Lost foam casting continues to grow in popularity among casting companies because it enables them to produce near-net-shaped components of high complexity with thin walls and other fine-scale features, parts that require fewer gaskets to assemble. And, since there is little need to use binders in the sand, the sand used for their molds can be re-used, saving more money. For the process to be successful there must be a high degree of control. To help casters address some of these difficult problems, FLOW-3D CAST has special models to simulate the lost foam process. With these models, a user can simulate the filling of a lost foam mold as well as the subsequent solidification of the metal. More importantly, FLOW-3D CAST allows the user to predict where folds or other defects associated with trapped foam products are likely to be located.
Simulation of lost foam residue. Courtesy of Alchemcast.
Lost Foam Filling
Many defects in castings are caused by the air and oxides trapped during the turbulent flow of molten metal into the mold cavity. The lost foam casting process reduces such defects by first placing a rigid foam pattern the cavity, which then burns away by the advancing melt. As a result, the filling speed is controlled by the pyrolysis rate, helping to maintain smooth flow at the metal front. FLOW-3D CAST‘s lost foam casting simulations provide engineers with the insight necessary to design the filling process parameters, such as pour temperature and pressure, gate sizes and locations, and foam properties.
Courtesy of GM.
Courtesy of BMW.
Simulating the solidification process aids in predicting and controlling defects such as segregation and micro- and macro-porosity which, in turn, affect the mechanical properties of the cast product. The simulation below is of the solidification of an aluminum V-6 engine block cast using the lost foam process. The video shows the location of shrinkage porosity after solidification.