Printing problems

[Laurie]

      We are using 3Dtin as our design tool and printing on a Makerbot Replicator 2.  One of my students has been working on a car, but he first design did not print well.  A raft is required in the print, but a raft is only printed for three wheels.  We cannot see anything in the design that would indicate the fourth wheel was not on the floor.  He redesigned his car and now only one raft is printed for the wheels.  Can anyone give us some advice?