@ Drayson : " is this possible to be machined with this material?? "
Yes it is !
PBI can be machined as the inox steel machining process
For getting a compact & easy access print head I redrew it in 3 main parts : the XY carriage , the PBI hot end support and the articulated cooling fan set , here my final working print head : PLATEC print parts

I machined the PBI hot end support from a 19.05 mm rod (Plasticstockist source), I think that would work as well if it's machined from a 12.7mm rod
cad images :

The Olsson bloc is screwed directely on the PBI support end tip, then this one is screwed on the XY support, it's adjusted in the right orientation then it's locked by the M12x1 threaded ring.
Finaly, the articulated fan set is slided by the back side on the XY carriage, no screws used !

Since my PBI print head works I forget all the different known UM issues, may be that would be different in hard professional uses, I don't know
