Gravimetric dosing with ProTec systems.

Functional principle

Gravimetric dosing is based on weighing the bulk material to be metered, so weight is the only measured variable. A number of load cells integrated in the dosing system constantly detect the weight of the individual components and report the values in real time at very short time intervals to the PLC-based controller. Dosing proceeds by the loss-in-weight principle, in which the reduction in weight of the materials bins over the course of the process is used as a measured variable.

The controller continuously compares actual throughput with a stored nominal throughput (nominal/actual comparison) and, in the event of any deviation, corrects the speed of the discharge screw. Gravimetric dosing systems also automatically equalize any differences in bulk density. Signal coupling to the extruder controller ensures that any abrupt changes in throughput are identified and control behavior is optimized accordingly.

ProTec can supply SOMOS^® Gramix gravimetric dosing systems to meet various requirements. Gramix stands for GRAvimetric dosing and MIXing. SOMOS^® Gramix dosing units continuously gravimetrically meter and mix flowable bulk polymer materials, such as pellets, microgranules, powders and regrind.