Improving Metal Flow in Lost Foam Casting Through Use of Low Thermal Degradation Hot Melt Adhesives

Lost foam casting minimizes pattern design limitations by using pattern segments and hot melt adhesives to create complex geometries. Defects in cast parts have been shown to be caused by the higher thermal degradation energy densities in hot melt adhesives as compared to polystyrene. A polystyrene-based glue was designed to achieve a lower thermal degradation energy, measured via thermal gravimetric analysis, while maintaining qualitative metrics such as low odor and proper viscosity to avoid stringing during application. Casting trials were performed for multiple developed glue mixtures to assess the melt front velocities at each glue joint. The resulting polystyrene-based glue increased the melt front velocity by 75% at the glue joint compared to a commercial glue. The addition of a wax component increased the melt front velocity further and eliminated stringing upon application.