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Critical Factors in Bending Aluminum Extrusions

Designing your aluminum-extruded components to get you to your final near-net shape is ideal. When this is not possible and your design requires a curved or bent feature, it is important to understand the critical factors during bending that can affect the quality of your component’s final shape.

Whether it is a 20-degree curve or a 180-degree u-shape, work with your extrusion supplier early in the product design stage to choose the appropriate bending equipment and technique for your shape’s needs. To form your product to its proper specifications, your extruder will address any pre-bending requirements during the design stage. Alloy choice and temper, for instance, need to be determined upfront. Your profile’s final geometry, tolerances, and surface finish requirements, also can influence the bending process used, as well as the consideration and management of spring back.

If an extruder makes changes to your design features and specifications, as they may often do, it is not to push their own ideas. They do it because they know how and where to avoid unexpected flaws in your extrusion caused by bending techniques that can affect your final product’s look, feel and functionality.

The extruder needs to maintain certain features to avoid problems with your part’s final fit and finish during the bending process, including:

  • Inside and outside diameters
  • Radii deformations or deviations
  • Critical surface areas
  • Mechanical strength
  • Length of the part

Why Does Lag-Time Matter?
Keep in mind when using extruded aluminum components in your product designs, aluminum naturally ages and becomes stronger over time. The longer the lag-time between the extrusion and bending processes, the more difficult it is to bend or stretch-form your components to the design specifications. If you transfer extrusions from the extruder to the bending supplier, it will be harder to bend or form them accurately, consistently, and without surface defects or deformations.

Some manufacturers may also be transporting their components from the extruder to a bending supplier and then back to the extruder for artificial aging. This can stack-up lead-times, and add redundant handling and freight charges. To improve the reliability and quality of your formed extrusions, and save money on shipping charges, work with an extruder who also can bend your components, and provide other fabrication processes, such as machining and finishing.

Bending Types
Aluminum extruded components can be extruded and bent to specified tolerances or to standard dimensional tolerances. Keep in mind, the formed dimensions and bend angles of your product will only be as precise as the bending equipment or method used. Different types of bending and stretch forming methods deliver different results.

  • Ram or push bending works best for simple operations, shaping parts with a three-part tool where the bending die pushes the profile against the wipers. This type of bending is ideal for components such as fish house frames, trailer parts, boatlift beams, and ambulance beds.
  • Twin head compression bending is a fast method to make parts that have two bends, such as solar frames, chair handles and furniture frames.
  • Rotary draw bending can create more complex, multiple bend parts, via CNC control, with or without a mandrel. This is best for applications that require multiple bends per part in close proximity to each other, or different radii bends for each. Ideal products for this type of bending, include swing set frames, and trailer side-rails.
  • Roller or three-roll bending pushes an extrusion around three different rollers placed in a triangle, and slowly moves the component across the power-driven rollers to create a curve This will bend extrusions in a large radius, and can roll a fully circular part. Compared to stretch forming, tolerances are looser and quality is not as great, but tooling cost is less and bends are programmable. Boat gunnels, trim components, bumpers, and signage trim are common product components made from using roller and three-roll bending equipment.
  • Stretch forming is for parts with a larger bend radius, as the minimum bend radius is generally two to three times greater than other forming/bending. Stretch forming is ideal for boat gunnels and trim, roof rails, medical imaging c-arms, and bumpers.

To learn more about Alexandria Industries bending and forming services, capabilities and expertise, please contact your sales specialist and see this white paper.