DanSilov, I would not recommend printing extruder parts with 100% infill however that print does look like it came out pretty good. I usually print them with 30% infill at a max and this could cut down on some over extrusion errors that could lead to a misshapen gear tooth.

As far as the knob goes, I can't see how your extruder would draw plastic in between the outer grooves in the knob unless something is mechanically wrong with your axes.

Try these and let us know that you have checked them:

1. Check all your belts and make sure they are tensioned pretty tightly (should ring out quietly when plucked)

2. Check for any wiggle in you x and y idlers by verifying that all delrin idlers are tight enough to the aluminum extrusions. You should have no play in any direction other than the axis is intended to move. Make sure the delrin idlers are not too tight where they limit rotation of the bearings.

3. Check the bottom of the x axis where the captive nuts meet the z threaded rods. Sometimes mine have come out of their holes underneath the x idler.

4. Try these prints again at 30% of your normal printing speed, just to rule this out.

Good luck and let us know how it goes!