Web Tension Controllers and Data Acquisition

Customer Question: The label industry is very sensitive to curl and we are finding that controlling web tension on narrow web printing presses is very important. I work with customers using our flexible packaging and labels and am interested in learning how your web tension systems work and how we might be able to use a data acquisition system to collect web tension data over time.

Answer: DFE manufactures components for monitoring and controlling tension in any type of application. For a useful primer on web tension control and PID controllers see the article Tension Control 101.

Basically, DFE tension controllers come in three different output versions to correspond to the tensioning mechanism being used by the customer. The controllers can produce a pneumatic output (P version) for clutches and brakes, a low voltage 0-10V output (D version) typically for motor drives, or high voltage (V version) 0-24, 0-45, or 0-90VDC outputs for eddy current or magnetic particle clutches or brakes.

For those applications requiring an interface to motor drives, our controllers can be used in a follower mode, where the control output follows the machine's speed. Our newer controllers can also compensate for roll diameter changes when used on an unwind or rewind — e.g. the WebHandler™3 controller. Line follower mode with diameter compensation is especially useful on machines with high accelerations. 

All DFE electronics, whether they are closed-loop controllers or just indicators, produce a 0-10V signal which represents measured tension over the calibrated range (for example 10V=250lbs of tension). This tension signal can be brought into a data acquisition card for logging over a period of time. We can supply an off-the-shelf generic data acquisition card for this purpose, or recommend a brand-name card to you, and assist with setup for acquiring useful tension data.

If desired, a second channel of the data acquisition card can be used to bring machine speed in. Software normally used with these cards can be configured to show actual line speed and tension. This provides the capability to observe whether tension upsets occur when the machine's speed changes, for example.

Some DFE tension controllers and electronics devices have RS232 and/or RS485 output capability. This allows a laptop computer to receive the data from the controllers and display it, using the serial port already present on most laptops. This can be the least expensive way to get tension information into a computer for analysis. DFE has an experienced software engineer on staff and we are pleased to be able to offer simple yet powerful Windows® based software for accessing and operating our digital WebHandler™3 Controllers remotely via laptop or PC. The software is included with the purchase of either of these controllers.