MMU2s Idler improved mounting for motor.

The 4th installment of my MMU2s overhaul

As discussed on the forums and here, the stock idler is prone to breaking if the set screws are too tight on the D shaft. In addition to the potential breakage when installing all the force of the motor is directed to the two set screws then to the two small washers, this could lead to problems with drift along the axis of the idler with the potential of breakage and mis-allignment of the bearings.

Goals:
-Improve mounting of stepper to idler to provide tighter tolerance and distribution of force from the motor to the idler.
-Reduce part count as much as possible.
-Print without supports.

Changes:
-Eliminated the two set screws with washers and replaced the with a single hex M5 20mm (or 5/16 1") coupling nut . The D face of the stepper is in full contact with one side of the hex nut providing better transfer of power and less tendency to drift. Net reduction in parts 3!
-Increased the depth on the flat face by 2mm. This gives extra support to the Hex Nut. The angle is pretty hard but I was able to print without supports or brim.
-Eliminated the hole going through the center of the idler as it is unnecessary.

This is a very precise part with very tight tollerances. If your printer is off by 0.1mm the hex nut may be too loose or too tight. I recommend printing the test .stl first to make sure the hex nut fits perfect. If it doesn't you can scale the model as appropriate. Start with +/-1% and go from there. I added the test .stl so you don't waste a 4 hour print just to find out it doesn't fit.

Update 2/12/2020. I modified the left side of the idler with a 5mmX24mm rod so that the idler will be centered perfectly on the body modified idler body. The original file works great especially if you are using the old idler body. Here is a link to the rods I used.

https://amzn.to/39vyYbX You will have 39 left over unless you want to do my Y tensioner mod that uses 1 as well.

Installation is easy, Insert the nut, put idler in body, insert the motor.

Here is a link to the 20 Hex nuts, Unless you have 5 MMU2s's you will have 19 leftovers https://amzn.to/2UNjn3e

Here is a link to the 5/16 1" Hex nuts. https://www.mcmaster.com/90268a206

Source files for this project are here..https://github.com/prusa3d/MM-control-2.0/blob/master/rev.03/MM-control.pdf

Next Up, Horizontal mount for the MMU (not nearly as exciting as this idler IMO)

Print instructions

Prusa PETG
Prusa Slicer 0.2 quality setting with the following changes..
All patterns rectilinear
4 layers all around
50% infill
YMMV