How Foundries Perform Flash Removal on Aluminum or Zinc Castings

Foundry engineers pour molten metal of zinc or aluminum into a mold cavity or die cavity with force in high-pressure die casting. Due to the applied pressure, the molten metal forms flash around the casting within the mold cavity. This flash is usually wafer thin, and should be removed prior to shipping the die cast component to the customers for surface precision.

In fact, the two common ways of flash removal in metal casting include using a Trim Die and a sander. Trim dies are created with the exact shape of the casting die. They necessitate precise design like metal casting tools. Based on casting’s shape, a trim die can be single cavity tool or multi-cavity tool. Trim dies can be used by global foundries for trimming operations such as flash removal of castings alongside overflows and runners.

If well designed, trim dies can remove the flash of up to 0.005 inches to 0.010 inches from the edge of the die cast parts. The tool has two halves, and both halves are fastened on the lower or upper platen of the trim press machine. It usually has a closing pressure of up to fifteen to twenty tons. The casting fits into the bottom half of the trim die, while the top half closes the part. In the process, it trims the flash from the edge of the casting.

Since trim die removes the excess metal from the casting’s surface consistently, the surface finish of the component is improvable if they are used for flash removal. The tool will reduce the lead time, labor cost, and provide cost savings to die casters in Mexico besides improving the component quality. Trim press functions at a rapid pace than metal casting machines, so removing flash wraps up quickly with less labor.

On the other hand, using a sander for flash removal necessitate more labor and is not as consistent as the machines are. Sanders are also open to operational interpretations from the part of the worker so perfect surface finish may not be achievable with that. Besides, techniques such as blasting zinc shots are also used for deburring or smoothing the ridges of aluminum die cast parts, for flash removal at a faster pace with the customer in mind.