Innovation and Improvement in Tension Control
Flexible Packaging recently caught up with Darrell Whiteside, regional sales manager, Maxcess, to get his input on all things tension control.
Q: What’s new with tension control?
A: The need for web tension control has and will always exist. Certainly, innovation will continue to be driven by the needs of the customer. Right now, we are seeing things such as carbon fiber, specialty fabrics and ever thinner films push the more traditional technologies beyond their limit, forcing customers to face long overdue upgrades to more sophisticated controls and capabilities.
Q: There seems to be some thought that tension control product development has become mature. Do you agree with this?
A: I do not agree. There will always be room for innovation and improvement. We have seen many new things in recent years such as weightless load cell calibration, auto-tuning, out of round roll compensation for load cell systems and gain compensation for large roll build diameters. These things were unheard of not too many years ago and have now become commonplace in the industry.
Certainly, communication has improved over recent years. This allows all of the systems to work in a more unified way, rather than treating each individual aspect of the machine separately. This has made the life of the end user much easier, which I believe is the goal for all of us.
Q: Web drifts. Poor printing. Roll curl. Wrinkles. Web breaks. Are we missing any other problems that may occur as a result of poor – or no – tension control?
A: Certainly the above items can be affected by poor tension control. Whether a customer admits it or not, there has to be some type of tension control, even if it is a strap laying over the roll or simply relying on the inertia or drag of the system to provide tension. The question is how effective the control is for what you are trying to accomplish. Other defect examples caused by poor tension are telescoping rolls, crushed cores, necking, starring of rolls… The list can go on and on.
Q: What’s one thing about tension control that a lot of people may not know – but should know?
A: It needs to be addressed first. Many people try to address multiple problems at once and end up putting the tension control lower on the priority list. An example would be a drifting or guiding issue. Many times a customer will blame the web guide or some other device when it is a tension issue. A web guide cannot do its job if the web does not have enough tension to engage the traction roller. The same goes for slitting. If you do not have good tension before and after the slitting section, how can you expect a good clean slit?
There is a universal lack of understanding surrounding tension control. Because of this, tension control does not get the attention it deserves on most applications.
Q: What are some factors to consider when looking for tension control components?
A: What are you trying to accomplish? How precise of a control do you need (manual, open loop or closed loop)? What types of line speeds am I running? Interestingly, extremely low speed lines are generally more complicated and difficult to control than a high speed line. How easy will the tension control system be for my operators to use? What are my future plans for the line under consideration? How large is my roll build? This is a big one. The larger the roll build, the more consideration should be taken in selecting a closed loop control. Large rolls require more “gain” than a small roll. A traditional system will allow you to tune somewhere in the middle, which means a compromise at full roll and core. You need to have a “gain compensating” control in order to run rolls with large builds ratios.
Q: Is there anything else you’d like to add about tension control or the flexible packaging industry?
A: We are seeing thinner and thinner films in the packaging industry. These require special considerations when it comes to tension control. Even though the machine worked fine for running thicker material, that doesn’t mean it will work now that the tension requirement has either decreased or become more critical.