Rolling Machine Plate

We are a professional rolling machine plate manufacturer with over 10 years of industry experience. Today, we would like to introduce a method for correcting excessively long straight edges on the ends of sheet metal during roll forming:

During roll forming, excessively long straight edges on the ends of sheet metal are a common process issue. This phenomenon can affect the overall roundness of the workpiece and the quality of subsequent welding. This article systematically explains the causes of this issue and provides practical correction methods, offering operators feasible solutions.

1.Analysis of the Causes of Excessively Long Straight Edges  

The straight edge phenomenon primarily stems from insufficient bending of the sheet material during the initial rolling stage. When the upper roller applies downward pressure, the central portion of the sheet material deforms first, while the ends remain straight due to insufficient pressure to maintain their flatness. As the rolling process continues, this unbent area forms a distinct straight edge.

Improper equipment parameter settings are the primary cause of excessive straight edges. Insufficient downward pressure or excessive feed speed can limit the bending extent of the sheet metal ends. Additionally, sheet metal properties significantly influence this issue; thicker or harder materials require greater deformation force and are more prone to straight edge problems. Operating techniques are equally critical; improper feeding methods can exacerbate the straight edge phenomenon.

2.Mechanical Adjustment and Correction Method

Pre-bending is the most direct solution. Before formal rolling, bend both ends of the sheet separately. Place one end of the sheet between the upper and lower rolls, and adjust the position of the upper roll to apply sufficient pressure to the end. Maintain the pressure to form the desired radius of curvature at the end of the sheet, then repeat the same operation on the other end. The pre-bending length should be slightly longer than the actual straight edge area, typically 1.5 to 2 times the thickness of the sheet metal.

Adjusting the roller spacing can improve the overall bending effect. Appropriately reducing the spacing between the side rollers and the upper roller can increase the force applied to the ends of the sheet metal. When adjusting, it is important to maintain symmetry on both sides to avoid distortion of the workpiece due to uneven force distribution. For thick plate processing, a stepwise adjustment method can be used, starting with a larger spacing and gradually reducing it to the target value.

The use of auxiliary rolls is particularly effective for special materials. Installing auxiliary support rolls on a conventional three-roll rolling machine plate provides additional pressure to the ends of the plate. Auxiliary rolls should be installed near the straight edge area, and their diameter should not be too large to avoid affecting the operation of the main rolls. When using them, adjust the height and pressure of the auxiliary rolls to ensure they are effective without leaving indentations on the plate surface.

4.Process Optimization Correction Method  

The multi-pass rolling method is suitable for thicker plates. The total downward pressure is distributed across multiple processing steps, with each pass completing a portion of the bending. The first pass focuses on the end regions, with subsequent passes gradually transitioning toward the center. This method effectively disperses deformation stress and is particularly suitable for processing high-hardness materials. The number of passes should be determined based on material thickness and hardness, typically not exceeding five passes.

The temperature-assisted method can reduce material deformation resistance. Local heating is applied to the straight-edge area to enhance material plasticity before rolling. The heating temperature should be controlled below the material's recrystallization temperature to avoid affecting mechanical properties. Flame heating or induction heating methods can be used, with a heating width approximately 1.2 to 1.5 times the length of the straight edge. Rolling operations should be performed immediately after heating to prevent rapid temperature loss.

The progressive feeding method improves results by altering the processing sequence. First, allow the sheet metal end to extend beyond the rollers by a certain distance, causing the extended portion to form a natural bend during initial rolling. Then gradually feed the sheet metal back, expanding the bent area toward the center. This method requires precise control of the feeding amount, with each feed-back distance maintained consistently, typically between 50 and 100 millimeters.

5.Operational Precautions  

It is very important to record parameters during the correction process. Each adjustment of the roller position, pressure value, and processing effect should be recorded in detail to provide a reference for subsequent operations. In particular, when processing batches of workpieces, establishing a standard parameter table can significantly improve efficiency.

Quality inspection must be conducted throughout the entire correction process. After each adjustment, the straight-edge area should be measured to confirm that the length meets requirements. During inspection, use a specialized arc gauge or a 3D measuring instrument to focus on the smoothness of the transition areas. Any localized unevenness should be corrected promptly to prevent issues from accumulating.

Safety regulations must be strictly adhered to. When adjusting the roller spacing, be sure to disconnect the power supply to prevent accidents caused by misoperation. Wear protective equipment when handling heated plates to avoid burns. When multiple people are working together, they must be under unified command to ensure coordinated movements.

6.Troubleshooting

When excessive springback occurs after straight edge correction, appropriately increase the overwind amount or extend the holding time. For high-strength materials, consider performing a second correction. If end warping is detected, check whether the rollers are parallel and the pressure is balanced, and recalibrate the equipment if necessary.

If surface indentations appear, reduce the roller pressure and clean any impurities from the roller surface. Deeper indentations need to be polished to avoid becoming stress concentration points. If the correction effect is unstable, check whether the material properties are uniform and whether the equipment hydraulic system is working properly.

Correcting excessively long straight edges at the ends of sheet metal processed by a roll forming machine requires a comprehensive consideration of equipment adjustments and process optimization. By implementing standardized pre-bending treatment, reasonable parameter settings, and meticulous operational control, this issue can be effectively addressed. In practical applications, the most suitable correction scheme should be selected based on specific material and equipment conditions, and experience should be continuously accumulated in practice to establish operational standards tailored to the characteristics of one's own production. Good correction results not only improve the quality of individual pieces but also enhance overall processing efficiency and product consistency.

If you are interested in roll forming machines, please contact us.