Use an auger filler for powders — anything that dusts, bridges in the hopper, packs down or sticks — and a volumetric cup filler for free-flowing granules and small solids that fall into a cup and level off the same way every cycle. Neither filler weighs anything: both meter a volume and rely on the product’s bulk density to turn that volume into grams. So the choice is made by how your product flows, not by which filler carries the higher accuracy label.
An auger filler doses by turning a screw — the auger — inside a close-fitting tube for a set number of revolutions; each revolution pushes one swept volume of product out of the nozzle into the bag. A servo sets the turn count, and the auger’s diameter and pitch set the dose range. An agitator in the hopper keeps the product loose and feeding into the flights.
What makes it the powder filler is that the flights move the product — a cohesive powder that would never fall through an open funnel is still dragged down the tube in a consistent state, and the dust stays inside the tube instead of drifting onto the seal jaws. The price is a product-specific auger and tube, more parts to strip for cleaning, and a higher machine cost.
A volumetric cup filler doses by letting product fall under gravity into a cup of fixed volume, scraping the top level, and then opening the cup’s bottom over a funnel so the contents drop into the bag. The cups sit in a rotating plate under the hopper; each pass fills, levels and discharges one dose. Dose size is set by cup volume — telescopic cups adjust height for small changes, and a larger change means swapping the cup set.
The whole method rests on one assumption: that the product fills the cup and levels off identically every cycle. Free-flowing granules do that; a cohesive powder bridges over the cup mouth and fills it partly — and with nothing but gravity moving the product, the cup has no way to correct it.
The auger filler takes powders and anything that dusts or sticks; the cup filler takes free-flowing granules and wins on speed, changeover, cleaning and price.
| Feature | Auger Filler | Volumetric Cup Filler |
|---|---|---|
| Dosing principle | Rotating auger screw | Fixed-volume measuring cups |
| Best for | Powders and fine granules | Free-flowing granules and small solids |
| Typical products | Flour, milk powder, spices, protein powder | Rice, sugar, beans, seeds, candy |
| Accuracy | High | Moderate to high |
| Handles dusty products | Excellent | Less suitable |
| Handles sticky powder | Better | Poor |
| Filling speed | Moderate to high | High |
| Changeover | May require auger/tool changes | Usually simple cup adjustment |
| Cleaning | More components to clean | Relatively simple |
| Cost | Usually higher | Usually lower |
Read the accuracy row as “on the product each is built for”, not as a property of the filler. On a free-flowing granule a cup holds weight as well as an auger and cycles faster; on a cohesive powder the auger’s edge is that it can dose the product consistently at all — a cup cannot fill or level it repeatably.
The auger filler, for almost every powder — flour, milk powder, cocoa, spices, protein — and the exceptions are the coarse, dry powders that behave like granules and pass the tap test below. The property that decides it is how much the powder’s bulk volume changes between loose and settled, because that is the spread in weight a fixed volume can deliver.
You can measure it at the bench. Pour the powder into a graduated cylinder and read the loose volume V0, then tap the cylinder until the level stops dropping and read the tapped volume Vf.
Compressibility Index (%) = 100 × (V0 − Vf) / V0
The USP <1174> flowability scale grades that number:
| Compressibility Index (%) | Flow character |
|---|---|
| ≤10 | Excellent |
| 11–15 | Good |
| 16–20 | Fair |
| 21–25 | Passable |
| 26–31 | Poor |
| 32–37 | Very poor |
| >38 | Very, very poor |
Excellent or Good, and a cup will hold weight. Fair is a cup at its limit — it fills, but the weight walks as the hopper level changes. Passable or worse means a fixed cup can deliver a weight that varies by that whole index between a loosely filled cup and a settled one, far outside any pack tolerance; that is auger territory.
What the auger cannot fix is the slow drift over a shift — hopper level, humidity, a new lot. The standard fix is a checkweigher after the bagger trimming the turn count, and because it corrects after a pack is weighed rather than while it is filled, a fast-drifting product still needs its hopper level held steady.
Dust decides the borderline cases. A fine powder dropped through a cup’s open funnel coats the forming tube and the seal jaws, and powder in the seal is the leaker you will be chasing all shift; the auger’s nozzle sits inside the forming tube and the flights hold the product until it leaves the tip. Cocoa is the extreme case — on a cocoa powder line the dust argument alone settles it.
The cup filler, for granules that flow freely and have a uniform particle size — rice, sugar, beans, seeds, candy. Their bulk density barely changes between loose and settled (the Excellent and Good bands above), so a fixed cup delivers a fixed weight, and the cup does it faster, with a cup change instead of an auger change and a rinse instead of a strip-down.
The auger is the wrong tool here for a mechanical reason: the flights shear whatever sits between them and the tube wall. Coated candy chips, seeds and freeze-dried pieces break, brittle granules make fines that then dust, and a coarse particle jammed between flight and tube stalls the drive. A free-flowing granule also has no use for the auger’s one real advantage — there is nothing to drag.
Two granule cases blur the line. Fine granules that flow but dust — instant coffee, drink-mix bases, some spice blends — run on either filler, and dust at the seal decides. Mixed-size granules segregate in the hopper as the fine fraction sinks, so a cup’s weight drifts through the run; an agitated hopper helps, and an auger built for granules tolerates the mix better.
A high-value granule that must hold a tight weight — a nutritional granule in a pouch, for instance — is not a volumetric job at all. A multihead weigher weighs each dose instead of assuming its density, and that is what belongs on the line.
Choose by how the product flows first and by what the line needs second: an auger if the product bridges, dusts or scores Fair or worse on the tap test; a cup if it flows freely and you want the faster cycle, the quicker changeover, the simpler wash-down and the lower price. Run the checks in this order:
The accuracy row is a cost row, and the law is what makes it one. For e-marked packs sold in the EU, the prepackage directive puts a floor under average contents at the nominal quantity, with no ceiling on overfill. A filler that scatters forces you to raise the target weight until the low tail clears that floor, and every gram of margin is product given away on every pack. On rice or sugar the cup’s lower price wins easily; on protein powder or infant formula, the auger’s tighter dosing recovers its premium in giveaway.
Do not bank the filler’s speed until you know the bagger’s. On a vertical form-fill-seal machine or a pre-made bag machine the dosing head is a module above the forming tube or the pouch station, and bag length, film and seal time set the cycle; the filler only has to keep up. If one line will run both a powder and a granule, specify the bagger with a dosing-head interface that accepts either and buy two heads, rather than compromising one product on the wrong filler.
Powders go to the auger and free-flowing granules go to the cup, and the tap test tells you which side of that line your product sits on. Classify the product before you ask for the quote, and the filler choice makes itself.
