Modifications to QU-BD extruder for reliable ABS printing.

thingiverse

I had been having trouble printing ABS using the QU-BD extruder on my Hadron Ordbot. The extruder runs fine for small models and but when I would do prints of larger models with long print runs, I would consistently get a feed failures after a couple of hours of printing. I tracked this down to hot section heat slowly creaping up the stainless steel feed tube causing melting outside of the hot section melt chamber. Research showed that this was not uncommon for QU-BD styles print heads because the top of the feed tube cannot stay cool enough when printing ABS. See How I did it below. Enjoy Instructions I had a local machinest make a new new feed tubes with a high temperature PTFE (Teflon) tube from McMaster Carr. This acts as filiment insulation for the feed tube of the qu-bd heater block. This design is derived from Matt Donley's work. Attached are my pdf drawings of what I sent and got back from my machinest friend. After running the modified head well over a 100 hours, I dismantled it and found that there was no melted filiment anywhere except in the melt chamber where it belongs. I now happily print ABS reliably for any size part running for any amount of time. As an FYI, I print ABS at 235C. I run my bed at 110C for the first layer and 100C there after. The bed is glass covered with Clear Monokote and the Monokote is sprayed with thin even coating of AquaNet Super Hold hair spray. I have NO PROBLEM with stick down and parts come off of the print bed absolutely clean. Better yet the Monokote surface only has to be remvoed and replaced every 30 or 40 prints and the hairspray surface every 4-6 prints.