I designed an i3-style frame for Prusa Mini parts, as the cantilever design was too flimsy for my needs. I will convert at least two of these, and it's not quick/cheap/easy to source a second Z motor/lead screw, so I decided to try using just the one. I think I ended up with a pretty good solution using pulleys and fishing line. I didn't see anything like it when I was searching for ideas, so I thought I'd share.
I mounted the Z motor/lead screw horizontally across the top of the frame. The X-axis is supported by braided fishing line (250 lb. test, 0.8mm dia.) that is routed through pulleys such that pulling both lines in the same direction raises both sides. On the left side, it's just a single 90° turn. On the right, there are two 90° turns to get to the back side of the lead screw and then a 180° turn to reverse direction. These two lines are attached to a part attached to the lead screw nut and is kept from rotating by sliding against the frame. I found discussions about using braided fishing line and many associated drawbacks, but none of them seem to apply to this application. I just got it printing yesterday, so I may still find some issues...
Video: [
youtu.be]
