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Solved Z-ribbing related question + coupler replacement

Discussion in 'Troubleshooting' started by CoenB, Jul 19, 2015.

  1. CoenB

    CoenB Member

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    Hello everyone.

    It has been a while since my last visit here, I see there have been some changes. I hope the level of activity and friendliness has stayed the same though.

    The problem I've been having for quite some time now is the famous Z-ribbing. I bought my Robo3D beta (?) in February of 2014. Since then I have been having the Z-ribbing issues. I have tried some things, but not really intensively since the problems weren't that much of a deal back then. After nearly 7 months of not using the printer, I have started using it again since about 1 month ago due to a spark I got from winning another 3D printer. Which is, sadly, also not printing correctly (might I say, broken on arrival). So I now have two unusable printers.

    That inspired me to fix the Robo3D. I looked up some information on the Z-ribbing subject and found a useful thread with the guide from Ziggy (with help from the other users).

    But first, I'd like to show you four 15mm blocks I printed with different settings.
    [​IMG]
    The one on the right is printed on 0.3mm layer height (low setting), no adjustments yet.
    After that I printed one on 0.1mm layer height (high setting). Problem is, I can't tell which one that is anymore...

    Anyway, after that I tried the height adjustment first, I went from 0.2 to 0.1905 on the medium setting. Those are the other two blocks that remain. This does show some improvement, but the Z-ribbing is still noticeable. As you can see, the difference between high (unadjusted) and medium (adjusted) is not noticeable.

    So I decided to follow up on the advise to dismount and check the couplers and threaded rods. It was at this point that I noticed that my right coupler wasn't put on askew, but it was bend. As you can see in the picture below.
    [​IMG]

    I've also got a video of this.


    The left one does not 'wiggle' as much as the right one though. But I think this might be one of the major causes for the Z-ribbing, along with the slightly bended threaded rods (tested on a glass table).

    My question is as follows. What now...? I've already contacted a local printer part reseller and asked for the metric M8 threaded rods, as suggested by the Z-ribbing guide. Also, about the couplers and if he might be able to get a hold of them new. He suggested the Zortrax couplers (I am a bit familiar with those), but I prefer to use the traditional ones.

    I hope someone might have me some tips for me.

    Kind regards,
    Coen
     
  2. Marquis Johnson

    Marquis Johnson Active Member

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  3. Ziggy

    Ziggy Moderator
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    CoenB

    Your bent coupler and rod are the most likely cause of your Z ribbing problem. As the threaded rod rotates there will be a very small variation in the Z height and that will cause Z ribbing.

    So I suggest you follow the steps in the Z Ribbing guide I posted about 12 months ago.

    http://community.robo3d.com/index.php?threads/z-axis-artifacts-known-issues-and-fixes.2576/

    Post #11

    Get some decent quality helical couplers to replace any bent ones and use the ball bearings in the couplers as I described in the guide. The aim is to eliminate any variation in Z height as the threaded rod rotates. M8 rods are not essential but if your 5/16" rods are bent then definitely worth replacing with M8.

    You could also replace the threaded rods and motors as Marquis has suggested. But these are expensive and care must be taken to eliminate any vertical misalignment of the rods or you will have some horizontal movement of the Z.

    I suggest you try the steps in the Z Ribbing guide first. Very low cost and many have found to be the solution to their Z ribbing troubles.
     
    #3 Ziggy, Jul 19, 2015
    Last edited: Jul 19, 2015
  4. Mike Kelly

    Mike Kelly Volunteer

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  5. jtn7040

    jtn7040 Active Member

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    That kit being 100$ or so have they had anyone successfully upgrade with that kit and truely have less z ribbing?

    Sent from my SM-N915T using Tapatalk
     
  6. Mike Kelly

    Mike Kelly Volunteer

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    I will let you know tonight after I install it.

    Everyone else who went with a non-OEM option had their ribbing completely disappear. Ribbing is entirely a function on helical coupler misalignment.
     
  7. jtn7040

    jtn7040 Active Member

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    Yeah I've seen the sain smart lead screw but even then it only saves about 6$ so I was curious.

    Sent from my SM-N915T using Tapatalk
     
  8. CoenB

    CoenB Member

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    Everybody, thank you for helping me with this problem.

    @Marquis Johnson
    Those do look very interesting, but same story here money-wise.

    @Ziggy
    I had those upgrades in mind, as they do not cost that much money (or energy) to perform.
    The rods was the next thing on the list I wanted to replace, but then I came across the problem of the bent coupler. No point in replacing the rods if one (or maybe two) of the couplers are not 100% OK.

    Is there a way I can get one replaced under warranty, as this was the condition in which it arrived?
    If not, where can I get them (new)?

    Also, I read the post from Mike which altered my opinion on the matter a tiny bit.

    And wow, that is one beautiful doggy you got there.

    @Mike Kelly
    I'd be very interested in hearing the results.

    I wish they would come up with some kind of reimbursement for the people stuck with the earlier versions with the massive Z-ribbing issues. $100 is a no go for me now... (especially if I don't know if that really does fix the problem), same story as the one linked by Marquis.

