Application Description
Thrust plugs made out of Vespel® polyimide are used in ITT’s powerful, reliable and economic automotive rear windscreen wiper motor (SW3P). Gears made from Delrin® acetal resin also feature in this application.
Benefits Gained
DuPont’s Vespel® thrust plug helped ITT to introduce a new lighter motor range using a plastic gear casing. A cost and performance driven material selection process encouraged ITT to select the thrust plug made of DuPont’s Vespel® polyimide. Because injection moulded thrust plugs made from thermoplastic material failed, ITT is satisfied by the excellent performance, durability, reliability and safety (Vespel® parts never melt) of these high performance parts.
Materials Selected and Why
Vespel® polyimide was chosen due to its heat and wear resistance. This polyimide doesn’t melt, resists high impact and can take high loads while maintaining very good dimensional stability between -40°C and +150°C — or even higher. The thrust plug is pressfitted into the armature shaft at the worm gear side and takes the axial load of the armature shaft. It runs against a polished steel plate fixed in the PET +45% GF gear casing and is grease lubricated.
In this application, Delrin® is used for the gear because it provides the optimum combination of mechanical properties including low creep and high fatigue resistance. Delrin® is easily and precisely moulded, and maintains excellent dimensional stability. Its impact strength ensures that the teeth do not break or crack. In addition, the low wear and low friction properties reduce noise without the need of lubrication.
Return to Case Studies Index Page
