BCN3D+ HD (high Z precision axis)

With this update your Z axis will be more precise and you will avoid common problems such as Z waving.
You will need:
- 2 x SWZ-063009 precision nuts (I bought them [here](http://bcndynamics.com/es/product/tuerca-husillo-8x15mm-swz-063009))
- 2 x threaded rod 8x1.5mm (lenght 360mm) (I bought them [here](http://bcndynamics.com/es/product/husillo-8x15mm-l390mm))

You will also need to modify your firmware, it's a simple line in Configuration.h but it's important because the new rods have a di