I have a question regarding wrinkles problems in BOPP slitting when the reel size increased more than 700mm or in thin film like 12micron. We are in trouble due to customer complaints.
Answer.
It would be worth checking where the wrinkles start to appear. Depending how the winding is set up it can be that as the reel diameter increases in size the tension in the web on the re-wind roll increases. As the tension increases there is a transverse compression force that also increases. Typically this can be overcome in two ways, either by modifying the tension with roll size or by use of a spreader roll used just before the rewind roll.
Some winding systems allow an automatic change in tension with diameter. This is sometimes called taper tension, where there is a linear reduction in tension with winding length. Again depending on the sophistication of the winding system other customised variations can be programmed in.
Keeping the tension under control should minimise the problem but even where winding systems have such control it is common to find a spreader roll also included before the web is re-wound to help make sure the rolls are wound as well as possible.
If you already have a spreader roll and still see the problem it is worth checking the type of spreader roll. If the spreader roll is of the grooved elastomer type then it is worth checking the age of the elastomer. Elastomers do age and this results in the elastomer becoming harder and less flexible which in turn makes the spreading action less. Thus what worked well originally can become ineffective with time.



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