I'm obviously not understanding something about the E3D v6. For background, I'm a relative newbie to 3D printing. I built a kossel clear, with a knockoff J head (0.5mm), and it's been working well, but it leaks (which causes the tape to not stick and the thermistor moves around), and my ultimate goal is to print materials that I know the J-head can't handle. Having said all that, I'm getting decent quality prints in both PLA and ABS. Looking at the v6 reviews, and documentation, it seemed the v6 E3D would be a nice upgrade-- so the last thing I printed with the J-head was an ABS mount for my shiny new v6 (1.75mm bowden from FilaStruder in the US), which in a side note, is the first item I designed and printed myself. Assembly: Very nice (followed Tom's video). Fit/Finish: Superb. By raising the central part of the mount a bit, I only lost 5mm of height compared with the j-head. Got everything wired up (fan direct to 5A rail on power supply) and verified working. First, some calibration issues-- to be expected, but my first print came out reasonably well. Then the pain started. I wanted to switch filament... J-Head: Heat to 170, let sit for a few seconds, release extruder clamp, pull filament. Trim strings, leaving slightly melted pointy bit, insert new filament, push it by hand a bit to get the last of the old filament out. Tried this approach on the E3D, no luck. Heated to 190, still no luck. Heated to 210, nope. Tried 230 (and this thing heats up fast... another good point), and even after 5-10 minutes at 230, still couldn't remove filament. Finally, dismounted hotend, removed bowden tube, cut filament about 8 inches above heat sink. Removed nozzle. Unscrewed heater block. Used a small drill bit (about 1.6mm) and very carefully drilled out center of plastic until I could remove plug from heat break. Removed heatbreak, slid PTFE tubing all the way through heatsink, pushed the PTFE into the end of the heatbreak, and while occasionally loosing bowden coupler, screwed heatbreak back in. Put nozzle in heatblock, screwed back in, heated up to 260, tightened nozzle (I skipped this step originally by accident). I had now completed a filament change in about 45 minutes, by disassembling a key component of my printer. Next print: Cancelled due to underextrusion. Pulled filament out while it was still hot, before head cooled down. Next print: Now the fun began... I couldn't get it to extrude. Eventually, by cranking it up to 230, letting it sit, and manually forcing the filament in, I got a print going-- but again, under-extruding (Yes, I changed my nozzle size from 0.5 to 0.4). At the moment, I have a jam in the heatbreak that needs to be cleared, and will probably require the drill again. Looking at the drawings, the heatbreak channel seems to be 2mm in diameter. This lets the filament swell to more than 1.8mm, and I can't see how removal can ever work well, or am I supposed to remove the PTFE tubing every time I change filament? While "large retraction" works when the hot end is hot, it appears that if I don't retract before it cools down (power outage, unattended print, etc.), I now have a jam in the heatbreak that can't be removed simply by heating the hotend. What am I missing? What's the "right way" to use this hotend without getting the filament well and truly stuck? It is a very nice design that eliminates nearly all the complaints I had about the J-head... but it seems the j-head is much easier to use.