Dosing Basics: How Dosing Works
A Doser, or Feeder is designed to introduce minor ingredients to the flow of main ingredients at the throat of a processing machine. Common components include a throat adaptor, DC motor, a metering auger and speed/interfacing control.
Dosing is triggered or speed-governed by the processing machine itself. In injection molding, as the machine cycles, a dose, calibrated to the shot size of the molding machine and amount of additive required is introduced into the gravity flow of the other materials by a rotating auger. In extrusion, as the machine operates continuously, constant dosing is provided at a certain rate, in step with the speed of the extruder.
In some cases, multiple dosing devices may be connected to a single machine throat for the introduction of multiple additives, or simply to provide rapid changeover ease with redundant dosing units already installed. In other cases, other materials, like regrind may be dosed into the flow in addition to or instead of additives. Often times, some form of mixer may be installed below the dosing device to enhance the blending of the newly introduced additives with the base resins.
The dosing device’s throat adaptor is critical to assure: