Grace Under Pressure
Posted date : May 27, 2009

With SOI-MEMS, Gefran’s Impact™ pressure sensors can go right into hot spots like the injection nozzles of plastics manufacturing systems.

An SOI-based MEMS device is at the heart of Gefran’s Impact™ I and J series sensor technology for the plastics processing industries. (Courtesy: Gefran)

Sensors are fundamental elements in the control of industrial processes. For plastic transformation processes such as injection, extrusion and blowing, “melt pressure” sensors help ensure plant safety, prevent excessive machine pressure, and increase performance thanks to a stable and optimum flow rate.

Gefran, a worldwide leader in systems and components for automation of industrial processes, is a top designer and manufacturer of melt pressure sensors. We have leveraged SOI-based MEMS technology in our new Impact™ range of sensors, which provides dramatic advantages over other market offerings.

Only on SOI

Because the sensing device sits directly behind the membrane that’s in contact with the molten plastic, sensors for these applications need to withstand up to 3000 bar of pressure and temperatures of up to 350°C (660°F).

The piezoresistor MEMS device is the “sensing element” that converts pressure into an electrical signal. SOI-MEMS is currently the only technology that enables us reach such high temperatures with optimal performance. Bulk silicon can’t go beyond 150°C due to the leakage current at the p-n junction of piezoresistors.

Moreover, with SOI we have good process yields and ease of manufacturing.

Heat & reliability

These SOI-based MEMS sensors are particularly well suited for plastic extrusion systems used in the food, beverage and pharmaceutical industries, where they can replace traditional mercury-filled sensors.

For blow-molding systems used in making plastic bottles for water and other consumables, the MEMS technology allows us to have a process membrane that is up to 35 times stronger and can function continuously for over three million cycles.

With the die-size reduction enabled by SOI, the system is so small that the entire sensing unit can be installed in an injection nozzle or other very narrow spot. That means the measurements can be taken at the right place in real time, for far greater process control and automation precision.

For our customers, this little piece of technology makes an enormous difference.

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