Characteristics of the Lost Foam Casting Process

1. High Casting Accuracy

Lost foam casting is a near-net-shape, precision forming process. It requires no pattern withdrawal, no parting line, and no sand cores. As a result, castings have no flash, burrs, or draft angles, and dimensional errors caused by core assembly are significantly reduced.
The surface roughness of castings can reach Ra 3.2–12.5 μm, dimensional accuracy can reach CT7–CT9, and machining allowance is typically only 1.5–2.0 mm. This greatly reduces machining costs. Compared with traditional sand casting methods, machining work can be reduced by 40–50%.

2. High Design Flexibility

The process provides great freedom in casting design. Highly complex castings can be produced by assembling foam pattern segments.

3. Elimination of Traditional Sand Cores

Since no sand cores are used, problems such as uneven wall thickness caused by inaccurate core dimensions or improper core placement in conventional sand casting are avoided.

4. Clean and Environmentally Friendly Production

The molding sand contains no chemical binders. Foam plastics are environmentally harmless at low temperatures, and the reclaimed sand reuse rate exceeds 95%.

5. Reduced Investment and Production Costs

Casting blank weight is reduced and machining allowance is minimized, resulting in lower overall production costs.

Like other casting processes, lost foam casting also has its limitations and disadvantages. Not all castings are suitable for production using this process, and a specific analysis is required. The decision to adopt lost foam casting should mainly be based on the following factors:

1. Casting Production Volume

The larger the production volume, the more significant the economic benefits.

2. Casting Material

The general order of suitability is as follows:
Gray cast iron → non-ferrous alloys → plain carbon steel → ductile iron → low-carbon steel and alloy steel.
Proper preparation is required to avoid excessively long process testing and commissioning cycles.

3. Casting Size

This mainly depends on the operating range of the relevant equipment, such as vibration compaction tables and sand flasks.

4. Casting Structure

The more complex the casting structure, the more evident the advantages and economic benefits of the lost foam casting process. For castings with narrow internal cavities or layered structures, preliminary trials are required before mass production.