Efficient packing of models with chains I have a model where several solids are linked with chains. The original design contains a lot of empty space. 

I am looking for software, which can automatically move the solids and fold the chains such that the total build volume gets smaller (total build volume is a major cost driver on shapeways.com). Obviously, the topology of the design must not change, i.e., it should be possible to return the model to the original state without breaking chains. 

I tried Blender - Rigid Body Physics, but that has stability issues.
This is relatively easy to do in any CAD/mesh software.  For example, if you load import the model into Meshmixer, you can select a given solid and N links of chain connected to it (using "expand selection to groups" or similar to be safe). Then use the "Separate" command to allow you to move/rotate that subset on its own. All you have to do is make sure the two chain links at the point of rotation remain disjunct.
Once you've moved everything around, just SelectAll and export.