What is the difference between product size, bag size and film width?
Product size describes the item being wrapped, bag size describes the finished sealed pack and film width describes the flat web entering the machine. The film must travel around the product and still provide the required longitudinal seal. Pack length must contain the product plus end-seal clearance and the geometry created as film passes around the product.
These measurements should not be treated as interchangeable. A 100 mm product width does not automatically mean a 100 mm bag or a 200 mm film web, because product height, former geometry, seal arrangement, tracking allowance and film behaviour also affect the required web.
How should a product be measured for a flow wrapper?
Measure the smallest, nominal and largest production examples in the orientation in which they will travel through the wrapper. Record length in the direction of travel, width across the conveyor and maximum height. Include toppings, curled edges, soft deformation, trays, labels or grouped components that change the real envelope.
- Confirm the intended orientation and which face must remain uppermost.
- Measure several representative products rather than one ideal sample.
- Record the maximum rigid or non-compressible envelope.
- Describe any safe compression that is genuinely acceptable.
- Identify areas that must not be touched by guides or film tension.
- Provide an approved finished pack or dimensioned pack drawing where available.
Can film width be calculated from a simple internet formula?
A simple formula can provide an early screening estimate, but it is not a safe final specification for the film reel or forming set. Formulas vary because machines, formers, longitudinal-seal arrangements, products and films differ. An estimate also cannot prove that the product will feed, that print will register or that the sealant layer will produce an acceptable pack.
Use the calculation only to identify likely machine territory. Lancing should confirm the film width, former, seal allowance and production trial against the specific product and machine. Do not order a production quantity of printed film from an unverified estimate.
How do bag length and product pitch relate?
Finished bag length is the sealed length of one pack, while product pitch is the repeating distance allocated to each product on the infeed. Pitch must support the intended pack length and leave the end-seal jaws clear of the product, but it may also include control space needed for detection and stable transfer.
The product-pitch and pack-length guide explains why reducing the gap is not automatically a safe route to more packs per minute.
What extra information is needed for printed film?
Printed-film selection needs the print repeat, registration-mark details, unwind direction, print side, code area and seal keep-clear zones as well as the web width. The artwork repeat and the machine cut length must be compatible, and the eye mark must be detectable in the real film and operating environment.
Provide the film converter’s reel specification and a production reel for the trial wherever possible. Use the film and seal specification guide to prepare the full reel data.