Flow-Wrapped Packs and How They Move Through Secondary Packaging
A flow-wrapped pack is a continuous film seal around a product, formed horizontally as it travels through a flow wrapper at speed. The film wraps around the item; biscuits, bars, crackers, cakes; overlaps on the underside and seals at both ends with a crimp or fin. It's the standard primary pack format across snack foods, bakery and confectionery because it's fast, airtight and uses minimal material.
Flow wrapping happens upstream of secondary packaging. The packs leave the wrapper at 200, 400, sometimes 600 packs per minute, and they need to be collated, oriented and loaded into outer cartons or multipacks without jamming, scuffing or tearing the film. That handover, from flow wrapper to cartoner, is where most line stoppages happen if the timing, product handling or carton spec isn't right.
How it works on the line and where it fits
Flow wrapping is primary packaging. It creates the sealed individual unit. Secondary packaging: cartoning, case packing, shrink wrapping; groups those units for retail display, warehouse handling, or bulk shipping. Tertiary packaging is the pallet and stretch wrap that moves it all.
On a typical snack line, flow-wrapped packs discharge onto a conveyor, pass through a checkweigher and metal detector, then enter a cartoner infeed. The cartoner collates them, usually in rows or stacks, loads them into an erected carton, and closes the flaps. That carton might be shelf-ready, with perforated panels and branding on the outside, or it might be a plain transit case that gets unpacked at store level.
The cartoner's job is to handle each flow-wrapped pack gently and consistently. Film is thin, often under 50 microns, and even a small snag on a guide rail or reject gate can tear it. If the pack wobbles or skews on the infeed, the cartoner misses the load window and stops. If the carton blank is slightly out of square, the pack catches on the inside flap during insertion and the carton jams. These failures are predictable, they trace back to how the wrapper output and cartoner infeed were integrated.
Risks if poorly specified or maintained
Film damage during handling
Flow-wrapped packs have no structural rigidity. The film holds the product but it won't survive sharp edges, high-friction surfaces or abrupt direction changes. If a cartoner's infeed uses bare stainless steel guides without rounded edges, the film drags and tears. If the reject mechanism uses a pneumatic pusher instead of a gentle sweep arm, it punctures packs on the way out. You lose product, you contaminate the line, and you stop to clear it.
Inconsistent pack orientation
Flow wrappers discharge packs in a predictable orientation; crimp up, crimp down, fin seal to the side; but conveyors can flip or rotate them if belts are worn or timing is loose. Cartoners need packs to arrive in a specific position because the loading head is tooled for that layout. If half the packs arrive rotated 90 degrees, the cartoner rejects them or tries to force them in and jams. The line stops every few minutes, and the operator spends their shift re-orienting packs by hand.
Speed mismatch between wrapper and cartoner
A flow wrapper running at 400 packs per minute needs a cartoner that can sustain 400 packs per minute with the same collation pattern. If the cartoner is rated for 350, it's always playing catch-up, and the conveyor backs up. Packs queue on the belt, press against each other, and eventually jam the infeed. You either slow the wrapper down, losing capacity you've already paid for, or you run the cartoner past its sustainable rate and wear components faster.
Carton design that doesn't suit the pack
Flow-wrapped packs are slightly flexible. If the carton is dimensioned too tight, packs compress during loading and film seals can split. If it's too loose, packs shift inside during transit and the carton arrives at retail looking half-empty. Worse, if the carton blank has a gusset or pre-fold in the wrong place, the cartoner struggles to erect it cleanly and loads become misaligned. Every third or fourth carton jams, and throughput collapses.
Substrate changes that weren't tested
A snack brand switches from polypropylene film to a recyclable mono-material because retail buyers are demanding it. The new film has different friction properties and static behaviour. On the cartoner infeed, packs stick together or repel each other depending on humidity. They don't separate cleanly, and the collation sensor misreads the count. You reject full packs, load short cartons, and spend two days adjusting sensor angles and belt tension to get it stable again.
You'll see these on any line running substrates or formats it wasn't originally spec'd for, or where integration was rushed.
How machinery and spec changes solve those risks
Cartoner infeed design for film-wrapped products
Jacob White cartoners built for flow-wrapped packs use rounded guide rails, low-friction UHMW surfaces, and gentle lane dividers that separate packs without touching the film surface. Reject gates use swept arms or timed drop-away sections instead of pushers. Collation is done with soft belts or vacuum pick-and-place heads that grip the carton-facing side of the pack, not the film seal. The result is consistent handling at speed without damage.
