Flow Wrapping vs. Overwrapping: Formats, Materials and Applications

Flow wrapping and overwrapping both enclose a solid product in film, so they are often discussed as if they were interchangeable. They are not. The two formats build the package differently, and that changes which products they can handle, how the pack looks, how the film behaves on the machine and where a leak or poor seal is likely to appear.

The choice usually comes down to whether the product can travel in a line and sit inside a film tube, or is a box or carton that needs a film skin. The comparison below is conditional. It does not say either format is cheaper or faster in general, because that depends on the product, the film and the machine specification.

How each format is built

The difference starts with the film path. A flow wrapper makes a tube around the product, and an overwrapper folds film around it.

Flow wrap (pillow pack)

A flow wrapper pulls film from a reel and forms it into a continuous tube. Products arrive in a line, usually on an infeed conveyor with lugs or a timed feed, and enter the tube one after another. A longitudinal seal joins the film edges along the tube. This is the fin seal, and it sits on the underside of the finished pack. Rotating or reciprocating crimpers then seal across the tube at the leading and trailing edge of each product. Both end seals are made in one operation and a knife cuts between them, so each pack gets a trailing seal and the next pack gets a leading seal.

Because the tube is continuous, pack length equals the product length plus the film needed for the end seals. On printed film, a registration mark lets the machine place the cut and the end seals relative to the print.

Overwrap (folded wrap)

An overwrapper takes a product that already has a defined shape, often a carton or rigid box, and wraps a sheet of film around it. The film is cut to length, laid around the product and joined along the body. The ends are folded into panels, much like wrapping a gift, and the folds are heat sealed. Some formats add a tear tape, a thin strip under the film where the consumer starts opening the pack.

The structure depends on the product holding its shape during folding. That is why overwrapping is associated with cartons, boxes and other rigid items, while flow wrapping can also handle soft or irregular products, as long as they can be fed in a line.

Why the seal layout matters

In a flow wrap, the fin seal runs the full length of the pack and the end crimp seals cross the tube. Leak investigations tend to focus on the points where the fin seal meets the end seals, because several film layers overlap there. In an overwrap, the sealed areas are the folded ends and any longitudinal overlap. The seal is made between layers of folded film rather than across a pressed tube, so sealing pressure and temperature act on a different geometry. Whether a seal is adequate for the intended use is settled by testing the actual film, not by the format name. One relevant reference is a standard test method for seal strength of flexible barrier materials. It defines how seal strength is measured, not what value is acceptable.

Conditional comparison

The table compares the two formats on the points that most often decide the choice. “Suits … when” means the format is a plausible fit under that condition, not that it is the only one.

Decision point	Flow wrap (pillow pack) suits when…	Overwrap (folded wrap) suits when…
Product shape	The product can be fed in a single line with consistent spacing, including bars, biscuits, trays, tubes and some soft or irregular items	The product is a carton, box or other rigid item with square or rectangular edges that can take folded corners
Product support	The film tube can carry the product, and a slightly loose or fitted pack is acceptable	The product must hold its shape while film is folded around it
Pack appearance	A pillow-shaped pack with a visible fin seal and crimped ends is acceptable, or printed film carries the design	A close-fitting film skin over a printed carton is wanted, so the carton graphics show through
Film type	The film must be heat-sealable on its inside surface and run through forming and crimping	The film is clear and often heat-sealable or coated, and it must fold and hold creases at the ends
Seal type	A fin seal plus two crimp seals meet the protection requirement	Heat-sealed folds meet the protection requirement; a fully hermetic seal may not be the aim
Opening and tamper evidence	Easy-open features, notches or tear strips are built into the film or the end seals	A tear tape, a visible film skin or a seal over the carton opening is part of the pack design
Format changes	The product size range fits within the former and the adjustable parts of the machine	The carton or box size range fits within the adjustable fold and sealing parts
Output and footprint	Line-fed products and a continuous process fit the plant layout	Discrete cartons arriving from a cartoner fit the plant layout

Product shape and support

Flow wrapping is flexible about shape because the film tube forms around whatever is in it. The limits are feeding and spacing. The product has to enter the tube in a controlled way, with enough clearance and a consistent pitch. Fragile products can break at the infeed or at the crimp, so the feeding method needs attention.

