cb32a7c7_rn_Casting_Centrifugal_Molding__Pros___Cons
[Foundry Process] Expandable Pattern Casting (Lost Foam) [Process] Also known as Expanded Polystyrene Molding or Full Mold Process, the EPC or Lost Foam process is an economical method for producing complex, close-tolerance castings using an expandable polystyrene pattern and unbonded sand. The EPC process involves attaching expandable polystyrene patterns to an expandable polystyrene gating system and applying a refractory coating to the entire assembly. After the coating has dried, the foam pattern assembly is positioned on several inches of loose dry sand in a vented flask. Additional sand is then added while the flask is vibrated until the pattern assembly is completely embedded in sand. A suitable downsprue is located above the gating system and sand is again added until it is level to the top of the sprue. Molten metal is poured into the sprue, vaporizing the foam polystyrene, perfectly reproducing the pattern. Gases formed from the vaporized pattern permeate through the coating on the pattern, the sand and finally through the flask vents. In this process, a pattern refers to the expandable polystyrene or foamed polystyrene part that is vaporized by the molten metal. A pattern is required for each casting. [Pros / Cons] 
Advantages No cores are required. Reduction in capital investment and operating costs. Closer tolerances and walls as thin as 0.120 in. No binders or other additives are required for the sand, which is reusable. Flasks for containing the mold assembly are inexpensive, and shakeout of the castings in unbonded sand is simplified and do not require the heavy shakeout machinery required for other sand casting methods. Need for skilled labor is greatly reduced. Casting cleaning is minimized since there are no parting lines or core fins. Disadvantages The pattern coating process is time-consuming, and pattern handling requires great care. Good process control is required as a scrapped casting means replacement not only of the mold but the pattern as well.
Metal Casting Processes Comparison Table - Green Sand Molding|No-Bake Molding|Resin Shell Molding|Permanent Mold|Die Casting|Investment Casting|Expandable Pattern Casting|Centrifugal Molding
Pros / Cons