Straightening machine is a metal-working process that corrects flatness defects and reduces residual stresses in the material. The process works by alternately bending the metal in different directions, passing through a set of rollers. By this means the material is strained past its yield point, thus reducing internal stresses and homogenizing those that cannot be removed.
Different types of metals have different yield points and therefore there is no one-size-fits-all solution for metal straightening. Consequently, the power requirements vary widely and must be carefully defined for each specific application. For example, the power requirement is influenced by the maximum material thickness and width to be processed. Also, the roller diameter and centre distance spacing will dramatically affect power demand.
In general, the more work rolls there are in a straightening machine the better. This is because the additional rolling action creates more plastic deformation and, in turn, improves the quality of the final product. However, it is important to remember that more work rolls will increase the bending moment and stress on the rollers, making the machine harder to control.
Another factor to consider is the maximum speed at which the straightening machine can operate. This is typically defined as the maximum progress of the material per minute through the machine. A common mistake in specifying a straightener is to simply look at the capacity to straighten wide material and ignore the effect that narrower materials will have on the machine. The resulting bending moments and forces on the straightener rollers can cause marking, deformation, gnawing, and correction cracks.
The straightening machines that are available in the market are generally of two main varieties: powered and non-powered. The powered straighteners have driven work rollers that are capable of removing coil set from most metals and thicknesses. Non-powered straighteners, on the other hand, rely on the feed to provide the necessary power for the straightening process. While these straighteners can still remove coil set, they are prone to other issues such as inaccuracy due to the feed slippage and slower speeds than a powered straightener.
Some of the more sophisticated straightening machines use a combination of both powered and non-powered work rollers. These machines are able to achieve greater precision than simple non-powered straighteners by providing the ability to apply a high level of pressure to the upper work rollers without causing significant deflection or bending. This allows the work rollers to effectively strain the tube past its elastic limit, thereby improving its quality and eliminating the need for subsequent annealing. The advantage of this type of straightening machine is that it can be used to straighten a variety of different materials, including steel and copper. However, it is important to remember that these machines are typically more expensive than non-powered straighteners and can require more maintenance because of the higher amount of power required to drive the working rollers. However, the benefits of this type of equipment often outweigh the increased costs associated with it.