This is a light diffuser for a Solar Power Bank I bought from GearBest - http://www.gearbest.com/power-banks/pp_374216.html?wid=21
The power bank has a very bright LED array on one side and when you put the diffuser on top of it, it becomes a very handy camping light for a table top.
The proper print should be completely hollow with bottom and walls that are 0.4 mm thick. No top. At this configuration the white PLA is semi transparent and does a great job diffusing the light. The hole on one side is used so you can put the diffuser like a 'hat' over the power bank. It fits nicely around the power bank and I did not cut off the brim, as it turned out to be a good handle.
Check the print settings I have posted on how to print on Prusa i3л
FIY: The powerbank I received had a ~ 3500mAh battery, not the claimed 8000mAh. Normal for a Chinese make, but it still could produce 7-8 hours of light on max brightness.
I printed the diffuser on a Prusa i3 with Cura 15.04.3 slicer. To print it properly just as a hollow shell with one end opened I used the following:
Layer height: 0.2 mm
Shell thickness: 0.4 mm
Bottom/Top thickness: 0.4 mm
Solid infill top: No
Fill density: 0 %
Speed: 15 mm/s
Adhesion: brim, 15 lines
Initial layer thickness: 0.2 mm
Expert -> Spiralize the outer contour: Yes
First rotate the shape 180° so the top becomes a bottom, so you can print the real bottom empty!