Improve Print Quality - Remove Stripes and Gaps

[chrismrutherford 0]

I'm printing a hollow object, but a I get slightly stripy prints and around the edges there are some small gaps. Also I see some small blobs in places. Please see photos. What could be causing this. I'm using the Ultimaker2+

[chrismrutherford 0]

I'm assuming its an under extrusion problem. I'm experimenting with lower print speed. Also might increase temperature slightly.

Some resources I found:

http://www.ideato3d.be/tutoriels/why-does-my-printer-under-extrude/

http://support.3dverkstan.se/article/30-getting-better-prints

https://www.3dhubs.com/talk/thread/best-printing-practices-ultimaker