Friedrichshafen, Germany — Sensors mounted inside injection molds have proven themselves in thermoplastic molding by monitoring pressure and temperature variations and using the data to adjust process parameters.
But such sensors may have an even more important role to play in LSR and multi-component LSR/thermoplastic molding, since the extremely low viscosity of liquid silicone rubber is difficult to control until it cures in the mold.
At Fakuma 2018 in Friedrichshafen, Robert Vaculik, head of the business field plastics within the industrial process control division at Winterthur, Switzerland-based sensor producer Kistler Instrumente AG, talked about the role played by sensors in injection molding LSR.
Kistler sensors monitor both temperature and pressure within molds in real time during molding, with a piezo-electric crystal for pressure and a thermocouple element for temperature. Molders use the technology to optimize process parameters and ensure they do not deviate beyond set tolerances.
Vaculik said Kistler has had sensors for LSR in the market for some time. Within 14 sensor models designed for direct integration into molds, seven are suitable not only for thermoplastics, but also specifically for LSR processing.
Within the seven sensor series for LSR, only the 4 millimeter 6190C series monitors both pressure and temperature, while the 6 mm diameter 6152A series measures only pressure, and all of the other five monitor only temperature.
The smallest 6193B series has a 1 mm diameter and senses only temperature. Vaculik admits that "We are a little too large for some LSR parts when it comes to combined pressure and temperature monitoring," referring here to the 4mm 6190C series.