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Solved Y-Axis shifts on large prints

Discussion in 'Troubleshooting' started by Titaniumboy, Dec 21, 2019.

  1. Titaniumboy

    Titaniumboy New Member

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    We have a Robo Beta that we recently resurrected from the dead (thanks Mark !).

    When we tried to print a full size snowflake, we got a layer shift at 40 minutes one time and a layer shift at 20 minutes during a second attempt. The layer shift both times was about 3/4” in the Y direction towards the front of the printer. When we lost steps in the past for whatever reason, the layer shifts were always very small. Nothing like the 3/4” layer shift we are currently randomly experiencing.

    Is this a symptom of the Y-axis drawer slides that were a “feature” of the Kickstarter Robo’s?
     
  2. Geof

    Geof Volunteer Moderator
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    Could be but I’d make sure the belt is tight and the set screws on the pulley are tightened. Also add a fan to blow on your ramps boards If you haven’t. Plenty of designs ready to print on thingiverse
     
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  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep, ditto that -- tighten the Y belt and make sure the RAMPS has a cooling fan.
    I inserted a 3" (right at 80mm) fan, that exhausts out the front , between the ramps and the front of the case.
    Wired to 12v from PS and runs all the time pulling air across the RAMPS and out.
     
  4. Titaniumboy

    Titaniumboy New Member

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    Thanks for the replies, Geof and Mark.

    The Y-axis belt could be tighter, I think, although it already is quite a bit tighter than the X-axis.

    I hear you guys on the fan for the RAMPS board, I burned my finger pretty good touching the heated bed MOSFET.

    It looks like tightening the X and Y belts could be a pain in the arse. Any tips or tricks?

    Is there a repository of posts on how to transform a Beta into an R1+? Or a prioritized list of which upgrades to do first?
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Tightening the X can be easy -- change your tensioner to something like this:

    Belt Tensioner.jpg

    The Y is more awkward because it is under the bed and yea, it is a pain. The R1 (but not he beta) had a tensioning screw that could be accessed from the front of the bed when it was full forward, but that was not the case on the BETA. you need to just do some tear down and reassembly. If it is pretty tight already then it is probably the RAMPS overheating.
     
  6. Titaniumboy

    Titaniumboy New Member

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    Thanks for everyone’s help. Putting dual fans on the RAMPS board seems to have solved the problem. We successfully ran a 2-1/2 hour print tonight of a full size gyroscopic snowflake, which so far is our longest Robo print to date.

    By the way, that power supply was a pure SOB to remove. It took nearly as long to get that power supply removed as the rest of the fan project. I literally had to beat the power supply out of the case with a mallet. I have no idea how the Kickstarter guys got those power supplies installed without breaking the case. I ended up doing some filing on the back of the plastic case tabs and now the case is still hard to remove, but not nearly impossible like before,

    The dual RAMPS fan sits a little below the bottom of the case, so I have the Robo up on some temporary wood spacers. I will be printing some Robo feet by Where’s Waldo later today.

    We will also have to work on tightening up those belts.
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yea, the power supply is a friction mount and you really have to work to pry it out.
    I spent an hour prying it out the first time convinced I was going to destroy the case :)
    Excellent job getting it going.
     
  8. Chuck Glenn

    Chuck Glenn New Member

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    Mine has been skipping lately (R1+). I've looked at the belt and Y cog on the stepper, and nothing appears to be wrong. I've tried it with the Y belt looser or ridiculously tight, and both will skip about 0.25mm toward the back of the printer. Which I guess is saying that it moves the bed rearward 0.25mm short at some random point at rare intervals, but enough to screw up about 1/4 of what I try to print. If the belt is good, clean, not missing any teeth, the cog on the stepper is on tight, and everything else looks fine, what else can I try? Maybe a new stepper for the Y?
     
