How to Run a Polythene Film Trial That Gives You a Clear Buying Decision

A sample reel that runs for a few minutes can tell you something useful. It cannot, on its own, tell you whether to change the film used across your normal production mix.

A worthwhile polythene film trial starts with a buying question. Are you trying to reduce material per pack, improve sealing consistency, accommodate a different product or assess an alternative supply? Agree that question before the sample reaches the packing area.

At Stretchband Packaging, we look at the film, reel presentation and packing process together. The following trial plan helps turn observations into a clear next step for manufacturers, fulfilment teams and contract packers.

Define what the polythene film trial must prove

Write a short objective that names the product, line and intended improvement. 'Test the new film' leaves too much open to interpretation.

For example: assess whether a proposed shrink film can meet the agreed finished-pack requirements on the current multipack format, while reducing film used per accepted pack. That is a trial objective, not a promised result.

Separate essential requirements from desirable improvements. A lower purchase price is of little value if the finished pack does not meet the customer's requirements. Equally, a better-looking pack may not justify a change if it creates unacceptable stoppages.

Agree pass criteria before running the sample

Define how the team will judge the pack and the process. Relevant checks may include seal integrity, appearance, product protection, tracking, rejects, stoppages and material consumption. Choose only measures that matter to the actual application.

State the inspection method, who will assess it and what counts as acceptable. Where an agreed customer specification or validated test method applies, use it rather than inventing a simpler substitute for the trial.

Do not set a universal number of trial packs. The required quantity and duration depend on the product mix, production risk and evidence needed. Agree enough material and time to assess set-up, steady running and the relevant operating conditions.

Confirm the reel and paperwork before booking line time

Check width, gauge, core, outside diameter, winding direction and machine compatibility against the proposed trial specification. Keep the sample label and batch reference with the trial record.

For single-wound sheeting or collation shrink film, the reel must suit the equipment as well as the product. A sample with the wrong reel presentation can consume the available trial slot without answering the buying question.

Confirm any required material documentation before production use. Also agree the production slot, responsible operator, inspection arrangements and a route back to the current approved specification if the trial cannot continue.

Record a comparable baseline

Run or record the current film on the same product and pack format under representative conditions. Note line speed, relevant settings, material use, rejects and stoppages, along with the time or quantity covered.

If the baseline comes from historical records, identify differences in product, operator, maintenance condition or shift. Those differences may make the comparison less reliable.

Keep the records specific. 'Normally runs well' is difficult to compare with a measured trial. A documented baseline helps the team decide whether an observed difference is useful, uncertain or explained by something else.

Log settings and changes as the trial progresses

Record the starting settings and each adjustment, with its timing and observed effect. Where practical, change one setting at a time during fault-finding so the reason for an improvement or failure is easier to follow.

Film and machine settings can interact, so a successful adjustment does not prove that one setting explains the whole result. Recheck the final combination across the agreed conditions before accepting it.

Any adjustments must stay within the equipment manufacturer's instructions and the site's authorised procedures. This guide does not prescribe temperatures, speeds or interventions for a particular machine.

Measure accepted packs and waste consistently

Record the film consumed over the measured period, including the agreed treatment of set-up waste. If using weights, distinguish net film consumption from cores and wrapping, and use a suitable consistent measurement method.

Calculate film cost per accepted pack by dividing the cost of film consumed by the number of packs accepted in that period. Use the same scope for the current and proposed films.

Keep start-up waste, running rejects, rework and stoppage time visible as separate figures. Combining everything into one percentage can hide why a trial performed differently. If an annual saving is estimated later, explain the usage assumptions and uncertainty rather than extrapolating an unusually easy short run.

Inspect the pack after it leaves the line

Immediate appearance is only part of the assessment. For a shrink pack, include the agreed inspection after cooling. Where normal handling, storage or distribution affects the requirement, include an appropriate assessment of those stages too.

Retain identified sample packs and photographs where useful. Record the product variant and settings with them so a good result can be traced to the conditions that produced it.

A trial on one straightforward product should not be described as approval for every SKU. Decide which sizes, weights and pack patterns the evidence actually covers.

Finish with a written decision

Use a clear outcome: approved for the defined application, further trial required, or not approved. State the agreed film specification, final settings, covered products and any outstanding checks.

An inconclusive trial is a reason to define the next question, not to present a change as proven. A successful trial should produce a repeatable specification and an agreed handover to production and purchasing.

If you are considering a new film, contact Stretchband Packaging with the current reel details, machine information and the problem you want to solve. Our film-audit service can help review the starting point and identify what a useful trial should assess. There is no obligation to change supplier.