How to Cut Your SketchUp Model into Parts for 3D Printing
Cutting a SketchUp model into parts is very similar to using the Intersect Faces tool to combine groups. You’re going to use a piece of geometry as a cutter that will be intersected with the larger object and become the new edges of the cut.
If your model is fairly simple and you have SketchUp Pro, you can use Solid Tools to short-circuit this process. Create a solid block as a cutting object and use the Solid Tools→Trim command. Remember to run CleanUp3 and Solid Inspector on the new parts when you’re done. For more complex models, or users with the basic version of SketchUp, use the Intersect Faces method:
1Select the group you want to cut and make a new group around it.
The original group becomes a subgroup.
2Working inside the new group, create geometry in the shape of the cut you want to make.
Work on top of the subgroup, so you get the placement of the cut right.
When you’re done placing cuts, make the new geometry into its own group.
3Select the Cutter object and choose Edit→Intersect Faces with Context (or choose Edit from the right-click menu).
Doing so draws a line at every place where groups touch. These new lines of intersection exist outside the subgroups and aren’t stuck to anything yet.
4Inside each group, use Explode to stick the intersection lines, cutting object, and base object together.
The surface of the cutting object will become the sides of the new part.
5Move back out to the master group and make as many copies of that group as the number of parts you’re dividing it into.
Here you’re dividing into two parts, so you need two copies.
6Move into each copy and erase everything you don't need in that part. Do the same in the other parts.
Just make sure you don’t erase what the object needs to do its job.