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Unresolved Really bad ribbing

Discussion in 'Troubleshooting' started by jbigler1986, Feb 28, 2015.

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  1. jbigler1986

    jbigler1986 Active Member

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    I have really bad ribbing. Nothing is loose. Belts seem tight. Idk what to do.
     

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    #1 jbigler1986, Feb 28, 2015
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #2 mark tomlinson, Feb 28, 2015
    Last edited by a moderator: Feb 28, 2015
  3. Mike Glass

    Mike Glass Active Member

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    Ribbing or overextrusion? Try lowering your filament flow to 97.
     
    #3 Mike Glass, Feb 28, 2015
  4. jbigler1986

    jbigler1986 Active Member

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    FR was at 80 percent.
     
    #4 jbigler1986, Feb 28, 2015
  5. Mike Kelly

    Mike Kelly Volunteer

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    Have you calibrated your extruder steps?

    I'd do a 1 on 1 with robo since they have the most experience fixing ribbing.
     
    #5 Mike Kelly, Feb 28, 2015
  6. Ziggy

    Ziggy Moderator
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    I am very curious to hear what Robo support have to say about the Z ribbing on a new model Robo.
     
    #6 Ziggy, Feb 28, 2015
  7. Mike Kelly

    Mike Kelly Volunteer

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    They try and get threaded rods and helical couplers to a close match to not need teflon tape to mitigate ribbing.

    I really think a large contributor is the motor being out of true center in it's seat.
     
    #7 Mike Kelly, Feb 28, 2015
  8. Ziggy

    Ziggy Moderator
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    All useful improvements but still missing the simplest of fixes.
     
    #8 Ziggy, Feb 28, 2015
  9. Mike Kelly

    Mike Kelly Volunteer

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    The bearing? That never did anything for me
     
    #9 Mike Kelly, Feb 28, 2015
  10. Ziggy

    Ziggy Moderator
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    Well you must be the only one ;) or had some other issues as well. The mechanics of why it works are very straight forward.

    And the firmware fix still hasn't been done AFAIK.
     
    #10 Ziggy, Feb 28, 2015
  11. Mike Kelly

    Mike Kelly Volunteer

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    Na there's been others with the same result. I think it has to do with the integrity of the helical couplers as well.

    The bearing just helps it bend, but it really shouldn't be bending much as it is.
     
    #11 Mike Kelly, Feb 28, 2015
  12. Ziggy

    Ziggy Moderator
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    The bearing stops the Z height variation if/when the coupler bends. That's the mechanics. The rest of the package of Z ribbing fixes (other than the firmware fix) is about minimising the coupler bending or slipping.

    Robo could/should be asking why new printers are still experiencing Z ribbing issues
     
    #12 Ziggy, Feb 28, 2015
    2 people like this.
  13. Mike Kelly

    Mike Kelly Volunteer

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    I think the Z ribbing isn't caused by height variation but rather translational pressures from the offset position of the threaded rod. That's why if you follow it around the object it matches the thread pitch exactly. I don't think it's really Z height but X-Y translation that's the cause of ribbing.
     
    #13 Mike Kelly, Feb 28, 2015
  14. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    In the end I think you are both correct.
    There are a number of things that contribute to and/or cause the effect.
    It is often not as simple as one variable (at least for this issue).
    I managed to get it by changing nozzles once, long enough to notice it and swap again.
     
    #14 mark tomlinson, Feb 28, 2015
  15. Stephen Capistron

    Stephen Capistron Active Member

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    I know on my printer one of the motors is out of position a bit. I've used up whatever clearance was in the holes to slide it into a better spot, but it is still off a smidge. One of these days I'm going to drop that motor out and open up those holes a little so i can fine tune the motor position.

    The motor not being in the right spot made my threaded rod come out at such an angle that it can hit the top of the idler carriage.
     
