Extruder calibration Prusa I3

I posted a thread in a different forum on here earlier regarding under-extrusion on a Prusa I3 that had been running just fine and did a perfect print. I just pulled apart the extruder and placed filament in it. I extruded 25mm out via the slicer program manual control, marked it, measured with calipers and it's only 20mm instead of 25mm. Should I crank the screw up on the chip or edit the firmware files? I think it's weird that all of the sudden it is out of whack. Could the motor and/or chip be going out?

Edited 1 time(s). Last edit at 10/16/2017 10:50PM by TPP1773.

Take care, you are not extruding to fast for the test. Hotend is only able to melt a certain ammount of filament per time.
Clean your extruder-gear, and check if you are able to pull out filament when stepper is enabled (should not be possible - else extruder gear is slipping)
Check by hand-extruding through whole system, if it is easy to do - if no, check where path is obstructed.
Check secure connection of wires from driver to stepper.

If all above is fine, measer VRef of your driver and change if necessary to increase current to stepper.

I will try all your suggestions later today. Is it possible for the Vref to need to be cranked up over time as the motors wear? I've had this printer for 11 months now. The only maintenance I've really had to do is routine - clean, lube, clean extruder, check belt tensions. What is the life expectancy of the electronic parts on it? I don't run it everyday, sometimes I don't run it for a week or longer.

Completely stripped extruder and the tension wheel had a small bit of plastic hairs in there, might have been giving intermittent jams. Was still having issues of underextrusion, changed from beige to black and the print was perfect except for a bump out. Figured it's a filament issue, put filament in oven to dry out and it has improved the quality greatly. Last week it rained here almost all week long and I had the window open when I was laser engraving, filament must've sucked up water.

glad you found the issue!