Fundamentals of Contact Temperature Measurement

Melt contact temperature can be measured in addition to mold cavity pressure. This is done using either separate temperature sensors or combined pressure/temperature sensors. The advantage of combined measurement is that both can be taken at the same place. Also, only one sensor is needed in the mold to measure both values.

Before the melt reaches the sensor position, the temperature sensors measure the temperature of the mold surface. After that, they measure the melt contact temperature.

Because of the high cooling rates in thermoplastic injection molding and the inertia of temperature sensors, the temperatures measured here are lower than the melt temperature. However, the maximum values provide a good reflection of the local melt temperature.

It is worthwhile using combined pressure/temperature sensors or additional temperature sensors if thermal influences on the injection molding process – such as mold temperature or melt temperature – are to be monitored or analyzed.

Temperature sensors on their own are not suitable for quality monitoring; for process control, they are only suitable up to a point. Temperature measurement represents only a local perspective on the molded part.