I wanted a new project to put the Ultimaker2 through it's paces, and try a few techniques to part the model up for molding and casting resin pieces. There's a number of other reasons why cutting up models into smaller parts is a good idea, such as, prints often fail for one reason or another, so if you're only printing parts at a time, it's not such a huge setback if one fails. Another reason is that the size of your model is not limited to your build envelope.
One particular challenge in using an FDM type printer for a project like this, is how to handle overhangs, and oddly shaped parts that do not have flat bottoms. While supports allow you to print odd shapes, the surfaces where they attach are typically less than desirable, so I'll be using a few tricks and techniques to optimize, and minimize the negative effects of these requirements.
I'll document the process as I go. So far, I've completed a ZBrush sculpt and have cut the model up. At this time I added "keys" to assist in accurately assembling the printed pieces.
I'll be using Colorfabb PLA for this project, which I'm finding to be very easy to print with and results in nice smooth surface finish.
Here's a quick visual description of how the parts are cut up, and how the keys work. Combining the oddly shaped hand with the flat bottomed skull means it's easier to print, and will sit nicely on the model's base.
Robert Vignone from mold3D has made an excellent tutorial explaining keys in more depth, check it out below.