Why Pre Bending Capacity Matters More Than Rolling Capacity When Selecting a Plate Rolling Machine Manufacturer
As a thick plate enters a rolling machine, the final cylinder or cone is not defined purely by the rated rolling capacity. In many cases the first bends may dictate the outcome: whether the plate will adopt the desired geometry.
This is a reason why the pre bending capacity becomes an important consideration when choosing a Plate rolling machine manufacturer. Rolling capacity may be defined, while the plate is being rolled, but a machine that does not perform well during pre bending tasks may leave straight ends that need to be cut and create inconsistency in the produced diameters.
Rolling vs. Pre Bending Capacity Explained Simply
Rolling capacity typically defines the plate thickness and width that can be accepted and processed in a rolling machine. This value is not the only influencing factor during pre bending: the plate edges are brought to a radius, allowing for a smaller flat area at the edge.
During standard three-roll plate bending, a certain amount of curvature needs to be induced near to both edges so that the machine can continue to deform the plate to the required specifications. If a rolling machine cannot produce such curvature, the extra length of straight edges will need to be removed by cutting. This waste of material becomes significant when thicker plates are processed.
How Pre Bending Influences Plate Geometry
A plate will not take any shape simply because it is placed between three rolls of a rolling machine. This process is influenced by the rolls’ diameter, the orientation of the rolls, the plate’s thickness and material, the pressing force, and the sequence in which the rolls act on the blank.
Edges are particularly sensitive, as the support from the rolls is not present at the beginning of the process.
A machine with good pre bending characteristics will be able to form the plate’s edge into a close approximation of the desired radius: reducing the amount of straight area to be removed.
Inadequate pre bending can lead to the following complications:
- More extensive straight areas at the plate edges, requiring additional cutting or bending to form the cylinder
- Inconsistency in diameter between shells
- Increased need for manual correction of the edge geometry
- Increased time spent on forming and adjustment
- More material waste due to the removal of straight areas at the edges
Rolling Capacity vs. Pre Bending Requirements
While it is common to evaluate a rolling machine’s suitability according to the pressure exerted by the rolls and their stated rolling capacity, the actual force applied during pre bending is not necessarily defined by this value. All the components of the machine, including the frame, the rolls’ diameter, the location of the bearings, the hydraulic system, and the roll adjustment mechanism collectively define the actual force that can be applied to the blank.
A sturdy frame prevents excessive roll displacement under pressure, preventing uneven deformation of the plate. If the rolling machine applies pressure inconsistently along the plate’s width during pre bending, this will affect the radius of the resulting shell.
Material Strength Determines Pre Bending Difficulty
The thickness of the plate is not the sole determinant of how easily it can be deformed. Two plates with identical thickness but different yield strengths will exhibit different behavior during rolling. The same applies to steel grades with different ultimate tensile strength (UTS) and yield strength.
Materials such as carbon steel, stainless steel, alloy steel, and other grades with increased strength do not behave identically during rolling, bending, and other forming processes.
Higher strength plate materials will typically require more force to be applied during deformation. They will also exhibit higher springback after pressure has been released.
Appropriate pre bending characteristics and rolling force capacity will ensure that the material can be formed consistently.
Material Savings and Reduced Secondary Processing with Effective Pre Bending
The overall savings that can be achieved by reducing the amount of material needed to form a shell is difficult to estimate. This value is not included in the rolling capacity of a machine, but it can affect the outcome significantly. If the plate has to be cut at both ends to remove the straight edges, the amount of wasted material can add up over the course of a series of components.
Such material cannot always be reused, depending on the required size and geometry. Further, additional processing will be needed to remove the straight edges. This adds to the time spent on fabrication and can also impact the quality of the finished product.
Plate Rolling Accuracy Requirements Affect Pre Bending
The accuracy with which a shell or a cylinder can be produced is of particular importance if the plate needs to be welded. In the case of a shell, a dimensional inconsistency can prevent the ends from being joined, or may require the use of more force during welding.
Welding large diameter shells and cylinders also requires additional control over the rotation of the rolls. Consistent pre bending prevents the need for excessive adjustment before the shell is welded.
Other Considerations for a Plate Rolling Machine Manufacturer
It is common to ask a potential supplier basic questions about the rolling capacity of their machines, such as the thickness of the plates that can be processed. A more involved conversation should also cover the conditions under which the machine will be used and the type of material that will be rolled.
Questions such as the maximum plate width and thickness that can be rolled for the intended material, the minimum diameter that can be achieved, the diameter of the rolls, the thickness of the plate that can be pre bent, or if the values apply to a specific yield strength should also be included. It is advisable to also ask how the rolling capacity is defined, as different manufacturers may have different conditions for this value.
A competent Plate rolling machine manufacturer will also be able to discuss the relationship between plate thickness, material, width, diameter, and pre bending.
The Importance of Control and Consistency
Rolling machines can be equipped with hydraulic controls, programmable options, digital measurement tools, or CNC technology. The ability to produce consistent results during pre bending is impacted by how well the machine’s rolls can be positioned, and how consistently they apply force to the blank. If the process requires operators to make repeated adjustments to achieve the desired edge radius, the overall productivity of the machine is compromised.
Considering Rolling and Pre Bending Capacity Together
Each rolling machine should be evaluated according to the conditions in which it will be used. A machine with a higher rolling capacity but inadequate pre bending characteristics may fail to consistently produce the required plate geometry.
For example, the same rolling capacity may not be achievable for a higher yield strength steel plate, if the rolling machine is used with the same plate width and diameter.
When considering a purchase, it is essential that the required rolling and pre bending capacity is specified, taking into account the most demanding combination of plate thickness, width, material, and diameter that will be encountered in production.
Siddhapura’s Approach to Plate Rolling Equipment
Siddhapura is experienced in providing solutions for industrial machinery, in which the design, performance, and production conditions need to be taken into account. When looking to purchase a plate rolling machine with appropriate pre bending characteristics, it is essential to consider the intended use, the materials that will be processed, and the anticipated production rate. More details on the products and solutions offered by Siddhapura can be found on the Siddhapura website.
Conclusion: Rolling Capacity Is Only Part of the Equation
Rolling capacity is one of several factors that define a plate rolling machine. Pre bending capacity has a direct impact on the resulting plate geometry, material utilization, accuracy, production rate, and the amount of secondary processing that will be needed.
A rolling machine may have an adequate capacity to process a thick plate, but if its pre bending characteristics are not up to the task, the result may involve the need for additional processing. Rolling machines should be compared according to their ability to produce consistent results under the intended production conditions.
A competent Plate rolling machine manufacturer will provide detailed information on the capabilities of their equipment, and will take into account the conditions in which the machine will be used. During the selection process, it is important to ensure that a rolling machine can fulfill the expectations in terms of pre bending and rolling capacity for the intended application.