Loss-in-Weight Feeder Applications by Industry | PEGE

Gravimetric feeding is not difficult in theory. It is difficult in practice, because material rarely behaves the way the datasheet says it will. Powder bridges in the hopper. Fine toner aerates and floods. Chopped fibre wraps around the screw. Maleic anhydride solidifies the moment the line cools down. A grade that ran perfectly in March arrives in June with a different bulk density and a different angle of repose.

PEGE has spent more than ten years designing loss-in-weight feeders around that reality rather than around a catalogue drawing. Our range now covers six feeding platforms and twenty-one models, from 0.3 kg/h of micro-additive to 2,000 kg/h of granulate. Each platform exists because a group of materials refused to run properly on a standard screw.

What follows is where those platforms do most of their work, and which process problem each one is there to solve.

Industries we serve

1. Lithium battery and energy materials

Battery materials combine the two hardest feeding conditions at once: very high value per kilogram, and very poor flow behaviour. Cathode powders are fine, cohesive and often need three or more components — active material, carbon source, additives — dosed continuously and in the correct ratio, hour after hour, on a line that cannot afford a drift event.

PEGE feeders run on cathode and precursor lines, on anode material preparation and on pilot lines feeding twin-screw compounders. Multi-component systems of three to six feeders are common; one reference installation in cathode material production runs fourteen continuous lines. Additive streams that sit below 1% of the recipe are handled by the PG-FT Micro twin screw at rates from 0.3 kg/h, while granulated material moves through the PG-FW single screw up to 2,000 kg/h. Refill sequencing, recipe management and trend logging are integrated so that a shift change does not become a quality event.

Typical duty: 0.3–1,500 kg/h per feeder, multi-component ratio control, continuous 24/7 operation.

Platforms: PG-FT twin screw, PG-FT Micro, PG-FW single screw.

2. Plastics compounding, masterbatch and sheet

Compounding lines live on recipe flexibility. The same machine may run an ABS two-component formulation in the morning and a silane crosslinkable cable compound in the afternoon, with a filler or flame-retardant stream that changes rate by a factor of five between jobs.

We build around that changeover. Pelletised polymer and granulate run on the PG-FW; filler, glass fibre and powder additives on the PG-FT twin screw, whose twin discharge and forced conveying cope with materials that would rat-hole in a single screw; colour and functional masterbatch on the PG-FT Micro, where a 0.3 kg/h minimum makes a 0.5% addition rate controllable rather than approximate. Sheet and cast-film lines use the same platforms in multi-component configuration, with all feeders reporting to one recipe controller so that a thickness change is a setpoint change, not a manual adjustment.

Typical duty: 0.5–2,000 kg/h, two to six components, frequent recipe changes.

Platforms: PG-FW, PG-FT, PG-FT Micro.

3. Petrochemicals and liquid additive dosing

Liquid additives are a different discipline: the medium is pumped, not conveyed, and the failure modes are thermal rather than mechanical. Maleic anhydride must be held above its melting point from tank to injection point or it sets solid in the line. Plasticisers such as DOP are easy to move but unforgiving to over-dose. Reactive and degradation-agent streams often need to be kept warm, isolated and traceable.

PEGE liquid loss-in-weight feeders cover 1–120 kg/h with 0.1–0.5 g sensitivity, a 316L pump head and check valve, and the balance of the wetted path in 304 stainless. Heated versions use a temperature-control unit for the jacket and separate electrical heating on the weighing tank, so that thermal expansion in the jacket does not show up as a false weight signal. A pre-melt configuration is available for solid-at-ambient products such as maleic anhydride, and refill tanks are themselves weighed so that the supply step never disturbs the dosing record. Installations run in Mexico, Turkey, Malaysia and across China.

Typical duty: 1–120 kg/h, heated or ambient, single or multi-stream.

Platforms: PG-FL liquid feeder (standard and heated).

4. Medical, hygiene and nonwovens

Hygiene and medical production punishes inconsistency quietly. Superabsorbent polymer, iron powder for exothermic products, SEBS for medical stoppers and meltblown polypropylene all share a property that screws handle badly: they are light, irregular or cohesive, and they bridge instead of flowing.

For these duties we often specify the PG-FZ vibratory tray feeder, which moves material by controlled vibration rather than by auger flight, at 50–2,000 kg/h. Flakes, agglomerates and irregular granules travel without being crushed or smeared, and the tray geometry can be matched to the discharge point. Where the additive rate is small — a stabiliser, an activator, a colourant — the PG-FT Micro takes over. One hygiene-material producer operates eight such lines; medical stopper and meltblown installations run on the same principle.

Typical duty: 50–2,000 kg/h, irregular or cohesive material, low additive ratios.

Platforms: PG-FZ vibratory tray, PG-FT Micro, PG-FT.

5. Fibres and films

Fibre and film lines are continuous by nature, so the feeder has to be stable over weeks rather than batches. Chopped carbon fibre bridges and wraps; BOPA and BOPP lines need a metering rate that holds flat enough to keep gauge variation inside tolerance; TPU cast film needs the plasticiser and colour streams to track the main extruder without hunting.

