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C-Bot

Discussion in '3D printers' started by Carl Feniak, Sep 29, 2014.

  1. Carl Feniak

    Carl Feniak Master
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    Carl Feniak published a new build:

    Read more about this build...
     
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  2. Mark Carew

    Mark Carew OpenBuilds Team
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    Great looking design Carl very smart on the belt layout, thank you for sharing.
     
  3. Tweakie

    Tweakie OpenBuilds Team
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    Excellent work Carl. :thumbsup:

    Tweakie.
     
  4. JCPhlux

    JCPhlux Veteran
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    I love this design. I was thinking about building an h-bot but a Core-XY design is much better.
    How long before you share the file?
     
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  5. Alan Chapman

    Alan Chapman Well-Known
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    Nice design. I really like your belt management.
     
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  6. JCPhlux

    JCPhlux Veteran
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    Now if we could get more than just pictures :) Hint Hint
     
  7. Carl Feniak

    Carl Feniak Master
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    I plan on posting some this weekend. I want to edit some parts to reduce the variety in bolt lengths required. I posted the BOM but accidentally put it in the wrong place. Will have to remedy, but I don't know how to remove the file (from the parts area).
     
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  8. Carl Feniak

    Carl Feniak Master
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    Also, I built a H-Bot first with the same basic concept, photo attached. Got it printing and it worked like a charm. Incredibly smooth, but... the the dreaded H-bar moment forces caused my circles to be slightly oval. Decided it was unacceptable, so I revamped the entire thing to this Core-XY. photo 2.JPG
     
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  9. JCPhlux

    JCPhlux Veteran
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    My plan is to build with a 12" x 12" heatbed.
    I noticed you just have the support on one end of your z-axis do you see any wobble?
     
  10. Carl Feniak

    Carl Feniak Master
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    The bed is very stable. I attribute this to using two lead screws and motors to stabilize it left and right. Plus it is clamped on both sides with eight mini V wheel (4 per side to preload them for "lift on nozzle move" bed motions). A modification I would make for beds with a front back length larger than 8" would be to replace the rear bar in the Z frame with a 20x60 instead of 20x40. The parts can already accommodate this change and you can either keep the 20x40s for the bed support and replace the bottom corner plate with a 90 degree corner (two bolt), or change them to 20x60 as well (i think it would be overkill). You will lose 20mm of Z height as a result, but it is up to you on how long the your lead screws are to start with.
    What will this accomplish? It will spread the moment (torque) forces on the Z axis mini V wheels of a large distance and reduce the normal force cause by the heavier and more distance bed.

    I would not recommend cheaping out and replacing the lead screws with M8 threaded rod, though it could be done. Open builds has the best price I've seen on the lead screws, but they didn't carry them when I bought mine (Ebay).
     
  11. JCPhlux

    JCPhlux Veteran
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    I am thinking about doing what I would call a Core Z axis. I added the counter weights to prevent the slamming of the table if power loss. It would only need one motor.

    Edit: bad design. See below.
    Core Z.jpg
    Edit: bad design. See below.
     
    #11 JCPhlux, Oct 4, 2014
    Last edited: Oct 4, 2014
  12. JCPhlux

    JCPhlux Veteran
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    ahh, I could call my design Core² or Core XYZ
     
  13. JCPhlux

    JCPhlux Veteran
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    after sleeping I figured out this design was flawed.

    Here is the correct Core Z design.
    Core Z.jpg
     
  14. Carl Feniak

    Carl Feniak Master
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    Yes, this revision will work much better! ;)
    What is your end goal though? Reduced cost? There will need to be two pulleys on the stepper motor shaft to offset the belts since they cross.
    Another option for a one motor set up: you could rotate the motor 90 degrees and shift it to the right or left. Then attach a bed length bearing confined shaft via a flexible coupling and attach two belt loops to it (looping over a pulley at the top like you have). You would still need counter weights as well, but this would keep the belts in alignment, reduce geometrical complexity, and increase belt contact with he drive pulleys.
     
