Infill vibrations and pressure buildup on Kossel Mini

I'm using my Kossel Mini (R2) to print a part with PETG filament, and i get a problem that at some point. I've also tried PLA and that gives the same problem.

Here is a picture of the printed part:
https://s31.postimg.org/8wc2fw1iz/IMG_1088.jpg

As you can see, the bottom of the cylinders are not coming out well, and they need to be precise.

I've been watching the printing, and I saw that the trouble is actually started at the edge on the side. It makes two perimeters fine, but to finish the inside it does another line right in the middle of that edge (see red line in picture). At that point the nozzle seems to be touching the perimeters too much, and the printer starts vibrating, which might causes some deviations in the x-y.
Another problem is that it seems to be trying to extrude too much plastic there, there seems to be a pressure build up in the nozzle (I have a bowden extruder), and when it tries to print a layer of the cylinder, it seems the build up pressure is releasing then and I get a very bad cylinder.

I'm not sure how to fix this, has anyone encountered this problem before? Anyone has some ideas on how to fix this problem?

Thanks!

Hi

The printer appears to be over extruding. Somewhere in whatever software you are using, there is a setting that tells it how many steps to make on the extruder to push a certain amount of plastic. From that and the information you gave it on layer height and nozzle diameter, it works out what a 100% fill would be. If any of the settings are off, it can either under extrude or over extrude. The normal way to work this all out is to print a bunch of hollow cubes and carefully evaluate the result.

Bob

Hi Bob, thanks for your reply. I have rechecked my extruder, but it was actually extruding less filament then it should. So first I fixed that and then I started printing cubes to test the extruder multiplier. I got the infill to connect with the perimeters at 0.90. The problem is much less now, but it keeps vibrating on in the infill in the edge. It seems like it tries to drag the nozzle trough an area that is just a little to narrow.
I'm using slic3r for slicing.
If you have any other ideas how to get rid of this vibrating problem please let me know!
thanks!