Interaction of tool and process design on the mechanical and tribological behaviour of an injection-moulded polyamide-steel gear set

In this work, the influence of gate design and mould temperature on the mechanical and tribological characteristics of a polyamide-steel gear set is investigated. Of special interest is the interaction of gate design and processing parameters, in this case the mould temperature, on the resulting properties of the polymer wheel. At 60 degrees C mould temperature the gate design has a high influence on the wear behaviour. Wear increases by 75% for gears with single pin-point gates compared to sprue gates. With triple pin-point gates manufactured at 60 degrees C mould temperature, the wear is 25% higher compared to sprue gate specimens. Increasing the mould temperature to 100 degrees C reduces wear for all gate designs to the level of a sprue gate. This is due to the formation of a finecrystalline and homogeneous morphology regardless of gate design, leading to better wear resistance. Therefore, with a coordinated tool and process design, significant improvement of the operational properties of polymer gears can be achieved without restricting economically efficient design choices.