    I would love to 'test' the difference between the hardware I have now (the bent rods and coupler(s)) and that upgrade kit. And with that I mean, I get a free (careful with that word) test kit as a 'reviewer'. Would be a great way to see if the kit does what it promises to do (for that price) in just one replacement (or should I say, improvement) session, instead of the DIY solutions (and don't take me wrong here, those are very useful and I really appreciate the amount of effort and time that has been put into this). If it does, that would be a great selling point for them.

    But I already think I know the answer to that idea...
    I'll just wait for the replies to my coupler question.
     
  9. Ziggy

    Ziggy Moderator
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    Mike Kelly has a far better idea how the Robo guys handle warranty questions. But..

    Helical couplers are cheap and widely available on eBay - you need 5mm / 8mm types.

    Threaded rods in stainless steel should be easy to find at a speciality hardware store - In the US McMaster-Car seems to be the popular choice
     
  10. CoenB

    CoenB Member

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    Alright, thanks. I now know which couplers / couplings I need.
    Getting the threaded rods was no problem, 't was the bent coupler that stopped me in my work.
     
  11. Mike Kelly

    Mike Kelly Volunteer

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    If it's been more than 6 months they don't technically need to replace it, but they're pretty nice guys and if you submit a replacement part request they'll help you out.
     
  12. CoenB

    CoenB Member

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    Alright thanks, I'll give it a try.

    Did you manage to find any time (and energy) to test the upgrade kit for the Z axis?
     
  13. Mike Kelly

    Mike Kelly Volunteer

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  14. CoenB

    CoenB Member

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    I wish I could print like that... But we'll have to wait and see what results the 'Parts replacement request' or 'Own replacement/improvement on budget' are when I get to that stage.
     
  15. CoenB

    CoenB Member

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    So, a few days later and I'm back with some good news. I send an email to the guys at Robo and they were kind enough to send over some replacement parts (quick shipment as well, within 5 days). I have received two new couplers, two new M8 rods with matching nuts and a new fan bracket.

    I noticed that the couplers I got, are different than the old ones. But in a good way, as these look and feel much stiffer.

    https://drive.google.com/file/d/0B7ita5Jp5GkZTEppMkMwZW5fUkE/view?usp=sharing

    The new stuff has been installed, I put a little bit of Teflon tape around the rods to ensure no slippage in the couplers. I'm trying the new stuff first to see of there is any difference in the Z-ribbing. After that I'll install the ball bearings.

    Now what do I have to do on the software / Arduino side? Now that I have the M8 rods, what do I have to change to make it work proper?
    I haven't tried to print anything yet.
     
  16. Ziggy

    Ziggy Moderator
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    For M8 threaded rods you need to change the steps/mm parameter for Z in the configuration.h file, recompile Marlin and reflash your firmware.

    The parameter to change is

    #define DEFAULT_AXIS_STEPS_PER_UNIT {80,80,2560,723.38} // default steps per unit X, Y, Z and extruder for RoBo 3D R1 8mm

    The new Z parameter is 2560 - the old value for 5/16" rods would be 2267.72
     
  17. CoenB

    CoenB Member

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    Alright, I've found the line I have to change. Problem is, I found out that I do not have the Marlin version for my printer anymore. I apparently loaded up one for a Ultimaker (had to flash one a few weeks ago).

    I tried to retrace my steps when I flashed my Robo for the Smart LCD XXL upgrade, but all internal links from the former forum software are invalid.

    I did find one, a zip file called Marlin 3_14_14. I think that is the one that is on my Robo now. So can I use that one? Of not, where can I download the correct Marlin firmware version? Or is there a possibility to read the current firmware on the board of my Robo, change it and re-upload?

    To be clear, it's the ABS+PLA version. It's not the kickstarter, R1 or auto-leveling, but the beta one (ordered it at a reseller in February of 2014). The only upgrade I have that is related to the firmware is the Smart XXL Controller.

    Also, what line do I have to change to change maxtemp error? It shuts down when it exceeds 235°C, which is kind-off annoying when printing ABS. I used to be able to set it to 240°C without the maxtemp error stop, that was before the flash for the Smart XXL Controller.

    I know I shouldn't print above 240°C and I assure you, I don't. It's just that the error (and auto-stop) occurs too often, even sometimes at 233°C. I'd like to 'up the limit' a bit.

    Many thanks.
     
  18. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The beta is the same as kickstarter (or what was sold until the R1 was released).
    I think mine is still using 3_14_14 if not something even earlier.
     
  19. CoenB

    CoenB Member

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    Alright, good. Didn't know that BTW, I always thought that those were different.

    I'll try to do it today, I'll update if it is working or if I have any additional questions.
     
  20. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Nah, the only differences in the Beta versions was the heated bed (some were sold without one). Then the Original R1 used a J-Head and then lastly they swapped the R1 to a Hexagon. I think that covers all of the versions*...

    Ask away :)


    *(not counting the Bed upgrade you could apply to the Beta so that it was the same style as the R1 -- the Original Beta was a wood and glass bed.)
     

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