Hello everyone, I have some trouble with a JHead, I previously use a QU-BD extruder, but had some problem with the gear and hot-end, so I decided to buy a JHead from RepRap.me. I use 1.75 mm PLA and pute the 2 mm ID liner inside to adapt to the filament diameter. It seems I need a lot of force to extrude at an acceptable speed, I mean that also “by hand” It is very difficult to push the filament to obtain a constant flow of extrudate, what can be the problem? Someone experience the same?
What temperature? Did you calibrate the thermistor? It should flow with almost no pressure from > 165°C
I use marlin firmware and I’m using the “default” table n°1 that is for EPCOS thermistor (4,7k pullup) I think and I read on reprap wiki that is one of the two possibilities that equip Jhead. The problem is that seems hard also at higher temperature (190° - 200°). Seems that the melting zone is too short and does not transfer enough heat to the filament.
When I put the liner I insert it until it stops in the internal part of the nozzle, it is possible that I have to “cut” the liner short in order to leave the filament in direct contact with a longer portion of heater block? I see a section of the Jhead and see that with the standard 3mm filament configuration the PTFE part stops above the brass heater block, while with the insert for 1.75 filament it will go straight through and until the lower part of the nozzle, like in this picture:
http://airtripper.com/wp-content/uploads/2013/01/j-head-iv-clone-illustraion-2.jpg
just to be sure, the thinner part of the lines goes upwards, not into the heater block.
The idea of that thinner liner is to adapt the 3mm hole of the extruder coldend so 1.75mm filament doesnt bend up there.
Thank you for the answers, I have some problem in calibrating the thermistor too, as a general question, where I can find a good and reliable HotEnd to be used with bowden extruder in europe? better in italy?
I finally got my QUBD extruder working properly by making this easy PTFE barrel mod. Check out my step-by-step tutorial here http://www.mastersketchup.com/qubd-extruder-jam-fix/
@MasterSketchup this is a very clear tutorial, thank you; actually I switch to J-head, but I have my Qu-Bd hot end somewhere and this mod can bring it to life 