This is a mod to use a single motor for Z to prevent the X axis from becoming untrammed due to normal 2 motor systems becoming out of sync. It uses Cupcake Z parts. Specifically: 2 each 5mm bore GT2 2mm pitch 36t pulleys (SDP-SI) 4 each 624ZZ bearings as idlers (Ultimachine) 1 each Cupcake Z belt GT2 2mm pitch, 6mm wide, 424 teeth (SDP-SI) 3 each 5x11x4mm flanged bearings for the 5mm Z screws (VXB) 1 each 5mm to 5mm flex coupler (Adafruit) 8 each 4mm bore fender washers (Ultimachine) 8 each regular M4 washers (Ultimachine) 4 each M4 x40mm capscrews (Ultimachine) 4 each M8 nuts used for spacers (not shown in picture, Ultimachine) 2 each M5 standard washers (between pulleys and top bearings (Ultimachine) 4 each M4 nylock nuts (Ultimachine) Also, the stock Z threaded rod would have been 5 mm for Z- Axis: 2 x 12" However, they should now be around 13 inches for the motor side and 15 inches on the right side since we don't use a motor and coupler so it needs to go all the way down into the lower bearing support on that side. The square "fake" motor plate is what also holds the right Z smooth rod. but the cutout allows for locknuts to rotate with the 5mm threaded shaft.Sorry, the picture doesn't show the Z smooth rods caps (last minute addition). The picture also doesn't show the M8 nuts spacing the 624 bearing idlers up and the pulleys need switched hub down, then M5 washer, then flanged bearing. The Z motor would remain on the left hand side as normal. The right hand side has a different motor bracket sized for another flanged bearing. The bearing should go in on the bottom side as should any lock nuts on the M5 threaded shaft to keep the rod in tension, not compression. More detailed finally assembly pics to come. The idea is to ensure the X axis always stays 90 degrees to the Z once initially adjusted. The original 2 motor design made it impossible to move the Z axis by hand when required without messing up tramming in X axis. One less motor and far less stress on the poor little Pololu than trying to drive 2 motors. Also, could allow for oldschool knob or crank on the Z axis for manual adjustments. Maybe this modified for 5mm threaded rod http://www.thingiverse.com/thing:1359 Note, it might be a good idea to leave the 5mm Z threaded rods a little longer for crank mods. It's easy to cut, it's hard to add back. SDP-SI.com 36t pulleys 2 each Part Number: A 6Z51M036DF0605 $6 each GT2 6mm wide belt Part Number: A 6R51M424060 $8 Ultimachine.com 624 bearings 4 each https://ultimachine.com/content/624zz-bearing $1.25 each Big fender washers 8 required comes in pack of 15 https://ultimachine.com/content/fender-washer-pack-15 $1.49 regular M4 washers 100 pack https://ultimachine.com/content/m4-washer-pack-100 $1.99 M4 x40mm 4 required 50 pack is https://ultimachine.com/content/m4-x-40mm-socket-head-cap-screw-pack-50 $8.49 --maybe buy local?M4 nyloc nuts 4 required 100 pack https://ultimachine.com/content/m4-nylok-pack-100 $3.59 Assuming you have 4 larger M8 nuts or something to use as spacers on the M4 capscrews to space up the idler bearing blocks. VXB Requires 3 each 5x11x4mm flanged bearings http://www.vxb.com/SRCH.html?Store_Code=bearings&Search=5x11%2C4+flanged