A pouch can reach the filling station gripped, upright, and present to every sensor on the machine, and still be closed. The dose then lands on the outside of it and in the seal jaws.
Filling an unopened pouch has no equivalent on a roll-fed line, because a form-fill-seal machine forms the bag it fills. A premade-pouch machine instead lifts a finished pouch off a magazine, pulls it open, and must prove the opening happened before it doses.
Everything worth specifying on this machine class follows from that sequence and from two inputs you control: the pouch format you buy and the way your material flows.
A rotary premade-pouch machine runs a fixed station sequence on an indexing carousel, six to ten stations per revolution with eight the common build. An operator loads the magazine, a feed roller advances the stack, and a vacuum arm lifts one pouch into the grippers.
Every station shares one index dwell, so the slowest station sets the ceiling on pouch-filler output.
Static cling, the tack of a matte laminate, and the weight of the stack above will all lift two pouches as one, and the second rides the whole cycle unfilled. Separation happens at the pick station, so run a full magazine to empty during acceptance testing, not the half stack a sales demo uses.
Paired vacuum cups on the upper and lower faces pull the pouch apart while compressed air from a nozzle inflates it. An open blade then moves into the gap and holds it there through the fill.
A photoelectric sensor confirms the result, with its detect point referenced to the carousel encoder and set on the touchscreen. If the pouch did not open, or only partly opened, the filling station does not dose and the sealing station does not seal.
The critical specification to verify is which condition that interlock reads. Two sensors under the grippers confirm a pouch is present, and a pouch can be present, gripped and still shut.
Four pouch features change hardware on a premade-pouch machine: a zipper, a spout fitment, a flat bottom or gusset, and the size envelope itself.
| Pouch feature | What the machine needs |
|---|---|
| Zipper, reclosable | Servo zipper opener plus jaws that separate the top |
| Plain top | Vacuum pads and air blower only, no mechanical jaws |
| Spout fitment | Grippers sized to the fitment, pouch held by the body |
| Flat bottom or gusset | Bag supports that keep the base square |
Stand-up, zipper and flat-bottom formats share one rotary premade bag filler frame, and only the opener, gripper and bag support change between them.
The size envelope is the limit buyers skip past: one published eight-station rotary family covers bag widths of 55 to 300 mm, lengths up to 350 mm and fill volumes of 5 to 2500 g.
Check your largest pouch against the width and length limits before the tooling conversation, because a format outside the envelope needs a different frame size, not a changeover kit.
Material behaviour decides two separate things on a premade-pouch machine: which dosing head can hold the weight, and what the product does to the seal on its way in.
Free-flowing granules run on a multihead weigher, where a bank of load cells weighs partial doses and the controller combines the ones closest to target weight.
Hygroscopic, non-free-flowing powders arch above the outlet and cling to the housing, so they need an auger with an agitator, a closed hopper and a pressure-equalisation vent.
Auger wear is the quiet accuracy problem. Rounded flight tips displace less per revolution than new ones, and an open-loop volumetric head has no way to notice.
Under actual production conditions the same powder behaves as two materials: below roughly 30 % relative humidity the fines cling to housing and film, above 50 % it clumps.
The pouch is held wide open by vacuum cups and a blade for the whole fill, which puts fines on the inner seal face before the jaws close. Machines built for powder answer with a dust-removal device at the opening station and a whisk-motor cleaner before the seal.
A contaminated seal can look closed and still peel below spec, which is what ASTM F88 measures. The dye-penetration method for a non-porous laminate is ASTM F3039, not the porous-only ASTM F1929.
A fill-accuracy percentage means nothing until a fill weight is attached to it. In the United States the tolerance a filled pouch is checked against is a gram figure that changes band by band.
NIST Handbook 133-2023 gives a maximum allowable variation, the shortfall one package may show: 3.6 g on a 36 to 54 g pouch, 21.7 g on a 489 to 571 g pouch.
Read as a share of the label, the allowance tightens as the pouch grows, from 7.2 % at 50 g to 4.3 % at 500 g. One percentage quoted across that whole range is generous at the small end and demanding at the large one.
The filling accuracy depends on the weight band. A dosing spec worth comparing quotes grams inside a stated range, such as ±0.1 g under 50 g and ±0.5 g from 50 to 500 g.
The same NIST handbook caps a checkweigher’s scale division at one sixth of the maximum allowable variation for that package size:
Scale division is therefore decided by your pouch size, not by the machine builder, and it belongs in the request for quotation.
Two questions change more about a premade-pouch quote than anything else on the datasheet, and both cost nothing to ask. Which condition does the no-fill interlock read, presence or open? And what is the dose tolerance in grams at your pouch weight?
Specifications fail the same way each time: the buyer treats a bag-present sensor as proof the pouch opened, and a percentage as proof the machine can hold a weight.
Neither error shows up on a demonstration run with a fresh full magazine and a free-flowing test product, which is why both belong in acceptance testing rather than the sales conversation.
