What joining methods optimize EV battery production efficiency? part 3

This third part of the multipart FAQ will discuss magnetic pulse welding, micro-TIG, and clinching for electric vehicle (EV) battery productions. While the first two mechanisms use high temperatures to make joints, the clinching mechanism is based on applying force to create mechanical interlocking to create joints. All three mechanisms are less popular than the earlier ones; however, they have applications in specific case scenarios.

Magnetic pulse welding

Magnetic pulse welding is an advanced noncontact welding technique used in EV battery manufacturing that uses electromagnetic pressure to join metallic components rapidly and precisely.

This technology uses strong but short magnetic fields to shape and form metal pieces quickly. At its core, it is a specialty power unit with capacitors that store electricity similarly to batteries but with the goal of quickly and powerfully releasing that electricity (Figure 1).

Figure 1. A schematic diagram of magnetic pulse welding where the metals to weld are sent through the coil under intense heat during high electricity flow. (Image: EMWorks Inc)

A fast switching mechanism is what makes the system work. It carefully controls when and how the stored energy is released. The heart of the process is a specially made coil that makes the magnetic fields needed to shape the metal. When the machine is turned on, a high energy amount is spent between 3,000 and 30,000 V.

Advantages of magnetic pulse welding

The process facilitates the metallurgical bonding of dissimilar metals through precisely controlled electromagnetic forces, particularly in copper-aluminum configurations. Through rapid, high-intensity energy transfer, the technology generates molecular-level bonds that exceed the mechanical strength of the constituent materials, producing hermetically sealed joints with superior structural integrity.

A noteworthy point about this technology is that it can make electrical currents that are tens of thousands to millions of amperes strong. These currents move through the system in short bursts, less than 10 to 100 microseconds. This fine control makes it possible to shape metal accurately and quickly while keeping the material’s structure.

Disadvantages of magnetic pulse welding

Magnetic pulse welding is especially challenging when working with non-circular weld configurations because the process naturally prefers circular designs. When makers encounter parts with odd shapes, they must develop unique and complicated coil designs to achieve the desired welding results.

Magnetic pulse welding tools and infrastructure require a large initial investment, so manufacturers need to make a big financial commitment. In low-volume production situations, where the return on investment may not be worth the initial cost, this high upfront cost makes the technology less viable.

Micro-TIG (Tungsten Inter Gas)

Micro-TIG welding is a precision welding process that uses a tungsten electrode to generate a high-temperature plasma arc for joining materials (Figure 2).

Figure 2. An illustration of the micro-TIG welding in a tab-joining setup. (Image: Springer Nature)

A high-temperature arc that hits 5000 °C is carefully kept between a tungsten electrode and the workpiece in this technology to make very precise welds. The technology gives very high accuracy with weld areas less than 18 mm² and the ability to make joints as small as 0.14 mm².

The system operates across a current range of 5 – 300 A, with precise pulse control extending up to 999 milliseconds. This level of control ensures consistent, reliable results for critical battery components.

Advantages of Micro-TIG

The micro-TIG welding system in EV manufacturing joins conductive materials essential to battery assembly. The technology creates strong and reliable connections for battery tabs, interconnects, and current collectors. Each weld provides both superior electrical conductivity and mechanical strength.

The system’s controlled heat application creates a minimal heat-affected zone, reducing the risk of damaging sensitive battery components. The technology successfully joins different types of metals while maintaining precise control over all welding parameters, eliminating the need for separate soldering processes.

The system also performs effectively with key materials in battery production, including copper, nickel, stainless steel, and aluminum.

Disadvantages of Micro-TIG

Even though the technology supports copper, nickel, stainless steel, and aluminum, it is important to note that materials with high zinc content, such as brass, are unsuitable for this welding process.

Additionally, to achieve optimal results, the system requires precise equipment and skilled operators who understand the technical aspects of the welding process.

Clinching

Clinching is a solid-state joining process that creates strong connections between sheet metal components without using additional materials like adhesives or fasteners. As Figure 3 shows, the process involves a unique mechanical interlocking mechanism that works through four key steps.

Figure 3. In the four-step clinching process, two metals are joined together to form an interlocking mechanism. (Image: Elsevier)

Technicians carefully align the metal sheets during the positioning stage to ensure proper overlap at the intended joining points. Surface cleanliness is also verified at this stage to prevent any contamination that could compromise joint integrity.

In the die formation stage, operators place the aligned sheets into a specialized clinching machine equipped with a punch-and-die system. The machine’s tooling is specifically designed for the thickness and material properties of the sheets being joined.

As the punch descends in the clinching stage, radial forces develop within the die cavity, causing the material to flow outward. This combined force application creates the characteristic button-shaped protrusion and underlying interlock geometry.

During the completion stage, the punch retracts once the desired joint profile is achieved. The result is a permanent mechanical interlock featuring a distinctive button shape on the punch side and a cavity on the die side.

Advantages of clinching

The material flexibility of clinching provides significant value in battery assembly operations. When joining dissimilar materials like aluminum bus bars to copper connectors, clinching creates secure mechanical connections without generating the problematic intermetallic compounds that typically form during welding.

The cold-forming nature of clinching addresses thermal safety in battery manufacturing. Since the process generates minimal heat during joint formation, it eliminates the risk of thermal damage to sensitive battery cells and electronic components.

Disadvantages of clinching

While clinching effectively works with pouch cells’ flat surfaces and flexible structure, it cannot readily be applied to cylindrical or prismatic cell designs. Additionally, EV batteries experience significant vibrational loads during normal operation, and any degradation of joint integrity could affect electrical connectivity and structural stability.

Summary

Because magnetic pulse welding is a noncontact process, it eliminates friction during joint making and leads to precise control. However, it normally supports welds that are circular in shape. Micro-TIG welding is particularly useful in interconnects and battery tab connections, but one must weigh zinc-content materials.

Clinching is a cold process that depends on mechanical pressure to make joints. However, under continuous exposure to vibrations, it can loosen and lead to increased joint resistance. In the next and final FAQ part, we will focus on two joining mechanisms that are the least used but had found applications over the past before industrial automation came into play.