Wanhao i3 stops printing after about 40 minutes I have a Monoprice Maker Select V2.1 (rebadged Wanhao Di3) with a microswiss all metal hot-end and machined lever and extruder plate. It had been printing very consistently for months with this set up - through 5 or 6 kg of filament - until a couple of weeks ago when it has started to under-extrude and then stop partway into a print, after about 30-40 minutes. It seems to clog and grind the filament, skipping steps. I first assumed this was heat-creep, and so disassembled the extruder, cleaned the heatsink and applied new thermal paste before reassembling, but to no luck. I also tried new fans on the cold-end but this didn't help either.

Other things I have tried:


various models - point at which the extruding stops seems based on length of time printing, not z position, suggesting to me that it is not an wires/electronics issue or an issue with the file.
various layer heights
various temperatures
dust filter
various filaments (changing reels of similar filament, different colours and brands, although all PLA)
cleaned, and subsequently replaced extruder gear to rule out wear to that
inserted washer under lever spring to add tension
clearing the nozzle (cleaning filament, atomic pulls and drill-bit)


I've now run out of ideas of what could be causing the issue and what to try. What other issues could cause the above symptoms or, if it is heat-creep, how else could I solve the issue?
Time to check things that usually don't need checking.  At this point I would check the power split. 

Check the power supply voltage (+12V or maybe +24V, I don't know the printer) at the controller before and after the extrusion stops or sputters.   Assure that the voltage stays the same.   If it drops you have a culprit.  While there, also check the +5V.  If the power is inconsistent,  check the connections for loose screws.  If the power is also bad at the supply,  replace it. 

If the extruder starts clicking,  it could be under voltage or under temperature.  You have already checked for heat creep, and not found it.  Either supply voltage can mess with actual temperature.

You have ruled out Z-height, so many possibilities are unlikely.