Straighteners flatten materials, a task that’s essential for virtually any organization that purchases production materials in a coil format.
By removing coil set, the straightener helps the organization produce a part that is fit for production. Without a straightener, the curve in the uncoiled material would result in subpar parts, and ultimately, lower quality products.
Arguably the most important parts of any straightener, as well as the parts that comprise the majority of the equipment’s price, are the straightener rolls. Every straightener has at least one row of 4 rolls on the bottom and another 3 rolls on the top to work out the coil set. To accommodate thicker materials, some organizations will outfit their straighteners with backup rolls. This helps prevent deflection, i.e., the rolls bending. In addition to backup rolls, powered straighteners have motorized pinch rolls on the entrance and exit. These rolls are responsible for helping the material move through the straightener, while the straightening rolls “break” the coil set to produce a flat, ready-to-work sheet of material.
Let’s take a moment to look closer at this integral part of the straightening process.
Construction
Straightener rolls must be harder than the material they’re working. Otherwise, the material will essentially eat away the rolls.
At EnSight, we avoid this issue by using either 1117 or 1018 cold-rolled steel, which are both low-carbon, high-manganese steels that are extremely hard. After we receive the material, our machinists use lathes to create rolls that are slightly larger in diameter than the final product. The rolls are then case hardened.
During this process, the rolls are either put into a gas oven or packed in carbon and then heated to a specific temperature. After they’re air quenched to shock the material and make it cool faster, the rolls are heated again to a different temperature that is lower than the first round.
This forms a hardened layer on the outside of the roll that is approximately 1/8” thick. The hardening only goes that deep to keep the center of the roll soft. If the entire roll were hardened, it would become brittle and break.
After they’re hardened, the rolls are machined again to ensure they’re perfectly shaped and ready to roll.
Surface
Depending on the material being run through the straightener, the OEM might recommend a special surface on the pinch rolls to help grip the material better and avoid slippage.
One common solution is to sandblast the pinch rolls, creating a surface texture similar to about 180–200-grit sandpaper. This is ideal for mild steel or other materials that are NOT surface sensitive.
For surface-sensitive materials, such as prepainted metal, the OEM might suggest covering the material-running surface of the roll with chrome. During this process, the organization or vendor applies chrome plating. This provides an exceptionally hard surface that won’t mar surface-sensitive materials.
Another suggestion, although rarer than the previous two, is to apply urethane to the pinch rolls. Like chrome, urethane provides enough grip to help move the material through the straightener without hurting the surface.
Because the straightener rolls aren’t responsible for moving the material, they are left smooth after they’re ground.
Size
The straightener manufacturer will size the rolls to meet the material needs–the thicker the material, the larger the roll diameter.
In addition, for wider materials, the organization might make the rolls bigger to mitigate deflection. At EnSight, we’ve installed rolls as small as 1.5” in diameter all the way up to 6” in diameter.
At EnSight Solutions, our team specializes in helping industrial processors use their coil to the best of their abilities. We offer everything from uncoilers to straighteners to feeds to meet all your coil handling needs.
If you’re interested in a quality straightener, or any other coil processing machine, please contact our industrial processing specialists now.
