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DuPont Vespel® parts for pusher fingers help lower maintenance costs and rejects

DuPont’s Vespel® SCP-5050 parts are now being used for thermal insulation by Emhart Glass, one of the world’s leading manufacturers of high-performance machines for the production of glass containers, to further reduce maintenance costs for users and, at the same time, minimize reject rates of produced containers.

Emhart Glass of Cham/Switzerland, one of the world’s leading manufacturers of high-performance machines for the production of glass containers, now uses DuPont’s Vespel® SCP-5050 parts for thermal insulation, replacing the standard carbon graphite components used in the liners for pusher fingers. This change has helped to further reduce maintenance costs for users and, at the same time, minimize reject rates of the produced containers. The pusher fingers are used to move up to four moulded glass containers – at temperatures up to 600°C and correspondingly soft – from the dead plate to the conveyor belt in less than a second. The bar-shaped liners, which are inserted within the pusher fingers, transfer the high acceleration forces involved in this process to the glass surface.
When compared with Vespel® SCP-5050, carbon graphite bears a couple of drawbacks in this particular application that can lead to higher production costs. Due to its high heat transfer coefficient, a lot of heat is transferred from the glass to the liner at the point of direct contact. This can lead to localized cooling and the build-up of high stress concentrations in the glass container, resulting in checks (micro-cracks) in the glass and its eventual rejection. The heat transfer coefficient of Vespel® SCP-5050 parts is approximately 50 to 100 times lower than that of conventional carbon graphite components. Stress concentrations are consequently lower, meaning production rates can be increased for greater plant productivity and energy consumption per unit is reduced. Carbon graphite also absorbs oil during operation, leading to a further increase thermal conductivity. In contrast, Vespel® SCP-5050 parts absorb almost no oil, meaning that the liners retain their low thermal conductivity for longer. In addition, the impact resistance of the Vespel® SCP-5050 parts is approximately twice as high as that of the carbon graphite components. Thus they can withstand higher mechanical loads, meaning fewer maintenance downtimes caused by broken liners.
Moreover, because the wear resistance of Vespel® SCP-5050 parts exceeds that of their carbon graphite counterparts, they are particularly durable with regard to the intensive and abrasive operational demands placed on them by the extremely hard glass surfaces.
Christian Fröba, Director After Sales at Emhart Glass, reports: “Whereas the graphite liners usually need to be replaced any time between 6 and 12 months, we expect the liners with Vespel® SCP-5050 parts to have up to three times longer service life, based on testing. Considering that an average machine to date is fitted with between 8 and 12 pushers, and that each of these is equipped with between 8 and 16 liners, this can mean a considerable reduction in maintenance time and costs.”
Fröba continues: “Based on the convincing results of tests conducted by our company, we now use Vespel® SCP-5050 parts as a replacement for carbon graphite for the pusher finger liners in all of our machines. This includes the standard SIS lines, the IS and AIS series machines for medium requirements as well as the new, servo-electric powered NIS high-performance machines, which are designed for production rates of 700 or more glass containers per minute. All machines installed for customers to date have met our high expectations with regard to increased productivity through fewer rejects and reduced maintenance costs.”
Vespel® SCP-5050 parts and shapes combine very low friction with very high wear resistance at high temperatures. As an alternative to carbon graphite wear parts, this technology offers both quick and convenient global availability as well as flexibility in sizing, charge-to-charge consistency, certified quality, rapid prototype development and the cost-efficient production of customer-specific parts – a service used by Emhart Glass for the liners of its pusher fingers.

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