Despite being designed with the best possible engineering and top grade materials, metal straightening machine are not without their limitations. A combination of pinch roll pressures, drag brake strength and work roller depth settings dictates the level of effectiveness for any given material thickness and width. The optimum combinations of these parameters are determined by the manufacturer for each specific application and machine design. Once the optimum settings are established, it is important to ensure that the machine is set up with consistent and reliable settings. In order to do this, a method of calibration for the work roller depth setting must be established and maintained.
Most of the current range of straighteners are designed for use on a wide variety of metal thicknesses. However, there are many applications where the material will only be processed to a narrower width. When this happens, the forces and stresses placed on the work rollers of the machine will be significantly greater than when it is operating with a wider width of material. This means that the work rollers are more likely to deflect and bend. A simple way to minimize this is by placing a single row of back-up rollers beneath the main work row of the straightener. This will reduce the amount of bending and deflection of the work rollers and improve the accuracy of the bending and straightening process.
Generally speaking, the higher the roller heights are on a straightener, the easier it will be to achieve a straighter product. However, it is also important to remember that aluminum is much more difficult to straighten than steel because of its elastic properties. This is why it is always a good idea to start with a lower set of rollers and then raise them to the appropriate height for the thickness of the material being straightened.
Straightening machines can be divided into two major types; those that utilize a roll stand in staggered rows and those that employ a stretching system. Both are used to correct defects such as residual stress, up and down bending, side bending and torsion. They do this by alternately bending the material around sets of rolls and allowing it to exceed its yield point, thereby reducing internal stresses and homogenizing those that cannot be removed entirely.