Lost Foam Casting Process

By: Kent Klein

Lost Foam Costing is a sub type of Investment Casting. Thistype of casting method uses foam pattern as the investment. This methodbenefits from the advantages of the foam properties helpful to make simple andcheap castings. These types of simple castings are impossible using the regularcope and drag method.

Casting process:

Foam Shaping: Theoriginal foam pattern of the Polystyrene is generally molded or carved.

CarvingPolystyrene: The formed foam or polystyrene is then carved usingtraditional carving tools or the new-age hot-wire cutting tools. It can also besanded easily.

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InjectingPolystyrene in a Mold: Polystyrene contains pentane as a blowing agentand is commonly used for beads. The beads are pre-extended, stabilized and thenblown into the mold to form pattern sections. A steam cycle forces the beads toexpand fully, after this the fuse together and then it undergoes an in-moldcooling cycle. The final shape if very complex, then it is molded in sections.A cluster is formed by aging and gluing together the shaped foam sections.?

Preparing FinalMold (Investment) for Casting: Gates and Raisers are generally attachedto the pattern, they are also the part of the casting as this helps reduce theshrinkage. Pouring, dipping or spraying are the different methods used forcoating the foam cluster with ceramic investment. The reason for this coatingis that it forms a barrier and helps to prevent the molten metal to penetrateor cause sand erosion while pouring. Structural integrity of the casting isprotected thanks to the coating. The cluster when dried is backed up withun-bonded sand and is placed in a flask. Proper and uniform compaction is thenachieved by performing mold compaction using a vibrating table. After all thisprocess and after proper compaction, the mold is ready to be poured.

Automatic pouring is the preferred method in Lost FoamCasting. This is the most critical process and also a bit difficult than thetraditional foundry practice. As there are no parting lines or fins to removethe cleaning is easier and requires far more less time and operations in theLost Foam Casting process.

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Advantages of LostFoam Casting: Due to its unique properties, foam is easy to carve glueand manipulate. It also provides accurate dimensions as Lost Foam Casting ismore accurate and effective than sand casting. There are no fins or partinglines the finishing process is easy and less time consuming. The elimination ofcores makes complex casting designs easy. Lost Foam Casting also allows us tocontrol the wall thickness and thus no core prints are required thuseliminating shifts or fins and also saves the trouble of sand mixing and coredefects. As there are no drafts multiple levels of casting is possible. Precisegate and riser replacements are achieved. Unconventional forms of casting thatare difficult or impossible to achieve in traditional cope and drag method areeasily achieved in Lost Foam Costing.?Due to simpler process and easy finishing workPsychology Articles, the process is very costeffective and lowers the overall price of the final product.

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