Sainsmart Genmitsu 3018 3040 Z axis bearing fix

My bearings kept popping out which was not ideal.

This is a simple cover that prevents them from falling out at the cost of 6mm of travel in the z axis.

It's a bit of a pig to strip and fit, be warned. Make sure you fit the spring and backlash nut before you fit the cover - its quite tight going on and not that easy to remove again.