Uneven infill

Hey guys.
Ive got a problem. My infills are verry uneven.
See pic

imgur.com/8thbChw

Any suggestions to fix this problem?

Cany ou give some more information on your print settings please?

Ofc.
E3d v6 extruder
0,4mm nozzle.
pla
200°c (measures 190° on external thermometer)
55-60 bed temp
Vellemans own glass plate on bed.
Recently pid tuned

Anything else?

Did you calibrate your extrusion length and set a correct filament diameter?

Which layer height did you use?

I have not callibrated extrusion lengt . How do i do that?

0,3mm layer height

Mark your filament at one point and let the printer extrude 100mm using repetier.
Then measure if it actually pushed 100mm thorugh.
If not, change your extruder steps/mm to get it to extrude 100mm when you tell it to.
This is important, cause the amount of extruded filament is calculated over diameter and length by the firmware.
If one or both values doesn’t closely match the firmware calculates wrong extrusion amounts and this leads to
over or underextrusion.