Straightening is a function to remove the “Coil Set.” When metal is wrapped in a coil, over time, the material can often still have some “memory” of being wrapped in a coil and have a curve to it. Machines with straightening have a set of rollers that remove this coil set, allowing for blanks that lay flat without this curve.
When straitening soft materials, opting for a slitter with CNC straightening rollers or “Sensitive Material Mode” is recommended. With CNC-controlled rollers, the rollers are automatically raised anytime the machine stops. This prevents dwell marks in the material. A great analogy is a steam roller on a newly paved asphalt road. A steam roller should never stop on the new, hot asphalt. Doing so would leave marks on the pavement!
This will, of course, vary based on a customer’s business. Most machines can have one to as many as nine knives. Typically, you want to find a balance.
A slitter with CNC knives is a much greater investment than manual knives. In terms of the finished product, both machines will offer the same high-quality finished product. In terms of speed, a CNC machine will likely be faster than a novice operator. However, an experienced operator can change knives faster, if not quicker, than a CNC machine.
Since stainless steel is a harder material than mild steel, a machine’s capacity will decrease. If processing more than about 25% stainless steel, HVC Hardchrome on straightening rollers is recommended to extend the life of the rollers.