Improving Foundry Practices: Venting Chambers in Blind Risers for Higher Casting Yield and Quality

The white paper aims to address the challenges that foundrymen around the world face in improving their operations, such as producing higher quality castings, decreasing delivery time while lowering costs. The paper also introduces the use of 3D sand printing technology for the production of sand molds and cores.

Blind risers are used by foundrymen to feed various sections of a casting. Blind risers are located in the lower sections of the casting or hidden below the top risers. They are somewhat handicapped when compared to open risers that break through the cope to the top of the mold and are entirely exposed to the outside atmosphere.

A vacuum pocket is sometimes created at the top of the blind riser due to the fact that their top front of metal is not exposed to the atmosphere. The Williams core principle was designed to overcome this limitation. However, it is not reasonable to assume that a blind riser is subjected to an even and limited exposure to atmospheric pressure. With extensive study, the white paper suggests the use of venting chambers on blind risers, which showed a significant improvement in feeding.

Blind risers with venting chambers remained open at the top, allowing atmospheric pressure to act through the chamber-vent system against the liquid front of metal at the top of the riser. This resulted in significant metal loss, but the efficiency of the riser improved when provided with an unobstructed passage to atmospheric air. The implementation of the new venting system resulted in an improved casting yield from 51% to 66.7%, and the metal saving over a one-year period was equivalent to the weight of 30 diffusers.