Freesteel is an applcation that can slice 3D models into 2D pieces. For downloading it, you should go to this link http://www.freesteel.co.uk/wpblog/slicer. This tool also comes in a web version http://www.freesteel.co.uk/slice.html. Freesteel is a command line tool, so, in order to access it, you will have to open the command line interface(Start, Run, type cmd). In the newly open interface, type c:>slice pathtomypart.stl to access the tool for loading your model. The software will also tell you the dimensions of the model, so if, for example, these are 0 to 5, type c:\slice pathtomypart.stl -z0,5,1 -o myslices.jpg. A presentation of the software can be found here http://www.freesteel.co.uk/wpblog/frontpage.