    #14 Carl Feniak, Oct 4, 2014
    Last edited: Oct 5, 2014
  15. Keith Davis

    Keith Davis Master
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    Reg the Core Z. I had a Fabbster (since cannibalized it). It has a motor on each side that ran a belt on each side to lift the X carriage. Simple closed loop belts with common idler & pulley. It worked great down to .1mm layer. I discovered that 16 step steppers was the problem when I junked their proprietary controller and used 32 step drivers on a RAMPS. Very good .05mm layer control then. I had a dual shaft nema 17 so replaced one of theirs with it and ran a shaft to the other side to replace that motor too (what Carl describes). That worked also. No counter weights though. Looks like on a CoreXY the bed would just fall down with power loss, no big deal. On the Fabbster the Z would fall down right into the object. Still not a big deal, an object is ruined when there's power loss anyhow.

    As for the belt management on X & Y - incredible! Staggered height obviously beats the crossover layout. Hiding the belts in the slots, cool touch, Carl, real cool.
     
  16. Carl Feniak

    Carl Feniak Master
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  17. Carl Feniak

    Carl Feniak Master
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    Have you thought about using this with fishing line (maybe that was your plan all along)? I only imagined it with GT2 belts. You could have the bed home to Z max (bottom) rather than at the top for when it is turned off, plus there could be a rubber or spring stop at the bottom to cushion a fall on power failure. The belt cross isn't an issue with fishing line since it is so thin and has to spool anyway.
     
  18. JCPhlux

    JCPhlux Veteran
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    I was going to use GT2 belt. and have the home at the bottom. also I will be hooking it up to a battery backup as we have brown out about once every other month.
     
  19. JCPhlux

    JCPhlux Veteran
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  20. Carl Feniak

    Carl Feniak Master
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    6mm.
    I haven't been able to really find any others widths commonly available. I think 8mm would fit in the extrusions if you aligned it just right, but the flanged bearings I used are 4mm wide with a 1mm flange. So there is exactly 6mm for the belt when the bearing are placed together.
    So build note--> I designed space for the two flanged bearings plus a M3 washer between them so that the belt isn't pinched. Is is a pain to align during assembly, but works well.
     
    #20 Carl Feniak, Oct 6, 2014
    Last edited: Oct 6, 2014
  21. JCPhlux

    JCPhlux Veteran
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    well I am building a Prusa i3 and it is a pain. as soon as I get it working good I will print these parts then I am going to sell it and build a C-Bot.
     
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  22. JCPhlux

    JCPhlux Veteran
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    @Carl Feniak in the BOM you list F24ZZ bearing. I am having a hard time finding this. looking at the way most bearings are listed it looks like it is missing a digit.
     
  23. Carl Feniak

    Carl Feniak Master
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    Woops, you are right:
    it should read "624ZZ" <-- wrong, actually 625ZZ
    This bearing is for the filament feed idler, don't prefix this bearing with an "F" as that is for flanged and won't work. I'll fix the BOM asap.

    Thanks, Carl
     
    #23 Carl Feniak, Oct 9, 2014
    Last edited: Oct 9, 2014
  24. JCPhlux

    JCPhlux Veteran
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    ok, great I just ordered a set of 10.
     
  25. Keith Davis

    Keith Davis Master
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    Carl - thanks for posting the thingiverse files for the bowden extruder setup. I printed them last night. Awesome. I want to change over to bowden from direct drive on my next design. With just changing the mount holes to 40mm spread it should work perfectly on new design layout.
     
  26. Carl Feniak

    Carl Feniak Master
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    What printer do you have? I designed the parts in AutoDesk 123D (free) and included the CAD file in the thingiverse post if you need to make tweeks.
    When I get the time I will post a .zip of all the 123D files to the open builds site.
     
  27. Carl Feniak

    Carl Feniak Master
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  28. JCPhlux

    JCPhlux Veteran
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    :eek:......:cool:
    No big deal I will find a use for them someday. But now I will have to save for months to afford a set of the proper bearing :ROFL:
    Ohh, never mind I found 10 for $2.45 in shipping.
     
  29. Keith Davis

    Keith Davis Master
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    Printing on my own design BldrBot. It is listed on this OpenBuilds as build under Cartesian.
    I downloaded your STL files, imported them into Sketchup (that took awhile to process). Exporting to STL and loading in Slic3r had no problem. Manifold and no errors. Did not have to do Cleanup in Sketchup to export a manifold STL. So doing tweeking in Sketchup should be fine. That extruder/bowden group of STLs at thingiverse look good to go with Sketchup imports. That's kinda rare for 123D produced STLs, but hey - cupcakes happen too.
     
  30. JCPhlux

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