Best Methods for Connecting Sheet Metal in Automotive Manufacturing

Sheet metal is one of the more versatile industrial materials. It is used for construction work across various industries. The automotive industry is not an exception; in fact, sheet metal plays an almost irreplaceable role in car manufacturing. All the body parts of a car, including its engines, are not made to fit at one point. Rather, they consist of different metal parts in automotive processes joined together using various joining methods.

Using the right connecting sheet metal method affects the longevity of the entire vehicle, its durability, the total cost of the assembly process, and the safety of the vehicle when in use. There have been leaps in technological processes to improve sheet metal connection methods, and while some old, tried, and tested methods still serve the industry to date, there are new innovative methods hitting the market to deliver even better results and meet the ever-evolving automotive needs.

Key Sheet Metal Connection Methods

There are a lot of connecting sheet metal methods available across the industrial scene, and while they can be great options for DIY projects, not all of them are appropriate for the serial production requirements of automotive manufacturing. When connecting sheet metal in automotive manufacturing, factors such as aesthetics, safety, the temporary or permanent nature of the joining, cost and accessibility constraints need to be considered. These considerations can help in selecting what joining methods work in certain conditions.

Fasteners are great for temporary connections as many nuts and bolts can be removed and replaced, as we will examine later. Adhesive is also a great connecting sheet metal option as they are cheap, can be applied flexibly and engineered to best suit the application. Depending on your need, there are sheet metal connection methods that provide a suitable solution, and today, we will look at the main connecting sheet metal methods and the respective benefits and considerations of each.

Metal Connection Methods

WELDING

Welding is the most common technique for automotive applications due to its strength and adaptability. It is an extremely efficient method for bonding sheet metal, resulting in strong and long-lasting connections. In welding, the base materials are melted together to make a joint. Welding provides very strong joints. When done correctly, the joint can only be separated by ripping the material itself apart, implying that the connection is usually at least as strong as the materials being bonded. Sheet metal welding is ideal for combining similar materials. It is extremely compatible with a variety of materials and can produce strong and long-lasting vehicle parts. In addition, it's great for producing durable automotive components like frames, body panels, and chassis because of how quickly and efficiently it works. There are a couple of welding technique options available.

Common Welding Techniques for Automotive Applications

• MIG (Metal Inert Gas) Welding is popular for high-speed production and automation. It is an ideal welding option for metals like stainless steel, aluminum, and steel.
• TIG (Tungsten Inert Gas) Welding: Provides more precise control for thin sheet metals. Works best for non-ferrous metals like copper, aluminum, nickel, magnesium, and titanium.
• Laser Welding: Ideal for high-strength, fine precision joins
• Friction Stir Welding: Used for larger, long sheet metal joins
• Friction Element Welding (FEW): Is a solid-state bonding process that can be used for high-strength sheet metal >1000MPa
• Resistance Element Welding (REW): A process that joins metals by applying pressure and passing a high electric current through the metal combination. This generates heat at the welding joint, melting the metals and fusing them together.
• Spot Welding: Automated process commonly used in car assembly lines

Benefits

• It can be used for various sheet metal materials.
• Suitable for various thicknesses.
• Works for complex shapes and large structures.

Considerations

• Heat can cause distortions and cracks.
• Limited light weighting potential, typically requiring dissimilar materials.
• It requires special equipment.

Brazing Automotive Sheet Metal

Brazing is a process of joining metals by melting a filler metal below the base metal's melting point. Joints from brazing are often used for tasks like joining electronic parts, as the risk of thermal distortion is lower since the joining metal usually has a lower heating point.

Benefits

• It can be used to connect sheet metals of different materials.
• Lower heat process reduces thermal distortion.
• Its joints are usually leak-proof.

Considerations

• Its connecting joints may not be as strong as welded joints.
• There is the potential for flux residue

Brazing vs Soldering

Brazing and soldering are quite similar in their process, but there are a couple of key differences, including:

• Heating temperature: Brazing has a higher heating temperature than soldering.
• Filler material: Both Brazing and soldering use filler materials, but while Brazing uses non-ferrous alloys like copper, titanium, nickel, etc, soldering uses soft alloys like tin or lead.
• Joint Strength: Brazing’s connecting sheet metal strengths are stronger than soldering.
• Durability: Connections with brazing have better durability and are more resistant to corrosion than soldering.

Rivets

Riveting is a mechanical fastening method used in areas where welding or adhesives aren't suitable and provides a more permanent result compared with simple screws and nuts. Riveting joins two or more layers of sheet metal, by placing the fastener through pre-prepared holes and deforming the tail of the fastener. This creates a reliable joint that can withstand high levels of stress and vibration.

Types of Rivets

There are various types of rivets for different conditions.

• Blind Rivets only require access from one side of the application piece and are ideal for fastening a wide variety of materials.
• Solid Rivets require access to both sides of the materials being fastened.
• Self-Piercing Rivets are the go-to solutions for body-in-white joints of dissimilar materials with double-sided access. These specialty rivets don’t require holes and work in combination with adhesive.

