Gear part with an overmoulded stainless steel shaft
Grinder shaft for the grinding unit of high-quality commercial bean-to-cup coffee machines. The POM gear part transmits force via the toothed belt and combines precise plastic geometry with a high-precision stainless steel shaft that is mechanically interlocked by overmoulding.
The material selection takes account of sliding properties, dimensional accuracy and strength, as well as requirements for food contact, continuous operation and noise behaviour. Two injection moulds for precision injection moulding were built for the different diameter variants.
The concentricity between the stainless steel shaft and the overmoulded pulleys, the positioning of the closely toleranced insert and the post-mould shrinkage of POM are particularly demanding. The mould shuts off against the shaft and compensates for its length tolerance. Quality assurance is based on optical and tactile sample inspections.