Servo-driven timing and quick changeovers
Modern cartoners use servo motors on every axis; infeed, erector, loading head, closing station. That means you can adjust timing electronically to match the wrapper's discharge rate without swapping gears or pulleys. If you're running 400 packs per minute in the morning and switch to a different SKU at 300 packs per minute after lunch, you call up the recipe from the HMI and the machine retimes itself in seconds.
Tool-less format changeovers for multi-SKU lines
Snack lines often run five or six different pack sizes in a shift; single bars, twin packs, mini multipacks. Each one needs a different collation pattern and carton size. Cartoners with tool-less changeover systems use sliding guide rails with indexed positions and quick-release loading heads. An operator unlocks two levers, slides the rails to the new width, locks them, swaps the loading head if needed, and selects the recipe. Changeover time drops from 45 minutes to under ten, and you're not calling an engineer every time you switch SKUs.
Carton design collaboration
Jacob White works with customers at the design stage to ensure carton blanks suit both the packs and the machine. That means checking internal dimensions against pack tolerances, positioning pre-folds so they don't interfere with erection, specifying board grades that erect cleanly without spring-back, and planning perforation patterns for shelf-ready formats that don't weaken the carton during loading. When the carton is designed with the cartoner in mind, jams drop by 60% or more.
Substrate testing and adjustment support
When a customer switches to a new film or carton substrate, Jacob White's service team can attend site to test the material on the machine, adjust infeed speeds and sensor positions, and update the recipe library. That avoids the trial-and-error phase where production loses two shifts trying to dial in the new material. It also means the machine isn't being blamed for a substrate problem that needs to be fixed at the supplier level.
Trends and what buyers should plan for next
Recyclable and compostable films
Retail pressure on single-use plastic is pushing snack brands toward mono-material films; polypropylene or polyethylene that can be recycled in flexible film streams; and compostable cellulose-based films. These materials handle differently. They're more prone to static, they seal at different temperatures, and they don't slide as easily on stainless steel. Cartoners need adjustable infeed surfaces and anti-static systems to handle them reliably. If you're planning a substrate switch in the next 12 months, test it on your secondary packaging line first, not just the wrapper.
Shelf-ready secondary packaging for flow-wrapped snacks
Supermarkets want cartons that go straight from the delivery cage onto the shelf without repacking. That means perforated display panels, tear strips, and branding printed on the outer case. It also means tighter tolerances; if the carton arrives damaged or the packs are misaligned inside, it doesn't go on the shelf. Cartoners need to handle shelf-ready blanks gently, load packs in a visually consistent pattern, and close cartons squarely so they stack without crushing. It's a higher standard than a plain transit case, and it shows up as jams if the machine wasn't designed for it.
Smaller pack sizes and portion control
Snack brands are launching 100-calorie packs, mini bars, and single-serve formats to meet health-conscious retail demand. These packs are lighter, shorter, and less stable on a conveyor. They tip over, they blow off course if there's air pressure from a reject gate, and they don't trigger optical sensors reliably if the film is clear. Cartoners need lower-profile infeed systems, better collation control, and smarter sensors to handle them without constant stops.
Higher SKU variety and faster changeovers
Ten years ago, a snack line might have run three SKUs a week. Now it's ten, and retailers are ordering smaller batch sizes because they want fresher stock and more variety on shelf. That means more changeovers, and every changeover is lost production unless the cartoner can swap formats in under 15 minutes. Tool-less systems and recipe-driven setups aren't optional anymore, they're the baseline for staying competitive.
Predictive maintenance and line integration
Flow wrappers and cartoners are generating more data; cycle times, reject rates, temperature curves, motor loads. The next step is using that data to predict when a component will fail and schedule maintenance before it stops the line. Sensors that detect worn guide rails, belts that are slipping, or erector units that are out of time can trigger alerts days before a breakdown. If your cartoner can't connect to a line monitoring system, you're troubleshooting blind.
If you're running flow-wrapped snacks or switching to new substrates, and the handover between wrapper and cartoner is costing you stops, we've handled most versions of this problem before. Jacob White builds cartoners that handle film-wrapped products gently, change over quickly, and integrate cleanly with upstream equipment. If film damage or changeover delays are holding your line back, we'd be happy to talk through what might improve it.
