Not sure what you mean…
You can’t CAST castable resin in a Silicone mold.
But of course you can use a print in castable as a master.
You can take Silicone molds off of jello…
Condensation cure silicones ( tin ) do not tend to stick to Acrylic based materials and so separate cleanly.
What we do is model a pattern split in two- with half of the pattern embedded in a separation plane, and the other half embedded in a complimentary separation plane- so we can pour silicone rubber on BOTH halves of the pattern at the same time and get a mold that fits together for casting parts.
here you can see 4 printed parts- the 2 outer casings, and the two split masters.
Put the outer casings on the split masters and they are ready to pour RTV.
When you pull off the outer casings, you see two mold halves on their respective masters.
You pull them off, flip them over, and put them in their casings
The two casing halves mate to form a single mold, and you don’t have to cut the mold open.
Plus, you can use this system to produce as many identical molds as production demands-
All you need is a separate set of casing parts for every mold you want online. Just one set of split masters with outer casings will produce a silicone mold every day.