Manufacturing range: Elastomer injection moulding
In the beginning of product development, materials are selected according to the application of an elastomer component taking into account ambient conditions, geometries and economically suitable manufacturing processes. etm exclusively applies discontinuous vulcanization. Vulcanisation is performed in autoclaves (freely heated tubes) as well as in injection moulding dies.
Vulcanisation is a thermal, irreversible process in which the plastic elastomer mixture is converted into an elastic component by cross-links.
In this process, pressure, temperature and time have to be coordinated.
etm uses modern elastomer injection moulding equipment (vertical and horizontal) for processing of all kinds of standard synthetic elastomers. For material-efficient manufacturing, cold channels featuring needle valve systems developed by etm are applied. For applications requiring increased temperature and media resistance, such as in the automotive industry, silicones (solid and liquid silicone) and types of fluorinated elastomers are used.
Insert moulding of plastic/ metal cores for special sealing and assembly requirements (targeted stabilisation) are also a part of the etm product portfolio.
Process sequence for injection moulding of elastomers
- The elastomer mixture is continuously supplied and fed into the machine and injected into the often multi-calibre mould via a screw conveyor. If the machine is equipped with a piston injection unit, the screw conveyor feeds the mixture into a separate cylinder for injection into the mould.
- When the mixture passes through the nozzle and the sprues, additional friction heat occurs and the viscosity is temporarily reduced, supporting optimum mould filling and speeding up the vulcanisation process.
- Afterwards, the moulded component is created by vulcanisation of the elastomer mixture for a defined idle period inside the heated die.
- After the vulcanisation period, the mould is opened at the parting line and the finished article is removed. Cavities and recesses are moulded from the die cores using pressurised air.
- After demoulding, the core bracket is automatically retracted, the die is closed and the next cycle started.