Overwrapping depends on the shape of the product. A carton with square edges gives clean folds, while a product with weak or uneven corners can crush or leave wrinkled folds. When the product is a carton, overwrapping typically sits downstream of a cartoner. Our guide to cartoners and case packers shows how that secondary packaging step is arranged.

Film and appearance

Flow wrap film is usually printed, because the film is the graphic surface and often the barrier layer. The machine reads a registration mark to position the print. If the film must also block moisture or oxygen, that is a film specification question as much as a machine question.

Overwrap film is often clear, because the carton underneath carries the graphics. Clear options include coated or laminated materials with different folding and sealing behavior. Cellulose-based film, often called cellophane, is a historical example associated with overwrapping. Whether it, a polymer film or another material suits a given job depends on the machine’s folding and sealing system and on the product. The guide on film and machine compatibility covers the film properties that affect running on either format: tension, coefficient of friction, sealing window and registration.

Where each format is used

These applications are examples, not rules.

Flow wrap is widely used for bars, biscuits, confectionery, bakery items, tubes, medical disposables and a range of non-food items. It is also used for multipacks of smaller packs.

Overwrap is common on cartons of cigarettes and similar products, boxed confectionery, stationery and other cartons sold with a film skin. For consumer products in cartons, the film overwrap sometimes serves as the tamper-evident or protective layer.

Either format may also appear as a secondary packaging step, for example wrapping a group of primary packs. That is why both appear in the secondary band of the line map in our packaging machine types overview.

Questions to ask suppliers

A supplier can only quote well when it can see the real product and the real pack target. Information to request or provide:

• Product dimensions, weight range, shape variation, surface condition and fragility, with samples for each size.
• A pack drawing showing the intended seal type, fin position, end seal style, any tear tape or easy-open feature, and print registration needs.
• The film specification you intend to use, and the supplier’s film requirements: layers, thickness range, seal layer, coefficient of friction range, core size, and maximum reel diameter and width.
• The rated speed in packs per minute, with the product, film and pack size the rating applies to. A speed quoted without those conditions cannot be compared between quotes.
• How the supplier handles product spacing and infeed (lug conveyor, timed belt, pick-up or robot) and what product orientation is required.
• The format change method: which parts are replaced and which are adjusted, what tools are needed, and the expected steps. The related guide on changeovers is a useful basis for that discussion.
• Evidence of seal performance with your film, such as the supplier’s test method, the number of samples tested and the acceptance criteria you agree on in advance.
• Safety documents: the risk assessment basis, the guarding concept, and the reference standards the machine is designed to. Relevant references include EN 415-10 for general packaging machine safety in the EU and ANSI/PMMI B155.1 in the US, depending on the market.
• A spare and wear parts list, such as crimper jaws, knives and heating elements, and the supplier’s recommended handling of them.

These items also feed a complete specification. A packaging machine RFQ checklist shows how to organize them so quotes can be compared fairly.

Worked comparison

Limits and on-site verification

This guide cannot settle which format your product needs. These points need confirming with real product and film on the actual machine:

• Sealing behavior. Fin seal, crimp seal and folded seals depend on film, temperature, pressure and dwell. The film supplier and machine builder provide acceptable ranges, and you confirm them with your materials. When seal faults appear in production, a structured seal defect investigation helps separate material, machine, product and method causes.
• Product feeding. Spacing, orientation and product damage at the infeed and crimper show up only in a trial with real product.
• Pack appearance and opening. The people who will run and sell the pack should judge fin position, fold neatness, tear tape behavior and ease of opening.
• Protection requirements. If the pack must meet barrier, shelf life or tamper-evidence requirements, define them first and check the pack against them with an agreed test.
• Regulations and labeling. Rules for markings, contact materials and tamper evidence vary by market and product, so check them for your case.

Related decisions

To see where flow wrapping or overwrapping sits in a whole line, the overview of packaging machine types shows the primary, secondary and tertiary stages. For carton-based secondary packaging, see cartoners and case packers. Film selection questions continue in film and machine compatibility.