Thin wall problems

Printing ABS with my rostock delta, solid parts come out fine, but I'm trying to print a shape that is just a thin shell, similar to this: [softsolder.com]

The problem is the layers aren't sticking together well and the entire piece is easy to pull apart. Also it looks like when it takes a corner, sometimes it drags the extruded plastic inward rather than laying on the previous layer. What setting is most likely to improve this?


Problem print with thin walls: [imgur.com]

- and for comparison -

Good print of solid object: [imgur.com]

Thanks

It looks like its under-extruding if not check your slicer settings(extrusion width)

I tried increasing my steps in firmware but it didn't improve the situation. I'm pretty sure I had my extrusion calibrated pretty close already. Could it be anything else?

I have a very visible layering in my prints that I don't see in other peoples' prints.