The window hardware system, designed for opening and closing casement and other types of windows, also relies on DuPont Delrin® acetal resin for a gear and carrier shoe. Glass-reinforced Zytel® DMX gives us the consistent strength, toughness, stiffness and precision dimensions for the track to perform its function in the Parallex system, said Sean Davies, CEO of Preferred Engineering Products.The resins flow properties and low warp are crucial in moulding long, flat parts like the tracks, which range from 53 to 107 mm in length.
The stable, predictable properties of Zytel® DMX help ensure reliable functioning of the Parallex window hardware system. In addition to the track, the systems parts include carrier shoes, which run along tracks mounted in the sill and head jamb of the frame, and a metal pivot shaft, which is mounted in the moveable window sash. The pivot shaft is connected at each end to a gear made of Delrin®. The gears are mounted in the carrier shoes, which are also made of DuPonts acetal resin.
The track has integrally moulded teeth that mesh with the gear. When the sash is moved along the track, it turns and causes the pivot shaft to rotate, simultaneously moving each of the carrier shoes and maintaining their parallel alignment. The sash can be aligned anywhere along the track, even from a fully closed position, according to Preferred Engineering.
In switching from hardened aluminum to Zytel® DMX, Preferred Engineering was able to redesign the track for improved performance. Davies said: The new track has thicker, stronger teeth that are less prone to jamming or breakage and allow our customers to use our hardware for windows twice as large as before. He added that the hardware is now suitable for windows up to 122 cm by 213 cm, according to Davies.
Another benefit of the new design is easier assembly. It has integrally moulded provisions for attachment and adjustment. The aluminum tracks, by contrast, required separate parts for those functions.
The switch from aluminum to Zytel® DMX also allowed Preferred Engineering to sharply cut lead-time on customer orders and has greatly simplified management of its supply chain. In the past, the company had to order custom-extruded aluminum profiles three months ahead. It then had to manage a sequence of four finishing steps involving three different outside suppliers. With three different lengths of tracks and inventory in various stages of production, supply management was a nightmare, according to Davies. The company now obtains finished, ready-to-ship parts from a single source: its moulder.
The carrier shoes and gears made of DuPont Delrin® have been providing reliable service in the Parallex window hardware system since its introduction in 1997. The parts are moulded from a blend of a glass-filled grade, Delrin® 570, and a masterbatch containing silicone for lubrication, Delrin® 500SC. Davies commented: The combination of these two DelrinÒ grades gives us the high stiffness and strength required to support window loads plus smooth, squeak-free operation.