Solved Rounded corners between bottom and top layers

Hi guys, having this problem when I print parts. Most of the time perfectly sharp corners doesn't mean much to what I am making but it has become a real pain when I am trying to make parts with some accuracy.

Material: ABS
Extruder Temp: 230°C
Heated Bed: 110°C for first 3 layers then 85°C
infill: 80
Software: Simplify 3D
Room Temperature: 73°F

I have no Y Axis Drift. You can notice the bottom and top have nice sharp corners... the middle part is what is causing me issues. I have been making adjustments such as not having the bed at 110°C for the whole print.

Thanks for any help/suggestions you can offer!

 

interesting, I turned the fan on at Layer3 and the sides got much straighter! I didn't think we were supposed to use the fan at all on ABS. But there you have it. Seems very consistent down the sides now.