For the first time in the history of injection moulded passenger compartment components, electrical heating systems can now be integrally moulded with the component. The injection moulding system is based on the use of decorative materials that are provided on their reverse sides with a special electrically conductive coating. This coating has been developed by the firm of Georg Kaufmann Formenbau AG, Busslingen/Switzerland, in exclusive collaboration with a partner company. These conductive decorative materials can be used in conjunction with various processes developed by Kaufmann and back-moulded in injection moulds manufactured by this company.
Electrically heated trim keeps passenger compartments warm When an electric current flows through a conductive layer, the latter becomes hot by reason of its electrical resistance and radiates heat to the interior of the passenger compartment. Thus it is possible to heat the passenger compartment uniformly and efficiently. Tests have shown that surface temperatures can be well over 40 °C, while the actually desired temperature can be regulated via the current input control. The electric power consumption per square metre of heated surface area is relatively low. Moreover, the poor heat conductivity of the plastic body of the component prevents dissipation of heat to the exterior of the vehicle.
For the electrical connection, copper wire or mesh are integrally moulded with the component during injection moulding, their precise position and configuration depending on the actual design of the component. Tests have shown that - apart from the conductive coating - no further adaptation is necessary, neither to the mould nor to the process. Mould design - the key to production integration Many of the innovative, low-cost technologies developed by Kaufmann are suitable for the production of surface-decorated moulded parts with integrated heating systems, the main ones being:
- Back-moulding technology - i.e. the decorative material is placed into the mould cavity prior to injection of the plastic melt.
- Injection-compression, i.e. the injection of the plastic melt while the mould is still slightly open. This ensures a more gentle treatment of the decorative material.
- Duo Lamination, i.e. the moulding of parts with two or more different decorative materials in just one injection moulding machine using a rotating cube-shaped mould.
- The Varysoft process, i.e. the use of a slide-table mould for the production of passenger compartment parts with soft-touch effects exactly where they are needed for comfort.
It is precisely in conjunction with the Varysoft process that virtually any shape of part can be produced not only with a layer of foam of varying thickness, that is to say, with comfort zones exactly where they are required most, but also with an additional heating function. These passenger compartment parts offer every possible advantage in terms of tactile and visual appeal, design and comfort, and can also be produced at extremely low cost.
Besides their suitability for automotive applications, these surfaceenhanced parts with integrated heating functions can also be used, for example, for the heating of railway and cableway carriages and for the warming of ski lift and stadium seats.