My setup is; Kossel mini printer, 1.75mm Colorfabb PLA filament, ~45cm bowden tube, 5:1 geared extruder, cooling fan on all the time, 50mm/s print speed , 250mm/s travel speed. The problems I'm experiencing: Hotend Jams at the start of a majority of my prints. - Hot-end sits idle @ 210C temp, I start a print it jams as soon as the extruder tries to push plastic through and before any plastic comes out the hotend. Only workaround I've found is retracting 20 mm followed by extruding 20 mm filament at 200 mm/min at the start of the print gcode. Hotend jams when print speed is less than 15 mm/s. - Haven't found any way around it. Hotend jams when retraction is more than 1.0 mm@40 mm/s. - Jams with 1.0 mm@50 mm/s and 1.5 mm@40 mm/s. When using the settings i've found to work; retract 20mm & extrude 20mm before print and using 1.0 mm@40mm/s retraction during print i am able to print without jams. The drawback is that there is a lot of stringing. Things that i'll try which might help: Retraction - 1.5 mm or more at lower speeds (30mm/s or lower). Temp - Lower print temp from 210 to 200 or lower which might help with the stringing. This might effect layer adhesion though. When printing on an ultimaker2 220C was the sweet spot for this filament but perhaps lower temps can be used on my printer with an e3dv6 hotend. Since I'm quite new to 3dprinting i don't really know what to expect; Is jamming with more than 1.0 mm retraction normal? Is Jamming when printing at speeds less than 15 mm/min normal? Is jamming at the start of prints normal? (Seems like a stupid question but someone else might have had the same experience) I mailed e3d about these issues a few days ago but haven't received any reply so i thought i'd take my chances on the forums... Edit - done some more testing: 1.5 mm retraction at 20 mm/s doesn't work so it seems speed isn't an issue. Printing at 200C didnt help with stringing, just as bad and also results in a bad result in general and bed adhesion was terrible. Colorfabb PLA needs 210 or more to be happy. And still no reply from the e3d support team. =(
Re: Hotend jams with >1.0 retraction, at low speeds e.t.c Problem solved. Was lack of cooling. There wasn't enough contact between the heat break and the heat sink - some thermal paste did the trick as described in the wiki; Like the heatsink and fan cooling your CPU, proper thermal conduction is necessary for the heatsink to work. In the case of your E3D hot end, the threaded heat-break tube should be snugly tightened into the heatsink otherwise the threads will not make sufficient surface contact to conduct heat. If you are printing in hot climates or continue to have issues, a liberal coating of thermal paste on the upper heat-break threads will ensure much better thermal contact with the heatsink.
