China Lost Foam Casting Foundry

Lost Foam Casting is a precision casting process that makes a mold of expandable foam plastic (such as polystyrene) in the same shape as the casting, assembles it, coats it with a high-temperature resistant coating, buries it in dry sand after drying, and then when pouring molten metal, the foam mold vaporizes and disappears due to heat, allowing the molten metal to fill the mold in place and finally solidify into shape. The Lost Foam Casting process has the advantages of high casting dimensional accuracy, good surface quality, reduced processing allowance and production cost, and is suitable for casting complex parts made of aluminum alloy, gray cast iron, ductile iron and steel.

Use expandable foam plastics such as polystyrene (EPS) to make a foam model with the same shape as the final casting through thermoforming, mold forming or extrusion.

In addition, the surface of the foam model needs to be carefully polished and trimmed by CNC machining, laser engraving, etc. to ensure that the model size is accurate and meets the design requirements and the surface quality requirements of the casting.

A layer of high temperature refractory coating needs to be applied on the surface of the foam model. The main components of the coating usually include high temperature resistant sand, adhesive and water.

The coating process usually uses spraying, brushing or dipping to ensure that the coating is evenly covered on the surface of the foam model.

The coating is cured and has sufficient strength by natural drying or hot air drying.

The foam model coated with coating is placed in dry sand, and the sand is usually dry sand without binder.

Through vibration or compaction, the sand is tightly wrapped around the model to form a sand mold.

Before pouring, the foam model needs to be properly baked to improve the strength of the coating and avoid the impact caused by rapid gasification when the molten metal is poured.

The sand mold should be preheated. Preheating the sand mold helps to improve the fluidity of the molten metal, reduce thermal shock, and effectively avoid surface defects of lost foam castings.

According to the material requirements of the casting, select suitable metals (such as aluminum alloy, cast iron, steel, etc.) for melting.

The molten metal is injected into the sand mold through the pouring system (such as gate, riser, etc.). Since the model is a foam plastic, when the temperature of the molten metal reaches a certain level, the foam will quickly gasify and disappear to form a cavity. The molten metal fills the cavity and finally solidifies and forms.

After the molten metal fills the model, it needs to wait for it to cool naturally. The metal will solidify during the cooling process and gradually form a casting.

After the metal is completely cooled, open the sand mold, remove the sand shell and take out the casting. Since the foam model is completely vaporized and disappears, there is no need for traditional mold removal.

After the lost foam casting is taken out of the sand mold, the surface needs to be cleaned, and the residual sand shell and coating are removed by shot blasting, sand blasting or mechanical cleaning.

Post-processing: The casting may require finishing, such as grinding, cutting, heat treatment, etc., to ensure that the casting meets the size, tolerance and mechanical property requirements.

Inspection link: After the casting is cleaned, the size inspection, hardness test, mechanical property test, etc. are carried out to ensure that it meets the design and use requirements.