Servo Torque Control Question

Hi Guys,

I have an application where I need to pull material off of a roll and maintain constant tension on the web. Can I put an AD SureServo in Torque Mode on the roll shaft and have it provide the resistance as I pull on the material?

If you want the tension of the unwound material to be constant, then you must consider the diameter of the roll of stock as it is unwound.

You can pull the material off of the core with a pull motor but then you have to deal with changes in tension at the letoff roll when the pull roll changes velocity.

Or, you can center-drive the letoff roll with your servo and come up with some means to taper the torque command as the diameter changes.

Tapering the torque command can be as simple as a pre-programmed ramp rate that has no feedback involved (except a reset when a new roll is started), or very elaborate with load cell feedback monitoring the web tension at some point in the process.

You are talking about a center driven "letoff" or "winder" application?

Paul

Hi Paul,

This machine design just changed dramatically over the past hour (It's a laminator). I don't have a drawing of it yet unless I can turn the conference room white board into a jpeg file.

The material is now cut to length (16') and placed on a 16' conveyor. It is then attached to one end of the conveyor (the servo end). The material is now pulled off of the conveyor from the other end during the laminating process. The idea was to get the conveyor servo to provide the resistance to keep the material taut. Nothing fancy or precise here and no roll diameters are involved.

Norm