E3D V6 05/11/2015 Complete Heatsink/Heatbreak/Hotend/heater/thermistor and 0.4mm nozzle - has worked well, good solid prints, no extruder grinding, has largely been used with a Mk8 direct extruder. E3D V6 31/12/2016 Complete Heatsink/Heatbreak/Hotend/heater/thermistor and 0.4mm nozzle. Also ordered a spare hardened steel nozzle, also 0.4mm. Intended for use as dual extrusion upgrade. Given how satisfied I was when I made my original move to E3D V6 hotends, I thought I couldn't go too far wrong by purchasing the same kit again when I wanted to upgrade my prusa i3 style printer to dual extrusion. I already had an Mk8 direct extruder, so the motor etc got used to make over into a Bowden extruder setup. I purchased a second Nema17 and Bowden extruder kit to push filament into my new E3D V6 hotend. I received the two new 0.4mm nozzles I had ordered with the kit, and was a bit surprised to find that the nozzle diameters appeared to be quite a bit smaller than my original 0.4mm nozzle that came with my first E3D V6 kit. I duly checked the nozzle coding, expecting to have been supplied with smaller nozzles, but the dot coding across all three nozzles is identical - 3 dots. I could conceivably put the larger nozzle diameter on my first nozzle down to wear, except that it has never had any filament other than PLA, ABS, PETG and EDGE put through it. One of the reasons for ordering a new hardened steel nozzle was to maybe try CF at some point in the future. And I remember that it has always extruded a good clean bead of filament. Cut to the new hotend/brand new 0.4mm nozzle. I have yet to get a decent print out of it. The bead it lays down is less than 50% the width of the old hotend/nozzle combination. The print gives every indication of being underextruded, but if I push the flow rate up I start to get signs that the extruder cannot push filament into the hotend - it's being bottlenecked somehow. The extruder starts grinding and clicking, and I cannot even manually push the filament in to assist. All I can do is pull the filament back, and let it retry to feed. By this time, the print is either very patchy, or ruined because layers have missed printing. Testing: Tool 1 Extruder motor/Driver/settings (because this was a new tool chain) - I switched the Bowden tube from the suspect hotend to the old hotend (Tool 0). All signs of underextrusion, jamming, poor filament deposition disappeared. 3DBenchy wasn't going to sink this time due to holes in it's hull! I have upped the temperatures, tried different materials, tried different retraction settings (because it's now a Bowden setup). Bed adhesion is now a major problem as it struggles to squish down a very thin bead (PETG on an aluminium bed has never been a problem for me before), but subsequent layers are problematic to the point where prints do not finish. I aim to try printing at less than my usual 0.2mm layer height, on the off-chance that the nozzles aren't really 0.4mm, but it's hard to see how I can push less filament into the hotend, and still have enough to print with.