Corrective Leveler
There are two main goals behind the science of leveling metal strips. One is to make the surface flat, and ripple-free. The second is to eliminate any hidden internal stresses that can cause the strips to twist and bow during subsequent operations, such as stamping.
When choosing the right corrective leveler, there’s some important factors to consider – the roll diameter, the roller pitch and the number of work rolls. A leveler is the best choice to a straightener as the leveler will remove more than cross bow or coil set.
There are three stages in the leveling process:
- No. 1 – Leveling is achieved by accurately bending the metal strip back and forth as it passes through a series of small-diameter offset rolls. The gap between the rolls is set independently on a leveler’s entry and exit. The entry rolls should be deeply nested, as this forces the material through extreme angles to erase memory caused by trapped internal stresses. This is also known as ‘plunge’, a technique for removing strip memory.
- No. 2 – A corrective leveler uses adjustable pressure points called flights, under the rolls to raise and lower them to an exact position. By adjusting a work roll’s shape, the material’s path length can be altered through the leveler. A longer path length allows the material to be stretched more because more work is being performed on it as it passes through the rolls.
With longer lengths of material, the outer edges can be wavy. To keep them from stretching further, a shorter path should be chosen for the outer edge flights. To achieve flatness, it’s important that the strip’s center be stretched. If all the material is of equal length, the strip will be flat when it exits the leveling rolls.
If the material has a center buckle in it, then the flights need to be adjusted higher on the edges, making a longer path for the edges of the strip.
- No. 3 – It’s now time to re-set the strip’s memory to flat as it leaves the leveler. The appearance of the material that will be 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, which will create an up-bow. It is normal to set the leveler’s exit gap near the materials’ gauge. This is a simple, but important rule to follow.
With over 60 years’ experience and a real focus on customer satisfaction, you can rely on American Steel when it comes to choosing the right corrective leveler for your operating needs.
