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Stretch Bending Metal Shaping at Global Forming

While the stretch bending and stretch forming methods of metal shaping originally emerged in the aerospace industry for creating aircraft skins, in recent decades it has become a go-to method for achieving superior results for a range of industries, including automotive components. Global Forming has developed expertise in stretch-bending and forming to meet the needs of customers who require this method’s unique benefits and advantages. Other industries making use of stretch bending and forming include architectural applications for curved building facades, boat and ship hulls, rail cars, industrial equipment manufacturing, medical applications, and many other commercial industries.
large blue and yellow stretch bending machine

The Rise of Stretch-Bending for Better Results

What makes stretch-bending unique in the field of metal shaping? It’s a cold-bending procedure, which means no heating of the workpiece is needed. This makes it less energy-intensive than a number of other metal shaping methods. Stretch-bending achieves its superior results by maintaining constant tension to the workpiece, stretching and then bending or forming it while under tension.

The workpiece is pressed onto or around a machined form (a die, also called a form block) to achieve a part with one or several different curve radii. In the industry, the machine accomplishing the work may be called a stretch bending machine, stretch press, a stretch former, and so on. The stretching is what compensates for the compression forces on the inner surface of the workpiece and basically pulls out any wrinkles or buckles before they can happen.

close up of stretch bending machine
The Many Advantages of Stretch-Bending and Forming
If stretch bending or stretch forming is the right choice for any specific metal shaping project, there are many advantages to be gained through this method, including the following:
Reduced Material Costs
While allowances must be made for gripping areas on the stock to maintain tension, the allowance for trimming is typically less than convention press forming.
Energy Efficiency
Because the “cold” bending process happens at room temperature without needing to heat the workpiece, less energy is used. Further savings come from the fact that much less force is needed to achieve the bend or stretch compared to other conventional press forming techniques.
Unparalleled Accuracy
Stretch bending and forming achieves some of the tightest tolerances in the entire metal shaping industry when it’s backed by engineering expertise.
Stretch bending and forming allows for non-symmetrical profiles to be formed without twisting. It also allows the minimum bend radius to be anywhere from 2–3 times greater than other forming and bending methods
Quality Parts
The stretching prevents wrinkling and buckling, minimal cross-sectional distortion, and therefore little or no deterioration of the material’s finish. In other words, it minimizes imperfections.
Stronger Parts
The material used becomes stronger through the stretch bending and stretch forming process, resulting in increased tensile strength, hardness, and yield strength.
Reduced Spring-back
While some amount of spring-back occurs, it is easily addressed with over-forming.
Low Residual Stresses
Metal parts shaped by stretch forming exhibit low residual stresses.
Lower Tooling Costs
Many form blocks or forming dies can be made of less expensive materials than conventional forming dies. There are also fewer dies involved since only one die is needed to create the part instead of the multiple dies required by other methods. Because tooling is expensive, this is a major advantage of stretch bending and forming.
Process Efficiency
Because stretch bending and stretch forming accomplish in one step what other processes would require multiple machines and steps to accomplish, there is greater task and process efficiency, resulting in saving time and money.
Cost Effective
Because of all the advantages listed above, stretch bending and stretch forming makes production runs of parts more cost effective than other methods of shaping metal into curved profiles.
wide shot of stretch bender

Is stretch bending or stretch forming the right metal shaping technique for your project? It depends on a lot of different factors. Feel free to contact us and our team of experts will help you determine if Global Forming’s stretch bending capabilities are the right fit for your project.