Unresolved Unwanted lines on box

Whenever I print a large box, I get slight imperfections in the form of bumps on the front/back, which is in the same plane as the infill lines. I've attached a few photos and documents for reference. What causes this and how do I fix it?

 

ABS or PLA?

Might be some resonance issues. What speed are you printing at. Also try increasing the number of perimeters.

 

I've calibrated the extruder using the marking of 10mm extrusion. Even accounting for that, it doesn't seem like too much extrusion since another print didn't have any infill in spite of showing infill on the preview tab of S3D.

PLA. My default printing speed is 3.6k mm/min. What are resonance issues regarding 3D printers? How do they affect the print?

 

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#ringing this is what resonance usually manifests as.

Try slowing down to 30mm/s and see if that improves quality

 

That did help a bit.

 

I have the same problem and it came out of nowhere. It was printing fine for a while. I am currently trying the extrusion multiplier tweaks. I'll post back if i figure it out.