How to Specify a Straightening Machine
Straightening machine is a type of industrial machinery that helps eliminate size inaccuracies in rolled, drawn or extruded ferrous and non-ferrous metals. The rotary straightening process removes residual stress, up and down bending, side bending, torsion, gnawing, correction markings and many other defects in the finished product. Straightening can also reduce material costs and processing times by reducing the number of passes needed to achieve the desired quality.
Several factors determine the effectiveness of straightening. Pinch roll pressures, work roller depth settings and drag brake strength all play a role in the final straightness of the bar or profile. The proper combination of these settings is key to achieving effective results for any straightening application.
As with all rolling mill equipment, a straightening machine must be correctly specified for the material and application. Due to the potential variation in material types, thickness and widths, no single straightener can adequately meet the demands of all applications. The manufacturer of the straightener must address these variables during the specification process. This allows for a better understanding of the application requirements and ensures that the correct straightener is selected for the job.
Most industrial rotary straighteners are designed to provide an even amount of contact across the entire width of the material being straightened. This is accomplished by providing a set of entrance side pinch rolls and, in some cases, a set of exit side pinch rolls. In addition, most machines are equipped with a series of back-up rollers that are positioned in one, two or three places (depending on the machine) between each pair of work rollers. These back-up rollers are designed to take some of the load from the pinch rolls and help prevent the work rollers from bending during straightening.
The design of the straightening machine and the way in which it is driven are also important to achieving effective results. Some machines use a separate feeder and straightener while others are all-in-one straightener-feeder models. Depending on the size of the machine, inertia can cause problems with the accuracy and effectiveness of the straightening operation if the feed system is not carefully controlled during starts and stops.
Lastly, the power required to operate a straightening machine is another important consideration. The most common method for driving the work rolls is through a set of drive motors. These can be used in conjunction with an electronic power sharing system to optimize the performance of the machine. Depending on the application, the power requirements can vary widely. In general, higher yield strength materials require greater power to straighten than lower yield strength materials. Additionally, the diameter of the work rolls and their center distance spacing (roller pitch) can significantly impact the power required to operate the machine.