Hi Guys, i'm at my wits end with this. I built a Hypercube (from thingiverse), I'm using a bowden E3D v6 (ptfe tube ~ 550mm long). Any amount of retraction will cause a Jam, even 0.5mm. It's never worked properly since i finished building this printer. If i hadn't bought this direct i would have sworn blind i'd been sold a clone. I also own a Prusa i3 MK2 which uses the same hotend, and i have never once had a problem with it, no matter what filament i've used (PLA, PET-G, ABS and FLEX), so i know these are good. I've made sure the fan is correctly fitted and connected directly to the 12v PSU, always on. I've stripped, cleaned and reassembled the hotend 5 times, made sure to put heat sink compound around the threads of the heat break. I replaced the PTFE tube 3 times with different brands including the one that came with the hotend. I've tried two different nozzles (0.4mm), I reduced my retraction rate to 35mm/s and increased it all the way to 200mm/s, no difference. I've made sure the PTFE tube is all the way in, cut it square, i chamfered it, doesn't make any difference. I use two bowden retaining clips at both ends. I've tried reducing the temperature to 190 degrees and increased all the way to 230 degrees, trying different brands of filament. I'm on my third type of extruder, i've tried a cheap MK8, a printed one from thingiverse and now running a wade setup (thinking the motor didn't have enough torque). Neither has made any sort of difference to the prints. If the print doesn't have too many retractions, it'll print spot on, otherwise it's a mess. Especially small objects. It'll start getting stringy, then massively over extrude. I've read through all the posts on the forum looking for a solution, I'm ready to throw this thing in the bin. Please someone help. Cheers Charlie.