Y-axis drift and other strange behavior

New Home Forum LowRider Troubleshooting – LowRider Y-axis drift and other strange behavior

This topic contains 6 replies, has 3 voices, and was last updated by  doc 2 weeks, 3 days ago.

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  • #116136

    doc
    Participant

    If visualizing the machine orthoganal to the X-axis/staring down the Y-axis I have 5mm of drift from right-to-left-front-to-back  (wrt the center of the Y-plate smack dab in the middle of the X-axis). This is over 2580mm.  Upon returning to home, it ends up right where it started.  My machine is square (ish) and I just want to see if this drift is normal for others and why most have some sort of routed or tacked-on wheel track.  All printed parts ordered from V1.  I can upload pictures later if needed – or do you all think this is normal drift and I should just route in some tracks?

    I also have a weird issue with the right Y-stepper.  I jog forward (y) any distance and park the axis for 10s or longer and when trying to jog back it sounds like the stepper on the right is energizing for the very first time.  This is not always an issue but sometimes it causes missed steps.  I have yet to investigate what currents are making it to the steppers (using mini-rambo purchased from v1) and have not updated the firmware/eeprom to disable stepper timeout (although this shouldn’t be an issue at 10s). The belts are tensioned equally on each side. The pulleys are tensioned fine, not binding, and are in line with the toothed gear. The grub screws are tight. Any thoughts on how to track this issue down?

    #116139

    Bill
    Participant

    Let’s get a bunch of pictures showing your build. If you start square there should almost no drift. If you have a motor lagging you could easily see drift, but I would be surprised if it just matched when moved back.

    No need to mod the firmware to disable stepper timeout. Stock the timeout is something like 30 minutes. You might not have the box unchecked in estlcam that disables motors at the end of a run.

    1 user thanked author for this post.
    doc
    #116146

    frosty
    Participant

    What board, what firmware, what drivers?

    As for the tracking, are you certain the gantry is starting off square to the Y belts? How are you verifying it? Are you able to measure the squareness of the wheels vs the X tubes? Any chance your parts were printed with a bit of a lean? You say the machine is only “square (ish)” and that sounds about consistent with a 0.19% (5/2580) trapezoidal error, honestly.

    Like Bill said, pictures would help a lot.

    1 user thanked author for this post.
    doc
    #116386

    doc
    Participant

    Thanks for posting trying to help but I sorted out the drift (and I think I fixed the stepper issue on the right).

    In case anyone has the trouble I did, it went like this:

    On the right half of my machine I could only orient the XZ part opposite of how it was on the left side of the machine (open side facing medially on the right and “closed” side facing medially on the left).  This was the only way I could get the shaft of the stepper to be in line with the lead screw.

    I tore apart the whole thing and saw that MAYBE the holes my MPCNC drilled were off (not perpandicular to the piece)… so I cut a brand new y plate and used a drill press to make my holes.

    I put it all together… same freaking thing! It will not line up.  It looked like the following pictures.

    IMG_20191002_134123__01

    IMG_20191002_123252__01

    IMG_20191002_135031__01

    So I take the right side all apart again and look at my known good side.  Here is a photo of that.

    image-20191002_135100__01

    See the problem between the left side (good side) and right side?

    Tldr: make sure you have your parts in the proper orientation! It is entirely possible to assemble this machine and have it still work (I drew a pretty awesome Iron Maiden album art that was half a sheet large and a characature of my dog that was 2ft wide and 4ft high).  Once I flipped the two superior z-rail holders to opposite sides, the spacing was perfect, the XZ part was able to be oriented properly, and the shaft of the stepper was pretty much dead center of the lead screw.

    After flipping the parts around, this is what the right side looks like:

    IMG_20191002_135704__01

    The net effect of all this? I no longer have 5mm of drift over 2500mm, I have 0.06mm and this is just slightly above the standard error for tools I used to measure the drift.

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    #116397

    doc
    Participant

    As far as the stepper issue is concerned, I turned up the “drive strength” option to 1000 (which is 1000mA) and the problem has disappeared all together.  I am pretty sure our steppers can handle 2A and the mini-rambo drivers (A4982) can put out 2A (the drive strength was set to 800mA by default  how Ryan shipped it). Pretty neat feature to control amperage output from the driver digitally and without having to touch a trimpot.

    And frosty, I say squarish because nothing can be absolutely square using our current technology – I am less than 0.5mm along the hypotenuse.  It is like that show Rick and Morty, where Morty attempts to “level” a shelf using a spirit level: Rick and Morty perfect level.

    #116401

    frosty
    Participant

    Glad to see you figured out the issues. Looking good!

    I wonder if that piece could be made a bit more asymmetrical so this is harder to do. Maybe radius the edge on the wheel-side of the part slightly? I don’t believe there is a need for those edges to be sharp and having a little radius will make the two sides different and make the part look a little more awkward if mounted on the wrong side.

    1 user thanked author for this post.
    doc
    #116417

    doc
    Participant

    Glad to see you figured out the issues. Looking good!

    I wonder if that piece could be made a bit more asymmetrical so this is harder to do. Maybe radius the edge on the wheel-side of the part slightly? I don’t believe there is a need for those edges to be sharp and having a little radius will make the two sides different and make the part look a little more awkward if mounted on the wrong side.

    Or just make a big fat note/caption on the instructions page with a picture.  I feel so stupid that I assembled it that way… oh well, you live and you learn ¯\_(ツ)_/¯

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