HOWTO engrave text using 3Drag/K8200

To create a 3D printed keyring for the awards of our Bridge club (also in http://www.thingiverse.com/thing:1235307), I wanted to engrave the text "GIOBRIDGE 2015" on the back of the PLA keyring, using 3Drag as CNC.
But after breaking two bits without an acceptable result I decided to stop for a moment and review the whole thing.
In this document are the results of my researchs and testings on engraving text. It includes also a toolchain using *regexfiler*, a my filtering program for text files