There is an article at MJSA by the owner of Casting House in Chicago
who did an extensive study on this subject. Contact Peggy Jo Donahue
through Facebook to get the link.
In my professional opinion, it is best to do your own research using
your own equipment. I have made several objects in Matrix/Rhino and
there are varying factors. After talking to the end users, clients
that is, I have seen results vary from casting heavier objects say a
25x30mm plate, 2mm thick, in Rhino, get cast and after finishing for
molding it dropped to 1.15mm thick. This happened because of two
reasons heavier object and casting was bad or over polished. The
lighter objects seem to fair better with less shrinkage. However,
you would have to go back to your original print job. Print it on the
highest resolution you can. Take an RTV mold of the printed model.
Now, cast the piece, finish, and do another RTV mold or use
non-shrink pink rubber. Compare the two models after shooting the wax
in both molds. Do this for a heavier object and a lighter one.
Determine the percentage of loss or shrinkage and make your models
in Rhino larger to compensate.
The printing machines only make what they are fed…your polygonal
stl or slc files.
Now that I have said all that…I would give yourself 10% larger on
the heavier items and 5% on the smaller ones. This will establish a
baseline for you. Knowing casting like I do, and have taught it at
GIA, you also get more shrinkage depending on when you cool the item
down. Follow protocol when doing small, large, and what metal you are
casting. There are countless articles on that alone.
I hope this helps.
The Jewelry CAD Institute