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Z Axis Ribbing Issues

Discussion in 'Troubleshooting' started by Montravont, May 12, 2014.

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  1. Ziggy

    Ziggy Moderator
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    What is the tolerance on the Z smooth rods? The Z bearings are 8mm but I believe the rods are only 5/16"
     
    #21 Ziggy, May 21, 2014
  2. Mike Kelly

    Mike Kelly Volunteer

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    The Z smooth rod is 8mm.

    The threaded rod is 5/16" going into a 8mm coupling. If it's not centered it will make an oblong circle.
     
    #22 Mike Kelly, May 21, 2014
  3. alberpao

    alberpao New Member

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    Hello, new on this forum after a week of usage of the RoBo 3D: I had the same impression even before reading this interesting thread: the Z axix rod move a lot during printing, especially when it come to print high objects.
    I was thinking a similar stabilizer as Montavont report here: I like this one because it give freedom to be fine tuned.
    As I understand they attach it using bi-adhesive tape on the plastic structure and would be better, I think, to have both Z rod stabilized... working free as original project is not the best.
    I will print them this week and will report here my experiences!
    Thanks for the thread!
     
    #23 alberpao, May 25, 2014
  4. Ziggy

    Ziggy Moderator
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    I've installed m8 threaded rods and Z Axis stabilizers but I am still seeing ugly Z artifacts on my prints. From other threads it appears that at least 4 out of 5 Robos are also having problems with Z artifacts.

    As a first step to pinning down the cause(s) I have a simple test stl model to analyse the artifacts. The test model was printed in PLA at 0.2mm layer height.

    IWF_2270.JPG

    I was surprised to find the artifacts are definitely Z Ribbing (not Z Wobble). The convex ribs are at exactly the same height on both sides of the model which is exactly what is expected with Z Ribbing.

    I was also surprised to see the Z Ribbing is very closely aligned with the Z thread pitch (as shown in the photo the pitch is M8 coarse 1.25mm). Clearly having M8 rods has not solved my Z Ribbing issues.

    I'm working through what is causing this Z Ribbing on my printer. But I thought it useful to post this now because I suspect that what many Robo'ers think is Z Wobble on their prints is actually Z Ribbing.
     
    #24 Ziggy, May 30, 2014
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  5. Kadows

    Kadows Member

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    Did you reflash the software after the metric upgrade?
     
    #25 Kadows, May 31, 2014
  6. Ziggy

    Ziggy Moderator
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    Yes
     
    #26 Ziggy, May 31, 2014
  7. Invertmast

    Invertmast Active Member

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    Has anyone thought to use a Ball screw and nut for the Z axis instead of threaded rod?
     
    #27 Invertmast, May 31, 2014
  8. savior2064

    savior2064 Member

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    Im seeing the same results with my print, the ribbing is match my z screws also.
     
    #28 savior2064, May 31, 2014
  9. Peter

    Peter Member

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    I'M thinking of the ballscew option.
    Aliexpress has SFU1204 x 300mm ballscrews with nuts for pretty cheap, under 100 usd for 2pcs of each.
    Thats 12mm diameter and 4mm lead, which will give 0.02mm per step.

    Another thread i'm watching is talking about z accuracy and apparently something like a 4mm lead ballscrew will have quite low resistance, though i'm not sure it's a good idea.

    It would be nice if there was a SFU1002 x 300 out there but I cant find one.

    There's no going back though as you will need to drill out the 8mm nut landing socket in the X carriage ends to allow the 12mm rod to travel smoothly through it.
     
    #29 Peter, Jun 11, 2014
  10. warlocke

    warlocke Active Member

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    Or just print a modified X carriage to test with. ;)
     
    #30 warlocke, Jun 11, 2014
  11. Peter

    Peter Member

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    Would if i could. glass plate cracked, getting replacements and doing major upgrade, again.
     
    #31 Peter, Jun 11, 2014
  12. Marcus T

    Marcus T Member

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    I printed 10mm, 20mm, and 30mm calibration cubes. All of them measured short at around 87.5% of the height that they should be.
     
    #32 Marcus T, Aug 22, 2014
  13. Ziggy

    Ziggy Moderator
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    This could be happening because the settings Z steps/mm is not correct.

    For example if you have 8mm metric threaded rods but the Z steps/mm is set for 5/16" rods the Z height will be 2267/2560 = 88% of what it should be.

    To check.

    Send the gcode M503 to the printer. You will see a lot of info returned by the printer in the log. The important info will be like this

    21:47:19.308 : N30 M503 *54
    21:47:19.308 : echo:Steps per unit:
    21:47:19.328 : echo: M92 X80.00 Y80.00 Z2560.00 E723.38

    The Zxxxx.xx in the M92 line is the Z steps/mm.

    Post the value you get back for your printer.

    Also check if you have 8mm metric or 5/16" Z threaded rods
     
    #33 Ziggy, Aug 22, 2014
    Last edited by a moderator: Aug 22, 2014
  14. Marcus T

    Marcus T Member

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    Okay, I'm pretty inept when it comes to software. How do I do what you've asked?

    I'm pretty sure I have the 5/16" rods. They're the stock ones that came with the printer.
     
    #34 Marcus T, Aug 22, 2014
  15. Ziggy

    Ziggy Moderator
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    What are you using on your PC to run the printer? Mattercontrol or Repetier Host or ????
     
    #35 Ziggy, Aug 22, 2014
  16. Marcus T

    Marcus T Member

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    I'm currently using Cura.
    Matter Control will randomly crash on my for unknown reasons.

    Edit: I'm having the same issue with the print on both programs.
     
    #36 Marcus T, Aug 22, 2014
  17. Ziggy

    Ziggy Moderator
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    For this use MatterControl. Only need to click a button.

    Connect your printer
    Go to the "Configuration" tab top right.
    In the "EEProm Settings" box click "Configure"
    In the panel that pops up, read the value for Steps per mm for the Z axis (ie first line in the pop up panel)
     
    #37 Ziggy, Aug 22, 2014
  18. Marcus T

    Marcus T Member

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    Z: 2267.72
     
    #38 Marcus T, Aug 22, 2014
  19. Ziggy

    Ziggy Moderator
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    That is the correct value for 5/16" rods.

    So you either have 8mm rods which would definitely cause the height to be about 88% of what it should be OR

    something else entirely causing the problem - possibly under extrusion.
     
    #39 Ziggy, Aug 22, 2014
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  20. Marcus T

    Marcus T Member

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    I can't think of any reason that I would have 8mm rods, unless the newer models are coming with them. Either way, I changed the value to 2560 and am currently printing another test print. I'll let you know if that solved anything or not.
     
    #40 Marcus T, Aug 22, 2014
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