“The way we wanted to make the
part would have been better for [us] but not work for [Besler] at all,” Pint said. “We had to regroup and come up with an alternative coring design [with a different parting line location].”
Zero Draft With a Core The tube clamp is cast with one
core to produce the internal holes, including two 0.75-in. (1.9-cm) holes and a single 1.5-in. (3.8-cm) hole. Pint said that while the casting was fairly straightforward, it involved a bit of engineering to meet the holes’ dimen- sional requirements. “The location of those holes was
fairly critical,” Pint said. “Having it all on one core required controlled dimensional positioning.” Further, the vertical face of the
clamp, where the holes are placed, needed to be cast without draft so the part had a flat surface for assembly. Typically, draft or tapered angles are required on castings to allow the pat- tern to be withdrawn from the mold without breaking the edges. Smith Foundry solved the zero draft
requirement by forming the face of the casting with a core. “[Hammond] wanted a part with
no draft, which is always a challenge, but in this case it worked out,” Pint said. “In all the critical areas, we found ways to eliminate draft totally through coring.” With this core design, the casting
was repositioned in the mold so the parting line cut across the width of the part, out of the way of where the spike would run through the clamp. “Once we got the design and parting
line down, it was pretty problem-free,” Pint said. Initial samples were cast without difficulty, and the part went into production shortly after approval. Besler Industries is able to place the tube clamp casting directly into the assembly as a raw casting, without any secondary machining or cutting. The casting conversion costs 60% less than the weldment, according to Ham- mond, for an estimated annual savings of $8,000-10,000. “I’m happy with the way it turned out,” he said. “The part came to the
Online Resource
Visit
www.metalcastingdesign.com to study other casting conversions.
May/June 2011 Metal Casting Design anD PurChasing 35
Converted from a steel weldment (right) to a ductile iron casting saved Besler Industries throughput time and 60% in cost.
shop and worked. And it has a good, finished look.” The casting also came with a bo-
nus improvement. The original steel fabricated piece had a lot of play in the two outer bolt holes, which
did not affect the part’s function but caused the assembly to rattle around, according to Hammond. “The holes are much tighter now and
don’t wobble,” he said. “It wasn’t a re- quirement, but it’s a nice benefit.” METAL
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