Benefits

• Provides excellent mechanical strength
• No heat needed for the joining process
• No cooling or hardening time required
• No smoke or fume production
• More permanent joint options
• More permanent joint options

Considerations

• Require drilling or specialist operation to remove the rivet, depending on the type used.
• Depending on the type of rivet, it can be more expensive compared to certain types of welding or adhesives

Adhesives

One flexible way to connect sheet metal is with adhesives. Because they are both inexpensive and resistant to corrosion, adhesives are an excellent choice for connecting metal sheets. They work best in situations when tensile forces are negligible. Adhesives, which come in liquid or semi-liquid forms, must be cured to reach their optimum strength. There are a few different ways to cure adhesives: by providing heat and/or pressure and/or UV light or simply by letting them cure naturally over time. Adhesives can seal even the tiniest cracks or holes in a material due to their liquid or semi-liquid state. Also, they work well in situations when you don't want any visible fasteners to diminish the final look. Even though adhesives dampen vibrations, they aren't always up to par when it comes to handling severe tensile stress or wildly fluctuating temperatures.

It is best to clean the surfaces of the sheet metal to be connected to make sure the surfaces stick together properly. When spreading adhesives, they should be done in thin layers, and thick layers are likely to give space for cracks. Adhesives are great options for people looking for a connecting sheet metal method that will leave the metals unmarked.

There are different types of adhesives, including:

• Anaerobic
• Acrylic
• Epoxy
• Cyanoacrylate
• Modified silicone

Most adhesive connecting solutions are not used by heavy-duty automotive sheet metal companies because they are more suitable for lighter sheet metals.

Benefits

• Can be used to join a wide variety of metals and materials
• No heat needed for the joining process.
• When spread well and cured, consistent joint properties
• No visible distractions

Considerations

• Typically used in combination with mechanical joining, rather than a standalone option to join sheet metals, as the unaided Curing time can slow down production.
• Heavy-duty applications require additional non-adhesive joints to ensure proper robustness.
• An unprepared surface can compromise the joining process.

Mechanical Fastening (Screws, Nuts, Bolts)

Mechanical Fastening involves the use of screws, nuts, and bolts for connecting sheet metals. They are often temporary connecting options that allow you to disconnect sheet metal without damaging it in any way. They need the sheets to overlap or the use of plates to link them, as well as a degree of accuracy in forming matching holes where the fasteners can pass. Apart from providing places for corrosion or tension around the connecting holes, mechanical fastening will add weight to components.

There are various types of fasteners. The most common include:

• Bolts, Nuts, and Screws in various shapes and forms, such as lock and cage nuts or thread forming screws for plastics or metals.

Benefits

• Fasteners allow for easy assembly and disassembly.
• There is no risk of heat distortion.
• Fasteners usually have reuse value.

Considerations

• Fasteners can create stress points on sheet metals.
• Vibrations over time can loosen screws and nuts.
• They are not airtight as connection options like adhesives and brazing.

Challenges in Connecting Sheet Metal

Some challenges come with connecting sheet metals, which need to be addressed early on in the planning process to ensure the correct fastening and joining methods are used to overcome them:

Cleanliness of Parts

This can be a big challenge with long-lasting effects for sheet metals with joining techniques such as adhesives, soldering, and welding, amongst others. Dirt can crack the surface joined, prevent complete joining, and threaten the integrity of joined sheet metals over time.

Accessibility

When fabricating sheet metals for automotive manufacturing, various parts require different connection methods due to the accessibility of the surfaces. A cost-effective connection method might work for single-sided access requirements, while another method might be needed for double-sided access, increasing cost and stress over the fabrication process.

Joining Directions

The joining direction of sheet metals can affect the overall design outcome and functionality of the vehicle. Certain joining techniques may limit design flexibility or require specific orientations that complicate assembly.

Pre-hole Requirements

Mechanical fasteners and rivets often require a drilled hole through either one or both sheet metals. There are two problems this process might present. First is an issue of alignment. In cases of two holes or more, there may be misalignments between them. There is also the issue of durability. The more holes needed for the joining, the easier it is to compromise the strength of the metal, especially when using thin or lightweight metals.

Structural and Functional Considerations

Structural and functional considerations are one challenge that manufacturers have to consider when joining sheet metals in fabrication processes. The structural integrity of certain body parts would require a certain connection method to ensure that the joined metals do not give way to water or air pressure, which could be difficult to achieve with some connection methods.

Knowledge Gaps

Insufficient knowledge of the proper connecting techniques and processes for certain materials or applications can lead to less-than-ideal connections. This problem is getting increasingly important as next-gen technologies continue to emerge in the manufacturing sector. It will take continuous training, research, and cross-industry cooperation to fill in these knowledge gaps.

Stanley Engineering Fastening (SEF) Solutions

Stanley Engineered Fastening offers top-notch connecting sheet metal solutions to solve even the more pressing challenges. Boasting years of refinement and quality, SEF represents one of the strongest full-service portfolios of connecting sheet metal capability.

Self-Pierce Riveting (SPR) and Plasma SPR

Tuckerâ SPR allows you to join materials which cannot be welded easily by combining two technologies in one modular system: self-piercing rivets with semi-hollow rivet and punch rivet. SPR offers advanced mechanical joining with minimal surface damage to reliably connect multi-material metal sheets. It stands out from basic mechanical joining due to its low-emission technique with no pre-hole required, making its procedure safe and easily replicable.

