Inconsistent tension on any running web can affect not only the print register of the impacted web but adjacent webs as well.

This is more noticeable on presses with mechanical tension systems such as those found on Goss Urbanite and Community presses, Harris “V” series, King and Atlas press units. Yet presses with automatic tension systems are not immune.

In fact, tension systems are being used incorrectly in many of the pressrooms I visit. Usually, the tension spring is compressed so tightly that the governor roller (also known as a floating roller or dancer) either cannot be moved or is very difficult to move.

Secondly, I’ve noticed operators, as the press is running, adjust the brake pressure so that the governor is just barely off its forward stop.

When brake pressure is altered as the press runs, web tension gets tighter as the newsprint roll gets smaller. This causes the process color images to go slightly out of register. The operator will correct the out-of-register image by adjusting the compensators and circumferential controls. Unfortunately, at some point, the decision to reduce the excessive tension will have to be made.

Avoiding the vicious cycle

Whenever the tension is altered on any web it will affect print register. The result is a vicious cycle between setting the tension and adjusting the print register. Most operators will address this problem by meticulously adjusting the tension system before deciding to adjust the print register, a process that will dominate most their time during a press run. But that time spent watching the tension system could have been put to better use monitoring the rest of the press throughout that press run.

The print register is even harder to control whenever problems — such as stuck or sluggish governor rollers, malfunctioning brakes, worn linkage, bent newsprint roll shafts or warped brake spools — begin to develop with the tension system.

The correct approach

The mechanical tension system is used properly by tightening the newsprint roll spindle brake to make sure the governor roller is centered between its two rubber stops while the press is running. The web tension should then be adjusted by turning the tension spring control knob in a direction that will compress the spring if the web through its unit needs more tension.

If the web needs less tension then the spring pressure should be decreased using the control knob. Once the governor roller is set to its center position and the web tension is set by using the tension spring control knob, the webs will remain constant through out the entire press run — keeping the print register consistent.

It is much easier to spot trouble with the tension system when the tension system is used properly.

For instance, if your tension system is operating correctly and you notice the governor roller swinging wildly the culprit is likely dirty brake shoes. They should be sanded, or better yet, replaced.

If the web goes slack over the governor roller, the governor roller is stuck or is sluggish. Normally, that will occur due to rust between the governor roller support arms and the frame.

Mechanical slack, rolls challenge

Mechanical slack between the printing units will also cause print register inconsistencies while the press is running. Finally, improperly wound newsprint rolls can create print register problems. Once you feed that roll through the press, print register can become inconsistent.

Rewound butt rolls pose another registration challenge — especially when they are used to print the front page.

To overcome poor registration in these instances, the rewound roll should be used as the bottom sheet over the former as much as possible. This will reduce the potentially negative impact rewound rolls have on webs with spot or full color images.

Frank Bourlon has more than 30 years’ experience in the newspaper industry. He is the executive and training director for the Newspaper Production & Research Center. He can be reached at 405.524.7774 or via e-mail at fbourlon@np-rc.org.