Above: Flatness, straightness and evenly distributed strength throughout the length of strips are the aims for two types of machines
July, 2026- Groups of customers—automotive suppliers, makers of aerospace components and construction products, fabricators and HVAC systems—have a lot of specifications native to their own processes and products. They may at least have to meet consumer quality standards or perhaps military and defense standards. The service centers and metal processors have to know how to shape the raw materials to reach those standards and specs.
In sheet metal processing, two machines often get confused with each other: coil straighteners and levelers. Both are used to improve sheet flatness, one more capable than the other. Understanding these differences is crucial for successful manufacturing.
Steel, as well as other sheet metals stored in coil form, experiences uneven stress. When the coil is uncoiled and curvature is retained after uncoiled, this is called a coil set. Crossbow is a curvature across the width of the strip where the sheet forms a smile or frown shape due to stress differences through the surfaces of the strip. Edge wave and center buckle are length differences in the strip. When edges are longer than the center of the strip, this is referred to as an edge wave. The opposite occurs when the center is longer than the edges and is referred to as center buckle.
COMPARISON
While similar, levelers and straighteners address different issues.
A coil straightener is primarily used to remove the coil set or crossbow. Feeding the metal strip through rolls that bend the strip up and down uniformly across the face. This reduces the internal stress created when the metal is coiled.
A properly sized straightener eliminates the coil set or crossbow caused by the coiling to prepare for further processing. Straighteners focus on surface-to-surface stress and cannot fix uneven lengths across the strip exhibited as an edge wave or center buckle.
Levelers provide a more advanced form of sheet metal flattening. Levelers can remove coil set or crossbow like straighteners but can also correct the length differences.
“Length tolerances can be affected, die crashes, down time, are all symptoms of edge wave and crossbow due to poor straightening equipment,” says Gary Moore, general manager at The Bradbury Group, a manufacturer of metal processing equipment based in Moundridge, Kansas.
Using closely spaced rolls allowing for greater bend angle, these rolls can be flexed under load to allow the machine to create areas of a longer path for the strip. The bending actions on the rolls allow the leveler to stretch specific areas of metal, equalizing length and stress to provide a flat strip. Levelers correct defects that straighteners cannot, such as edge waves and center buckles.
CORRECTION
Although coil straighteners and levelers look similar, their capabilities are different. Properly sized straighteners can remove coil set or crossbow, while levelers can do this and improve the overall flatness of the material by correcting length issues as well.
Jason Bartel, a technical sales engineer for the Athader/Bradbury Group team, notes that Bradbury builds both straighteners and levelers. “We are able to provide a straightener that has the capability of removing coil set or cross bow and the material will not spring back.
We are also able to build a leveler to remove length issues such as edge wave or center buckle to avoid issues in the stamping die. A leveler will equalize stress in the material within its capacity range to significantly reduce or eliminate springback in the material after stamping,” Bartel says.
Using closely spaced rolls allowing for greater bend angle, these rolls can be flexed to create areas of a longer path for the strip.
Both leveling and straightening equipment can be integrated into existing shearing, cut-tolength or slitting lines.
INTEGRATION
The company has integrated equipment into existing processing lines on numerous occasions. For example, says Bartel, Bradbury has installed controls for a straightener or leveler that provides points for integrating control and safety.
“In a stamping line, the straightener or leveler typically pulls material from an uncoiler and feeds a loop of material that is monitored,” he explains. “The loop monitor input adjusts the speed of the straightener or leveler accordingly.”
Levelers have become the most versatile and efficient metal flattening machine available. With brute hydraulic force, focused tension and power at the point of plasticity, the machine equalizes stress and delivers premium flatness day after day. World-class controls, automatic leveler adjustment, and unique options have made levelers easy to operate and continue to be the most productive roller leveler available.
The Bradbury Group, 620/345-6394, bradburygroup.com
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