The PG-FT twin screw handles short fibre and mineral fillers, with a mirror-image U-shaped hopper that breaks arching before it starts. For very low addition ratios — below 0.5% — a gravimetric belt feeder is sometimes the better instrument, and we supply that as well, so the recommendation follows the duty rather than our product list.

Typical duty: continuous extrusion, 0.5–1,500 kg/h, low add ratios.

Platforms: PG-FT, PG-FW, gravimetric belt feeder.

6. Toner and difficult powders

Some materials are simply not free-flowing, and no amount of screw geometry fixes them. Toner is the classic case: extremely fine, highly cohesive, low bulk density, and prone to compacting against any surface that touches it. Flame retardants and fine functional fillers behave in a similar way at higher rates.

For these we use the PG-FP flexible paddle feeder. The hopper wall itself is flexible; external paddles massage it from the outside, so the material is kept in motion without any paddle, blade or agitator ever contacting the product. There is no smearing, no work-hardening, no metal-to-powder contact in the flow path, and the hopper can be pulled out and cleaned without tools. Throughput runs 20–800 kg/h, and the same principle is used on toner, flame-retardant and fine chemical installations.

Typical duty: 20–800 kg/h, cohesive or low-bulk-density powder.

Platforms: PG-FP FLEXHOPPER flexible paddle feeder.

7. Laboratory and pilot lines

Pilot lines are where a material is proved before anyone commits capital, so the feeder has to be accurate at small rates and honest about what it measures. Laboratory extruders, twin-screw compounders and research institutes use our micro and single-screw platforms from 0.3 kg/h upward, usually with quick-release hoppers and screw elements so that a formulation change takes minutes.

Data matters as much as mechanics here: weight trends, feed-factor history and alarm logs can be exported to Excel and reviewed offline, and the controller can be tied into the customer‘s own data system. Several of these units are installed alongside third-party compounders, including machines from European OEMs, where our feeder is the metering element and the host machine remains untouched.

Typical duty: 0.3–100 kg/h, frequent formulation changes, full data traceability.

Platforms: PG-FT Micro, PG-FW, PG-FZ.

Quick reference

Built for your process, not for a price list

PEGE does not compete on volume. We are not the supplier who ships a standard screw in a standard frame at the lowest price per unit and leaves the material problem with the customer. A feeder that is cheap to build and wrong for the material is the most expensive component on the line — it costs you yield, batches and, eventually, a shutdown.

Every system starts from the material: bulk density, particle size, angle of repose, moisture sensitivity, temperature window, required rate and turndown. From there we size the hopper, choose the discharge principle, set the refill logic and define the interfaces — inlet flange, discharge point, host extruder, control protocol, clean-in-place access, and the electrical and hazardous-area classification of your plant. Customers send us samples; we run them on the test stand and report what the feeder actually did before a purchase order exists.

That approach produces a lot of non-standard machines. Some have a heated jacket and a pre-melt circuit. Some have three feeders on one frame, or a hopper sized to fit a space no catalogue model would fit. Some run at 0.3 kg/h into a compounder from another manufacturer. This is the part of the business we are set up for.

Accuracy is a control problem, not just a screw problem

We specify ±0.5% of setpoint on most platforms, and ±1% on the smallest micro model. Those numbers are only meaningful with the conditions attached: continuous operation over at least thirty seconds, at a bulk density of 0.6 g/cm³, on a feeder that has been calibrated against the actual material. We state them that way on the datasheet because a precision figure without conditions is a marketing number.

Holding them is a systems job. The weighing hopper hangs from a cantilever beam with load cells selected for the actual working range, not oversized for safety margin. The drive is servo with a planetary reducer, so the response to a weight-loss deviation is fast and repeatable. Control runs a dual loop — speed-based PID combined with time-based correction — and the PI parameters self-tune and adapt to disturbance, which is what keeps the feed factor stable when the hopper refills or the material density shifts.

A platform that keeps moving

PEGE‘s feeder range has been revised continuously since the first unit went out. What began as a single-screw machine is now six platforms and twenty-one models, and most of the changes came from field reports rather than from a product plan: a hopper that bridged in a customer‘s plant in Russia, a seal that failed on a heated liquid line in Turkey, a refill cycle that disturbed the weight signal on a battery material line.

Because the architecture is modular, an installed feeder can be upgraded rather than replaced. Control platforms, hoppers, discharge elements and communication interfaces can be changed on site. Standard units support Ethernet remote diagnostics and optional PROFIBUS-DP, Profinet or Modbus RTU, so a support engineer can look at a trend curve without a flight. Hoppers pull out for cleaning without tools. The mirror-image U hopper that prevents bridging is fitted as standard on powder platforms, not sold as an option.

From one feeder to a complete line

Most projects start with a single feeder replacing a volumetric unit. Many end up as a full gravimetric system: multiple feeders on a common frame, refill and buffer hoppers, pneumatic or mechanical conveying, batching control and a single HMI that the operator already knows how to use. We have delivered multi-component systems of three to six feeders, and complete feeding packages for plants running more than a dozen lines.

If you are at the specification stage, send us the material data sheet and the target rate. If you do not have one, send a sample. We will tell you which platform fits, what accuracy is realistic for that material, and where the risk sits — before you commit to a line design.