Stretch forming (stretch bending) machines can be divided into rotary-type stretch forming machines and double arm-type Stretch forming machines and various special bending machines, such as a special stretch forming/stretch bending machine for shower room, special stretch forming machine for train roof beam, and special stretch forming machine for the elevator. The stretch forming machine adopts full hydraulic control and can cold-form various steel pipes, square pipes, H-beams, I-beams, channel steels, angle irons, flat irons, and aluminum profiles with a section below 500mm.
4 advantages of the stretch forming process
Advantage 1#: Various profiles can be bent
- Almost all sections of aluminum, steel, stainless steel, copper, and other metal profiles and pipes can be bent.
Advantage 2#: Good bending quality
- After spraying, electrophoresis, electroplating, polishing, wire drawing, etc., the material can be bent directly without damaging the surface of the material.
- Profiles with cavities and complex cross-sections can be formed at one time. When the relative bending radius allows, the inner wall will not be wrinkled and the section will not be distorted.
- Bending can effectively eliminate the residual stress inside the material, and the product has good dimensional stability.
- Due to the cold work hardening of the metal material, the comprehensive mechanical properties of the material can be improved after the material is stretched and bent.
Advantage 3#: Can bend a variety of curved shapes
- In addition to bending conventional standard arcs, it can also bend a series of complex curves such as U-shaped, S-shaped, W-shaped, elliptical, parabolic, and circular arcs with straight segments, conical surface curves, and a curve with multiple radii. shape.
Advantage 4#: Strong bending ability
- Stretch forming (stretch bending) arc length: 12 meters
- The one-time forming degree can reach 12 meters, which can improve the installation efficiency, reduce the installation cost, save materials and improve the quality of the project for projects that require a long arc length.
- Cold-formed section: 500mmx350mm
- Stretch forming (stretch bending) radius: Unlimited as far as the mechanical properties of the material (elongation) allow.
3 important parameters of the stretch forming process
Stretch Forming Radius
- Minimum stretch forming radius: aluminum profile (R outside – R inside) / R outside ≤ 8%
- Stainless steel profile (R outer-R inner)/R outer≤30%
- Maximum bending radius is not limited
Stretch Forming Arc Radius Tolerance
- The radius is less than 1 meter, and the deviation of each meter length is less than ±1mm
- The radius is greater than 1 meter, and the deviation of each meter length is less than ±2mm
Stretch Forming Material Calculation
- The amount of reserved chuck at the end is 300mm. Simple symmetrical small-section profiles do not need test materials, complex sections, or large sections
- Surface profiles need to provide 1-2 test materials, and the material utilization rate is 95% based on a 6-meter profile.
Top 11 parameters of the stretch forming process
- Material Selection: Choose the appropriate material, typically aluminum alloys, based on the application’s requirements for strength, ductility, and corrosion resistance. The material’s behavior during forming is crucial.
- Tooling Design: The design of the forming die (tooling) is critical. Smooth radii, proper clamping mechanisms, and consideration of the part’s geometry help ensure uniform deformation and minimize stress concentration points.
- Lubrication: Apply a suitable lubricant or release agent to the die surfaces and the aluminum sheet. This reduces friction and prevents the sheet from sticking, improving surface finish and material flow.
- Stretching Force: The controlled application of stretching force is a fundamental parameter. It must be adjusted based on the material properties, sheet thickness, desired curvature, and the specific requirements of the application. Overstretching can lead to thinning or other defects.
- Stretching Speed: Control the speed at which the stretching force is applied. Uniform stretching helps maintain even deformation and prevents localized strain.
- Temperature Control: Maintain a controlled temperature environment during the forming process. Excessive heat can affect material properties, while rapid temperature changes may lead to thermal stress or deformation.
- Hold Time: Some stretch forming processes involve introducing a hold time at the maximum stretch. This allows the material to “settle” before releasing the force, reducing springback and improving dimensional accuracy.
- Springback Compensation: Anticipate the springback effect, where the formed part returns slightly to its original shape. Adjust the initial shape or tooling to compensate for springback.
- Quality Control and Inspection: Regularly inspect the formed parts to ensure they meet the required specifications, including dimensions, tolerances, surface finish, and structural integrity.
- Post-Forming Treatment (Optional): Depending on the application and material, consider stress-relief annealing or other treatments to relieve residual stresses and enhance the part’s properties.
- Documentation: Keep detailed records of the forming process, including material properties, forming parameters, adjustments made, and quality control measures. This documentation is valuable for future projects and quality assurance.
4 characteristics of the stretch forming process
- After spraying, electrophoresis, electroplating, polishing, wire drawing, etc., the material can be stretched forming (bending) directly without damaging the surface of the material.
- Profiles with cavities and complex cross-sections can be formed at one time. When the relative stretch forming(stretch bending) radius allows, the inner wall will not be wrinkled and the section will not be distorted.
- Stretch forming(stretch bending) can effectively eliminate the residual stress inside the material, and the product has good dimensional stability.
- Due to the cold work hardening of the metal material, the comprehensive mechanical properties of the material can be improved after the material is stretched and bent.