Earlier this year, Sigma Technologies located in Tucson, Arizona, identified unfavorable product issues that were believed to be caused by roll misalignment. Sigma operators often detected tracking of the web in their vacuum metalizer. There was an obvious need for an alignment procedure, but the enclosed nature of the machine caused many limitations for standard alignment technology. How can the rolls be measured accurately and in a timely manner?

The PARALIGN® device designed and developed by PRUFTECHNIK houses three ring-laser gyroscopes that are strategically placed perpendicular to one another in order to measure in the x,y, and z planes, respectively.

The basic principle of operation is that a single ring-laser gyroscope can measure any rotation about its sensitive axis allowing the device’s orientation in space to be known at all times. The patented software tracks each roll’s center axis in space. The ring-laser gyroscopes possess high sensitivity and stability, quick reaction times, insensitivity to acceleration, and immunity to most environmental effects. Additionally, the same gyroscopes are actively used in military aircraft and space technology.

Reinventing Roll Alignment Maintenance

The device’s non-optical feature allows previously inaccessible rolls to be measured accurately in a fraction of the time required by traditional methods.

Instead of measuring the rolls against a centerline or baseline, the technology determines the center axis of each roll, and then compares the center axes internally to a single reference roll. Typically, the reference roll is deemed the most critical roll in the process; one that is difficult to move or cannot be moved in a timely fashion. It is important to note that the reference roll can also be reassigned on the fly during the service with the click of a button in the patented software.

In order to measure the parallelism of rolls, one technician holds the device as it sweeps at least 20 degrees across the surface of each roll. Using the patented sweep mode method and Bluetooth technology, the second technician instructs the program on the laptop to start collecting data as the device moves along the roll face. While it travels across the circumference of the roll, the software tracks points. When enough reliable points are collected, the second technician instructs the device to cease measuring.

The amount of time needed to measure one roll is roughly 30 seconds. Internally, the software combines the points found along the roll surface with trigonometric equations to calculate the angle of the center axis of the roll. The angle is used in conjunction with the bearing-to-bearing length (in) of the roll to calculate its vertical and horizontal offset in relation to the chosen reference. The horizontal and vertical offsets are displayed instantly next to each roll as the measurements are collected.

Conclusion

During the five-hour PARALIGN® service, a total of thirty-three rolls were measured and of those, eight rolls were found to be askew. Misaligned rolls were properly adjusted according to the corresponding vertical and horizontal offsets determined by the PARALIGN® measurement method. Adjusted rolls were remeasured to find their final position.

As a result, the service was able to aid in making the necessary adjustments needed to correct misalignment and enhance overall quality of the product, while reducing the required downtime.

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