Given the abundant and yet-to-be-exploited wind resources, wind power is poised to significantly boost economies for the foreseeable future. This presents an excellent opportunity for manufacturers involved in producing essential components, including the towering structures themselves. PRV variable geometry 3-roll bending machines are well-suited for shaping the conical plate sections required in wind tower construction, offering greater efficiency compared to widely used 4-roll plate rolling machines.

Precision Plate Feeding and Alignment

To commence plate infeeding and alignment, the plate is initially positioned onto a supportive, motorized rollway and fed into the three bending rolls. Subsequently, alignment is ensured through the assistance of two hydraulic side arms: one placed opposite to the material infeed, and the other acting as a rollway.

Given that the plate will transform into a circular section with a ring shape, it is imperative that the side designated for the smaller diameter of the cone possesses a lesser amount of curvature. Consequently, alignment at the plate’s central axis is crucial, with the plate fed into the rolls at a slight angle rather than in parallel.

This conical section underscores the advantage offered by PRV variable geometry 3-roll bending machines over four-roll bending counterparts. Unlike four-roll bending machines that mandate material presentation in parallel to the rolls to prebend the entire leading edge, PRV variable geometry plate rolling machines allow for material presentation to the rolls at an angle, deviating from the parallel alignment with the top roll axis.

First Prebending and Roll-Bending

Subsequently, the leading edge of the plate undergoes pre-bending as it traverses through the rotation of the rolls, reaching the midpoint between the top and left-side rolls. Simultaneously, the top roll descends, exerting pressure and bending the plate. The top roll specifically targets the leading edge, leaving the rest of the plate in a horizontal position on the rollaway. To enable smooth sliding of the plate, the side rolls are inclined at the cone angle.

The pre-bending process highlights another advantage of 3-roll bending machines with variable axis over 4-roll bending machine counterparts for wind tower sections. With a three-roll bender, pre-bending can be accomplished on the angled edge of the plate. In contrast, a 4-roll plate rolling machine utilizes the top and central rolls to pinch the plate, while the side roll lifts the plate for prebending. Due to the considerable length of the plate for wind towers, a bridge crane or an exceptionally long “scissor lift” table is required for lifting and repositioning.

Following prebending, the plate proceeds with its clockwise rotation. The left hydraulic side arm with double articulation supports a medium to large diameter and guides it towards the hydraulic central arm. To achieve optimal bending, the plate should be closed to 80-90 percent of its final diameter during this initial cycle.

To streamline operations and enhance efficiency, PRV 3-roll bending machines can be equipped with a control system displaying the position of the rolls and the tilting of the lateral roll. This panel assists operators in roll movement and retains operation memory for plates of identical dimensions. Additionally, the panel may provide information on anomalies, alarms, diagnostics of all electro valves, and monitoring of automatic lubrication.

Second Prebending and Roll-Bending

During the second phase of prebending and bending, the focus shifts to the trailing edge of the plate, which undergoes prebending in a manner similar to the leading edge. As the plate completes its rotation within the machine, the top roll applies pressure to the final section of the plate, effectively prebending it. Meanwhile, the lateral rolls maintain their positions, now inverted from their previous configuration during the prebending of the leading edge. Following this, the plate is closed by rotating it counterclockwise, with additional support provided by the two side arms equipped with double articulation and the central arm. This phase ensures that both ends of the plate receive the necessary prebending to achieve the desired shape for wind tower construction.

Calibration

Following prebending, the plate enters the calibration phase, which is crucial for stabilizing internal plate tensions and ensuring precise alignment. This phase also plays a key role in maintaining tight tolerances and eliminating the need for post-weld calibration in the machine. During calibration, the plate is rotated clockwise once again, ensuring uniformity in the bending process. In total, the plate undergoes three rotations from one side to the other, allowing for comprehensive calibration and adjustment. However, despite the efficiency of this process, variations in tolerance may still occur due to differences in the mechanical properties of the material and internal strains.

In instances where tolerance variations are observed, additional steps may be required to achieve the desired outcome. This may involve reinserting the plate into the machine for recalibration or implementing extensive welding to address inconsistencies in shape and alignment. Despite these challenges, the calibration phase ultimately ensures that the cone is completed with precision and accuracy, ready for extraction from the roll bender.

Conclusion

Each step in the plate rolling process serves to illustrate the benefits of utilizing a translating geometry three-roll system, particularly in the context of wind tower production. This innovative approach offers advantages not only in terms of efficiency and precision but also in its versatility for various other plate rolling applications. By leveraging the capabilities of PRV 3-roll bending machines, manufacturers can achieve superior results in the fabrication of wind towers and other structural components, contributing to the advancement of renewable energy infrastructure worldwide.

One of the more popular of these concepts is the PRV variable geometry plate rolling machine. This style machine allows you to have the pre bending capabilities of a four-roll plate roll, as well as the rolling ability of a double pinch three-roll plate rolling machine, with a wider range of capacity and functionality of both.

Works Cited: Plate Rolling for Wind Towers