Lifting at corners on a large print

Hi, I'm a little new to this so here goes. I have a Prusa Mendel and I'm trying to print this relatively large part. It started off fine but about half way through the corners started lifting. The nozzle is set for 225 and the bed is set for 110 but it only seems to be able to reach around 95. I'm using abs I got from Ultimachine. I believe I'm using the Sprinter firmware and I used Skeinforge to create the gcode.

Any tips?

thanks in advance

The heated bed needs to get up to temperature. They are always colder towards the edges, due to the plate moving around causing airflow. You could try putting it in a chamber - try putting a large cardboard box over the whole Prusa, it should elevate the temps, but watch it doesn't get too warm in there! Also, insulate under the heated bed, especially if it's an aluminium bed.

Another thing that might help to keep temperature up is to print a skirt that is several layer high.
See Nophead's blog: [hydraraptor.blogspot.com]

Thanks for the suggestions. The part might be too big for the skirt to go around it but that's definitely an interesting idea. I've built a box out of mdf per droftarts suggestions. It seemed to help with the edges though it still wasn't perfect. Then the spool jammed and derailed the extruder. Here's an interesting fact about a heated build chamber, the pla bearings get hot enough to get flexible enough to pop off the roads without breaking.

So now I've almost got it working again and I'm going to put a few fluorescent light bulbs in the build chamber to help out with the temperature. I figured more heat might be the answer here.