Extrusion Problems

Sorry if this is long winded, I am just inexperienced enough that I’m not sure what details are important.

Our school purchased the TAZ 5 spring of last year. Someone other than myself set the printer up and performed the initial test prints. So now this year, I got the printer, and tried a couple of quick prints of just some basic shapes such as a convergent, divergent rocket nozzle, and it printed fine. So I tried a larger print of a two-part skeleton jaw, using a basic 3.00mm PLA filament. The print started out fine, but as time when on, I noticed the print getting stringy and became worse and worse until it was clear the print was a failure. After much frustration and hair pulling, I noticed one of the extruder idler tension screws was not even screwed in. I readjusted the idler tension and tried a test print, thinking it was the problem. Now, however, it begins by starting to print the raft, but then skips and jumps around, with the filament balling up and extruding without even being against the bed. Pausing the print, I raised it up and noticed the filament was continually extruding. (Is that an idler adjustment issue?)

I’ve checked a few other places for tutorials and troubleshooting tips but so far, nothing has helped. (For example, I’ve tried tweaking extrusion speed and having a separate fan on the bed to assist in cooling to solve the stringy problem, but so far I can’t even get back to being able to print something big enough to have the stringy problem again.) Any ideas?

You could have several potential issues here. To start with, check the bed leveling. Let the machine heat to operating temperature, then move the nozzle manually to each of the 4 bed corners, and use a nonflammable metal feeler guage to check that its the same distance from each corner. Next run the bedcalib.gcode file from the SD card or download.lulzbot.com and make sure the spacing and thickness is right. Then attempt some calibration objects and post them here.

Your idler arm tension springs should have about 8mm space between the washers on either side of the springs. Also make sure the fillament can feed smoothly off the roll.