Tension Control For Paper Roll

At constant velocity, the tension in the paper sheet (once you overcome the inertia of the roll itself) is developed by the force required to overcome the drag within the unwinder. That drag is likely to change with load (amount of paper on the roll). So you need a graph of the drag force applied by the unwinder with various loads. You can then use the known physical properties of your paper and the unwind rate to calculate the rate of change of the load on the unwinder, and consequently the drag force, and consequently the tension in the paper.

So, in addition to the parameters you have provided, you need to know the unwind rate and the drag characteristics of the unwinder.

If you want to know the tension in the paper when you start pulling on the paper from a stopped condition, you will also need to know the acceleration rate. you can then use F=ma to determine the additional force required (and additional tension in the paper) to start the roll moving.

Does any of this help?

thanks for reply i can control the unwind rate how it could help me to find tension variation...can you tell me any mathematical relation between these parameter..

thankyou

There is not a direct mathematical relation...it all hinges on the internal drag of the unwinder...you will have to measure it at various loads. Once you have collected the data and created a chart of drag vs. load, you can then form a mathematical relationship between unwind rate and the amount of paper (load) on the unwinder to determine where you are at on the drag chart and therefore the tension in the paper.

There is one other indirect way to determine the tension in the paper, but it will still require an additional measurement as well as allowing the paper to sag between the unwinder and the machine that it feeds. I am assuming a horizontal configuration between the unwinder and the next machine. If the paper is allowed to sag, it will follow the path of a catenary. If you can measure the amount of sag from some steady horizontal reference point, and knowing the physical properties of your paper, you can use catenary formulas to calculate the tension in your paper. But, again, you will need to make constant measurements of the paper sag.

Let me know if any of this is unclear, and I will try to describe in more detail.

sorry but how can i measure the drag rate , i do,nt have any feedback...

yes, a heuristic brake.

I would directly measure the tension by doing something like this.

to measure the tension in paper whatever rakesh has explained is correct is easy method.

tension in unwinding paper will be always equal to the tension setting of Ur brake.

also from Ur paper manufacturer u can get the tensile strength of paper.

u can also found it by gradually loading the paper and find out at what load it tear-off.

The drag from the paper will change daily depending upon the static charge developed as a result of the air humidity and the temperature. Also the composition of the rollers will also have an effect.

You need to discharge the static as much as possible to make sure nobody gets a shock from it, this will also reduce static charge drag.

Paper can be very dangerous......

Go and look at a Van de Graaf machine before designing anything!!!