Torque motor uses polymer for stator moulding

, which are predominantly used in electronically-controlled exhaust gas recirculation valves for automotive diesel engines. Daniel Sigg, one of the original developers of the torque motors at Sonceboz, said that the main reasons for choosing to use DuPont's LCP Zenite were the material's "high thermal resistance" and "extremely good melt flow characteristics". He continued: "We can fill the tool cavities completely in spite of the bobbins' very thin wall thickness of 0.3mm, even with short cycle times. The type 6130L we use is 30 percent glass fibre reinforced and combines high toughness with a heat deflection temperature of 260°C." In joint development with DuPont's distributor Dolder, Sonceboz achieved another key objective. As Sigg explained: "The type of Zenite we use produces clean weld lines so that the thin-walled bobbins can safely withstand the relatively high mechanical stresses during welding." Sonceboz also uses Zenite to overmould the ready-wound coils as the material's low melt viscosity prevents the windings from being displaced by the melt as it is being injected. Since the overmould functions at the same time as a housing for the stator, Zenite also serves as a plastic bearing for the rotor shaft, replacing the original separate bronze and PEEK bearings. DP To access this and other related articles go to www.eurekamagazine.co.uk click "Reference Library" and key in 'plastics' to the search box DuPont Enter XXX Pointers * A Swiss manufacturer is using a liquid crystal polymer for its coil bobbins and for overmoulding the stator on its torque motors. * DuPont's Zenite 6130L gives very good melt flow characteristics, high thermal resistance and produces clean weld lines * The polymer also acts as a plastic bearing for the rotor shaft, replacing the original bronze and PEEK bearings