Bollard Cap Case Study
Case Study: Cast steel Bollard Cap
In 2001 the Architect of the Capitol requested bids for perimeter security around the US Capital and Supreme Court.
Penn Steel of Hamburg, PA had ceramic shell casting capability. Tempo supplied beautiful smooth surfaced foam patterns with detailed American Eagle medallions. Every pattern was individually wrapped in foam blankets for safe transit to the foundry with no scratches. These patterns were encased in a ceramic coating. Then the foam was burned out in an oven before molten steel was poured into the ceramic shell and cooled. The Bollard Caps were welded onto the steel post embedded in cement to prevent vehicular access.
Injection and steam heating of polystyrene beads into lightweight pattern forms smooth, accurate, lightweight replica of product to be cast. The Replicast method provides exacting reproduction of clearance holes, surface patterns, loose parts (like the chain retention, and engraved markings.
The polystyrene replica is coated with ceramic slurry to form a ceramic shell coating over the polystyrene replica.
Replica is coated with sand and stucco prior to being placed in an oven which vaporizes the polystyrene shape and further cures and strengthens the ceramic coating. The shell hardens to refractory tolerances.
The ceramic shell is imbedded in a flask containing dry sand. The shell is then filled with molten steel. Sand never comes into contact with the steel casting.
After cooling, the casting is removed from the loose sand. The ceramic shell is then broken away to show the finished product before the final riser removal and normal cleaning. Welding, machining and surface treatment are minimized
This process was developed by the Casting Development Centre in Sheffield, UK