Section Bend Types
Section Bending Types
Section bending (also called profile bending) is done in a wide variety of metals in various ways.
First of all, the curving of standard mill shapes—angles, bars, beams, channels, tees, pipe, and tube, are all part of section bending. It is also the case that aluminum extrusions, even extremely complex sections of aluminum, can be rolled and formed into a ring.
Section bending, therefore, comprises all types of profile bending. Steel tube bending is one of the most common types of profile bending.
Compound steel bending also called “elevation and plan view curve” or “camber and sweep” or “hard way and easy way,” Compound bending can be used in a number of different construction projects such as arched roofs, domes and canopies.
Additionally, this type of bending can be performed on a range of steel shapes such as angle, tube, beam, bar, channel, sheet and plate and more. Sheet metal and plate metal can be bent into a compound curve that matches the needs of any project.
BIT’s CNC aluminum profile bending machine can realize Compound Bending
“Helical spiral bending” can be done with virtually every structural steel section as well as with plate. Actually, spiral bending most accurately refers to curved steel that has the shape of a hose coiled flat on the ground or the shape of the heating coil of a cooking range. The resultant coils are sometimes called “pancake coils.”
True helical steel bending is also called “pitched rolling” or “sloped rolling.” Helical rolling is commonly used for curved steel stair stringers, curved steel stair handrails, and helical transfer conveyors. Stringer members are checked for radius, pitch and plumb for ease of fabrication. As an alternative to true helixes, handrails can be rolled to an approximate flat radius for a lower price but may require field fitting.
The best way to visualize helical bending is to imagine the heating coil on the top of a stove. Although almost every structural material can be bent into a helix, as with anything, some materials and shapes can be bent more easily than others.
Rolling pipe into a helix presents a problem due to the fact that if you roll a pipe into a helix that matches a plan view of a project, you can end up with a piece of material that does not meet required tolerances. It’s vitally important that bending services include the pitch of the helix in the calculations made before bending, or the final result will not match what was expected for the project.
The application of helical bending in both residential and commercial construction projects adds a visual appeal and enhanced experience to the architecture. In more practical use, helical bending can be used to create stairs that wrap around storage tanks, they can also be used as stiffeners and wind deflectors on stacks exposed to the elements.
Minimum Radius Bending
Minimum radius bending can be performed with many different forms of metal, including structural steel, plate, bar, pipe, or tube and can be used on any variety of metal alloys. Naturally, the products will have to meet extremely specific requirements for your project, and each project can have its own set of special difficulties.
Distortion of a rolled product can occur during the bending process, leaving customers with products that can’t be used because it doesn’t meet project specifications. Because of the tight radius, metal can experience added stress in the bends. Cracks can then form on the outside of the bend, making the part easier to break.
Additionally, the size of the piece being bent can cause problems for inexperienced benders. Pieces that are particularly large or small can be difficult to bend correctly, and the variety of available metal alloys also adds to the complexity of bending to a tight radius.
Multi-Radius steel bending can be accomplished within the same part, saving customers splices and material wasted at the ends of the bending. Ellipses, parabolas, and special cambers would fall under this category. Flat, “pancake” coils or true spirals can also be produced.
When bending parts in multiple radii, special attention needs to be paid to the process of creating the bends. Parts need to be bent in multiple directions, and with varying tightness in order for it to meet the requirements of a project. At times, parts may be fabricated from different lengths of metal which have been bent then welded together, but this can result in lower quality than a single part. Multi-radius bending allows for a single part to be produced with all of the necessary bends.
No matter if the part is decorative, functional, or a bit of both, multi-radius bending can be used to achieve the desired look and function, while eliminating the need to weld parts together. The use of ellipses, parabolas and specialized cambers can all be accommodated through multi-radius bending.
Off-axis bending is a process that takes a material, bends it out of square, and then introduces a radius to it.
Also called conical rolling and is specified by citing a major and a minor diameter along with the height and degree of arc of the curved steel.
Ordinarily, this type of bending would take place only on a single plane, and off-axis bending presents a unique set of difficulties, since non-round materials can easily experience deformation during the bending process.
Because of the difficulty involved in multi-axis bending, specialized tools are needed for a company to correctly bend metal to specification. Deformation can be a real problem for inexperienced companies, and it’s a good idea for you to ask a company for distortion estimates in order to be sure that the final product will meet all of your requirements.
Commonly used for roofs and domes, off-axis bending can provide shapes bent from angles, bars, beams, channels and tubes, as well as plate and sheet metal. Industrial funnels, transitions and stacks are other common uses for conical steel bending.
In construction applications, off-axis bends are commonly used on roofs and domes and can be formed from many shapes including angle, bar, beam, channel, tube, sheet and plate.
Conical steel bending is also commonly used in industrial equipment such as funnels, transitions, and stacks.
Reverse Curve Bending
Reverse curve bending is also known as an S-Curve.
In this type of bending, the radius center changes from one side of the part to the other.
With reverse curve bending, it’s ideal for there to be a few feet of straight between the two curves, but some steel sections can still be successfully bent without the straight.
Often, multiple pieces need to be bent to meet a project’s needs, then the pieces welded together. Doing so may create an inferior piece while also adding the expense of the welding process.
Reverse curve bending allows for the creation of a stronger, single piece of bent metal without the need for welds or splices which may compromise the quality of the piece.
Using reverse curve bending, structures can be created which look both aesthetically pleasing, and are also functional. Roof structures, canopies, and trusses are all possible applications of the reverse curve bend, while metallic art puts the process to use on a purely visual level.
American Institute of Steel Construction: Curved Member Design Guide