worked, but it wasn’t clean and neat.”
Parting Line Position Hammond consulted with Smith
Foundry on material choice since the part would be converted from A36 mild steel to ductile iron. “They told us the grade of steel
they were using, and we conferenced with our metallurgist to come up with the cast product that met the physical properties of that grade of steel,” said Jim Pint, sales manager for Smith Foundry. T e metalcasting facility suggested 65-45-12 ductile iron. “T ere wasn’t a real high strength
requirement, but they wanted high ductility, which is why we went with that grade,” Pint said. With the material selected, Ham-
mond sent over his fi rst drawing of the redesigned component. Smith Foundry responded with a redesign of its own that would make it easier (and less costly) to cast. But Smith Found- ry’s version inhibited key features of the tube clamp. T e main culprit to a quick and easy design: the casting’s parting line location. For ease of setting the core into
the mold, Smith Foundry initially wanted to position the casting so the parting line would run through the center of the Besler Industries name on one of the fl at ends and across the top hole (Fig. 1). “Since I had never designed for cast-
ing, I would send them a picture,” Ham- mond said. “T ey would draw on that picture showing where the parting line would be, spelling it out pretty easily.” T e parting line in a mold is typi-
cally located at the largest cross section, and the patternmaker develops the pattern and corebox around it. Often, gates and risers are located on the part- ing line and will require removal via grinding, which may confl ict with the customer’s requirements for the part. Hammond determined the initial
parting line location would not allow the redesigned component to include an important design element—a recessed diameter surrounding the top hole. Each clamp is bolted onto the tube through the top hole. Sometimes the clamp is positioned onto the tube
36 | MODERN CASTING June 2011
Converted from a steel weldment (bottom) to a ductile iron casting saved Besler Industries throughput time and 60% in cost.
so that a spike, which drags through the farm soil, must go through the hole instead of just a bolt. Besler found that the fabricated clamp often required modifi cation to allow the spike to fi t, adding expense and time. “In some places, the threads on the
spike would be a hair short,” Hammond said. “We decided to dish the hole down and put a recess there so we wouldn’t have to modify the spike every time.” With the recess at the hole, the
parting line location had to change. “T e 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 diff erent parting line location].”
Zero Draft With a Core T e 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’ dimensional requirements. “T e 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
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