This is a mecanum wheel based off of Zaggo's design. I beefed up the area around the bearings and made the rollers a little wider. I found that without the thicker area around the bearings, the plastic cracks and breaks off. I have uploaded two versions. One accepts an 8mm shaft and the other accepts the standard 5mm stepper motor shaft.
A short video of their operation:
Print two regular wheels and two mirrored wheels. Each wheel takes 16 rollers. I printed the wheels at 70% infill and the rollers at 40%.
To assemble 1 wheel the following is needed:
8x M4x60mm bolts
8x M4 nuts (lock nuts are ideal)
8x 624 bearings
32x M4 washers