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

Partial Answer Z-axis offset, adjusting.

Discussion in 'Troubleshooting' started by joea, Aug 15, 2021.

  1. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    The only thing that would (or should) affect the home position is the location of the Z switches and where they activate. you can adjust them on the R1 series, they sit in brackets mounted to the crossbar and the smooth rods. You can adjust the positioning of them to react sooner / later depending on their position. You do want them both to actuate at close to the same height... but the height can be altered*.

    If you haven't watched it the video Marquis Johnson did for autoleveling on the R1 is probably a good watch:

    This is really all done external tot he firmware or software, HOME is a mechanical stop on each axis and that is what you should adjust.



    *it is however always related to the nozzle striking the bed and then lifting the crossbar (which seems obvious, but needs mentioning). One thing you can change i how the Z switches are wired in. By default they are in series so either switch triggering is a Z HOME indication. You can wire them in parallel which then flips that around so that BOTH switches must trip to indicate Z home. Not needed really, but throwing it out there...
     
  2. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    OK. I was expecting there to be some parameter that related to how far the motors would continue to raise Y after the switch(es) clicked on the way back up. But I guess it just stops upon switch changing states. I have the nozzle removed right now so cannot refresh my recall of the Z home action.
     
  3. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    Picked a bad day to quit sniffing filament fumes . . .

    So, after fiddling with the Z axis switches, having noticed that, after a "Home". if I moved Z in + direction the lead screw followers would continue to move "up" into the carriage, until they "seated" and then Z would begin to move up. I thought that might be contributing to my confounding test results for first layer.

    (Full disclosure, the lead screw follower "mounts" are not Robo parts, but leadscrew conversion "kit" parts I print on this very printer, back in the dark time. It seemed a good idea at the time.)

    First thing I did was attempt to bend the levers to actuate "later". That did not seem sufficient, so (after I ordered new switches) I boldly went where no dweeb has gone before and snapped off the levers. Well, I really had no choice since after a few ":adjustments", the dang thing fractured and . . . well, there you have it. So, naturally, I took this as a positive development and forged ahead. As reality would have it, (you know how stubborn it can be), the Z would sit far too high having clearance under the nozzle after a home.

    AHA! says I and rigged up a way to put spacers between the limit switch and the carriage arm to adjust the make and break distance. I got that to where it would home nicely and have essentially zero clearance on home.

    Unfortunately, I find the printer does not lay down filament at all. preferring it seems, as the legendary porridge bird, to "lay its egg in the air". . . .I find that even with 0 (zero) in MC for z-offset and having removed the M565 code from "custom startup codes) it will still not lay down filament, instead collecting all over my brand new hardened steel nozzle. How rude.

    In a series of brief (very brief) flashes of brilliance, I broke down and started looking at g code as seen in terminal. I even managed to break it into semi manageable chunks, one being the auto leveling sequence. It sure appears from that one, that the Z axis is being told to lay down at Z1.299, which is about what I measured running the same job with no filament. To avoid the mess, you know . . .

    But, bless me, if I can figure out why it thinks Z should be that high.

    Also noticeable are numerous errors, like this:

    -------------------------------
    <-Error:Line Number is not Last Line Number+1, Last Line: 27 [31.032]

    <-Resend: 28 [31.033]

    <-ok [31.033]

    ->N28 M104 S225*9 [31.033]

    <-Error:No Line Number with checksum, Last Line: 27 [31.037]

    <-ok [31.037]
    -------------------------------

    Which are troubling me. Especially since, once or twice, MC has reported unable to connect, suggesting the USB communications has gone pear or even peanut shaped.

    Oh,, dear, the little needle is pointing to E and the yellow light is on. Better go refuel . . .
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    OK, random comments :)

    If the nozzle is too close the bed the backpressure will prevent the extruder from being able to, well, extrude. :)
    If it is to high of course that is not the problem.

    For the filament being more attracted to the nozzle than the bed -- usually that is a sign you are printing too hot, You should be able to (with the nozzle in the air, off the bed) extrude say 10-20mm and have it extrude and pretty much hang down from the nozzle. It should not curl back to the nozzle. If it does it is probably too hot. I say "probably" because while this is true for PLA and ABS, it is not true for all filament types.

    this:

    "-Error:Line Number is not Last Line Number+1,"

    Is almost always a communications issue (USB). It can be a bad cable, it can be a bad arduino (USB port failing on the Arduino board). The USB port for the Arduino wants to talk at 115200 (115 kilobaud) but some of the Chinese knock-off boards will struggle to make that happen and are even worse at higher baud rates. The Marlin firmware wants to default to 250,000 :) For a Genuine Arduino board that is certainly workable, for the cheaper knock-offs... not always.

    Start with a new USB cable.
     
  5. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    The temp with a steel nozzle seems to be a question. I'll try a lower temp. A response from MatterHackers, where I got the nozzle, suggested he runs 5 degrees C hotter. Seems it does extrude fine, manually. Just when attempting to print it globs up on the tip.

    That's probably the cheapest first step.
     
  6. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    Where can I look to resolve the issue of Z being too high? Can I safely make Z-offset a negative number in MC? Is the M565 command necessary in startup Gcode even if it is set to zero value?

    I do not understand why it seems to be attempting to extrude at 1.299mm
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    M565 should normally be negative. Positive numbers will drive it to the bed.

    I always suggest starting with -1.0 and tweak from there.
    It is important that it get in the correct place in the startup GCode and if you are using OctoPrint or something else to do the host control you need to add it to that startup Gcode. If you print from the slicer then just use the startup gcode block for the slicer.

    G28;
    M565 Z-1.0;
    G29;

    Letter case is critical as well as the other characters :)
    m565 z-1.0;

    will not work :)
     
  8. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    It's already too high, so I want to drive it toward the bed, no? Again, is there any reason I cannot, or should not, in this case, put a negative value in the MC z-offset. Not, the M565 command, that would have to be positive.
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    If you make the M565 a positive number it will drive the extruder below the bed.
    More negative is further from the bed, less negative closer to the bed and positive would be under the bed,

    A positive offset in MC -- is likely a global offset and will disregard any auto bed leveling adjustments, but other than that <shrug> I can't say. I don't use MatterControl.
     
  10. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    So, now I seem to hear the Z-offset "global offset" (?) in MC and the M565 business do not work "in concert" at all. That if there is ANY value in Z-Offset (MC) the M565 business has NO effect? Previously I had the impression they worked, effectively, as an "algebraic sum: to determine the actual nozzle height above the bed during extrusion.
     
  11. joea

    joea Active Member

    Joined:
    Nov 12, 2019
    Messages:
    351
    Likes Received:
    51
    Additionally, I can state, with great assurance, my current inability to lay down any filament is due to excessive height above the bed.

    After autoleveling I have inserted paper about .008 (2mm) under the nozzle in the print area and the expected pattern does lay down on the paper. Not too well as it tends to move a bit, but filament lays down and does not collect on the nozzle.
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

    Joined:
    Feb 21, 2013
    Messages:
    23,912
    Likes Received:
    7,338
    Nope, The M565 will do nothing if you do not use the G29 and if you get the commands in the wrong sequence.
    The global Z offset in MC is always applied regardless of anything else. Even if you used M565 correctly the MC global Z would be laid on top of the autoleveling adjustment.
     

Share This Page