Stage No. 1. Roller leveling is achieved by precisely bending metal strip back and forth as it’s passed through a series of small-diameter offset rolls. The gap between the rolls is set independently on a leveler’s entry and exit. To roller leveling, deeply nest the entry rolls. This forces the material to pass through extreme angles to erase memory caused by trapped internal stresses. It’s also called the plunge, a technique for removing strip memory.
Stage No. 2. A leveler uses adjustable pressure points called flights under the rolls to raise and lower them to a precise position. By adjusting a work roll’s shape, you can alter the material path length through the leveler. A longer path length allows material to be stretched more because more work is being performed on it as it passes through the rolls.
Outer edges can be wavy with longer material lengths. To keep them from stretching further, choose the short path for the outer edge flights. To achieve flatness, the strip’s center must be stretched. Adjust the central flights upward to nest the rolls deeply, forcing the strip through the long path. If all material is equal length, the strip will be flat when it exits the leveling rolls.
If center buckle is present, the center is long. The flights need to be adjusted higher on the edges, making a longer path for the edges of the strip. It’s human instinct to want to work the material where it looks the worst. But, in fact, you should always work the material where it is flat and tight because it’s shortest and needs stretching.
Stage No. 3. Finally, it’s time to reset the strip’s memory to flat as it leaves the leveler. The appearance of the material shipped to the end user is achieved in the final three roll clusters. If the roll gap is set too deep, the material will be forced upward by the last roll, creating up-bow. It’s normal to set the leveler’s exit gap near the material’s gauge, a simple but important rule of thumb.