Layers not fully fused (ABS) (2 replies)

I'm just starting to do some printing with ABS and getting parameters tweaked. One of my test cases is a 3 perimeter hollow shell, about 3" tall with a 0.25mm layers. The prints look good, but the layers are not fully fused - when I stress test the part (ie, break it) it always breaks cleanly at the layer lines. Also, it looks like the perimeters are not always fused. I'm using an extruder temp of 230 and an bed temp of 110. The part is stronger at the base than at the top. It does take some force to break it, but it seems like it could be a lot stronger.

Should I increase the the extruder temp? Increase the bed temp? Increase the extrusion multiplier? Any suggestions to improve the fusing would be most appreciated.
-Jeff