At 180C the plastic flowed perfectly for about 10 cm (raw filament) - then abruptly stopped! Even using pliers I could not force any more filament through the nozzle. Pulling out the filament I noticed a small plug at the end. Cutting this off and re-threading the filament let me extrude again, but as soon as I made a stop, or after about 10 cm, it would stop again. Feeding and then retracting before feeding again helped some of the time, but no matter of increasing/decreasing the temperature made any difference.
After a lot of fiddling and reading the various threads at Fabric8r I concluded that there was no use even trying the motor before I disassembled the print head. Which was easier said than done considering the plastic had leaked and clogged up the inside of the heater block. Instead of warming it up I soaked it in isopropanol over night - which kind of worked.
|More plastic at the bottom and inside.|
Fixing this should be easy enough, cleaning the parts, re-tighten and reassemble the whole thing. Although I'm not going to do that. I'm sure one can get nice prints with this head, but after reading about all the other issues people on the Fabric8r forum are having with not just the hot-head, but the feeder as well I can't be bothered. All very fixable I'm sure, but requiring a lot of fiddling and even then the prints tend to not be that stable between sessions.
So being kind of fed up not being able to print I decided to order a new print head. This time a more proven design: the J-Head Mk V-BV recommended on the RepRap wiki. The one I ordered has a .4mm nozzle and is made for 1.75mm filament. A .4 mm nozzle (the same as I've been using from the beginning) should be easier on the motor as well although I won't be getting as fine details as with a .35mm nozzle (like in the QU-BD head). The bigger nozzle should be more forgiving in regards to filament as well and not clog up as easily.
I got an e-mail yesterday that it has been shipped so back to playing the waiting game...