SWOPtec (Steel Welded Opposed Plug) is a joining process for joining aluminum with steel materials. The special thing about it is that the equipment normally used for classic resistance spot welding can also be used here. Swoptec's core competencies lie in the production of the joining element. Dr.-Ing. Vitalij Janzen, has been working for around five years at ARNOLD UMFORMTECHNIK GmbH & Co. KG in the field of research and development. As a specialist in resistance element welding, he now also wants to take SWOPtec forward. He describes how SWOPtec was developed: “The initial impetus came from Benteler Automobiltechnik GmbH. The company approached us in 2018. A process solution was developed over 1.5 years in a development project, which was presented in mid-2019. This was associated with an exclusive right of use from SWOPtec for Benteler,” he says, looking back on the beginnings. However, the original SWOPtec fastener was not able to meet all of ARNOLD's customers' requirements. Further developments and areas of application followed. The first series application in several model series was launched at the Hyundai Motor Company in Korea.
Processing technology can be adapted to customer requirements
In principle, the process can be used both in the press shop and on the C-frame in body shell construction. The C-frame applications are available in different versions. On the one hand, there are stationary systems in which the component is handled by a robot. On the other hand, there are systems in which the C-frame is handled by a robot and the component is held by a second robot, for example. The processing technology can be designed flexibly. For example, different C-frame sizes are possible. Various options for feeding can also be implemented. ARNOLD UMFORMTECHNIK is currently setting up systems in which different element lengths can be processed with one C-frame. Here, a C-frame is controlled by several feed hoses.
Know-how in the production of SWOPtec elements
In principle, the SWOPtec process is used to join aluminum components (cast aluminum, extruded aluminum or sheet aluminum components) to steel components using spot welding technology. SWOPtec is a two-stage process. In the first stage, the connecting element is punched in. The component assembled with fasteners is then fed to the core line and welded in the second stage. “Element production requires a lot of expertise, for example the production of the groove. Precise feeding during processing is also a challenge due to the geometry of the element,” says Vitalij Janzen. The connecting element itself has a relatively large diameter: 12 mm head diameter and 10.5 mm shaft diameter. It is also relatively flat to cover sheet metal applications from 1.15 mm to 4.5 mm thick. The SWOPtec element has a circumferential groove on the shank, which ensures that aluminum flows into the groove during punching and creates a small undercut. This prevents the element from falling out of the sheet when components are transported. The element material is an easily weldable manganese-boron steel 20MnB4. The coating of the elements can be adapted to customer requirements. The standard coating is electrogalvanized - with a thickness of at least 8 μm.
“Element production requires a lot of expertise, for example the production of the groove. Precise feeding during processing is also a challenge due to the geometry of the element,” says Vitalij Janzen, Research & Development Fastening Systems at ARNOLD UMFORMTECHNIK.
Resistance and friction element welding and Swoptec
Whether Flexweld® (ARNOLD designation for resistance element welding with T-shaped connecting elements), Flowweld (ARNOLD designation for friction element welding) or SWOPtec (Steel Welded Opposed Plug) the aim of the three processes is generally the same: Aluminum is to be joined with sheet steel. “Every customer has their own philosophy and their own constraints. This cannot be covered by just one process,” says Dr. Janzen, who has a doctorate in resistance element welding. In addition, each of the three similar processes naturally has its own specific key data. Swoptec, for example, can transfer higher joining forces and compensate for larger positional tolerances. In addition, the Swop element lies flat on the surface. This is particularly interesting if, for example, seals need to be applied afterwards. However, the Swop element is heavier and larger than the Flexweld® and Flowweld® elements and therefore requires a little more space on the sheet for installation. Whichever of the three elements is used: The aim of the Forchtenberg-based fastener manufacturer is to develop an application-specific solution for every customer component.
Existing system technology can be used
With Swoptec, the customer can act very flexibly. Both steel-steel connections and steel-aluminum components can be manufactured on one production line. This means that a large number of model variants can be produced with the same welding systems. “Asian customers in particular still rely heavily on spot welding. Resistance welding has proven itself there over many years and is well established. In addition, the existing systems can continue to be used with Swoptec. Purchasing new system technology is often a much bigger problem in Asia than in Germany, for example, due to space constraints,” says Janzen, describing the situation. Accordingly, SWOPtec is often preferred to completely new processes in Asia. And in the USA, too, companies are still focusing on spot welding.
Diverse areas of application and prospects for Swoptec
The focus for SWOPtec applications is on the automotive industry, both OEMs and their suppliers. The process, which was originally developed and patented by Benteler Automobiltechnik, can be used for a wide range of applications and is suitable for all component joints where aluminum is to be joined to steel. In cars, for example, this includes the A-pillar, B-pillar, seat cross members or roof cross members. SWOPtec was first used in series production in mid-2021. In the meantime, several applications are underway at the Hyundai Motor Company and there will also be applications in China from 2023. “There is great interest in SWOPtec applications in Asia. However, inquiries from the USA and Europe are also increasing,” says Dr. Janzen. The inquiries are primarily coming from companies where spot welding is highly relevant. ARNOLD UMFORMTECHNIK is also constantly developing the process further. For example, various feeding concepts are being worked on and the geometry of the swop elements is also being continuously adapted.
About ARNOLD UMFORMTECHNIK
The ARNOLD GROUP, internationally renowned for innovative fastening technology, has developed into a leading supplier and development partner for complex fastening systems thanks to its extensive expertise in the production of intelligent fasteners. Under the umbrella of “BlueFastening Systems”, the company positions itself as a comprehensive provider of engineering, fasteners, functional parts, feeding systems and processing technology. This holistic combination of experience and know-how offers efficient, sustainable solutions on an international level. ARNOLD has been part of the Würth Group since 1994.
