and JBT continued to buy them for about two decades. But in the early 1990s, another green sand casting supplier offered the airbridge producer a lower price, and the buyer accepted. “Every year, we re-bid our


parts,” said JBT materials manager Nicholas Manning. “We always are looking for lower cost, quality suppliers that can deliver on time.” In the succeeding years,


State Brass won its customer back. The company installed a vertical centrifugal caster, which allowed it to deliver JBT a bid that was even lower than the green sand competition, without sacrifi cing quality or lead time. The company was re- warded for its efforts with a best-in-class supplier award in 2000, and a year later, it became a certifi ed supplier to JBT. “It was kind of the Field of Dreams


theory,” said Don Archer, a fourth generation employee of State Brass.


The airbridge rotunda castings are poured in CDA 836 brass and cut into two pieces.


in static casting methods. The process, which is often linked to the production of ductile iron pipe, also can produce large parts in unexpectedly intricate patterns. State Brass began operating


a small horizontal centrifugal casting machine in 1985. In 1995, the company installed


a vertical centrifugal casting machine for about $500,000. The


“If you build it, they will come.”


Going Upright Centrifugal casting machines are


ideal for customers seeking cylindrical parts with microstructures and mechan- ical properties superior to those made


machine is capable of reaching outside diameter sizes of 72 in., and according to Archer, it offers signifi cant advan- tages for the metalcaster’s cleaning room. In addition to sending more consistent parts to fi nishing, centrifugal components are made without the use of a gating and risering system, which takes time to grind away from green sand castings. This alleviation of clean- ing room requirements—as well as a reduction in cooling time provided by centrifugal casting—is critical for the 14-employee staff at State Brass. “In centrifugal, you cast [a part] and


pull it out of the mold in less than 15 minutes,” Archer said. “Then, you throw it in the [shot blast] and send it over to the machine shop.” Today, State Brass boasts a near


zero scrap rate on its centrifugally cast parts. While this is primarily due to the inherent benefi ts of solidifi cation during spinning, the company also has retrofi t- ted a ceramic sprue to hold a fi lter for parts where it needs an added level of cleanliness in the melt. In addition, it only uses certifi ed alloys for parts poured on the machine. The vertical centrifugal casting ma-


chine also allows State Brass to produce parts with considerably lower draft than can be produced in static casting. Because castings shrink away from the walls of the mold in a centrifugal ma- chine as they cool, the draft can be as low as 1 degree, with 3 degrees being the standard. “A lot of it depends on how big the


part is,” Archer said. “The taller the part, the more draft you would want on it.”


A historically green sand metalcaster, State Brass Foundry and Machine has found centrifugal casting to shorten its lead times and lower its man hours.


MODERN CASTING / October 2010 31


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