Lost Foam Q & A

Commonly cast metals include cast irons, aluminum alloys, steels, and nickel alloys.  Less frequently cast metals include stainless steel and copper alloys.  Metal pouring temperatures of at least 1000 degrees F are usually required to decompose the lost foam patterns and gating systems.

Casting tolerances will vary depending on the size, complexity, and geometry of the part.  You can expect to achieve tolerances equal to or better than shell molded and permanent mold castings.  Significant improvement over sand casting tolerances is possible.  Subsequent coining or straightening procedures often enable even tighter tolerances on a few specific dimensions.  An effort between ACH Foam Technologies (the lost foam pattern manufacturer) and the casting user will often result in a lost foam casting that substantially reduces or eliminates previous machining requirements.

Due to a thin permeable refractory shell that is applied around the smooth foam pattern, the finish is much improved over traditional sand castings.  Depending on finish practices, you can expect a surface finish of 60-300 RMS.  In comparison, shell molded castings will exhibit 120-300 RMS, and sand coatings 560-900 RMS.  The refractory shell also provides a barrier to sand inclusions, which benefits subsequent machining processes.

Although lost foam castings are generally more expensive than castings made by other processes, however they make up for this increase by reducing the overall manufacturing cost.  The near-net shape tolerances achieved by lost foam casting allows for a reduction (or total elimination) of additional machining steps required during other manufacturing processes to complete a part.

Lost foam castings are used in many critical applications in automotive, construction, heavy truck, railroad and marine applications.  The process has fewer gating and feeding restrictions, and casting soundness is normally easier to achieve than with traditional molding methods.

Tooling is typically 100% machined from aluminum billet.  Multiple die cavities are usually constructed to minimize foam pattern cost.  The tooling is highly specialized and must be built by expert tooling manufacturers familiar with the requirements of the casting producer.  The quality of the casting can be no better than that of the foam pattern used to produce it.  Tool life is excellent - approximately 500,000 to 3,000,000 cycles depending on tool complexity.  Some moving parts of the tool may require re-build after a given number of cycles.