Hey guys, need some advice with extruding issues I have been having. got some new proto-pasta filament for Christmas and have been trying to do some printing. My Rostock Max v2 is SEVERELY under extruding EVERYTHING. I am printing at 50 mm/s at 100% flow. I have measured the diameter of my filaments and STILL, under extrusion nightmare. I get about 5 mm of height on a print and then the under extrusion just wont stop. I adjust flow, nothing changes. these filaments were printing just fine, for months and now I feel like every kind of filament, Im wrestling PETG.
anyone know what I can do to try to fix this? I cant stand wasting any more filament 
HB PLA, PLA wood and PP PLA carbon fiber all same problems. I am printing them at around 200 to 210 c with no heated bed. 0.5mm nozzle.
Check your slicer software–many times a 0.4mm nozzle is the default, so a mismatch like that would likely cause under-extrusion (or over? I can’t do time-zone maths either).
I don’t know the Rostock, but if it has an idler, check that. I had under-extrusion going recently due to not enough tension on the idler pulley.
Good luck!
Rostock has ez struder. Spring pushes an idler bearing against extruder hobbled gear. My wood pla was grinding and I noticed once a groove was made and filament wasn’t being pushed. I figured my retraction settings were too agressive so I turned them down. That stopped the grinding, but not the under extrusion. How did you stiffen up your idler on the extruder?
You might want to check your hobbed gear and see if the teeth are full of filament chip. That will cause under extrusion symptoms on everything.
Also Could be a blocked nozzle or because of the filament change do a cold pull for good measure.
@Jules_Hoehn I stiffen mine up with a pair of screws that increase / decrease the tension of the gear against the pulley. It’s a recent Prusa. Yours may be different, of course.
So I disassembled my extruder and brushed off any chips on the gear. And I did a few cold pulls. I didn’t see anything come out with the pulls, still have the same problem… I wonder it it’s a Bowden tube issue? Since the issue seems to get worse as the brunt goes longer? Maybe it’s a peek cooling fan problem? I’m really just guessing at this point 
How do / did the gear teeth look? Any chance they’re a bit rounded and not gripping reliably? You said you’ve sent some composites through there.
If the hobbed gear is clear and a cold pull did not reveal anything the next thing to check is any PTFE tube (or something similar) inside the hot end. Given that the problem shows up over some time indicates it is possibly heat or buildup related. If it is deformed, discolored or looks in any way damaged, replace it. Your filament should be able to slide through without restriction.
PTFE tubes wear out periodically but there could be a hot end cooling problem allowing heat creep to degrade it quicker than expected. If it is a restriction in the PTFE tube it will cause more chip to build up on your hobbed gear so that will need to be checked again as well.
If replacement of a PTFE tube does not help or is not an option then replace the nozzle tip. You could have a worn/smashed tip (carbon fiber eats brass) such that the diameter is no longer what you think it is. This is less likely to be the cause because issues will typically show up immediately so you would be unlikely to get your 5mm of print before having problems.
so after that dramatic cold pull and cleaning up the ptfe tube, im printing PLA Iron REALLY well. carbon fiber was ok, but not the greatest. I think i need a better hottend and probably a nozzle larger than 0.5mm to do CF justice.
thanks for the tips everyone! so happy im printing better now!