When bent and formed aluminum extrusions, need to consider factors, such as inside and outside diameters, critical surface areas, and mechanical strength can affect a part’s final fit and finish. Different types of bending and stretch-forming methods deliver different results.
3 factors to decide which aluminum profile bending method to choose
Aluminum can be extruded and bent to specified tolerances or to standard dimensional tolerances. While a product’s dimensions and bend angles can be methodically measured and re-measured, the end product will only be as precise as the bending equipment or method used. Deformation of the inside or outside radii can be a design issue and can also determine which forming process to use in bending or forming the aluminum profile.
So several 3 factors should be considered when choosing which bending process is appropriate for a certain product.
- What tolerances, or deviations, are expected on the inside radius, the outside dimension radius, and the overall length of the part?
- What surface areas are critical for appearance?
- What mechanical strength is required?
5 common bending and forming methods for aluminum profiles
Each of these following 5 bending methods has various benefits. Designing for success and determining the best method ultimately comes down to an end product’s desired tolerance, appearance, and strength.
Bending and forming methods 1#: Ram or Push Bending
- Definition: Ram or push bending, as the name implies, uses a ram to force the extruded metal piece on a bending die.
- Work principle: A die pushes the extrusion onto the pressure dies, forcing the extrusion into your desired bent form.
- Features: With programmable bend angles, this form of bending allows close proximity to multiple planes bends, though only one radius can be bent at a time. Ram bending offers inexpensive tooling and good bend precision with low per-bend cost.
- Application: Ram or Push Bending is ideal for components such as boat gunnels, portable structure supports, wheelchair frames, and medical beds.
Bending and forming methods 2#: Rotary-draw bending
Rotary-draw bending involves rotating a piece of steel around a solid die and pulling the material around a specified radius while internally supporting the material with a mandrel (if it’s hollow).
- Hydraulic Rotary Draw Bending:Rotary-draw bending involves rotating a piece of steel around a solid die and pulling the material around a specified radius while internally supporting the material with a mandrel (if it’s hollow). Definition and work principle: In the hydraulic rotary draw bending process, manufacturers place extruded aluminum onto a bender and hold it in place with a stationary or sliding pressure die and clamping block. The round bending die, powered by hydraulics, is rotated up to 90 degrees, bending the extrusion as it rotates. Features: With Hydraulic Rotary Draw Bending method, an extrusion can only be bent one radius at a time. Incorporating a mandrel or other tool component to grip the rotary die can prevent creasing or misshaping of the product, though its use isn’t required. The single-axis-controlled revolution can bend within one-tenth of a degree for extremely precise bend angles. Application: Hydraulic bending is often used when forming round tubes or pipes for applications such as handrails, and is ideal for extrusions with a large diameter, such as building signage.
- Electric Rotary Draw Bending – Definition and work principle: Electric rotary draw bending uses the same process as the hydraulic method, but allows faster setup. Features: The bends also are more accurate and easily repeated because angles and rotations can be automated in a machine’s programmable logic controller. Rotations of the extruded aluminum also can be mechanized for variable plane bends. Application: The electric rotary draw method is best for applications that require multiple bends per part in close proximity to each other, or different radii bends for each part.
Bending and forming methods 3#: Incremental bending
Incremental or camber bending is a process in which pressure is applied at the third point of the member via a hydraulic ram or press. This process is often used for curving steel to very large radii.
Bending and forming methods 4#: Three-Roll Bending
- Definition: Three-roll bending pushes an extrusion around three different rolls placed in a triangular shape.
- Work principle: The rolls are adjusted to form a precise angle, up to a 360-degree rotation, that can roll horizontally or vertically. As the extrusion is slowly moved across the power-driven rollers, it begins to curve and bend.
- Extrusions are limited to a single bend per cycle, meaning a higher angle of the bend would take longer to reach the desired angle.
- Though it may take longer, the maximum bend radius is unlimited.
- Application: Symmetrical profiles are preferable for roll bending.
Bending and forming methods 5#: Stretch Forming
- Definition and work principle: During stretch forming, an extrusion is placed along a rounded, fixed bending die and clamped in place on each end. The machine begins to swing the clamped ends downward to angles up to 180 degrees, and the extrusion is bent around the die to reach the desired form.
- The bend radius is unlimited with this method.
- A stretch forming machine can bend, twist and lift an extrusion simultaneously to create unique, specified shapes and angles for parts up to 25 feet long.
- This method also offers the most accurate and consistent bending through elongation control.
- Because of the way the rounded, fixed bending die pushes on the extrusion, stretch forming has the least amount of surface distortion and traffic marking on the extruded piece.
- Application: Stretch forming is commonly used for parts with a larger bend radius, as the minimum bend radius is generally two to three times greater than other forming/bending methods.
Read More: Bending Machine Wikipedia