Monitoring & Control Systems ensure contant product quality in Injection Molding

Machine monitoring in injection molding

Custom solutions for manufacturers of injection molding machines and hot runners (OEM)

The cavity pressure signal is a valuable means of monitoring the injection molding process and controlling the injection molding machine. Kistler offers customized charge amplifiers that provide injection molding machine manufacturers with latest-generation solutions at reasonable cost. Special sensor solutions for melt pressure measurement make it possible to control the melt flow in the plasticization unit and the hot runner nozzles.

Connectivity of our charge amplifiers for process monitoring with the injection molding machine

Charge amplifiers from Kistler for piezoelectric sensors enable easy connectivity to the injection molding machine.

The piezoelectric input signal of a charge amplifier requires a highly insulated connector. Kistler charge amplifiers come with a multichannel connector that connects 4– to 8 channels with just one cable. Each input channel is also equipped with a standard BNC connector. 

The preferred output signal in most cases is a digital bus signal, because this eliminates the additional effort of A/D conversion in the PLC. The VARAN bus has now become the standard in the injection molding machine segment of the mechanical engineering industry for injection molding machines. Our charge amplifiers are additionally equipped with conventional 0 to 10 V analog outputs, because these are also used frequently.

Using piezoresistive pressure sensors to measure melt pressure in the injection molding machine and hot runner

Melt pressure measurement in injection molding can be done with semiconductor-based piezoresisive sensors from Kistler.

When measuring the melt pressure in the injection molding process, there are many cases where it is impossible to define a zero pressure that can be used for the Reset-Operate signal of a piezoelectric charge amplifier. In this application, the process requires a continuous measurement for an indefinite time. 

Given the dynamic, high temperatures and the high mechanical load, a piezoresistive sensor is the best choice. This measurement principle is based on a resistance variation depending on pressure or tension within piezoresistive semiconductor chips. The resistance variation when the measurement chip is loaded is significantly higher than with conventional metal-based strain gauges.