Web speed control by winder motor

[ControlThis]

I'm looking for good techniques to get consistent / adjustable speed control of a web that is pulled from a motor that winds material onto a shaft. To get the web speed to remain steady, the motor will have to constantly adjust speed because the diameter of the roll will change as material is wound onto the shaft. What are some good techniques or components that I can achieve this with? I was thinking maybe an encoder on the web hooked to a plc that controls a VFD???? Is this a clean method or is there a better way? Never done this before and don't have a ton of r&d time to get it right. Any ideas would be greatly appreciated!
Thanks
Kevin

 

[CheeseSarge]

Hi Kevin,

I have never done a rewind application using a VFD. I have either used servos or a DC motor with a high quality controller. You should have a dancer that controlls the tension on the rewinder otherwise you get sections of the roll that is wound tighter and others sections that are wound looser. This causes out of round rolls and areas where the web is narrower (high tension) then what it should be. The motor has to run faster at the beginning(small diameter) and slower at the end of the roll where the diameter is much larger. I have used a speed command and then have the dancer either add or subtract to the speed signal into the drive. Good Luck.

Darrell

 

[itsmoked]

What HP requirement ControlThis?
Perhaps a vector VFD.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Most high end Vector Drives have "Web Control" macros for doing just this, it is a very common application. It does it primarily by maintaining a constant torque output and modulating speed as necessary as the diameter changes. Closed loop control (external encoder feedback) will provide the highest accuracy and repeatability, but several of the best drives out there now are reportedly able to do this in an "open loop" mode (in quotes because it really isn't open loop, the feedback is just internal to the drive). That said, it still is not easy compared to say, pump control or conveyor control.

My advice is to find a supplier local to you who has demonstrable experience in this and/or find an experienced integrator to help you; it is a somewhat specialized talent. Most of the integrators who do this are good enough to work all over the country because when word gets out that they know what they are doing, people who need them come to find them. Here is one I know.

http://www.drivex.com/

and they were just written up in last month's Control Engineering magazine.

http://www.controleng.com/article/CA6475619.html