Here is exactly what a caser does:

Mold Maker
777.684-018
Alternate Job Titles: block and case maker; blocker; **caser**
Casts plaster block molds, case molds, and working molds used in forming pottery ware, using models, clay, and plaster: Places model in clay with upper half of model exposed. Brushes soap solution on exposed half of model. Places wooden form around model or builds up wooden box sides. Mixes plaster and pours it over exposed half of model to form one half of block mold. Allows plaster to harden, removes wooden box sides, and turns mold over, leaving model in plaster mold. Removes clay, smooths surface of mold, using knife and scrapers and applies soap solution. Replaces box sides around mold and pours in plaster to form other half of block mold. Casts case mold in similar manner, using block mold as pattern. GOE: 06.02.30 STRENGTH: H GED: R3 M1 L2 SVP: 6 DLU: 78

http://www.stepfour.com/jobs/777684018.htm

Based on the main job title here, maybe you could try something like "fabricante de moldes"?

Hope it helps.