PE Films rolls slack edge

Incorrect winding?

You want to speak with Jeffrey Damour at Converter Accessory Corporation in Pennsylvania, USA 610-863-6008. He deals with this stuff day in and day out.

your take up roll is not square to the web?

your take up roll is not fixed into a location?

your web has some lateral movement, or the edge cutoff wheel isn't keeping a straight line?

You probably have a gauge band problem. Are the rolls larger on one side than the other? Is your film produced on a rotating die or oscillating haul off?

If not a gauge problem, you should next check alignment of your equipment.

I do this for thousands of miles of film a day, and 99.999999% of the problem is gauge band.

Joe

Thanks for the confirmation.

Here is my theory: There might be a temperature difference between the ends and the center tends to produce a material stretching. The more temperature cycling you get, the more likely you are to see a difference in tension between the center of the material and the edges. It will be more pronounced if the roll has been in a cold location for many days and you unroll it in a warm factory.

I have encountered this myself with Polyethylene. It is more pronounced in thicker material (.030" for example). I tracked the problem to the slitting process using shear type slitting blades. This type of blade tends to stretch the material beyond its elastic limit (PE has an elongation more then 300% in tension)along the slit so the edges of the coil are longer than the center. If the coil is rewound with sufficient tension, this is not appearent in the wound coil, but shows up when the coil is unwound.