To calculate rolled outer diameter

Hi

Thank you CSM Engineer.

Greatful to you getting needy info.

Regards

You are most welcome. If you are interested, what you're doing is calculating the length of an Archimedes Spiral. The formula I gave you is an approximation to use when your material thickness is much, much less than your roll diameters. There is a calculus formula to calculate exactly. For more information, you can look here.

What CSM is describing for controlling speed is called a dancer and although crude, it is still the most common method for film tension control. Your idler roller mounted on the pivot arm can be counter balanced and then tension applied with an air cylinder as well.

Another option instead of the potentiometer is to use an off centre cam on the lever's pivot and then use a proximity sensor.

Thanks, Poison. I thought I had seen this system in use before, but had no idea what it was called. It's good to still be learning new things.

There is another simple system - to use spring loaded disc clutch.Film tension is maintained by machine operator adjusting clutch spring tension.

Ratnagiri

That works for film tension control, but how do you automatically maintain a constant linear film speed as the feed and take-up roll diameters change?

A good way (probably not the best) to control the film feed speed would be to remove the drive from the feed roll and instead drive a pinch roller applied against the feed roll to drive the film at a constant speed.

Then you can mount a small (relatively cheap) shaft-end-encoder on the feed roll shaft to be used as a speed feedback to a motor controller used to drive the take-up roll. So when the feed roll speeds up as film is removed the take-up roll will reduce speed inversely as the roll size changes thus maintaining a constant speed.

Just an idea. Hope this helps.