IKEA LEDBERG Z-Axis (Printrbot) holder version 2

This is an improvement over the previous version, with a sturdier frame that does not require the additional brace though there is room if required.

Ver 2:
- Cantilevered arm mounted on Z-axis head instead of cross beam for more strength
- Arm re-designed for load
- Head reduced to 15mm with a 3mm screw hole to secure rod
- Arch connecting arm to cross beam to reduce horizontal vibrations