Process Development Moulds for sensor with multiple tasks need special hot runners

Editor: Eric Culp

The combination of extremely small hot runner nozzles and a valve gate together with a sophisticated mould allows for the production of small automotive rain/light sensors.

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This mould allows for all three of the polycarbonate materials needed for the sensor to be run through a single manifold.
This mould allows for all three of the polycarbonate materials needed for the sensor to be run through a single manifold.
(Source: Heitec)

As a motorist, one values anything that helps make driving easier, and rain/light sensors play that role. For example, when dusk settles in or a certain brightness value is no longer attained, the headlights turn on automatically.

A computerised friend in weather both fair and foul

Car wipers spring into action when the rain sensor reacts accordingly, or else the sun sensor sends corresponding data to the climate control unit and the air conditioning responds. Another function of the sensor is that the blower starts when humid air is detected inside the car.


Component supplier Friedrichs & Rath, their mould shop SK-Werkzeugbau and hot-runner supplier Heitec Heisskanaltechnik co-operated to create an innovative version of a small rain and light sensor, the RSL 4.0, which is only 34 mm in diameter. The sensor has been designed for today’s cars and only measures 50 mm in total length.

See:Companies form group to research lightweighting

Three firms, three materials, a seven-year partnership

The three companies have been working together successfully on multi-component and sensor solutions for more than seven years and are familiar with the three different polycarbonates, the sensors are made of: a clear type, an infrared type and black for the housing.

According to Heitec, the first such sensors produced were significantly larger and had more space for hot runner nozzles and the internal workings of the tool. Over the years, the devices have been getting smaller. In the beginning, the plastic articles were also injected via cold-runners and later injected directly with hot runner nozzles using a hot tip. Today’s applications, however, require small hot-tip nozzles that allow to gate directly onto the lenses and valve gates to attach the housing.

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