center. I couldnt do it with matter control. If you give me all your specs(all of them or it will fail) i can slice it in s3d and send you the gcode to see if that helps
     
  9. mjensen2k

    mjensen2k New Member

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    I had a failure with head temp crashing... I got the print completed yesterday with some warping, so I'm doing it again with some homemade rafting around the trouble part (cold plate). I'll take you up on your offer, Geof, I appreciate it! Today, though, is graduation for my youngest, so I probably need to get focused there!

    BTW, marking this as answered... between my failed print and some other trials, I confirmed that homing does exactly what you said it would do. Not only move to the limit switches, but also reset this spot to 0,0,0. Duh.

    What threw me was trying to home the z axis itself. It kept changing the relative number farther and farther below zero. Until I looked in the terminal and it told me to home x and y first. Then z went to 0. Nothing in the MC ui helped me understand that.
     
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  10. Geof

    Geof Volunteer Moderator
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    Matter control always has confused me :)
     
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  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I think the Marlin firmware requires X/Y to be homed before the Z.
    Sort of a safety check to prevent the head from crashing into the model.

    Pretty sure S3D bitches about that if I try to home the Z first after a print.
     

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