1. Shell Molding

2. Mold making process metal pattern halves heated to 350-700 Deg
coated with parting agent (silicone)
fine sand/resin mixture applied to patterns
mixture bonds to heated patterns
excess sand/resin removed
shells removed from patterns

3. Shell molds two halves clamped together
wall thickness controlled by contact time
5-10 mm wall thickness
decomposition of sand binder produces gas
requires good venting
molds may be supported by sand

4. Process Advantages close tolerances (.002”) less draft required
thin wall sections with low temps
sharp corners, small projections
small cored holes
smooth surfaces due to fine sand
high quality finish
less finishing operations

5. Process Disadvantages
expensive pattern equip
captial for shell molding machine
size limitations
resin bond agent adds to sand costs
need high volumes to justify costs

6. Applications small mechanical parts requiring high precision
gear housings
connecting rods