Where Resistance Welding Meets Medicine

When people hear the term resistance welding, they often think of joining sheet metal, attaching automotive fasteners, or spot welding an HVAC duct. Those more familiar with the process might even think of cross-wire welding, a form of projection welding used in everything from store fixtures and fencing to rebar grids for concrete construction and mezzanine or bridge grating. Others may think of resistance welding for aerospace applications, such as exhaust components or the enclosures for emergency oxygen generators.

What is less widely recognized, however, is that resistance welding also extends to microscale metal joining and even the welding of living tissue. In that sense, the human body itself presents potential applications for resistance-based processes. This article explores several of these applications with a focus on resistance welding in healthcare and medical contexts.

Healthcare Equipment

Ease of sterilization is a key design aspect of reusable medical equipment. Materials must withstand repeated disinfection in pressurized environments using high-
temperature steam or chemical cleaners. Case carts (also called procedure carts) typically use type 316 stainless steel. Resistance spot, seam, and projection welds are often used to fabricate the cabinet frames, as well as the drawers, shelving, and doors for holding operating supplies and containing hazardous medical waste during transport. Projection welding, in the form of cross-wire welds, is used to make baskets that hold surgical tools during autoclave sterilization or petri dishes in tissue incubators — Fig. 1.

Medical Devices

Resistance welding is commonly used to manufacture implantable and interventional devices, such as pacemakers, stents, and surgical tools. In these cases, required joint strength may be relatively low — often only a few pounds of pull force — but consistency and reliability are paramount. Failure of even a single weld can compromise patient safety and device performance.

An example of resistance welding in medical device assembly is the fabrication of a cannula used in a suction coagulator — Figs. 2, 3. A cannula is a small tube designed for insertion into body cavities, such as veins or the nostrils. This surgical device uses suction to remove fluid while simultaneously coagulating or sealing blood vessels, helping reduce infection risk. In this application, a 24 AWG (0.0201 in./0.51 mm diameter) stranded wire is welded to a brass or stainless steel cannula (0.010 in./0.254 mm diameter). Each strand within the 24 AWG wire is approximately 32 AWG (0.008 in./0.2 mm) O.D., and both conductivity and mechanical strength of each strand must be preserved throughout the welding process.

Electrode placement and design are also critical variables. In the cannula example shown in Figs. 2 and 3, vertically oriented electrodes are required to maintain alignment and properly contain the wires. When welding multiple wires to a cannula, a saddle groove electrode helps contain the strands and minimize splaying. This results in a cleaner weld appearance and reduces potential failures, such as improper performance or short circuits caused by severed or loose wire strands; however, it demands precise wire placement. A simple chisel-point upper electrode offers a forgiving setup and can accommodate a range of wire sizes with a single design, albeit with increased strand deformation compared with a flat electrode.

A related, smaller-scale application involves welding fine wires to platinum rings — Fig. 4. The platinum rings with connected wires are typically used as electrodes and also serve as radiopaque marker bands in minimally invasive devices such as catheters, stents, and pacemaker leads. During ultrasound-guided procedures, their visibility in ultrasound images allows clinicians to track the position, depth, and orientation of devices such as catheters and guidewires in real time.

Surface preparation is especially critical for these types of applications. Any coatings, such as insulation or plating, or residual contaminants on the wires can introduce unpredictable resistance at the weld interface, leading to localized overheating, inconsistent nugget formation, and increased electrode sticking. Therefore, all insulation and plating must be completely removed from the wire prior to welding. Because of the small wire size, low current and very low force are required for success, minimizing deformation of these delicate components. The best electrode geometry for this weld is a horizontal lower electrode supporting the ring, and a vertical electrode that attaches the wire to the inner part of the ring — Fig. 5.

Electrosurgery

Electrosurgery is another resistive process. Borrowing heavily from standard resistance welding principles, it uses a high-frequency (HF) power supply (typically 
350 kHz–1 MHz) with impedance measurement to deliver electrical energy to the treatment site through various clamp configurations (Fig. 6) while monitoring parameters and, in some cases, adjusting algorithms to control the outcome. The electrodes differ, and no metal is being joined, but the core challenge is familiar: insufficient force, current, or time leads to joint failure, while excessive levels can cause irreversible damage to the base material.

HF welding enables connections that restore physiological function rather than just closing wounds. As with any resistance welding process, weld quality can be evaluated both visually and mechanically. For intestinal seam welding, known as intestinal anastomosis, the acceptance criteria include zero visible defects and verification through pressure-to-failure testing. This is conceptually similar to pressure testing tank seam welds, as well as full-ring projection-welded “spud” connectors on water heaters and fusite connectors on scroll compressors. Reported results for seam welded intestines show performance that can exceed stapled seams while avoiding the introduction of foreign material into the body.

Other tested uses cover a surprising range of “weldments,” including arteries, retinas, tendons, and severed peripheral nerves. Blood vessels have been successfully welded, and ophthalmic procedures have used HF welding to replace laser coagulation for reattaching retinas to their choroids (Fig. 7), which suggests lower-trauma outcomes with fewer postoperative complications. Recent experimental work has demonstrated that this welding could even be an option for strong tendon repair, hinting at future breakthroughs in orthopedics.

Conclusion

Resistance welding has been in use for nearly 150 years and is often viewed as a legacy process. The fundamental principle of resistance welding and heating — using a controlled combination of force, current, and time to join metal — has not changed since Elihu Thomson first patented it in the late 1800s.  However, it remains highly relevant in modern applications. The examples in this article highlight advantages that many alternative joining methods struggle to match: no added filler material or flux, low heat input, a minimized heat-affected zone, and high repeatability when properly controlled.

The precision and control required for microscale welding applications, including medical and surgical devices, has helped drive innovation in process analysis and traceability. While only limited testing (for example, fatigue testing and pull strength) was available in the early years, today’s zero-fail applications benefit from evolutions in process monitoring and control, weld verification, and traceability. Modern weld-checking devices gather and monitor electrical and mechanical data in real time, providing instantaneous feedback on whether the weld fell within predetermined limits. Process data can be tracked back to individual joints. The documentation gathered by these systems supports accountability and patient safety.

Elihu Thomson’s foundational principles still apply, even as process implementation continues to evolve. As surgical applications such as HF tissue welding adopt the same force-current-time framework, the boundary between industrial and medical resistance processes continues to narrow. As in other areas of advanced manufacturing, resistance welding is poised to play a key role in hybrid multiphysics joining, further refined by process-control feedback and smarter process algorithms. In short, this legacy process remains thoroughly modern.

Acknowledgments

This article was a collaborative effort, combining the author’s experience in resistance welding applications with insights shared by active members of the Resistance Welding Manufacturing Alliance (RWMA) and other industry stakeholders. Special thanks are extended to Dr. Mark Boyle of AMADA Weld Tech Inc., Monrovia, Calif.; O. V. Romanenko, S. V. Tkachenko, and N. A. Chvertko of the Paton Welding Institute, National Academy of Sciences of Ukraine, Kyiv, Ukraine; A. G. Dubko, Paton Welding Institute and Department of Biomedical Engineering at the National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute,” Kyiv, Ukraine; Craig Kilbane of Spot Weld Inc., St. Paul, Minn.; and Mike Gaskill and Jason Lisko at Taylor-Winfield Technologies Inc., Youngstown, Ohio.

This article was written by Niels Johnson (sales manager for industrial resistance welding and specialty markets at RoMan Manufacturing, Wyoming, Mich.) for the American Welding Society.