Lost foam casting is a evaporative – pattern casting process that uses some of the methods used in investment casting except that a polystyrene foam is used as the pattern instead of wax.
The foam pattern is made using by a process similar to injection molding. Pre-expanded beads of polystyrene are injected into an aluminum die at a low pressure and then steam is introduced which causes the polystyrene to further expand to fill the die. Once this pattern is made, pre-made pouring systems, runners and risers can be hot glued to form the final pattern.
The final foam pattern is coated with ceramic slurry by either spraying or dipping. The dried coating forms a barrier so that molten metal does not penetrate or cause sand erosion. The coated foam pattern is placed into a flask and backed up with dry un-bonded sand which is then vibrated to compact the back-up sand.
Global casting Resources offers castings using this method in both grey and ductile irons. The castings are available from about 1 pound up to 500 lbs. The minimum wall thickness is approximately 0.10” and there is no upper limit.
A variety of secondary operations can be performed on these types of castings. They include machining, plating, painting, assembly services and even custom packaging.
