Thursday, May 2, 2013

Build Log #24 - More like a rant

No pictures for this log this time and instead, would rather document my experience switching from ABS to PLA 1.75mm filament. I literally spent 4 days trying to get this Blue 1.75mm PLA from Justpla off amazon to work with the QU-BD's MBE Extruder. Didn't want to forget what I did since I'm always working on the fly instead of documenting at the same time. Just going to list in chronological order.

Note 1
Swapped ABS to PLA and setup slic3r for PLA filament. Attempted to print 15mm x 15mm hollow cube for extrusion calibration, failed. Little to no extrusion @ 210 C. Pulled out filament to inspect, slightly mushroomed/blunt at the end? Cut off end of filament and installed fresh PLA, extrudes normally by hand but will eventually stop extruding after a few seconds sitting in the hot-end. Repeated process ranging from 180C to 240C, can't extrude without getting clogged.

Review 1
- QU-BD 608 lever mod with modded Raptor gear seems to be working fine, grips the filament without a problem. Only grinds when the PLA clogs the barrel.
- Heat creeping up the ss (stainless steel) filament barrel?
- ABS residue from previous operation blocking the ss filament barrel?

Note 2 - ABS residue may be blocking the filament path causing it to clog.
Partially dissembled the heater block, soaked nozzle in acetone and cleared any debris. Mostly at the junction between the nozzle and ss barrel. Used M6 x 1.0 tap to remove debris from the threads inside the heater block. Re-assembled and tightened both ends to ensure plastic will not leak inside the heater block. Insert fresh PLA, extrudes fine when pushed by hand or extruding at a constant rate. Again, clogs when it sits in the hot-end. Tried changing the temperature ranging from 180C to 240C to no avail, still clogs. Switched to ABS 1.75 filament to see what would happen. Works like a charm. While removing the extruder off the printer, one of the thermistor wires broke off. FML.

Review 2
- ABS blocking the barrel isn't the problem
- Next, will look into the possibility of heat creep.
- Note to self, be careful not to bend the thermistor wires, too fragile.

Note 3 - Heat creep
Performed a full rebuild on the hot-end, applying fresh thermal paste and new insulation. Drilled a small hole into the heater block to house the new thermistor instead of taping it on the surface, hoping to get better reads on the temperature.  Re-bored the ss barrel with a 3/32 drill bit (2.38mm), allowing more freedom for the PLA to swell inside as suggested from the QU-BD forums. Assembled and started out @ 190C up, still clogged and going up to 220C without any success. Decided to swap the extruder fan input voltage from 5v to 12v, fan is now loud as a tornado. Insert PLA starting @ 185C and it still clogs when sitting for a few seconds. Bumped it up to all the way up to 195C, still clogs. Bumped it up to 200C, oh hey it's not clogging. Set the temperature to 205C, it's finally extruding!

Review 3
- Can't tell if re-boring the filament barrel, bumping up the fan speed or a combination of both fixed the problem. Whatever the case, these are probably the two solutions to look into when dealing with PLA clogs.
- Compared to the Ubis Hot-end I have on my Printrbot+, I can see why the MBE extruder is a pain in the ass to use.