Why is this happening?? 
bought the E3D extruder, and after I started using it it seems like too much filament is coming out… Which setting should I adjust ?
E steps/mm (firmware), nozzle size (slicer), filament diameter (slicer) (trust me, measure it!).
When I read “why is this happening” I thought you were asking why your printer was printing holy crosses. I would ask that if it was my printer. 
@Daniel_Bailey If the owner is Christian, or knows Christians who might like them, these would make pretty good, non-wasteful calibration pieces. 
Agree @Nick_Kloski2 , if you use Marlin firmware for example I found more accurate readings for temperature with thermistor setting n°6 rather than n°1 (thermistor table)
@Daniel_Bailey hahah! Agree
@Carlton_Dodd Thanks!
@Nick_Kloski2 Thanks!
Don’t want to hijack but 1 Q:
@Carlton_Dodd when you measure the filament How far down the filament do you keep taking measurements to get your average diameter? (making sure I’m doing mine right)
@David_Cushing The more data points the better, but I generally go for ten total measurements, each about 20-30cm apart.
ok, cool. Tnx @Stephen_Baird .
@Stephen_Baird I’ll do that and see what happens. thanks.
@David_Cushing Yep, what @Stephen_Baird said.
I’m a noob, but once I got that tip, I measured and found my average (pretty consistent) diameter to be 1.85mm; about 5% greater than advertised! BTW: Also check along different diameters at same point to determine roundness (mine is good, but I hear some are more oval).
At the end of the day, if the filament maintains a consistent diameter and roundness, even if it is not perfectly round and is significantly off the nominal diameter, you should be able to get a decent print after you tweak your numbers.
Out-of-roundness tends to maintain their orientation, so as long as your filament feedpath does not allow the filament to twist around, the drive gear will tend to engage consistently.
This assumes, of course, that the diameter and roundness is reasonable - not so extreme that it can’t feed the material.
Now, that said, if you do have a bad roll where the diameter is all over the place, or the roundness fluctuates, it’ll turn out poorly.
Jesus doesn’t like 3D-printing, that’s why.
@1111136 I think he does and I have had the same problem with other models…
the power of jesus christ compels you! that’s why your prints are failing…
Is the density of that material the same as before you printed it out? There is a “packing density” referred to by some of the slicer software out there. You might want to consider accounting for that.
I can’t claim to be a pro at this. Some of my prints are still a little off. I think I have interference between nearby wires on my delta printer. I figured my simple input would be useful though and so I brought up this possible cause nobody else mentioned.
@NathanielStenzel I did not find that setting… but thanks anyway!
They might call it flow ratio.