Tucker Plasma Riveting (TPR) integrates plasma technology with traditional self-pierce riveting (SPR), expanding the capabilities of SPR beyond its current limits. This innovation enables the joining of even stronger ultra-high-strength steel (UHSS) top-layer stacks with reduced force and makes it possible to assemble previously unachievable material combinations using SPR.

As a result, lightweight sheet metals, including aluminum and mixed materials, can continue being joined without pre-drilling holes, now at tensile strengths up to 2,000MPa and thicknesses of 2mm. This not only reduces the setting force with no punch stroke but results in lower noise emissions and a more equipment-to-material-friendly process, ultimately enhancing durability and longevity.

Tucker Plasma Joining (TPJ)

Tucker Plasma Joining is a plasma-based joining technique that uses a single-side access solution to locally soften the top sheet of the material. Using ‘plasma pins’ to penetrate the sheet metal, TPJ enables the joining of steels with tensile strengths of up to 2,000 MPa without the need for a pre-drilled hole. This method creates strong and reliable bonds, even when joining dissimilar materials, enhancing the versatility and effectiveness of the process.

Automated Blind Fastening (ABF)

The Automated Blind Fastening (ABF) method makes blind rivet installation precise and efficient. The system is designed using a novel ‘floating’ front end as a means for mechanical hole finding based on industry standards of +/-1.5mm linear offsets and +/- 3° angular compensation. ABF's lightweight design, 30kN pulling force, and support for 3.2mm-6.4mm (1/8”-1/4”) in various forms make it compact, fast, and reliable. For sophisticated manufacturing, its robotic and stationary adaptability, blind rivet presenter, and Tucker-backed reliability make it a perfect fit for automated automotive applications. Supported by custom designs, setup, training, and integration services, it redefines fastening efficiency and precision.

Tucker Automated Cleaning (TAC)

The TAC system is an innovative plasma-powered surface cleaning solution that is revolutionizing the way we approach large-scale cleaning operations. Designed specifically for longer cleaning lines, TAC offers unparalleled efficiency and effectiveness, making it an invaluable addition to any industrial or commercial cleaning setup.

One of the key advantages of the TAC system is its integration of proven plasma components from our cutting-edge plasma technologies, as well as the use of our UPA-software (Universal-Platform-Architecture) kernel. Attached to an industrial robot, or pedestal mount, it eliminates surface contaminants and thereby prepares sheets for subsequent processes like welding or soldering without the need for chemical washes.

Stud Welding with Tucker CleanJet

Once your sheet metal is connected, the material challenges don’t stop there. To fasten components to the car body, that's where Tucker stud welding comes in. Unlike traditional welding techniques, Tucker stud welding offers a precise and efficient solution for attaching various elements to the car body. Stud welding involves creating a welded joint in split seconds using an electric arc established between the base of the weld stud and the workpiece.

Clean and stable conditions of the application area improve the weld results. Especially for aluminum, there are challenges. However, there is an advanced surface preparation process to ensure that there are no complications and the resulting fastening is without error: Tucker CleanJet. Here, the plasma-powered Tucker CleanJet system plays a crucial role in maintaining a stable and consistent welding process, ensuring strong, reliable connections without compromising the integrity of the surrounding material.

Future trends in automotive sheet metal

As targets for emissions reductions continue to become more stringent, more sustainable solutions for both internal combustion engine (ICE) and electric vehicles (EVs) is expected to rise. Not only are automakers looking to reduce emissions from their vehicles when in operation, but they’re also looking to employ new eco-friendly manufacturing processes. In fact, materials such as low-carbon aluminum alloys can reduce CO2 emissions by up to 50% during the production process – and automotive, aerospace and construction companies are reaping the aluminum benefit. In 2024, the International Aluminum Institute reported that global demand for sustainable aluminum will grow by 50% by 2030, with these three industries leading the way.

Other innovative aluminum alloys will also play an even bigger role in lightweight vehicle production. High-strength alloys allow manufacturers to cut kilos while maintaining strength and durability. Alloys such as Aluminum Zinc and Aluminum Magnesium are on the rise in the aluminum die casting market, along with the corrosion-resistant Aluminum-silicon (AlSi) and Hybrid Composites. While these new materials bring benefits along with them, it will also influence the sort of sheet metal connecting methods that will need to be adopted across the automotive industry in order to properly join them.

Conclusion

When it comes to the structural and functional integrity of vehicles, the automotive industry depends on efficient and dependable ways of connecting sheet metal. Strong and versatile techniques such as brazing, riveting, and welding are still essential, but new solutions like Tucker Plasma Joining (TPJ) and Tucker Plasma Riveting (TPR) are changing the game. Considerations including the type of metal, design intricacy, and intended durability dictate the procedure to be used.

Future trends like ultrasonic welding, and nanotechnology adhesives can help improve the connection of sheet metals. If properly implemented, this will guarantee safety, increase efficiency and durability, and upgrade the overall sheet metal connection process.