Skip to content

The Solution for Roof Rack: Stretch Forming and Roll Bending

Roof Rack

Load-Bearing Requirements

Depending on the requirements of the main manufacturer, roof racks have different rated load-bearing requirements: non-load-bearing roof racks, as exterior decorative components, have zero load-bearing requirements; small and medium-sized passenger cars generally have a load-bearing requirement of 50kg; large or off-road vehicle models typically require 75kg. Roof racks must not exhibit looseness, abnormal sounds, or inability to bear the rated load during the entire vehicle design and development process, as well as during subsequent customer usage. Relevant industry standards should be consulted during the design phase.

Disassembly and Maintenance Requirements

Most roof racks are installed internally, so when repairs or replacements are needed, the dismantling of the roof and interior panels is required, which is a relatively cumbersome process. Given the current low repair rates, this method is still acceptable. However, from the perspective of convenience in disassembly and assembly, it is suggested that roof racks could be changed to external installation or that space for disassembly could be reserved on the roof/interior panels. These requirements should be considered during the initial design phase.

Technical Requirements

The main processes for roof rack aluminum bars are extrusion and stretch forming. Due to the particularities of these two processes, it is necessary to ensure manufacturability in the initial design phase. The extrusion process requires the aluminum bar section to be of uniform cross-section, while for the stretch forming process, it is necessary to first determine whether it is a two-dimensional or three-dimensional stretch forming, and then confirm whether the supplier’s equipment capabilities meet the manufacturing requirements based on the specific stretch forming process.

Stretch forming is a cold working stretch forming method where the workpiece is subjected to tangential tension while bending, and is formed by the combined action of bending moment and tension. During stretch forming, the stress inside the workpiece section is generally dominated by tensile stress, with minimal or no compressive stress, resulting in minimal springback, good fit to the mold, less wrinkling, and high forming accuracy. Depending on the principles of stretch forming and the equipment used, stretch forming can be divided into rotary stretch forming and arm-type stretch forming, with roof racks generally using arm-type stretch forming.

Roof Rack Stretch Forming Machine

The roof rack stretch forming machine is mainly used for the cold bending forming of automobile roof racks, and can bend various styles of roof racks, door frames, glass guides, window frame trims, and roof trims with different molds.

Equipment Characteristics

  • Adopting a welded bed with good structural rigidity and vibration absorption performance, subjected to strict aging treatment. All moving parts can operate stably for a long time, achieving precision machining.
  • The lifting force of the left and right arms is controlled separately by two oil pumps, and the lifting torque is controlled by proportional overflow valves, with a deviation between set pressure and actual pressure of about 3%, and a repeat stability coefficient of 3% (30°C-40°C). The bending oil cylinder and clamping oil cylinder of the left and right arms are controlled by two oil pumps, with bending controlled by proportional directional valves. The lifting of the left and right Z-axes is controlled by two oil pumps separately, using proportional directional valves to control, and can be opened according to the arc radius requirements of the processed products, which is conducive to better energy saving.
  • In addition, the equipment is equipped with 8 sets of spare hydraulic interfaces and 4 sets of spare pneumatic interfaces, all of which are connected to the hydraulic, electrical, and other systems of the entire machine, and can be set according to the requirements of different molds of the equipment.
  • The equipment is quite convenient in terms of mold replacement, with generally one operator replacing a pair of common intact molds in about 2 hours (the time may vary depending on the simplicity of the mold). The equipment can store multiple sets of mold information, and after replacing the mold, the production data of the previous mold set can be promptly retrieved for production (and if necessary, minor adjustments can be made to the saved and retrieved data), effectively reducing debugging time and processing cycle.

Roll Bending for Roof Rack Forming

PBA aluminum profile bending machine

Roll bending, often facilitated by advanced machinery like the aluminum profile bending machine, stands as a pivotal technique in the manufacturing process of roof racks. This method offers a precise and efficient means of shaping aluminum profiles into the desired form, ensuring that roof racks meet stringent standards for load-bearing capacity, aesthetics, and functionality.

By utilizing the capabilities of the aluminum profile bending machine, manufacturers can achieve precise control over the curvature and dimensions of the roof rack components. This level of control is crucial for tailoring the design to fit the specific dimensions and load requirements of different vehicle models, whether they be compact cars, SUVs, or trucks.

Moreover, the aluminum profile bending machine ensures excellent repeatability and consistency in the manufacturing process. This consistency is vital for maintaining the structural integrity and appearance of the roof rack components, enhancing both their performance and visual appeal.

In addition to its precision and consistency, the aluminum profile bending machine offers cost-effective solutions for mass production. Once the bending parameters are established, the process can be automated to produce large quantities of roof rack components efficiently. This scalability makes aluminum profile bending an ideal choice for meeting the demands of automotive manufacturers and aftermarket suppliers alike.

Furthermore, the use of an aluminum profile bending machine results in components with smooth surfaces and precise contours, meeting the high standards expected in the automotive industry. These formed aluminum profiles exhibit excellent strength-to-weight ratios, offering a lightweight yet robust solution for supporting luggage and cargo on the vehicle’s roof.


In conclusion, roll bending, powered by advanced machinery such as the aluminum profile bending machine, plays a vital role in the fabrication of roof racks. It provides a versatile, efficient, and cost-effective method for shaping aluminum profiles into functional and aesthetically pleasing components that enhance the utility and versatility of vehicles.