Hobbed bolt slipping

Hello guys!

I've just assembled my prusa i3 and calibrated all the axises and now I am at the extrusion part.
This is my problem, When pushing the filament by hand or helping the filament, while the hobbed bolt is turning, down to the hot end it extrudes fine. Nice strings of PLA plastic comes out. However when I try to let the hobbed bolt and the motor do all the work by themselves the bolt starts slipping. The hobbed bolt makes marks on the filament so probably it isn't too lose right? First the filament got stuck so I had to pull it out with quite much force (I add a picture of the pulled out filament).
And everything extrudes fine when I push it myself but I have to apply quite much force though, so the temperature should be okay I guess? I have turned up the stepper driver current in case it got to litle power but that doesn't seem to be it either, the motor gets a litle bit warm but not so much.
I saw on a similar topic that the idler might have been tightened to hard but I don't know, It feels like a too tight idler isn't the problem.
So what do you guys think? thanks for all the help, I really want to get printing soon (:

are your gears turning when it is slipping?
is your hot end holding temp when you are extruding withthe motor?
If you move the big grear by hand to extrude, does it flow good?
Make sure your small gear is tightened down good, and you have good tenion on the hobbed bolt.

Your stepper motor doesn't appear to have a flat on the shaft - is the stepper shaft slipping around inside the small gear?

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cat.farmer
are your gears turning when it is slipping?

Yes the Big gear is turning, which also means the small gear is turning.

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cat.farmer
is your hot end holding temp when you are extruding withthe motor?

The hot end holds the right temperature, 185 degrees, and when I manually push the filament it extrudes fine so I guess the temperature is correct.

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cat.farmer
If you move the big grear by hand to extrude, does it flow good?

I have not tried that yet 'cause I've heard you shouldn't move the motors when the ramps and the motor is powered. And the ramps need to be powered to heat the hot end.

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cat.farmer
Make sure your small gear is tightened down good, and you have good tenion on the hobbed bolt.

the only solution I can think of is tightening the idler even more.

The motor shaft do have a flat side and I have made sure the small gear is fixed but I will check it once again.

Thanks guys!