A Straightening machine is a device designed to flatten and straighten a metal strip or coil. It consists of several sets of rollers, usually with different heights (more on that later), which bend and stretch the metal to re-flatten it. Metal straightening machines are used to re-shape rolled, drawn or extruded ferrous and non-ferrous metals, particularly steel and aluminum. They can also be used to straighten solid bar, square and rectangular tube, hollow profile and welded sections of material.
When designing a metal straightening machine, it is important to consider the maximum yield strength of the material being processed. As the yield strength increases, so does the stress placed on the work rollers and drive system. This stress can cause the work rollers to deflect excessively, resulting in reduced contact between the work rolls and the material. This can lead to slippage of the material through the machine and, in severe cases, broken work rollers.
The power requirement of a straightening machine is another variable that must be considered. The power required to straighten a metal depends on the maximum width, material thickness and yield strength of the material. The type of work roll material, diameter and center distance spacing is also an important factor in determining the power needed for straightening. The combination of these factors is why there is no such thing as a one-size-fits-all straightener.
Generally speaking, there are two types of straighteners: roll-type and stretching machines. The most common roll-type straighteners are based on the principle of rolling stresses. They use a series of large, usually circular work rolls that are spaced to accommodate the desired work radius. These work rolls are then driven by a motor to rotate in the same direction and apply a pressure against the work piece.
The advantage of the roll-type straightener is its versatility and simple construction. This flexibility allows it to straighten a variety of materials, including thinner and wider materials. However, it is difficult to achieve high levels of flatness and dimensional accuracy with this method.
A straightener’s ability to effectively straighten a particular coil or section of material is contingent upon the correct and consistent set-up of the machine. The combination of pinch roll pressures, drag brake strength and work roller depth settings are all critical to the straightening process. Attention to these variables at the time of straightener specification provides the manufacturer with a comprehensive understanding of the application requirements, and helps ensure that the right machine is selected for the job.