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Product category: Materials and components
News Release from: DuPont (UK) | Subject: Zytel
Edited by the Engineeringtalk Editorial Team on 01 December 2003

Nylon resin replaces aluminium in
washing machines

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A novel plastic pulley, among the first in the world and a cost-effective alternative to its cast aluminium counterpart, is now being used across the full range of Hotpoint washing machines.

A new plastic pulley, among the first in the world and a cost-effective alternative to its cast aluminium counterpart, is now being used across the full range of Hotpoint washing machines, designed and manufactured by Merloni Elettrodomestici UK, Peterborough, England, formerly known as GDA The injection-moulded pulley, made of glass reinforced Zytel nylon resin from DuPont, offers lower part costs versus casting, and there are no compromises in mechanical properties

Design, analysis and manufacture of the pulley was carried out by Rolinx Plastics Company of Manchester, England in conjunction with Merloni UK.

Most domestic washing machines use a pulley to transmit torque from the motor to spin the washing machine inner drum.

Rolinx identified the opportunity to replace the commonly used cast aluminium option with a reinforced nylon resin, a mechanically stiff plastic used to make reliable, high-performance and cost-effective components and systems.

Such an injection-moulded part would not only cost less, on the basis of lower tool wear, but also offer sustained mechanical performance.

Zytel nylon resin from DuPont was nominated following a successful supplier evaluation exercise.

In order to act as an effective replacement for an aluminium pulley, the dimensions of the Zytel part needed to remain identical, whilst the centre boss section had to withstand a compressive force of 105N.

At the same time the pulley was required to withstand a belt tension of over 300N and operating temperatures of 70C and above, with noise levels not permitted to be greater than the aluminium variant.

The final design for the Zytel part was able to meet all design constraints, and with the aid of finite element and mould flow injection analyses, it was confirmed that it offered the most mechanically sound option.

Additional physical testing, involving the continuous running of the washing machine for the duration of the machine's "lifetime" was carried out by Merloni UK and backed up the analytical data.

Rolinx's own production and quality programmes are responsible for ensuring that the pulley part can be manufactured continuously to cost, to set quality standards and delivered to Merloni's assembly site to schedule.

The new pulley was introduced to Merloni's Hotpoint production line in April 2003.

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