Design freedom as well as alloy choice made investment casting the best, and perhaps the only choice for producing an assembly of parts used in “Cable-Tite” tie down system for fixing the walls and roof of a home to its foundation to protect the structure against high winds.
A finalist in the Investment Casting Institute’s recent casting contest, the three-piece assembly manufactured by Precision Castings of Tennessee (PCT), illustrates not only the flexibility of investment casting as a manufacturing process, but also how pervasive investment casting is in everyday life. Investment casting components not only serve in critical applications on aircraft and automobiles, they also keep homes safe and secure.
PCT Director of Engineering Clay Cooper indicated that these are parts are the first of their kind in the construction and home reinforcement industries.
“While the construction and home reinforcement industries traditionally have used the cheapest means of manufacturing a product, there is a rising demand for a quality tie-down system as building codes along the coastal regions of the US have adopted requirements for wind resistant designs in all new homes,” Cooper said.
“This product uses the investment casting process to meet the unique design needs in a user friendly, cost competitive product which exceeds all other products on the market in strength and installation flexibility,” he added. “These parts showcase some of the great design capabilities of the investment casting process specifically to industries that have traditionally used others means of fabrication for hardware and parts.”
“From the beginning, there were several critical design limitations. Primarily this assembly had to be completely contained in a standard 2”x4” framed wall so that it was undetected once the home was completed,” Cooper explained. “Furthermore, the new components had to be designed in such a way to interface with existing parts used to hold the high-strength cables.”
He pointed out that the three areas of design– form, fit and function– were met in distinctive ways in the design of the tie-down system, thanks in large part to the investment casting process and its unique flexibility.
The investment process allowed for the parts to be designed to a form or shape that was easily enclosed within a standard wall. The design of these parts also took into consideration the shape of the existing parts being used in the assembly. In doing so, two of the castings have a channel in them to allow the mating strand-vise (cable holding part) to freely slide them.
“These are small design features, but they are critical for the castings to have a proper fit in the assembly,” he continued. “Additionally, with investment casting process’s nearly unlimited alloy choice we were able to create a design for the form and fit of the assembly and then choose an alloy to achieve the required mechanical strength of the assembly.
“Also, the primary design feature for the assembly, the patented external cam on the anchor casting, allows the system to be consistently pre-tensioned after installation. This unique design feature is nearly impossible with many manufacturing processes, but with the investment casting process it is a reality,” he said. “The external cam and the alloy choice allow the tie down system to meet the function requirements of the design after the form and fit portions of the design process had already been established.”
“In addition to meeting the design requirements, the investment casting process allowed for the parts in the assembly to have a modern, aesthetically pleasing look with extra features such as a alignment guide lines, no-slip knurling, ribbing for strength, and company logos cast right into the parts,” Cooper said.
“While some of these unique design features would be possible in some way in other manufacturing processes, all them together in the same design would be nearly impossible outside of the versatile investment casting process.”
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