OpenBuilds ACRO Z Axis

This is a Z-Axis for OpenBuilds ACRO system. I designed it with a few key requirements in mind:

* has to be sturdy enough to able to carry a small drill. I drill small holes (2mm in diameter, 15 mm deep, plywood / MDF) with it. This was very important to me. This is why I tried to get the drill to be as close to the 20x40 bar as possible.
* simple tool changing. For example, I want to quickly go from using a drill to using a laser.
* should not deviate from original ACRO design too much
* most parts should be be 3D-printable or easily sourceable.

I am very happy with how it turned out and I hope you like it too.


### Hardware BOM

I bought all of the hardware, except for M3 screws, M4 screws and coupler on openbuildsstore.com. It was about $80 + shipping.

Main Z-Axis Body:
* 2 x V-Slot® 20x20 Linear Rail, Length: 124mm
* 1 x 8mm Metric Acme Lead Screw, Length: around 140mm, depends on the motor
* 3 x Screws M3, Length: 35 - 40 mm. This one also depends on the motor