Loss In Weight Feeder
A loss-in-weight feeder is a gravimetric metering device that controls discharge by measuring the rate of weight loss over time from a weighed hopper and feeder assembly. The controller compares the measured weight-loss rate to the target feed rate and adjusts screw speed, belt speed, or vibratory output to maintain precise mass flow in units such as kg/h or lb/min.
In a manufacturing setting, a loss-in-weight feeder sits on load cells and continuously weighs the entire active section, including hopper and material. It is used where ingredient consistency matters, such as plastic compounding, food blending, additives dosing, and any process feeding powders, granules, or other bulk solids at a controlled mass rate. Because the system measures actual mass drawdown rather than inferring flow from screw speed alone, it produces a reliable consumption signal. On the shop floor, operators monitor setpoint, actual feed rate, hopper level, refill timing, and alarms for bridging or starvation. During refill, the controller shifts to predictive or volumetric mode until gravimetric operation resumes. This supports tighter raw-material reconciliation by converting physical drawdown into a controlled process-use signal, reducing overfeed and underfeed while improving batch accuracy.
Why is a loss-in-weight feeder more accurate than a screw feeder run only by RPM?
Because it measures actual mass loss per unit time, not assumed volumetric output. That allows the controller to correct for bulk-density changes, moisture shifts, particle segregation, and flow variability.
What variables does the controller typically use?
The controller uses live hopper weight, calculated rate of weight loss, feed-rate setpoint, refill threshold, and historical speed/weight data during refill transitions.
What happens when the hopper reaches minimum weight?
The system pauses pure gravimetric control, refills the hopper, and temporarily estimates output using prior behavior or volumetric assumptions until the weigh section stabilizes again.