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Promoting safer oven use

By Elisenda Falcó and Oscar GarciaGaona
DuPont Engineering Polymers, Spain

The new ‘Impulse’ system to access hot oven trays in ovens from Fagor Electrodomésticos (Basauri, Spain) has been developed and patented by the company with the support of Hettich International. It includes self-extracting Quadro runners, which allow total access to food without touching the oven tray. By simply opening the oven door, the tray automatically glides forward with the food – when the door is closed, the tray slides back in. The operation of this application relies on gravitational force in order for the Quadro runners, mounted on stainless steel ball bearings, to glide out in a lineal movement. In order to achieve this, Fagor Electrodomésticos worked with Hettich International, a supplier of runner systems, whose Spanish subsidiary, OBE Hettich S.L., is based in Aizarnazábal (Guipúzcoa, Spain).

The runners have an end-cap made of Zenite® liquid crystal polymer resin. The material, already widely used in the electronic industry, was selected for this application due to its benefits in cooking. The particular grade of Zenite®, FG7145L BK011, is resistant to high temperatures, is approved for use in repeated food-contact applications, delivers high performance and an appealing surface finish.

“We were looking for a material for the end-caps that could withstand the high temperatures encountered in domestic ovens, which can be as high as 240°C (464°F). Moreover, the parts were required to support the weight of the oven tray plus food, at simple compression and supported by a stainless steel guide, but this was no great challenge”, explains Urtzi Zubiate, innovation leader at Fagor Electrodomésticos. “The sole mechanical stress the end-caps encounter is the impact against the oven’s door. The material needed to be of sufficient strength to withstand the initial impact until the tray begins to glide back, yet it shouldn’t be as hard as metal, so as to avoid scratching the glass door. That’s how we arrived at engineering thermoplastics providing the best possible solution.”

Further unexpected benefits were gained through the adoption of this particular grade of Zenite®. These included the opportunity to reduce achieve an impressive wall part thickness to justof 13 mm (0.5 inches), in for a part which is 80 mm (3 inches) long, as well as the ability to assemble the stainless steel and plastic parts, without the need for additional components, for further cost savings. Indeed, with regard to cost, the reduced cost of tooling for the Zenite® part makes it the most cost-effective alternative. Fitting with the Quadro guide is ideal, due to the high dimensional stability of the end-cap’s neck, and the elimination of additional production steps – all of which will help make Zenite® the material of choice for applications in other oven ranges in the future.