. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Casting innOVatiOns
Boiler Castings Take Shape With Intricate Cores
growing demand for high efficiency commercial heating equipment. After conducting an unsuccessful search for a metalcasting facility in North America that could produce prototypes of the intricate, hollow-core castings, Burn- ham Commercial turned to Burnham Foundry LLC, Zanesville, Ohio. Burnham Foundry is a wholly-owned
B
subsidiary of Burnham Holdings Inc. The in-sourced facility produced gray and ductile iron castings for residential and commercial boilers, heat distribution radiators, automotive applications and other custom OEM parts. MPC boilers consist of multiple
gray iron castings assembled together to make up a complete boiler block. Each cast iron section measures 54.813 x 33.25 x 6.845 in. (139.2 x 84.5 x 17.4 cm) and when assembled together can handle inputs between 500 mbh to 3,657 mbh. Casting these sections requires large, intricate cores that were challenging to handle, set into the mold and vent. “The core is large
in dimension, but the surface area is much less than other cores we make of similar size,” said Jeremiah Clegg, Burnham Foundry’s plant manager. “There are several open voids.” The cope and drag
mold halves for the cast- ings are hand-filled with the help of a continu- ous mixer on Burnham Foundry’s airset phenolic
Burnham Foundry cast these 500-lb. cast iron boiler sec- tions, which require large, intricate cores.
May/June 2010 Metal Casting Design & PurChasing 57
urnham Commercial, Lan- caster, Pa., recently launched a new line of commercial multi-pass cast iron boilers (MPC) designed to meet the
urethane nobake line. The core is thin and fragile but still heavy, weighing between 225 and 315 lbs. (102 and 143 kg), depending on the section. Its weight, coupled with its size, make handling the core a challenging task. “The large core must be precisely
hand-set in the mold without any damage to either,” Clegg said. “In fact, we developed a special lifting fixture designed around the gripping areas to assure proper fit and function. The placement of chaplets, which
are used to keep the core from moving when iron is introduced into the mold, was also difficult because of the lack of surface area on the core. Metalcast- ing personnel added chaplet seats in areas too thin to support chaplets. The design of the casting, like the
core, exhibited thin walls and intricate shapes, leaving little surface area avail- able for the placement of vents, which provide exit paths for gases that form when molten iron is poured into a mold. If the gases are trapped, they
can cause multiple defects. Burnham Foundry used computer modeling to determine the location of the vents so they would not interfere with the tongue and groove interlock sealing the two halves of the mold together. “The experience of our chief tooling
engineer designing and modifying the gating system was also an important part of the process,” Clegg said. “While computer aided design can be a valu- able asset, the final system often needs the touches that only an experienced engineer can offer.” “The sections are unmatched in
quality and appearance,” said Jim Schnorr, director of sales and mar- keting for Burnham Commercial. “A total team effort from design to production has given Burnham Com- mercial a domestically-produced, world-class, highly-efficient, cast iron boiler to market.”
METAL
Visit
www.burnhamfoundry.com or
www.burnhamcommercialcastiron.com for more information.
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