The process itself utilizes unbonded sand and a foam pattern in order to create the casting shape. Once the foam pattern is glued and coated this unbonded sand fills into all the voids. With compressed sand in the casting flask, all shapes are supported, along with the pattern’s external form. Next, the flask is moved to the pouring area. The aluminum is poured, evaporating the foam as the metal becomes the casting shape. Sand and metal are then separated. The lack of binders required makes this process far easier than the separation process in sand molding.
There are multiple benefits of using aluminum lost foam castings over other methods. These include the fact that no sand cores are needed; meaning no core defects. Using dry, unbonded sand to support the foam avoids the risk of moisture or binder related defects. Since the aluminum takes the shape of the foam part, there are no shape limitations. Other processes involve draft meaning the part cannot have areas where the part “hangs up” in the mold.
Relatively simple to undertake, this process is more cost effective than other techniques, with less machine tooling damage from entrapped, hard sand particles as well. Energy demands from lost foam casting are also reduced the cluster then undergoes sprue, gate and riser elimination, with the sand cooled and recycled back into the process. With far more accurate casting possible, the lost foam technique endures as ideal for many uses.