Lulzbot Taz 6 Filament change process


I am currently troubleshooting an issue once i neared the end of one of my 2.85mm spools.

I was trying to be fancy during a headphone holder print for the headphone interface area versus the base and try switching the filament in between for a layering scheme on the final outcome and now i can’t seem to change the filaments and get it to print consistently.

Anyone have a problem with the change, unload, and/or load filament process?

I tried doing all three processes and just had to cut the filament after setting the temperature on the tool head to that near the spools recommended threashold.

Thanks for the replies!

So, you can set color changes in Cura LE with the Extensions → Post-Processing → Modify G-Code.

First issue with that: The filament change command used by the extension has priority and interrupts movement. When it goes back to trying to move, it sometimes forgets that it moved in the Z axis, Y axis and X axis from where it was when the filament change was requested. So, to have any consistency the script buried in your Cura folder needs to have the line that reads:

color_change = "M600"
changed to
color_change = "M400\nM600 B10" #added m400\n to finish movement buffer, and do 10 beeps

Second issue: The layer numbers are inconsistent since the plugin was made for the way Ultimaker did layer numbers, but the plugin wasn’t changed. You have to subtract a layer number for where you want the change from what Cura shows in the layer view (or was it add? I forget).

Third issue: The retraction amount isn’t set quite right for some toolheads in the firmware, so it might not retract enough to get the old filament out, require manual rotation of the gears… which isn’t possible with some toolheads. You need to configure the retraction amount in the filament settings on the Taz.

Fourth issue: If you aren’t there during the change different things happen. First, the toolhead will cool off, and usually you just hit the button to heat it back up and you can then insert the next filament and finish loading. But… if you wait too long, you lose X/Y position and have to manually re-home (send a G28 X Y via terminal), and pray to the endstop gods that the position is accurate. Bonus issue: Sometimes, the printer only reheats to 140c instead of the proper loading temperature, so welcome to stripped filament country. If you see this, you might be able to send a M109 S215 command (or whatever temp you need to load) through the terminal before you start loading filament.

Once you counter these issues, color changing at layers isn’t bad, and since you’re using a single toolhead, offsets from multiple toolheads isn’t an issue.

that sounds like a way more complicated solution than what i was attempting.

I hit the pause print or whatever command held the print to do a filament change. then during a whole different print, i was getting issues of the forward driving gears not engaging the filament to be pushed through the tool head.

so its either not taking while i have the bearing clamping mechanism to engage with the driving motors or something i am unawares. I wouldn’t think the code was the issue.

before i get any change in code i have to know that the initial loading of the filament and the tool head heating up to the preheat recommended temps on the spool actually getting the intial sample dripping out of the tool head. That is not happening at the moment.

Prusaslicer’s change color at layer works fairly well too, but I generally assume people here are using CuraLE.

mmmm, i guess you and i are talking about totally different hardware. I am touching the buttons on the actual lulzbot printer.

If you’re running older Marlin 1.x.x firmware, there was a known bug. If you pause before trying to change filament, it won’t resume correctly, but if you go straight to change filament without pausing, it should work.

I had grief using Change Filament, it went to the wrong temperature, stripped filament, wouldn’t extrude properly until I cleaned the extruder. Best solution I found was to use Pause Print, swap filament, push it through manually until new colour emerges then re-engage extruder, then Resume Print. The nozzle keeps correct temperature, doesn’t get lost etc. You don’t get accurate start / stop to the colour, it may be halfway through a layer, but it works for my purposes eg change colour on raised lettering