Comparing stretch-film trials with the same load mix
Compare film consumption within equivalent load groups before interpreting an overall average. A trial containing mostly small loads can show a lower average than one containing mostly large loads, even when it uses more film within both groups. Keep the load mix visible when reviewing a proposed film purchase.
Separate the group rates from the group counts
The following hypothetical records describe two evaluated processes, A and B. The letters do not identify actual product performance. All values are invented to illustrate how the composition of the trial changes the average.
| Load group | A consumption per load | A load count | B consumption per load | B load count |
|---|---|---|---|---|
| Small | 100 grams | 10 | 110 grams | 90 |
| Large | 200 grams | 90 | 210 grams | 10 |
A's total is 19,000 grams across 100 loads, averaging 190 grams. B's total is 12,000 grams across 100 loads, averaging 120 grams. The overall average appears lower for B, yet B consumes ten grams more within each load group. Most of B's trial consists of the smaller loads.
Apply one stated reference mix
For a purely illustrative fifty-fifty reference mix, A averages (100 + 200) ÷ 2 = 150 grams per load. B averages (110 + 210) ÷ 2 = 160 grams. Reweighting the same group rates makes the comparison use the same mix.
Choose a reference mix relevant to the purchasing decision and record its basis. Equal weighting is not automatically the operation's actual mix. Retain the group results as well as the reweighted result, because an average can still conceal a problem in one group.
Keep actual film identities with actual observations
MSF20805C is 20-inch, 5,000-foot, 80-gauge cast machine stretch film, supplied as one roll. MSF2090C is a 20-inch, 5,000-foot, 90-gauge cast machine stretch-film roll. Their listed dimensions do not assign them the A or B results above.
Evaluate each proposed material in the approved equipment and load process. Preserve the exact film, load definition, consumption method and completed-load acceptance results. Reweighting consumption cannot establish containment, compatibility or an acceptable wrapping program.
Use the adjusted comparison for the next review
If historical trials have different mixes, report that difference and compare valid group results on a common basis where the data permits. If a group is missing, collect the necessary evidence rather than inventing its rate. Use the cast machine stretch film buying guide to identify product candidates, then distinguish a change in film use from a change in the jobs represented.