Fixing eccentric drive pulleys?

  • Hi all,

    I'm building a large CoreXY machine - about 800mm x 800mm, and I'm struggling with belt tension issues. In particular, I notice that the stepper motor pulleys are slightly eccentric - they're secured onto the motor shaft with 2x grub screws. When you move the print head by hand you can feel alternating loose and tight spots, and you can visually observe the motor pulley moving slightly eccentric. In industry, we'd use taper lock shaft bushings to maintain concentricity, but I doubt they exist at this size. My next thought is maybe I can buy the blank gear tooth extrusion (teeth only, solid bar, no other features) then turn down a shaft that's supported in bearings, and driven by the stepper motor via a coupling - however, I haven't found the extrusion available anywhere.

    Any suggestions?


  • Either from SDP-SI or Misumi if you are in the US.

    Both carry the extrusion stock as well.

    If you really want taperlock or similar, you would need to go up to something like a 3mm pitch belt with a 34 tooth pulley.

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