last i checked the f306 uses and e3dv6 hot end. that hot end is very common and very easy to service. you will need to unplug the hot end, remove it from the machine and disassemble it. do a good nozzle cleaning, check the heat break to make sure that is clean inside and also check the condition of the ptfe liner. if you dont know how to do it then you should call chris at fusion and maybe he can walk you through it or go on the e3d-online.com and look at the diagrams. in any case its something you need to become real familiar with since its routine maintenance for any 3d printer.