    #15 Stephen Capistron, Feb 28, 2015
  16. Ziggy

    Ziggy Moderator
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    Mike

    What you are describing as X-Y translation is Z wobble (ie horizontal movements). Z Wobble can also match the screw pitch especially if the Z axis is not firmly constrained. There are examples of this Z wobble problem on many other forums and with particular printer designs (eg cupcake).

    It is easy to create Z Ribbing by simply varying the Z height (ie vertical movement). In fact it could be generated by the firmware if the Z height were varied by manipulating the numbers of z steps layer by layer. All it takes is a few 100ths of a millimeter variation in Z height.

    A more thorough discussion of Z artifacts is here

    https://groups.google.com/forum/#!topic/makerbot/xAFBbD2xlys

    My Z Ribbing fix package is targetted at issue (5) which has been (and continues to be) the major cause of Z Ribbing on the Robo.

    Issue (1) Z Wobble remains an potential issue with the Robo design. And there are many Z stabilizer designs aimed at fixing it.

    Issues (2, 3, 4, 6, 7) Are not inherent issues with the Robo design or firmware parameters IMO. I haven't seen X-Y wobble produced by tight belts but could imagine that is possible. Loose belts obviously are a problem.

    Issue (8) again is not inherent in the Robo design, but users should take care to make sure the filament comes off the spool with no jerking movements.

    Notice this analysis did not mention metric versus imperial rods - which makes no discernable difference.

    Finally, I think this analysis has missed the variation in extrusion volume issue. I have never seen this myself but there is enough evidence around that Z ribbing artifacts can be caused by over extrusion.
     
    #16 Ziggy, Feb 28, 2015
  17. Mike Kelly

    Mike Kelly Volunteer

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    I understand what you're saying, but from my experiments I don't think it's intrinsically caused by height variation, maybe partially but that doesn't really explain why it follows the Z threads on all dimensions.

    For (1) I think we can both agree it has to do primarily with helical coupler driven systems. If you were to switch to a linear stepper driver where the lead screw replaces the drive shaft the problem will go away completely. This is primarily what people have when they get the Z ribbing you're trying to solve.

    At least this is what my attempts to solve it on my system led me to believe.

    Even after replacing the Z screws with lead screws I still had Z wobble. It wasn't until my 3rd set of helical couplers combined with loosening and centering the Z stepper drivers was the issue mitigated. My original HC's were really bad and was probably the primary culprit of the severity of the ribbing. Though I think since the problem appeared in such severity after my Y axis upgrade it was also in part to motor center-ness. I feel like if I tried M8 again it would work with the current arrangement.


    For 5 I think your solutions would work, but I feel like most people have 1, not 5.
     
    #17 Mike Kelly, Feb 28, 2015
  18. Marquis Johnson

    Marquis Johnson Active Member

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    If that's the core to a gear cube/heart, and the image is not distorted in anyway...it looks short. The Z axis may not be raising in the correct increments. Or there is slipping in your couplers.
     
    #18 Marquis Johnson, Feb 28, 2015
  19. Ziggy

    Ziggy Moderator
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    Mike

    I was able to reproduce/eliminate Z ribbing by allowing/not allowing the Z height to vary as the couplers turned. Z height variation is definitely a cause of Z ribbing. The ribbing also matched the pitch of the screw. All of the beta testers eliminated their Z ribbing when the package of Z Ribbing fixes were applied.

    I agree Z "wobble" remains an issue inherent in the Robo design, but can be minimised by centering the motors, centering the couplers, and firming up the Z axis smooth rods. Unfortunately many of the Z axis mods I have seen on the forum actually have the potential to make the Z wobble problem worse or make no real difference at all.
     
    #19 Ziggy, Feb 28, 2015
  20. Mike Kelly

    Mike Kelly Volunteer

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    I think some people found solution from your guide, but certainly not all. I for one never found solution in any of your ideas. I think that's because of the Z wobble and not ribbing (my head hurts from these acronyms).

    I haven't seen "Non-standard Z movement" in quite some time. Pretty much everyone has Z Wobble from what I've encountered.
     
    #20 Mike Kelly, Feb 28, 2015
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