The first hot-end I used was the Makergear unit that came with my RepRap Mendel Prusa kit . It worked well enough, but I often managed to jam it, and looking back I think the biggest cause of this was the distance between the heating element and the nozzle. This can result in the filament freezing before it’s able to be pushed out the nozzle, and conversely this arrangement the heat source closer to the “cold-end” of the extruder which can cause the filament to melt too high up and in my case, ooze out over the top of the hot-end and encase everything in a plastic tomb.
It’s hard to see in this photo, but liquid plastic has backed-up and began to flow outside of the extruder barrel, which is bad.
This is what led me to the QU-BD, thinking that instead of replacing the Makergear hot-end for almost the same price I could get two complete extruders (and they looked so pretty!). As it turns out, you get what you pay for.
The design of the J-Head addresses these heating problems by placing the heating element inside the nozzle itself, far away from the cold-end of the extruder. This design looked to me to address the problems I was encountering so I put the QU-BD’s in the parts bin, ordered a J-Head and dug out my old Makergear extruder.
The J-Head from Hotends.com arrives as a “kit”, but there’s really only three pieces to assemble and the hardest part is crimping on the appropriate connectors to the heating element (a resistor) and the thermistor. The resistor needs to be installed into a hole in the head and based on the instructions on the RepRap Wiki I wrapped the resistor in aluminum foil to ensure a tight fit (I didn’t have any of the muffler compound they suggested on-hand).
Next the thermistor is mounted by simply taping it into the pre-drilled hole with some Kapton tape and it was ready to mount to the cold end.
The J-Head using the same mount as my stock Makergear hot-end so installation was easy and I had everything back on my RepRap in a few minutes.
After about an hour of updating firmware & host software (lots of new code since the last time my printer worked) I hit the extrude button and cheered.
I’ve waited six months for this moment…
I had planned to add a glass build platform as well but this all came together so quickly I just had to try out a real print. Here’s a couple of shots from the tests I did, there’s still plenty of calibration to be done and adjustments to be made but overall I’d say that the J-Head has out-performed everything else I’ve worked with.
I had good luck with this on Steve’s Printrbot so I gave it a shot with the J-Head for comparison.
This is a S-Hook I’ve printed dozens of times so it’s a good “eyeball calibration” piece for me.