cyclical or pulsing extrusion?
Hi all.
After finally fixing the dumb first layer problem, I now can't get good consistent extrusion. The nozzle, bowden tube, and extruder are all clean and clog free, for sure. Even took the extruder apart and brushed the gears to be sure. The PTFE tube in the hot end was changed a few weeks ago and cold pulls show no problems with the hot end.
As you can see in the picture below, there a sort of pattern to the underextrusion. The stepper motor rotates freely, mind you - I took apart the extruder and instructed the printer to purge the filament. Motor rotated on command as expected.
My best guess is the extruder tension. Tightening it does show improvement but doesn't fully resolve the issue, even at the point where the filament is being crushed and flattened before getting to the hot end. So clearly that's not really the problem.
Printer is a Prusa mini (obviously) with a new, hardened steel nozzle, though it's exactly like one used extensively previously. That one got clogged and I couldn't clear it, so replaced. Although, the clog was... producing eerily similar results... hmm. Also have the silicon bed level mod, but thats it. Extruder, hot end are both stock.
Filament is polymaker poly terra PLA. I've printed this color without problem before, and many spools of different colors of the same wonderfully. Heck this exact spool was working fine earlier today! Got my first layer nice and flat, did a couple calibration cube prints to check things were good, and everything was fine. Then tried a real print, with fresh g-code, same settings as the calibration prints, boom, underextrusion that happens cyclically, pulsing out filament.
Any ideas?
RE: cyclical or pulsing extrusion?
Forgot to mention: the cooling duct is different - https://squishworx.com/prusa-mini-integrated-optimized-cfd-fan-duct-x-carriage/
Ran a PID autotune and saved that, seemed to help some.
But Yea, I'm really confused. As I said, I cleaned the extruder gears and the entire filament pathway so it shouldn't be clogged. And I've used this filament with these print settings before too.
RE: cyclical or pulsing extrusion?
Talked with Prusa live chat - supplied pictures of extruder tension screw, extruder rear, space between beatbreak and heatsink, nozzle and heaterblock. Made suggested adjustments to tension (screw is now flush with housing) and hotend.
Small differences, but problem remains. Only change I couldn't make was the x-axis carriage/cooling duct itself, as I don't have an original on hand. And I've had very nice prints with that installed. such as:
So I'm not really inclined to buy a printed part and pay the shipping from Prague. Probably will when I get paid friday though, if nothing else comes up.
RE: cyclical or pulsing extrusion?
After speaking with support as I mentioned in the last post, here's pictures of the changes they asked for, except for the cooling duct. I don't have the original anymore, as I said.
Just for documentation's sake.
RE: cyclical or pulsing extrusion?
Issue resolved.
Ultimately I determined the extruder gear to likely be worn - I may not have been correct, however replacing the stock extruder with the bondtech IFS extruder has resolved the issue, so either way, it's fixed.