COMPLETE Toothed Y-Idlers

Discussion in 'Guides, Mods, and Upgrades' started by Ephemeris, Feb 18, 2018.

  1. Ephemeris

    Ephemeris Well-Known Member

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    I really like the basic BigBox platform but my endgame has always been a basically industrial quality machine. This is one of my smaller incremental improvements.
    Left Y-Idler.jpg

    One of the short cuts in the original design was using flanged bearings as idler pulleys.Toothed idler pulleys are manufactured because they are better than using smooth flanged bearings in two ways

    1. The effective diameter of the toothed idler will be the exact same as the matching toothed drive pulley. In the case of our 20 tooth pulleys, the outer diameter of the GT2 belt wrapped around the toothed pulley is about 13.35 mm while the belt wrapped around the flanged bearing about 14.75. That means it acts like a 22T pulley instead of the desired 20T. Pretty close but it makes the belt not quite parallel to itself.
    2. The belt teeth slapping against the smooth flanged bearing surface causes vibration. Gates recommends using toothed idlers for anything smaller than about 40 teeth. Again this is a small effect

    Neither of these is a big source of error, but this is a case where it's easy to do it right instead of close to right. I redesigned my ultra compact Y-idler brackets to accept 20T toothed idlers from RobotDigg.com. The pulleys are mounted on 4mm diameter M3x12 shoulder screws

    Assembled.jpg
     
    #1 Ephemeris, Feb 18, 2018
    Last edited: Feb 19, 2018
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  2. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    What are the z axis lead screws terminated in? Are they bushings of some sort?
     
  3. Ephemeris

    Ephemeris Well-Known Member

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    Good eye. Those are plastic pillow blocks made by Igus fitted onto the ends of the custom Tr10x2 precision leadscrews Patrick Notton and I had made. Standard steel UFL pillow blocks could have been used instead.
     
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  4. gonzalo

    gonzalo Well-Known Member

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    Nice work! Would you share your step files for the Y brackets? Is the tensioning mechanism the same? Thank you!
     
  5. Ephemeris

    Ephemeris Well-Known Member

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    I'll be happy to share, but it's a little harder than it sounds. The brackets in the pictures are for my redesigned "EphBox" frame. The hole patterns are different because I wanted to be able to pull the Y-guide rods THROUGH the front panel. (My redesign focused on NEVER having to disassemble the frame for maintenance operations.)

    Long story short, it should be fairly easy for me to adapt it to create a version that fits the original BigBox mounting pattern. I'll take a look at it tonight.
     
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  6. Ephemeris

    Ephemeris Well-Known Member

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    Looks easy enough to do a mashup retrofitting the the 20T idler into a bracket that fits the original bolt pattern. I did a quick pass at it last night. I'll clean it up tonight or tomorrow and get it to you
     
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  7. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    BTW, what type of plastic filament did you use when you printed the plastic parts? Are you happy with it? (I have been looking for the best mix of stiffness and glass temp and curious about what other people have decided to use when making printer parts)

    Gene
     
  8. gonzalo

    gonzalo Well-Known Member

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    Thank you!
     
  9. Ephemeris

    Ephemeris Well-Known Member

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    I used HT for almost everything because it's tough, it resists heat, and I have a lot in stock. Its heat resistance is only critical for the part cooling fan shroud that gets very close to the hot end. For most things I'd think a good quality PETG would be a pretty good choice.
     
    #9 Ephemeris, Feb 21, 2018
    Last edited: Feb 21, 2018
  10. gonzalo

    gonzalo Well-Known Member

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    I’m redoing mine with Nylon CF it will match my all black B.B. nicely.
     
  11. Ephemeris

    Ephemeris Well-Known Member

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    See if these models work for you. They should fit the original BigBox frame. These brackets give you about 20 mm of extra Y travel. The original laser cut limit stop arm can't accommodate this much travel, so you need to remove it, and install the Y-limit stop screw in the arm of the right side bracket. You'll need to run an M3 tap for the end stop screw.
    Eph BigBox Y Front Bracket 20T v30.jpeg
    You may need shorter M4 socket cap screws for tensioning depending on how long you make your belts. The 20T GT2 idlers can be found here:
    https://www.robotdigg.com/product/637/2GT-Idler-Pulley-w/-Bearings
    Make sure you order the 20 toothed idlers with a 4mm inner diameter.

    The toothed idlers are mounted on these shoulder screws.
    https://www.mcmaster.com/#90265a122/=1bo10tf

    I've attached STL and STEP files. No promises on how useful the STEP will be because of all the blends I used.
     

    Attached Files:

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