Kossel XL driver shaft support
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I recently added a bearing to support the free end of the drive shafts on my kossel XL, and have been surprised how much print quality has improved.
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The main effect is that you can tighten belts with more confidence. The design is on thingiverse at link text. I have made various other changes to my kossel XL, most notably doubling up the vertical 1515 extrusions using this clamp link text, which also allowed me to double up the carriage wheels which better rotational stability I think.
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I printed my own wheels in nylon 12.
This is my most recent benchy, with 0.2mm layers in pla
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Interesting to see you get good results with 3d printed wheels. Did you do much post processing on those to get the completely smooth? I ask because slightly asymmetric wheels have bitten me in the past.
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I was concerned about that too. I made a couple of simple jigs - one to hold the wheel with axis vertical, to sand the flange flat and a smooth fit into the slot; the other to smooth the contact surface of the wheel. I found that a fine emery board (that my wife uses for her nails) was good mounted under the wheel. I used an old set of feeler gauges to slot under the emery board, gradually raising it to smooth the surface to a diameter of 13mm. The holes for mounting the wheels are 28mm apart vertically, so 13mm wheels give a good fit to the 15mm extrusion. I belatedly found that a 13mm cylinder printed continuously in vase mode can be made to slot over the wheel like a tyre. If you play with the dimensions you can get the tyre to just slide on, and it then locks in place when you press in the bearing. Gives a really smooth surface.
I tried all this because I thought that the delrin v wheels I originally had were tending to stick in the slot, and there would be less "stiction" with hard flat surfaces in contact. Not sure if this is really the case. The other problem with the delrin wheels for me was getting them tightened correctly - ruined several sets by overtightening. My solution is to put an 8x4x3 bearing between the 10x4x3 bearings - you can then tighten really firmly, and they still rotate freely. -
@adrian52 good to know!
