Film sizing guide
Measure the production pack in its real orientation, identify the film presentation and match the reel to the machine path before ordering or approving shrink film.
Direct answer
Shrink film width or layflat should be selected from the product in its actual running orientation, including the tallest and widest production extremes, protrusions, the loose film envelope, seal allowance and the reel arrangement used by the machine. Centre-folded, single-wound, tubing and printed sleeve materials are measured differently. A calculated starting width must therefore be checked against the machine limits and proved with the intended production film.
| Film presentation | Measurements to provide | What must be confirmed |
|---|---|---|
| Centre-folded film | Pack width, height and length in running orientation; corners, projections and the smallest and largest formats | Opened web, bag or cut-off length, seal position, side clearance, reel width, core and outside diameter |
| Single-wound web | Group width and height, product pitch, required side opening or overlap and bundle support | Web width, film overlap, tracking, sealing path, reel direction and the relationship to the tunnel |
| Tubing or preformed bag | Maximum circumference or profile, product length, insertion method and closure requirement | Layflat, bag length, opening method, air release, seal allowance and product movement |
| Printed shrink sleeve or band | Container profile, circumference by height, sleeve placement, cut length and print position | Layflat, seam position, print repeat, material shrink direction, registration and the selected heat process |
Measurement sequence
A repeatable measurement record prevents the reel from being selected around one easy sample.
Define which face leads, which face is presented and whether the product can rotate, tip or spread before sealing.
Record the smallest and largest width, height, length, complete weight and any variable component such as a handle, flap or closure.
Confirm centre-folded, single-wound, sleeve, tubing or bag presentation, then check reel width, core, outside diameter and winding direction.
Run enough film to establish tracking, seal quality, air release, tunnel response, cooled finish and repeatability after a restart.
The machine handles the product while the film is still loose. The loose envelope can be wider or taller than the final pack because of product corners, trapped air, overlap, side fins and the way the film is drawn through the sealing area.
Record supplier, code, material, construction, gauge, width or layflat, batch, winding direction and perforation. A reel that looks similar can process differently and should not inherit an approved recipe without verification.
The largest format sets physical limits, but the smallest can expose weak film control, excessive scrap, poor sensing or a seal position that is difficult to repeat. Include the complete proposed format family.
Gauge, shrink curve, seal range, perforation, friction, print and product heat tolerance affect the result. A width that physically covers the product is not automatically a suitable production film.
Common mistakes
These checks help separate a dimensional problem from a film, sealing or tunnel problem.
| Observed issue | Sizing check | Related process check |
|---|---|---|
| Long side fins or excess loose film | Confirm web width, bag length, product orientation and the intended seal position | Check air release, film shrink response, product centring and tunnel airflow |
| Film pulls against the product or seal | Check maximum product dimensions, protrusions and the actual loose-film allowance | Check seal quality, shrink force, temperature, speed and sharp product features |
| Small formats run poorly on a wide reel | Compare the minimum format with the machine’s practical film-control and seal range | Check tracking, sensing, product position and repeatable changeover settings |
| Printed sleeve distorts or sits at the wrong height | Confirm layflat, cut length, print repeat, seam position and container profile | Check sleeve placement, heat distribution, container stability and cooling |
Buyer questions
The opening answer gives the practical rule; the detail identifies what still needs to be proven.
Sometimes, but the practical range depends on the machine’s film path, seal position, tracking and the acceptable amount of excess material. A reel that covers the largest product may create unstable sealing, long fins or unnecessary waste on the smallest. Test the complete format family and record the approved changeover range.
Layflat is the measured width of a flattened sleeve or tube. For printed sleeves and tubing it is a key ordering dimension, but it does not describe cut length, film construction, shrink direction, seam position or the container profile. Those details must be supplied together.
No. Film is handled before it shrinks, so the machine must accommodate the loose envelope, seal allowance, product movement, air release and the way the web opens around the product. Provide the unwrapped product dimensions and the intended running orientation as well as an approved finished pack.
Gauge does not replace the dimensional calculation, but it can change stiffness, seal behaviour, shrink force and the way film tracks or bridges over a pack. Width, gauge, construction and shrink curve should therefore be qualified as one production film specification.
Excess film can create long fins, folds, trapped air and uneven contact with the product. It may also move the seal into a poor position or require more thermal work. Before reducing width, confirm the approved air-release route, seal allowance and product extremes so the cure does not create tension or open seals.
Send supplier and code, material, gauge, width or layflat, reel core and outside diameter, winding direction, perforation, print repeat and shrink data. Add product dimensions, orientation, smallest and largest formats, target output and photographs of the required finished pack.
This guide provides an engineering measurement brief, not a universal ordering formula. Final film width, layflat and reel construction must be confirmed for the selected machine, production film and accepted pack.
Film and pack review
Include dimensions, orientation, film format, reel label, target output and an accepted pack so the film path and machine envelope can be reviewed together.