Precise temperature-compensated pressure measurement
But now, the measurement technology experts at Kistler have unveiled the innovative 4004A melt pressure sensor: with an operating and measurement range of up to +350°C, it can be used directly in the hot runner to deliver precise measurements of pressure and temperature in injection nozzles and extruders. Thanks to its ultra-compact dimensions – its frontal diameter is merely 3 mm – this sensor can also be installed in small nozzles with no critical changes to injection behavior.
For the two different applications, the pressure sensor 4004A features two separately calibrated pressure ranges that ensure high accuracy: up to 2,500 bar for the hot runner in injection molding, and up to 1,000 bar for additive manufacturing. "The measured melt pressure can be used to control the plant in order to optimize the flow behavior of the plastic melt," according to Dr. Robert Vaculik, Head of BU Plastics at Kistler. "If the process parameters remain constant but there are changes in the pressure signal, that would suggest possible anomalies – deposits in small nozzles, for example, wear in the mechanics or melt backflow. Process monitoring with this degree of accuracy was never possible until now."
Intelligent hot runner and melt pressure control
The new pressure sensor allows easy access to its internal key parameters via TEDS (Transducer Electronic Data Sheet). Thanks to a sensor diaphragm made of hardened steel and its IP65 degree of protection, the 4004A can be used for applications involving fiber-reinforced plastics. It can also be operated without problems in the medtech and food packaging sectors – no media such as oil or mercury are used to transmit the signals.
The temperature-compensated pressure signal can be accessed via the analog output or the sensor's RS232 interface, so it can be acquired and visualized with measuring equipment such as the ComoNeo process monitoring system by Kistler. Closing words from Dr. Vaculik: "With this innovation, we’re offering our customers a digital measuring chain for hot runner and additive manufacturing applications – the key to smarter monitoring of the melt flow in hot runner systems as well as additive manufacturing systems."