Connecting sustainably

Cold forming, trilobular groove zones or polygonal tip geometry: what used to be "the screws" are now complex fasteners. ARNOLD UMFORMTECHNIK has been developing and manufacturing them for over 100 years - and impresses with what is technically possible.

In December 2023, ARNOLD UMFORMTECHNIK opened a new new plant in Forchtenberg-Rauhbusch, Baden-Württemberg. Rauhbusch in Baden-Württemberg. The new plant is the company's latest commitment by the company at its headquarters. In the community of just under 5,300 inhabitants up to 400 future-proof new jobs will be created jobs. The employees use cold forming to produce formed parts from aluminium and copper: Connecting elements for batteries, coolant nozzles or parts of connectors in the vehicle electrical system. According to ARNOLD, the process avoids rejects and excess metal chips almost completely. Compared with a turned part and depending on the geometric shape the company saves over 70 per cent of CO2 emissions.

It all began 125 years ago in the so-called Kochertal with the production of screws. In the meantime ARNOLD UMFORMTECHNIK has developed into a supplier of fasteners fasteners and operates five sites in Germany, North America in Germany, North America and Asia. Since the mid nineties, ARNOLD has been part of the Würth Group – whose whose first supplier of screws was the company. A brief digression: The first order for screws from ARNOLD was placed by Adolf Würth in May 1945. He was the founder of the Würth Group. He collected the screws together with his with his ten-year-old son - Reinhold Würth, today Chairman of the Supervisory Board of the Würth Group.

Development and production from a single source

ARNOLD UMFORMTECHNIK summarises its activities with fasteners today under the name "Blue Fastening Systems". In detail, this means Engineering, fasteners, functional parts, feeding systems and processing technology from a single source combined with many years of experience and expertise.

Under the "Conform" brand, the company develops and produces the company develops and produces complex cold-formed parts for multifunctional applications. "The design possibilities for these parts are almost unlimited," explains Lukas Schmieg, Senior Director Functional Components, "The areas of application are correspondingly broad".

Drive shafts for electric motors are possible, for example small and medium-sized electric motors, for example for window regulators, windscreen wipers or seat adjustment. In addition, bearing bushes and nuts for sensor housings, union nuts for hydraulic, brake and fuel lines. The fasteners can combine several functions combine several functions with their shape: For example, they can connect and seal or create a functional connection between the connection and the bearing, drive or a joint mount.

Lightweight construction with the right plan

Toothing, customised external geometries, press-smooth surfaces and material savings are also possible. Lightweight construction: ARNOLD can realise additional functions using plastic-coated bushes: For example, absorbing the preload forces of screw connections or further reducing weight with aluminium bushes. All this together with the customer. "In order to manufacture components that were previously produced by machining using cold forming, a few basic considerations are necessary in advance," says Schmieg. "For example, the area of application in the vehicle, inside or outside. Or what surface and what type of corrosion protection the component must have. We also need to know whether, for example, the geometry of the component may change in principle or whether there are functional features such as sealing surfaces or fits. In other words, all the parameters relevant to the customer that we have to take into account in our production." Based on this information, ARNOLD UMFORMTECHNIK creates a so-called proposal drawing for cost-optimised implementation using cold forming. In addition, a manufacturability assessment. "At the start of development, we also talk to our customers about the production technology, possible cost savings and quantity scenarios," explains Lukas Schmieg.

New requirements from e-mobility

With electrically powered vehicles, the requirements for the connecting elements change. They often need to be lighter and conductive: The most suitable materials for this are usually copper and aluminium, which have to be re-evaluated for the respective application, for example in terms of their strength. "Aluminium and copper have different properties to steel. This needs to be considered throughout the entire process chain. For example, we have the option of dispensing with bulk material handling and processing precision parts with high requirements in a particularly gentle way by feeding or discharging individual parts. The decisive factor here is the technical coordination with the customer during the project phase - then we can select the optimum manufacturing process and offer the customer the desired quality." ARNOLD manufactures the Conform parts on its own machinery. This includes multi-stage presses with up to seven forming stages, machines for complex internal and external machining, post-processing centres, cleaning technology and surface treatment systems. The diameters of the parts vary depending on the material used. For steel, 30 millimetres are possible, starting from a maximum wire diameter of 20 millimetres. For components made of copper or aluminium, the outer diameter can be over 30 millimetres, depending on the component geometry. Depending on the diameter, the parts can be up to 100 millimetres long.

