Heat creep / filament jam on long prints - a solution

General Hardware
1

One of the reasons many have purchased the TAZ printer is because of its larger print volume. If you have tried to actually print something large, you may have experienced having the filament jam in the extruder and nothing coming out of the nozzle while the printer keeps moving around thinking all is ok. What happens is that the hot end heat drifts above the aluminum Budaschnozzle mount plate into the drive area. When the heat gets up there, it softens the filament before it goes into the teflon filament tube and this can let the filament buckle. When it buckles, the filament jams and cannot be pushed down into the hot end. The drive gouges out a section of the filament and can no longer even push it.

Some have added fans in various ways to solve the problem. I fabricated a larger aluminum mount plate which let me put a small cpu fan on it. This cools the mount plate and heat simply does not go higher up into the drive area. I was able to make this using a drill press, several drill bits, including a milling bit to give the flat bottom hole in the middle. I tapped the 3 holes needing threads. Touch up was done with a Dremmel tool. The slot was cut using a radial arm saw. This slot allowed me to easily run the hot end wires through. There is a 24 volt DC supply on the controller board which I used for power for the CPU fan, running a pair of #24 guage speaker wires from Radio Shack to the extruder. I soldered a 150 ohm 5 watt resistor in series with my 12 volt fan which drops the 24 volts to 12 volts for my particular fan.

While I was at it rebuilding the head, I used some high temperature red silicone to mount the heater resistor to give it better conduction to the aluminum block and also keep its windings from potentially shorting through the aluminum. My old resistor had lost much of its insulation. You should probably go through the heat calibration procedure after this modification. See: https://www.lulzbot.com/support/fine-tune-your-marlin-pid-settings

Anyway, since doing this, I have not had any filament jam ups and can do long prints now.

HeatFix.jpg
HeatFix.jpg1024×683 476 KB

NewMountPlate.jpg
NewMountPlate.jpg806×596 190 KB

Filament_Problem.jpg

2

Thank you for this info. Very helpful. We are having the same issues here at our school. Do you have specs on the plate you added to the Taz4?

Thanks

3

original.jpg
This modification was done on my TAZ 3. I’m not sure how TAZ 4 differs. Basically, if you take out the exisitng aluminum plate and make new one (using the old one as a pattern) that sticks out far enough to hold your fan, that should work. It might even work without a fan if there is enough surface area to let the plate cool, but probably not as well as with a fan. The original mount plate can be seen here: https://www.lulzbot.com/products/budaschnozzle-20-mount-plate

4

that looks exactly like the one on the taz4, we had to take the hot end apart to get the filament out of the teflon tube

5

It probably is the same part on the TAZ4 and the same modification would probably work for it too.