Stage No. 1. 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 level, 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 (see Figure 4).
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.
The Three-stage Leveling Process
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.
Over time sheet metal has been subject to many evolutions in order to adapt to the increasingly new performance qualitative demands from producers of capital goods. Levelling is an essential stage for modern uses with a high added value.
Levelling is a fast and simple process for obtaining flat sheets cut to size and free from internal stresses which at the same time permits high savings and an optimum end-product, thereby eliminating subsequent treatments.
Levelling is highly recommended for preventing the well known problems in some coil machining processes such as cutting, profiling, pressing and shearing. Sheets exiting the rolling lines often reveal a series of defects, generally due to widespread phenomena of poor flatness. Unlevelled metal sheet creates difficulties for any type of subsequent machining operation because, as it is not even, it can cause problems in various processes downstream that will provoke inevitable slowdowns in production. When cutting, the internal stresses in the original material are released and cause visible deformations; the flatness of the material becomes of major importance in order to obtain a high-quality end-product without additional stages that would entail further costs. The leveller is a machine the purpose of which is, by definition, to eliminate the various warps and undulations in the sheets and reduce these effects.