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Trying to resurrect my R2

Discussion in 'Mods and Upgrades' started by Joseph Stevens, Jul 6, 2021.

  1. Jerome Helbert

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    My comment about it not working was specific to using the EVA carriage system. Excessively customizing that design to fit with the R2 defeats the purpose of a universal printhead system.

    I still have no doubt the 8mm carriage rods and accompanying bearing blocks are entirely possible though. Your mockup does deviate significantly from what I've been planning though. I had planned to use shorter carriage rods that could be installed without drilling a hole in the side of the shell. Similar to the ultimaker design that inspired this, I intended the carriage rods to be planar to the gantry bushing and would be clamped in place.
     
  2. Lance Weston

    Lance Weston Active Member

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    I can not visualize your description. can you provide a sketch?
     
  3. Jerome Helbert

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    The pictures attached to this thingiverse design are pretty much exactly what I am picturing (Although I do like your approach of using a manually adjustable open loop belt better)

    https://www.thingiverse.com/thing:45236
     
  4. Lance Weston

    Lance Weston Active Member

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    That is exactly what my block implements. The only difference is I am using open loop belting.

    You need my block to be able to hit the x,y limit switches.
     
  5. Jerome Helbert

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    In your block, isn't the hole marked with the red arrow where the 8mm carriage rod is going to go, and then the 8mm bushing goes where the blue arrow is? In what I am planning and the ultimaker model, the hole for the 8mm carriage rod would also be up in the same plane as the bushing.
    [​IMG]

    The XY limit is a good idea for anyone else wanting to follow this, but isn't necessary for me. I've been using the sensorless homing function on the TMX2209s with pretty good success. Basically during a homing cycle the printer moves the carriage along until it bumps into the gear pulley and the 2209s detect the increase in stall current, then signals to the processor that the axis has hit its homing point. Currently I am using some printed spaces so that the bearing blocks hit the gear pulleys instead of the carriage.
     

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  6. Lance Weston

    Lance Weston Active Member

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  7. Jerome Helbert

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    No... The carriage rod (a 6mm rod in the case of the thingiverse model) is quite clearly in the same plane as the bearing and X/Y Rods... The thingiverse page actually has an scad project included for easy customization, that makes it even easier to see that the the carriage rods are not above or below the bushing.
    [​IMG]
     

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  8. Jerome Helbert

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    Oh wow... Actually looking at the scad script and they really made this thing infinitely customizable... They have variables you can edit for bushing OD, XY gantry rod (they call them slidebars in the script) diameter, carriage rod (they call it a headbar) diameter, distance from the sliding bar to the belt, dimensions of the belts, etc.
     
  9. Lance Weston

    Lance Weston Active Member

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  10. Jerome Helbert

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    I've been slowly putting in some work on modelling this, and one concern I have is that when aligning the bearings like this:
    [​IMG]

    The printhead starts to get appreciably larger than the stock design (stock design is 60x55 and a 15mm OD 45mm long LM8LUU bearing will drive the print head to be at least 65mm in both directions), leading to a loss in print area and an overall growth in the size of the print head (my primary goal in all of this is to reduce the size and mass of the moving components of the R2.

    I'm still working towards a solution that will put the new 8mm fixed printhead rods in the same place as their associated rotating rods. I took another look at dimensions and realized that the vertical spacing between the rotating X rods and rotating Y rods is 19mm (correct me if you have a different measurement than me on that) and that this is appreciably more than the 16.8mm vertical spacing that you provided for the current 6mm fixed rods.

    This would give 4mm spacing between the LM8LUU bearings they are overlapped, and that starts to get into the realm of possibility. If I wanted more meat between the two (not sure that I do) I could always offset the the printhead rods slightly up/down a few mm to increase that spacing. Using an overlapping bearing design could feasibly get the printhead Xy dimensions down to a 50x50, and possibly even offsetting the lost area from the bearing block holding the fixed rod in the same plane.
     
  11. Lance Weston

    Lance Weston Active Member

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    The vertical distance between the 8 mm rotating rods is 19.2 mm You need to maintain the same footprint for the head so that you can use the aluminum base to clamp the print head. The aluminum base is also a heatsink protecting the plastic above.

    Change the vertical height of the print head instead.
     
    #51 Lance Weston, Sep 7, 2021
    Last edited: Sep 7, 2021
  12. Jerome Helbert

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    Lol, I just spent 20 min measuring and remeasuring because I only looked at your original post in the email notification where you first said 32.43mm :p

    I came in here to post that that cant be right and that at most its 19.5mm (using a straight edge laid across the top of the r2 for reference and then measuring down to the tops of the rods) and I now see that you corrected it to 19.2mm :) But yeah, I can definitely see it being 19.2mm.

    I did away with the aluminum clamp a few months ago, so it's not a driving factor in my design. As for the heatsink/shield component of it, as long as you use something with better heat tolerance than PLA then heat should be no issue for a plastic based mounting bracket. I've used PETG for a couple months without issue after converting to the mosquito and the piezo sensor without any signs whatsoever of warping. I am now currently using a carbon fiber polycarbonate piece that is considerably more dimensionally stable and heat tolerant.
     
  13. Lance Weston

    Lance Weston Active Member

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    I looked at the wrong drawing first. 32.43 was from my 8 mm rod design.
     

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