Here is a very easy upgrade that will keep you Z axis bearing mount from dropping. While I have added this upgrade to all my builds, it is especially important when using PVC or MDF for your Z axis mounts.
What you will need
3, #10-32 x 1” Machine screw
3, #10-32 Hex nut
3, #10 Plain Washer
3, #10 Lock washer
Plate stock 7” x 3-1/2”
If you have installed your upper drag chain, remove it by removing the outside nut on the threaded rod. Move the chain out of the way, you will be reinstalling the threaded rod once the brace is in-place.
Cut your plate stock to 7” x 3-1/2” if you have not done so. If you are painting your plate stock, do it now.
Slip the stock into position, as shown here.
Re-position your bearing mount as needed. It should sit on the brace.
With the brace in position, mark the four holes in the Z-rails with a marker.
Use a 1/4” drill bit to make the four holes.
Place the brace back into position and reattach the upper drag chain threaded rod.
secure with the 3 machine screws and washers.
That’s it. A very simple upgrade that will keep your Z axis bearing mount from dropping.