Some short comings of the McWire design have shown themselves after the build.
The first one concerns the method of attaching the drive screw to the Z sled. I seems the constant pressure on the tape covered coupling nut made the tape move over time. It telescoped out until the holding pressure in the conduit ran out. Then slipped out of the strap.
My solution was to build a bracket that presses the coupling nut against the Z sled, holding it in place. Overall this is a better way to go as you can adjust the height from the Z sled with a shim to get the drive screw parallel to the sled. This was a pain to do with the tape wound design.The X and Y have not been changed out but I will use the same solution if they become a problem.
The bracket material came from an L bracket that is used to hold drapery rods. A piece of 1/8"thick aluminum would do as well. It's held in place by 2 - #10 screws and tapped holes in the sled.
To make one of these :
- Use a template to mark the outline and hole locations.
- Cut it out roughly with the outline markings and the drill 1/16" pilot holes for all 3 holes. (larger for aluminum)
- Drill the clearance hole (23/64") for the 5/16" bolt holding it to the sled.
- Mount the bearing with a small washer (M5) under it using a dry wall screw.
- Screw in a #2 sheet metal screw to hold the spring.
- Dremel off the length the the screws protruding from the other side and grind them down just below the surface so the don't scratch the plastic on the sled.
- File the shape of the swing arm down to the outline marks.