Unexplained Under Extrusion
Bought an MK3S+ from a friend with a thermistor problem. Successfully installed a new thermistor/hot end and thought everything was fine. I've been printing basically non stop since 2020 and to me it looks like it is purging filament perfectly when loading. Perfectly even line with no bubble or weird stuff/curling and appears to be as thick as it should be. When actually trying to print though, or do Live Z Adjust, it under extrudes like crazy. I have changed nozzles multiple times, printed a new door that the gear goes on because I noticed the shaft holding the gear was very loose and allowing the gear to move back and forth, I've flashed the newest firmware and gone through the setup wizard successfully multiple times, I've taken the entire hot end apart and visually inspected the PTFE tube and all other parts. I've made sure the nozzle gap is perfect according to prusa documentation, I've PID tuned, I've tried everything I can think of. The extruder does not click or strip, even when pulling against it fairly hard it will continue to pull the filament out of your hand so I don't think it's a gear slipping (also checked the grub screw on the gear on the stepper) or anything like that.
I felt the extruder motor when it was under extruding, and it did feel warm but nothing out of the ordinary for stepper motors in my experience. Does anyone have any idea what this could possibly be? I've already ordered a replacement stepper motor but I honestly don't think that is going to fix it.
I spent literally all night last night trouble shooting and got absolutely nowhere. I did install a brand new .5 nozzle and the first layer went down without under extrusion it seemed, but when I looked at the finished print the top had massive gaps and looked awful.
Here is what the live z adjust test gives (with the hw setup on the printer set to the correct nozzle size) with a brand new never used before .4 nozzle:
Here's what happened with a .5 nozzle (with .6 selected in hw setup on printer since there was no .5 option)
If anyone can help me with this I'd sure appreciate it. Happy to post pictures of anything that may help.
RE:
Oops I posted the wrong pic for the first layer calibration and accidentally called it live z adjust, but it looks identical on there or an actual print like what is pictured. .5 nozzle with .6 selected in printer hw setup on live z adjust actually prints okay on the first layer in first layer calibration, although with thinner lines than I sould expect from a .5 nozzle, but starts under extruding like it shows in the picture on an actual print.
RE:
Sorry for the triple post but I can no longer edit. Another thing I forgot to mention is it seems like there is excessive oozing from the nozzle while preheating/after prints. I know nozzles will ooze in general, but this is excessive. Almost like it's still extruding but the motor is completely stopped.
RE:
Update:
I measured that my extruder is pulling nearly 25% too little filament. I measured 20mm filament and when I told pronterface to extrude 20mm there was 5mm left over. Set it to 125% flow and marked the filament at 40mm. Told pronterfacd to extrude 30mm and there was almost exactly 10mm left. I also started a print at 125% flow and it over extruder a little but was much closer to perfect.
Does this mean the extruder is dying or something? It sure doesn't show any signs of being weak or over heating.
RE:
Update: It is now printing absolutely perfectly with a .4 nozzle at normal flow rate. I'm incredibly confused. When you set the flow in Pronterface, it doesn't save it unless you tell it to right? Because it's acting like it saved it, but I didn't issue a command for it to save.