Seems like your issue is identical to the one I fixed a few weeks ago.
http://www.ft86club.com/forums/showp...1&postcount=57
If you want to fully split them, then ovens the best bet but if you just want to dremel a hole big enough to fix the dry joint then you will need to guestimate where to do it, also you dont need a 3d printer to fix it back up, just some pieces of bicycle inner tube cut to size/plastic cut to size and a hot glue gun so you can seal up any holes you make outside of the sealed rim.