The Type 4004A piezoresistive melt pressure sensor from Kistler opens up a new chapter in the evolution of measurement technology. Thanks to its front diameter of a mere 3 mm, this sensor can be operated directly in injection nozzles and small extruders: it can measure both pressure and temperature in direct contact with the plastic melt. The 4004A is equally ideal for use with hot runner systems in injection moulding, and in additive manufacturing.
The plastics processing industry is following a clear trend: intelligent moulds, injection moulding machines and 3D printers are supplying users with the maximum possible information about the process. As well as enhancing transparency, this allows ongoing optimisation of the production process.
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 behaviour.
For the two different applications, the 4004A features two separately calibrated pressure ranges that ensure high accuracy: up to 2,500 bar for the hot runner in injection moulding, and up to 1,000 bar for additive manufacturing. “The measured melt pressure can be used to control the plant in order to optimise the flow behaviour 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 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 fibre-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 analogue output or the sensor’s RS232 interface, so it can be acquired and visualised 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.”