Consequently, Progress Casting evaluated four different drying techniques to determine which one would work best. The high intensity lights and drying tunnels did not dry fast enough to prevent coatings from dripping and losing thickness uniformity. Microwave drying used nonselective heat that penetrated the sand cores and caused them to disintegrate. Infrared ovens, however, quickly dried the coatings without damaging the sand cores. To accommodate this requirement, Progress Casting worked with vendors to design custom equipment to automate dipping and drying the smaller sand cores.
Automation is a key factor in producing consistent coating thickness and quality.
First, a row of sand cores is placed on one of the racks, and then lowered into the dip tank containing continuously recirculating corewash and held in the coating solution for approximately one minute. With the corewash forced upward in the tank, the countercurrent effect facilitates wetting of the core surface and helps ensure uniform coating. The aeration action also minimizes bacterial growth in the corewash. After dipping, cores are then lifted out of the tank and rotated into place over one of the infrared ovens as the operator adds another row of cores to the second rack. The racks then simultaneously lower the cores into either the dip tank or the infrared oven.