How the electric vehicle market is driving changes in tube bending technology

A fully automated tube bending cell incorporates upstream and downstream processes, combining fast, error-free processing, repeatability, and safety. While such integration can benefit any fabricator, it's especially attractive for fabricators in the emerging yet competitive field of electric vehicle production.

Electric vehicles (EVs) are nothing new. In the early 1900s electric-, steam-, and gasoline-powered vehicles were available, and EV technology was more than just a niche. Although gasoline-powered engines won that round, battery technology has returned and it's here to stay. Many cities throughout the world have announced future bans on the use of vehicles powered by fossil fuels, and many countries have announced intentions to ban the sale of such vehicles, so alternative powertrains will dominate the auto industry. It's just a matter of time.

Sales data shows that autos based on alternative fuels have been making inroads for years. In the U.S. in 2020 the passenger car market for EVs, plug-in hybrid vehicles (PHEVs), fuel cell vehicles, and hybrids other than PHEVs was 7% of the total, according to the Environmental Protection Agency. This market barely existed 20 years ago. The figures provided by Germany's Federal Motor Transport Authority speak for themselves: Among all newly registered vehicles in Germany in the period from January to November 2021, the share of those with alternative powertrains amounted to almost 35%. The share of newly registered vehicles with purely electric drives was around 11% in this period. The increase of new EVs in Germany becomes particularly clear when looking at passenger cars. In that segment, the EV share in all newly registered passenger cars was 6.7% for the entire year 2020. This share rose substantially, to more than 25%, from January to November 2021.

This shift brings big changes to automotive manufacturers and their entire supply chains. Lightweight construction is a major theme—the lighter the vehicle, the less energy it needs. This also increases the range, which is crucial for EVs. This trend also leads to a change in requirements for tube bending, with a growing need for compact yet high-performance components, especially thin-walled tubes made from high-strength materials. But lightweight materials such as aluminum and carbon fiber-reinforced plastic are usually more expensive and more challenging to process than conventional steel. Associated with this trend is a substantial increase in the use of shapes other than round. Lightweight construction increasingly requires complex, asymmetrical shapes with diverse cross sections.

A common automotive manufacturing practice is to bend round tubes and bring them to the final shape through hydroforming. This is suitable for steel alloys, but it can be problematic when working with other materials. For example, carbon fiber-reinforced plastic cannot be bent when it is cold. Complicating the matter is aluminum's tendency to harden as it ages. This means that an aluminum tube or profile is difficult or impossible to bend just a few months after it is manufactured. Furthermore, if the desired cross section is not round, it is much harder to adhere to the predefined tolerances, especially when using aluminum. Finally, the substitution of aluminum profiles and rods for traditional copper cables to carry electrical current is a growing trend and a new bending challenge in that the components have layers of insulation that cannot be damaged during bending.

The shift toward electric mobility is leading to a change in tube bender design. The traditional standard tube bending machine with predefined performance parameters is giving way to product-specific special machines that can be customized according to the fabricator's needs. Bending performance, geometric measurements such as bending radius and tube length, tool installation space, and software are aligned to conform more closely with the fabricator's specific processes and product requirements.

This shift is already ongoing and will intensify. To bring these projects to fruition, systems suppliers need the necessary expertise in bending technology and the requisite knowledge and experience in tool and process design and must incorporate this knowledge at the beginning, at the machine design stage. Complex tool shapes are needed to produce aluminum profiles with various cross sections, for instance. The development and optimal design of such tools thus becomes increasingly important. Furthermore, bending carbon fiber-reinforced plastic requires a mechanism to apply a small amount of heat.

The growing cost pressure sweeping across the automotive industry is also being felt throughout the entire supply chain. Short cycle times and extreme precision are more important now than ever before. Companies aiming to remain competitive need to use resources efficiently. This not only includes time and material resources, but also human resources, specifically the employees who are central in the manufacturing industry. In this field, user-friendly and reliable processes are a key factor in boosting cost-effectiveness.

Tube fabricators and OEMs that handle tube fabrication in-house are likely to respond to the relentless cost pressure and other stresses by seeking high-performance machines tailored precisely to their needs. A modern bender must use a multilevel technology strategy that includes features such as customizable multiradius bending tools, which facilitate simple and precise bending with very short lengths of tube between bends. Such developments in bending technology shine when fabricating tubular components with several radii, making bend-in-bend systems, or fabricating otherwise complex tube systems. A machine built to handle sophisticated bends can reduce cycle time; for high-volume producers, even a few seconds saved per component can have a huge, positive impact on production efficiency.

Another key component is the interaction between operator and machine. The technology has to support users wherever it can. For example, the integration of bend die retraction—a case in which the bend die and swing arm operate separately—allows the machine to adjust and position a variety of tube geometries during the bending process. Another programming and control concept begins to stage the axes for the next bend while the current bend is still in progress. While this requires a controller that continuously and automatically monitors the interaction of axes to coordinate their movements, the programming effort yields substantial benefits, reducing cycle time by 20% to 40% depending on the component and the desired tube geometry.

In view of the shift toward alternative powertrains, automation is more relevant than ever. Manufacturers of tube bending machines need to focus on extensive automation and the ability to integrate work processes that go beyond bending. This is not just the case for tube bending in large-scale series production, but also increasingly for very low-volume series production.

Modern benders for high-volume manufacturers, such as Schwarze-Robitec's CNC 80 E TB MR, are well-suited to the requirements of fabricators in the automotive supply chain. Attributes such as short cycle times and high resource efficiency are critical, and many manufacturers rely on options such as weld seam detection, built-in cutoff, and a robotic interface.

In fully automated tube processing, the various stages of the process must be reliable, error-free, repeatable, and fast, ensuring that bending results are consistent in quality. Upstream and downstream processing steps must be integrated into such a bending cell, incorporating cleaning, bending, assembly, end forming, and measurement.

Handling devices such as robots and additional components such as tube loaders/unloaders must be integrated as well. The primary task is to determine which processes are the perfect fit for the application in question. For example, depending on the fabricator's requirements, a belt-loading magazine, chain magazine, lifting conveyor, or loose material conveyor might be the right system for the tube feeder. Some bender manufacturers make integration as easy as possible by providing a proprietary control system that works in conjunction with the OEM's enterprise resource planning system.

Even though each additional step makes the process chain longer, the user does not have to experience any delays, as cycle times generally remain the same. The big difference in the increased complexity of such an automated system is in the stringent control requirements needed to integrate bending cells into existing production chains and company networks. For this reason, tube bending machines should be Industry 4.0-ready.

Overall, integration is paramount. It's critical that OEMs work with machine manufacturers that have deep experience in developing machines that are compatible with the various subsystems in a fully automated manufacturing process.