Benchmarks

Dosing and Loss-in-Weight Feeding KPIs: Benchmark Ranges and Targets

The KPIs that matter on gravimetric dosing lines, world-class versus typical benchmark ranges, how to measure each, and the practical levers to improve them.

Dosing coefficient of variation is the headline accuracy KPI. Typical bulk feeders run a CV of 1.0 to 2.0% at rate; well-tuned LIW feeders on free-flowing material hit 0.5 to 1.0%, and world-class twin-screw units on cohesive powders reach 0.25 to 0.5% (2 sigma). Measure it from at least 30 consecutive catch samples, never from the controller's own display. If CV sits above 2%, the lever is usually screw geometry and refill frequency, not the loop tuning. The Dosing Accuracy calculator gives you the CV to compare against these bands.

Batch pass rate, the share of batches inside the tolerance window on the first attempt, should sit at 98 to 99.5% for a mature line. Below 95% you are losing an hour or more per shift to rework. Track it per recipe, because a single cohesive or micro-heavy formula often drags the plant average down 2 to 3 points. The improvement lever is matching feeder resolution to the tightest ingredient: widen the window only as a last resort. The Batch Tolerance Window calculator shows how per-ingredient bands combine so you target the real offender.

Give-away percentage is the money KPI that plant managers under-watch. World-class fill lines hold average give-away to 0.1 to 0.3% above target; 0.5 to 1.0% is common and quietly expensive. Measure it as the mean of (actual minus target)/target across a week of batches, weighted by mass. On a 4,000 t/year line at $2.40/kg, moving from 0.8% to 0.25% is roughly $53,000 recovered. The lever is reducing feeder scatter so you can lower the safety bias without dropping below minimum weight. The Ingredient Variance Cost calculator converts the percentage into dollars.

Feeder utilization separates a rate problem from a scheduling problem. Continuous process lines target 85 to 92% utilization; batch and high-mix plants realistically run 60 to 75%. Compute it as running time over available time per shift. If throughput is short but utilization is already 88%, you have a speed limit, not idle time; if utilization is 58%, chase changeover, starvation, and refill dwell first. The Feeder Utilization calculator buckets available time into running, refill, and idle so the gap is visible rather than assumed.

Refill frequency is an underrated stability KPI because every refill drops the feeder into volumetric control. Target fewer than 3 to 4 refills per hour on a primary feeder; more than 6 means the hopper is undersized for the rate and open-loop time exceeds 5% of run time. Measure it directly from level trips, and pair it with usable-mass ratio, ideally keeping the low trip at 20 to 30% so you carry 70 to 80% usable inventory. The Hopper Refill Interval calculator shows how bigger hoppers or lower trips extend the interval.

Gravimetric-to-volumetric delta during refill is the KPI that bounds accuracy loss. Keep the delta under plus or minus 1% by controlling bulk-density swing and keeping refill dwell short. A world-class line sees density variation under 2% batch to batch and refill dwell under 15 seconds, so the diluted batch error stays under 0.1%. If the delta creeps past 2%, the levers are pre-blending for density consistency and faster refill valves. The Gravimetric Vs Volumetric Delta calculator lets you test the combined effect before it shows up in reject data.

Calibration drift is a maintenance KPI: the feed factor k should not move more than 1 to 2% between scheduled checks. Verify weekly on high-volume feeders and monthly on micros using a timed catch test, and log the drift. A feeder drifting 3 to 5% between checks needs mechanical attention, worn screws, bearing drag, or a loadcell zero problem, before you retune software. The Loss-In-Weight Calibration calculator reports linearity across the speed range so you catch a low-speed factor drop that a single-point check would miss.

Roll these into a scorecard reviewed weekly: dosing CV under 1%, batch pass rate above 98.5%, give-away under 0.3%, feeder utilization above 80%, refill frequency under 4/h, volumetric delta under 1%, and calibration drift under 2%. Set a stretch target one band tighter than current and attach one owner and one lever per KPI. The common failure is chasing utilization for output while give-away and CV erode margin unwatched. Pair the Feeder Rate and Feeder Utilization outputs with the accuracy and cost calculators so throughput gains never come at the expense of yield.

Published 2026-07-01.