Screw Ground Contact Rethought

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Baier & Michels GmbH & Co. KG

Taiwan Machine Tool & Accessory Builders' Association (TMBA)

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Machine manufacturer Kurtz Ersa has worked with cold forming specialist Baier & Michels to optimize the assembly of coated components: thanks to a metric screw that also makes the electrical connection—and can do even more.

In industrial production, electrical ground contacting plays a central role in the operational safety of machines. Particularly in the case of coated components, it places high demands on the connection technology. The machine manufacturer Kurtz Ersa has identified potential in this area to further improve its own assembly processes—with the aim of saving material, simplifying processes and increasing process stability.

As part of a development project for reflow soldering systems, the Kurtz Ersa design team set out to pursue new approaches—beyond additional earthing cables and contact washers. This is because problems with electrical potential equalization can occur, particularly with painted or cathodic dip-coated components, without grounding cables; this then does not function consistently and reliably. In such cases, industry players repeatedly report delays in acceptance and increased costs for reworking.

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Martin Aulbach, Reflow Design Engineer at Kurtz Ersa, describes the initial situation as follows: "We wanted a solution that radically minimized sources of error and at the same time met the highest technical requirements—without the need for time-consuming and cost-intensive work, such as masking or recutting threads." With this in mind, Kurtz Ersa turned to Baier & Michels (B&M), a specialist in cold extrusion parts and a member of the Würth Group.

Screw With Additional Function: Fastener And Tool in One

The b&m technicians analyzed the current situation and developed initial proposals in the company's own application laboratory. Olaf Ambros, member of the management board at B&M and responsible for technology and research and development, was involved from the very beginning: "We came to the line walk at Kurtz Ersa with a concrete idea, discussed it with the customer and continued working directly on real components. Thanks to our fully digitized production in Ober-Ramstadt (Germany), we were able to provide technical drawings and sample parts in the shortest possible time."

The result is a tool and connecting element in one: the B&M contactscrew. As a metric screw with an additional function, it replaces additional earthing cables or contact washers and ensures reliable electrical earth contact—certified by the VDE testing and certification institute. Its technical centerpiece is a ring cutter under the screw head, which penetrates the coating of the clamping component when tightened and thus creates a conductive connection.

The design ensures that both the thread is cleared and the surface of the mating component is penetrated when the screw is screwed in. This creates a reliable earth contact via the screw itself—without any additional earthing cables.

Olaf Ambros

Special Pin Geometry Improves Assembly Behavior

"The optically high-quality copper-nickel surface coating, which also improves the electrical conductivity, also fits in with this. This is particularly advantageous when the B&M Contactscrew is used in visible areas," explains Olaf Ambros. In addition, the screw—manufactured in M4 to M10 variants—has a special tang geometry that improves installation behavior.

There are also three grooves in the first four threads, which remove coating residues such as paint, welding spatter or blasting material. "The design ensures that both the thread is cleared and the surface of the mating component is penetrated when screwing in," explains Ambros.

"This creates a reliable earth contact via the screw itself—without any additional earthing cables."

The fact that this solution was ready for series production in such a short time is also the result of close and targeted cooperation. Kurtz Ersa design engineer Martin Aulbach emphasizes the dynamic nature of the cooperation with B&M: "It took just four months from the initial inquiry to the final screw connection and order placement—that's remarkably fast."

According to Martin Aulbach, the B&M Contactscrew is a "connection technology game changer for Kurtz Ersa. It simplifies our processes, increases safety and saves resources."

The machine manufacturer is currently examining the extent to which the B&M Contactscrew can be used not only for new developments, but also for existing machine platforms.

The aim is to utilize the advantages of the new solution across the board—for even more efficient assembly processes and consistently safe ground contacting.

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