  9. Geof

    Geof Volunteer Moderator
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    Yes can swap drivers with another one on the board and see if the problem follows (with power off). The other thing is to watch your print and be sure the nozzle isn’t colliding with the print (like say a curling print )
     
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  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I would certainly swap the stepper driver as @Geof suggests before I swapped the stepper motor.
     
  11. Chuck Glenn

    Chuck Glenn New Member

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    Ok, I just went ahead and ordered one from partsbuilt. I'd rather just replace the existing one for $7 than swap things around. Thanks.
     
  12. Geof

    Geof Volunteer Moderator
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    The swap was so you knew for certain what the issue is. Would be bad to spend money and wait for shipping and it end up not being the problem. I’d keep troubleshooting so you knew for sure
     
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  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Exactly. Bad stepper motor, bad stepper driver, bad channel on the RAMPS board... all can have the same symptoms.
     
  14. Chuck Glenn

    Chuck Glenn New Member

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    I'm willing to just try a $7 replacement first. I'm doing at test print right now. If that doesn't work, what's the next most likely part? RAMPS? or the stepper itself?

    I did notice it gets really hot being centered under the bed heater, compared to the Zs which are nearby, but off to the sides. Are these all the same stepper? like can I swap the X and Y without any ill effect?

    Thanks!
     
  15. Chuck Glenn

    Chuck Glenn New Member

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    Ok, still skipping with the new driver. Next thing to try would be a new stepper motor I suppose.
     
  16. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes, X and Y are the same steppers (so are the Z really) and on most machines the extruder was the same stepper as well.
    Some later ones had a slightly different extruder stepper (smaller, same electrical specs)
     
  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    You can measure them and look on Amazon for nema-17 with 200 steps/rev and the sizes you want/need in millimeters.
    Here is an example that I used on an older R1:

    https://smile.amazon.com/gp/product/B00QEXSCE8

    You don't need a 5-pack, but that one worked for the units I tried it on. Like I said some R1+ extruder steppers were slightly smaller apparently

    Those are 42x42x40mm (the shaft size matters too)

    Nema 17 just describes the mounting (face) of the motor and screws.
     
  18. Chuck Glenn

    Chuck Glenn New Member

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    ok, so I replaced the Y stepper after having to order a cable (4-pin to 6-pin), re-wiring the cable since it was wrong, installing that above gears...

    And it still skips. So what is next? the RAMPS board? I did have to replace that a few years back, so it's not the original. I had to put some of the "constant on" fans in with the 12v power connector. Anyway... what is the recommended next step? If it's the RAMPS board, which would you recommend?

    FWIW, The new stepper is way louder on fast vertical runs, making a very loud buzz. So since the motor is not the problem I might put the quieter one back in.

    Thanks.
     
  19. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I'd still say adjust the current on the driver to see it if helps (regardless of which motor you end up using).
    If however that fails to help then you are left with the RAMPS or the Arduino (and the Arduino is rarely ever the fault).

    There are a lot of RAMPS 1.4 boards available on Amazon... pick one :) [search Amazon for RAMPS 1.4] I have had mixed luck buying just RAMPS boards regardless of which one I picked. Some worked, some came in dead. Just choose a seller that you know you can get a refund form if you get a bad board (like an Amazon Prime seller -- you can always get Amazon to make that right and you get a 30 day no-questions-asked return).

    Last time I ordered RAMPS boards I went through 4 to get 1 that worked. I know have tested working spares ... (and I returned the faulty ones). I have had better luck when I purchased the all-in-one kits (and I don't mind the extra spare parts)
     
  20. Chuck Glenn

    Chuck Glenn New Member

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    Thanks Mark,

    Is there any harm in using a RAMPS 1.6?

    Plus, I already replaced the stepper driver / A4988 for the Y and it really didn't make any difference. I got a the new A4988 from partsbuilt, designated specifically as being for the R1+. But it wouldn't hurt to try I guess. Can you point me to a tutorial for that? Thanks again.
     

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