Cavity temp sensor fits anywhere

Cavity temperature sensors are gaining in importance, especially for open and closed loop control during injection molding. When the plastic melt reaches a sensor, it sends a real-time control signal. This manufacturer of these sensors argues that, in contrast to cavity pressure sensors, cavity temperature sensors ensure the position of the melt front is known and can be systematically controlled. For instance, programming of delay times can be used so that weld lines can be moved to a certain position during the process and kept at this position constantly. In order to react fast enough for real-time controls, both sensors as well as the equivalent electronics must be designed accordingly. The delay time from the melt reaching the sensor until sending a switching signal may not exceed very few “milliseconds” because otherwise valve gates or core pullers react too late, and the melt fills the cavity without control.In order to reach these fast reaction times, first of all the mass of the sensor body must be kept very small. A cavity temperature sensor in the body of a cavity pressure sensor is usually far too slow to detect the melt front on time. Combined pressure/temperature sensors also do not make much sense because they must be placed separate from each other due to the different measuring principles: cavity pressure always near the gate, and cavity temperature usually near the end of fill or wherever they shall be used for control purposes. A new extremely small cavity temperature sensor (type 4009A/4010A) with only 0.6 mm front diameter is offered, and claimed to be the world’s smallest cavity temperature sensor. Type 4011A/4012A is equipped with the same front diameter but has a longer measuring body.These miniature sensors are used in applications such as in the optical or medical industry. Priamus System Technologies, Schaffhausen, Switzerland; +41-52-632-2605; www.priamus.com