Plastic Roll Blocking

Hi Gary,

By blocking, I am guessing that you mean the layers of the wound roll are sticking together. Is this correct? Are you experiencing this in rolls you are purchasing? This is common in polyethylene and there are additives that can allieviate this.

To measure this, you may be able to use tension measurements by use of load cells. Set a baseline by running some unblocked material at a specific brake setting. Then, leaving the brake setting the same, run some of the blocked material. The roll widths will need to be the same. The tension due to blocking will be the blocked roll tension minus the unblocked roll tension. Let's call the resulting value the Blocking Tension. The numbers will likely be ambiguous, but if you have decent load cells, it should be repeatable. You can then begin collecting data to determine at what Blocking Tension the rolls start causing problems with your process.

I have no idea if I am on mark at all, so a little beedback please?

Mike

You are correct in your interpretation of blocking. This is a poly olefin based product and the material is sticking to itself. We have been able to control the blocking but are looking for a way to measure or quantify the number. Controlling the unwind tension may not be the precise way as there are too many variables such as, precise load cells, no slippage in the cores etc. I appreciate your suggestion!

This is done everywhere with a "dancer" roll. It is a roller that can go up and down, spring loaded or air piston loaded for big rolls.