Tiny Cavity Temperature Sensor Offers Control For Injection Molding Processes

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Tiny Cavity Temperature Sensor Offers Control For Injection Molding Processes

Boasting a 0.6 front diameter, a company's product is being touted as the smallest cavity temperature sensor in the world. "A lot of [manufacturers] are making smaller and smaller medical devices with more moving parts inside," says Susan Montgomery, president of Priamus System Technologies LLC (Brunswick, OH). "In order to measure what's going on when they're manufacturing these parts, we created a smaller sensor."

The sensor is placed directly in the mold cavity, enabling operators to monitor and control the injection molding process. By measuring both cavity pressure and temperature, the quality of a molded part is more accurately assessed, as compared with measuring only the pressure, according to the company. The sensor can withstand temperatures up to 600°C.

"We've always been looking at cavity pressure as part of the pressure-volume-temperature relationship...and what cavity temperature does is it gives you the ability to see where your melt front is," explains Montgomery. "For example, if you have a shift in material viscosity, you can see that quite clearly with cavity temperature."

When the sensor is used in conjunction with the company's signal conditioning unit and control system, molders can go beyond just observing temperature changes. Operators can use the signals from the sensor and initiate an action in real time, according to Montgomery. In less than half of a millisecond, a worker can perform a function such as open or close a valve gate, she adds.

A Type N thermocouple was selected to make the sensor since Type J thermocouples consist of corrosive materials and Type K thermocouples can show inaccuracies to 3°C even in lower temperature ranges, according to Priamus. The sensor has been specially designed to meet the needs of small medical devices. Suited for use during the injection molding process, the sensor has applications in the molding of such products as pipettes, syringes, implants, and connectors.

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