Changed the extrusion multiplier on my #printrbot simple from 1 to 0.75. Got much better and more accurate prints!
#one-step-ahead
The other way is to actually change the steps per mm for your E axis in the firmware. Then, if you change software, your machine is still calibrated.
Steps per mm in your e axis should be constant. Always. You measure the e steps by removing the hotend, marking a section of filament and measuring the distance relative to the extruder. Then extrude about 100mm from the software, and measure how much it actually moved. Take this number, divide by 100, and divide your current e steps by it.
The multiplier is only required when measurement of the filament is off, or if you want to change the amount of extruded filament to fine-tune the print.
I noticed that the results of extrusion are different with different types of filament. Maybe because of differences in the filament diameter. I use the extrusion rate to compensate for this and have different slicer settings for different types of filament.
0.75 is still way off from what would be a normal modifier. 10%+/- is fine, but 25% is crazy. Something’s off.
I would also recommend changing the steps on your extruder. Get that as fine tuned as you can and then work with extrusion multiplier for your different filaments in different profiles.
Calibrate your esteps, confirm your diameter, tell us what filament, tell us where you got the filament, beware the affect of humidity on some filaments, listen to the filament as it prints. The Spectrumview android app could be useful to “listen” to your printer stuff if your ears are bad or insufficient.
Good luck.