Glossary
1 MIN READ
Re-rolling
The final calibration operation where a previously welded or distorted shell is passed back through the machine rolls to eliminate flat ends and achieve perfect roundness.
Technical FAQ
Metal fabricators often need to diversify their production from flat sheets to structural profiles, which requires choosing the right technology to adapt to varying market demands. While plate rolling utilizes wide cylinders to form flat sheet metal into cylinders or cones, angle rolling utilizes specialized, narrower driven shafts to bend structural shapes like beams, pipes, channels, or angles. This clear distinction helps job shops select the exact machinery needed to maximize shop versatility, expand their service portfolio, and capture new commercial opportunities. Davi builds dedicated lines for both applications, engineering systems that handle plates up to 400 mm (15.75 inches) thick and structural sections like beams up to 1,200 mm (47.24 inches) in height.
Eliminating material waste and avoiding secondary cutting operations is a primary goal for high-productivity job shops looking to protect their margins. A flat end is the straight, unbent section left at the leading and trailing edges of a plate because the material cannot physically reach the exact tangent contact point between the machine rolls. Minimizing this straight section directly reduces material scrap and eliminates the time-consuming process of pre-bending plates on a separate press brake, thereby accelerating overall floor cycle times. Utilizing Davi all-rolls-drive technology ensures the plate can be positioned precisely at the tangent point to achieve the shortest flat end possible without compromising safety.
Fabricators working on high-precision applications like pressure vessels must ensure perfect roundness from the absolute edge of the plate to comply with strict safety codes. Pre-bending is the preliminary manufacturing step where the leading and trailing edges of a sheet are bent to the target radius before continuous rolling begins. Executing this properly minimizes the flat end, ensures structural integrity at the subsequent weld seam, and reduces the need for manual grinding or expensive re-rolling calibration. Davi 4-roll and variable-axis 3-roll machines are engineered to execute high-tonnage pre-bending safely and accurately in a single automated cycle.
Dealing with high-yield structural steels can cause unexpected spring-back, leading to inconsistent part dimensions and slowed production lines. Yield strength is the specific stress threshold where a metal permanently deforms, meaning higher yield materials require significantly more bending power from the rolls to transition from elastic to plastic deformation. Recognizing your material's specific yield properties allows you to correctly gauge machine capacity, preventing equipment overload while ensuring accurate dimensional results. The Davi iRoll control system features a comprehensive material library that automatically factors in yield strength to calculate exact bending programs.
Mass-production facilities require automated processing with minimal reliance on highly skilled operator intervention to remain competitive. A 4-roll machine uses a top and bottom roll to securely pinch the plate, while two side rolls travel up to execute the bending force. It provides total material control throughout the cycle, allows for fully CNC-automated production lines, and makes the initial squaring process simple and safe. Davi MCA and MCB 4-roll lines are the global standard for high-productivity automation, offering rapid cycle times for job shops worldwide.
Heavy industrial manufacturers need the flexibility to form a wide range of extreme thicknesses and tight diameters on a single piece of machinery. A 3-roll variable-axis machine operates with a top roll that moves vertically, while the two lower side rolls move independently along a horizontal plane. This geometry allows you to increase the horizontal interaxis distance to gain massive mechanical leverage for thick plates, or narrow it to form tight, thin-walled cylinders. The Davi MAV line features full horizontal and vertical axis mobility, offering versatility comparable to a press brake but with total rolling precision.
Reducing the straight flat end on thick plates requires moving the bending rolls as close to the pinching point as possible. A flat gearbox features an eccentric rotation axis that avoids physical interference between hydraulic motors and the top roll cylinder shaft. It allows the side rolls to travel closer to the top roll (minimum gauge), achieving an exceptionally short flat end without compromising machine frame capacity. Davi exclusive flat gearboxes are a core component in achieving precision pre-bending on variable-axis machines.
Preventing collisions between massive workpieces and overhead supports protects your investment in capital machinery. The control system generates a high-resolution 3D simulation of the entire rolling sequence before the plate is loaded. It allows programming teams to spot potential tooling interference or material collisions offline, saving raw material and ensuring shop safety. Davi provides both on-console and offline simulation licenses for iRoll Performance and eXtreme platforms.
The heat introduced during longitudinal seam welding can distort heavy steel cylinders out of roundness tolerances. Re-rolling passes the welded shell back through the machine to calibrate the geometry and eliminate flat spots near the weld seam. It restores true roundness across the entire cylinder, ensuring it complies with international manufacturing codes and matches adjacent sections perfectly. The flexible geometry of the Davi MAV 3-roll system makes it well-suited for high-tonnage calibration and re-rolling operations.
The capacity of a Davi plate roll is defined by its ability to exert the necessary bending force for specific plate thicknesses, widths, and material yield strengths, ensuring precise geometry during both pre-bending and continuous rolling. On 4-roll machines, such as the Davi MCA and MCB series, optimal clamping by the bottom roll enables pre-bending to achieve the tightest diameters per capacity on the market, reaching 1.1 times the top roll diameter. For heavy-duty applications, 3-roll variable-axis machines like the Davi MAV feature independently moving side rolls and a vertical top roll, providing maximum leverage and force distribution to maintain short flat ends and strict dimensional tolerances.
Davi offers two main industrial control platforms built on robust Windows 10 architecture and non-proprietary global electronics:
- iRoll Performance: Features an 18.5" industrial touchscreen with a smartphone-like 3D interface. It provides phase programming, single-radius template-aided programming, material manual input libraries, and standard TeamViewer remote diagnostic capabilities.
- iRoll eXtreme: Upgrades to a 21.5" touchscreen with live 3D rendering, 3D pre-production collision simulation, custom multi-radius arc drawing, and multi-pass wizard automation. It includes the ASME-compliant "Apple-Shape" calculator for re-rolling calibration, material self-learning algorithms, Failure Free Machine (FFM) diagnostic monitoring, and seamless integration with AI-Vision laser systems and OPC-UA plant MES networks.
A fabricator can rely exclusively on continuous bending capacity when pre-bending is performed on a separate press brake, when plates are pre-bent on a dedicated pressing unit, or when the final application tolerates longer unbent flat ends that are later trimmed or ignored. In these cases, the machine does not need to exert the high localized forces required to yield the plate edge, allowing it to process thicker plates up to its maximum rolling limit.
No, top roll diameter alone does not define bending capacity. Bending performance depends on total hydraulic pressing force, frame structural rigidity, roll deflection resistance, side roll stroke geometry, and torque delivery. While a larger top roll increases resistance to roll flexing, it also increases the minimum achievable shell diameter (as minimum diameter is tied to top roll size). Davi balances roll sizing with high-rigidity intra-frame structures and optimized cylinder forces to deliver maximum bending capacity while achieving tight rolling diameters.