I am experimenting with a new low-friction Y-carriage using standard ball bearings instead of bushings. As this changes the height of the printing platform, it also requires installing the Y-motor at a different height. Doing this, I found that the usual Prusa i3 Y-motor mounts have two disadvantages: firstly, to replace them you need to completely disassemble the (carefully adjusted!) Y-frame, and, secondly, they are provided only for one vertical height of the motor axis. So this project tries to address both of these shortcomings.
These Y-motor mount brackets are split into two halves, so that they can be mounted and unmounted without having to take apart the entire Y-frame. The vertical position of the motor axis with respect to the center of the upper short threaded rod is parametrized, so brackets for any (reasonable) motor height can be generated.
Given that the optimal height of the Y-belt depends on the diameter of the pully and the height of the Y-carriage, being able to change the Y-motor bracket without quickly without demounting (and readjusting!) the Y-frame is very useful.
The two halves of the bracket have rail cutouts leading from the rod hole to the outside, so that the two half can be slid from two sides around the threaded rods to form a complete and strong motor bracket.
In order to make sure that the motor does not give way and always remains perpendicular to the belt, a J-shaped shim is also provided which slips over the threaded rods and keeps the rear end of the motor at the same distance as the front.
The SCAD file is fully parametrized, so that it can easily be adapted to just about any Prusa i3 variant: The main parameters of the Y-motor brackets are:
- diameter of the short threaded rods
- center-to-center distance between the short threaded rods
- vertical offset of the motor axis with respect to the upper rod
- motor outer size and screw hole spacing
- horizontal offset of the motor from the rod center
Auto-make modules for producing ready-to-print STL files are provided for the following standard configurations:
- 8mm rods at 20mm distance for Nema17 stepper motor
- 10mm rods at 22mm distance for Nema17 stepper motor
For both configurations, vertical offsets of the motor axis are provided for -9mm, -6mm, -3mm, 0mm, +3mm, +6mm and +9mm.
Motor mounts for other rod configurations, axis offsets or motor geometries (e.g. for Nema14 or Nema23 steppers) can easily be produced by changing the values of the corresponding parameters in the SCAD file.
I printed these motor mounts from 3mm ABS on my DIY box-frame Prusa i3, using a 0.40mm nozzle with 0.25mm layer height and 0.56mm extrusion width. I always print on a clear mirror without Kapton tape, but thoroughly cleaned with acetone and double concentrated lemon juice.