Lost Foam

The lost foam process is a pioneering casting technique and an innovative alternative and addition to conventional foundry methods. It permits the production of complex components, and opens up new scope for casting design. This method is not only extremely environmentally friendly, it also offers outstanding potential for cost savings.

Storopack has been producing lost foam models for almost all casting materials since 1981.

• Economical selection of suitable castings for the lost foam method in comparison to conventional casting methods
• Lost foam-oriented design support
• Prototype development (foam models in segments, gluing of segments, development and assembly of the casting cluster, casting in customary materials)
• Design and construction of series tool
• Just-in-Time delivery of foam models in accordance with DIN 9001:2008

The sand casting process using lost molds and models includes a method known as lost foam casting. The polystyrene foam models (such as expandable polystyrene) used for the lost foam casting process are coated and embedded in casting sand in a casting flask. When molten metal is poured into the coating, the foam decomposes, leaving a hollow cavity which is filled by the molten metal to produce a precise reconstruction of the model geometry. The design and processing quality of the lost mold made of EPS particle foam are decisive to the quality of the castings when using the lost foam method. It is vital that the foam model developed is capable of producing an optimum result. It should not have sharp corners or edges, as these will prevent adhesion of the coating slip and so impair inflow of the molten metal. Softly rounded contours help to reduce flow turbulence and so improve the quality of the casting. To ensure that shadow sides are adequately filled out when pouring in the casting sand, and that the sand can be compacted in these areas, it may be necessary to plan for auxiliary openings.

To be sure that the desired result is achieved during series production, a consistent foam model quality is essential. The vital factor here is even density distribution and optimum welding together of the particle foam. When the molten metal meets the EPS model, the high temperature of the metal causes it to decompose into smaller fragments (depolymerization) and evaporate. The metal is then able to enter the vacated cavity.

• Manufacture of complex components made of all commonly used alloys
• Greater design freedom for designers than when casting in permanent molds
• Undercuts, angled channels and contour-optimized cavities in the component are possible
• Reduced number of machining processes
• Use of rapid prototyping
• Additional facility for weight reduction
• Clear production cost benefits
• Very environmentally friendly process

The benefit of this process for casting foundries is that it allows the reproduction of extremely complex components to be brought forward by a complete process: The problem of creating undercuts, angled channels and contour-optimized cavities is solved in advance by the foam model supplier. To achieve this, a foam model may need to be glued together from several individual segments. Using 3D CAD modeling, it is possible to determine how the overall mold must be divided into segments so that the position of the dividing seams does not impair the casting. At the same time, the dividing seams must be properly placed to ensure individual segment shapes which can be efficiently produced using the molding method. Experience has shown the ideal gross density for moldings to be around 20 to 22 gr/litre.