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Converting a Bumper for Landscaping and Grounds Care Companies are always looking

for ways to improve their products. Whether its efficiency, durability or simply performance, there are paths to serving consumers better. One manufacturer was looking

to improve the efficiency of a rear bumper on a mower. For this machine, the original bumper wrapped around the mower and displaced the center of gravity, which presented multiple problems. Te bottom surface had an angle and position that made it scrape on inclines and steep grades. Te original also had a thin sec- tion in the center that could crack if it backed into large objects, forcing users to remove a broken (and costly) 67-lb. bumper, potentially causing lost revenue. Also, since the part was one piece, a third-party was required to drill and tap holes needed to mount the bumper to the mower after the

bumper was cast by Waupaca Foundry (Waupaca, Wisconsin), raising the price of the final product. In recognition of the problems and

opportunities for improvement, the manufacturer and Waupaca worked together to make the product bet- ter. One of the first decisions was to transform the casting into two parts. Originally, the bumper was cast as a one-cavity mold on a 32 x 32 ft. vertical molding machine, but casting the bumper on a two-piece made it possible for Waupaca to make 1 ½ bumpers per mold on a machine that was just 28 x 34 ft. A challenge of designing the cast- ing was to position the offset parting line so it could fit three cavities into each mold. To do that, Waupaca’s designers reduced its height by 3.5 in. (89 mm), a critical difference that let the foundry team fit three halves of

the bumper in each mold. Waupaca also aided the manufacturer in the de- sign of the attachment of the bumper castings to the mower. Te focus was specifically on the mounting holes that are now cast without the use of cores, as opposed to features requiring a core and/or any secondary machin- ing operations. As-cast slotted features that did not require additional fasten- ers were designed into each half of the bumper, providing a second point of securing the casting to the mower and the adjacent other half. Following early and extensive

involvement in the design and tooling of the casting, the new bumper was implemented into the production design months ahead of schedule. A key result of the new design was

how it eliminated the machining once required to drill and tap mounting holes, reducing costs. Te manufac-

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42 | MODERN CASTING April 2017

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