"Powertite®" series for special requirements

ARNOLD UMFORMTECHNIK has developed the "Powertite®" thread-forming screw series for small installation spaces and high assembly forces. Powertite screws have a higher load-bearing capacity than comparable products on the market. This is made possible by a so-called trilobular groove zone. This This means that where the forming work is carried out, the screw has a slightly triangular cross-section with rounded corners. "With the combination of a trilobular groove zone and a round load-bearing cross-section, we have significantly improved thread-forming screw connections," says Bernd Weidner, Senior Director Fastening Solutions. "The load-bearing capacity of the grooved nut thread and the thread-forming screw is significantly increased at the same time with low thread-forming torques and high failure torques. This makes it possible to optimise screw connections by increasing the preload force level, optimising the installation space or simplifying casting processes in the case of cast core holes in light metal screw connections." Application scenarios for the screws are, for example, in die-cast aluminium, solid steel, die-cast magnesium or sheet steel pull-throughs - specifically: in high-voltage battery housings, actuators in the steering column or gearbox housings. The potential of the technology is demonstrated by the example of the screw connection of the gearbox housing. The manufacturer was able to replace the previous M8x40 bolts on a load transfer gearbox with Powertite M7x40. This means 42 grams less weight per gearbox and around 72 grams less CO2. That doesn't sound like much. However, extrapolated to around six million screws used in all of the customer's gearboxes, the amount of CO2 saved adds up to around 33 tonnes per year.

Example number two: For an electric motor-gearbox unit connected with 33 screws, Powertite® screws reduce the weight per unit by around 213 grams, approximately 364 grams of CO2. Based on 80,000 planned units, the Powertite screws save around 29 tonnes of
around 29 tonnes of CO2. "In addition to these effects, Powertite screws have other advantages for users: they can be used in steel, aluminium and other light metals, are highly reliable during installation, are vibration-resistant and allow repeat fastenings. If servicing is required, they can even be replaced by metric screws," explains Weidner.

Pre-hole-free and fully automated joining

ARNOLD has had its "Flowform®" flow-hole moulding screws on the market for some time now. This enables pre-drilled, one-sided accessible and fully automated joints. "The Flowform® screw heats and penetrates the sheet metal. With its polygonal tip geometry, it forms a flow hole and forms a thread that can also accommodate a metric screw in the event of a repair," explains Thorsten Lienhardt-Schuster, Senior Director Fastening Systems. After screwing in, the moulded pull-through adapts perfectly to the contours of the screw, according to Lienhardt-Schuster. The thread torques during application are low. The process is chip-free, with low component deformation. A further development of the screw is the "Flowform® Plus". "Depending on the sheet thickness, the application limit for joining steel applications with the conventional Flowform® was a maximum of 600 MPa, with the Flowform Plus it is 1,000 MPa," says Thorsten Lienhardt-Schuster, describing the further development. The further development was the result of a customer project in the automotive industry. Here, the developers changed the dimensions of the conventional Flowform® from five millimetres in diameter to four millimetres. Depending on the head and length, the "Flowform® 5" weighs around four grams, while the new "Flowform® Plus 4" weighs around three grams. This means 25 per cent less weight per screw. arosserie, that adds up to quite a lot," says Lienhardt-Schuster. "500 Flowform® 5 elements weigh two kilograms per vehicle. If we replace them with Flowform® Plus 4, it's only 1.5 kilograms," explains Thorsten Lienhardt-Schuster.
The "Flowform® Plus" screws are best suited for higher-strength steel sheets and thicker sheet combinations. "By using aluminium components, thicker joining combinations with several layers can be created. In the past, the cover and centre layers of three-layer joints were pre-punched," explains Lienhardt-Schuster. Now, depending on the joining material, thicker material combinations of up to 7.5 mm are possible – without pre-punching. The reason: the smaller screw diameter reduces material displacement. This results in smaller gaps between the sheets. The smaller dimensions reduce the friction surface. The thread forming torque is correspondingly lower than with Flowform® 5.

Customer tests in our own test laboratory

But when is which type of screw suitable? To find out, ARNOLD UMFORMTECHNIK has built up a great deal of expertise over the past few years. In the laboratory for sheet metal joining technology in Dörzbach, which is integrated into the research and development department, test set-ups and all standard system technologies are available for this purpose, as well as a robot cell for near-series testing. "The customer's ideas for a particular joint are usually quite specific. Accordingly, we carry out feasibility studies in the sheet metal joining laboratory using original material, for example. A joining point test goes into a little more detail. Here, the customer has already defined certain material pairings that they want to use," explains Thorsten Lienhardt-Schuster. "Based on this, we give a recommendation and specific strength values that he achieves at this joining point." Customers appreciate these recommendations. So much so that ARNOLD UMFORMTECHNIK can already think about the next expansion of its production can already be considered. It is due to start as early as 2025. Then, right next to the next building will then be constructed right next to the plant opened in December – and ARNOLD UMFORMTECHNIK will also ensure sustainable connections there: with its customers and in their projects.

 

Companies that are active in the mobility sector and are looking for innovative fastening solutions, functional parts and suitable processing systems know us as a competent development partner and value our problem-solving skills.” says Dirk Döllner, CEO ARNOLD GROUP.

About ARNOLD

ARNOLD has been part of the Würth Group since 1994. The company employs a total of 1,469 people at its five locations in Ernsbach, Dörzbach, Forchtenberg-Rauhbusch, Rochester Hills (USA) and Shenyang (China). In 2023, the ARNOLD GROUP generated an annual turnover of around 300 million euros and produced seven billion parts. In December 2023, the company opened a new production facility in Forchtenberg near the company headquarters.

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