Meaning
Continuous loss-in-weight systems control discharge rates by measuring mass depletion from a hopper over time. A loss in weight feeder adjusts internal screw speed or vibratory tray frequency to deliver precise mass flow rates of resin pellets or powders into compounding extruders. The system isolates material metering from bulk density variations that disrupt volumetric feeding devices.
Operation stops functioning in gravimetric mode during hopper refill cycles, temporarily shifting to volumetric control until weight measurements stabilize.
Dosing Mechanism
Digital load cells monitor hopper mass continuously while microprocessors calculate the time rate of mass loss. The loss in weight feeder dynamically adjusts motor output to match target mass flow rates during production.
Process Control
Dynamic extrusion operations rely on stable material feed to maintain consistent pipe wall thickness or film gauge. Fluctuations in bulk density caused by regrind size variations do not disrupt a loss in weight feeder because the controller continuously corrects screw speed based on actual weight loss. High-precision load cells damp mechanical vibration from surrounding plant machinery to protect gravimetric metering accuracy.
Proper controller tuning prevents feed rate oscillations during masterbatch and flame retardant addition.
Refill Refractory
Material replenishment introduces transient weight increases that temporarily disable active gravimetric control. During hopper refill, the loss in weight feeder locks its dosing speed at the last calculated volumetric rate until mass readings stabilize. Poorly timed refills or turbulent hopper loading create volumetric feeding errors that shift additive concentrations in the compound.
Automated refill valves open and close rapidly to minimize volumetric operation time.
