Metal bonding options: the pros and cons

There is no one-size-fits-all solution in manufacturing, as there are too many products, too many materials, and competition to find new methods is intense.

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Nevertheless, when a material can’t be shaped or moulded in one piece, only a few basic approaches are possible. When metals are involved, these usually boil down to welding, soldering, clamping, riveting, glueing or taping.

Mechanical bonding methods

Clamping and riveting use a variety of methods to physically hold the component in position. Bolts may be considered a form of clamping, as are components that screw or click-lock together. In practice, click-lock joining is rarely a design possibility in metal fabrication.

Bolts and rivets share several disadvantages. Firstly, they require additional operations and tooling, such as threading and drilling, which raises costs and lengthens lead times. Secondly, bolts and often rivets leave protuberances proud of the surface that must be designed for – if they are possible at all. Thirdly, perhaps the greatest argument against bolts and rivets is that they focus all the stresses and strains in both surfaces onto the connectors; as a result, bolts and rivets can fail catastrophically, as the captain of the Titanic would confirm.

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Welding and soldering

Basically, welding fuses points or edges together by melting them into one another. Some of the disadvantages are immediately evident; for example, heat can destructively disrupt the structure of the metal being used and damage the surrounding materials. Welding requires heavy-duty equipment and a skilled workforce, not only to perform the weld but also to expertly evaluate its success and strength afterwards. There are fire and fume hazards, and the result is often aesthetically unappealing.

Soldering is a similar solution that uses an intermediate metal that has to melt at a much lower temperature; as a result, the bonding is very light.

Metal bonding adhesive

Applying a metal bonding adhesive is usually a much quicker operation, requiring fewer tools and less training. In the past, it has been difficult to formulate adhesives suitable for metals; however, that is no longer the case. Today, in addition to epoxies, silicones and cyanoacrylate (superglues), there are some very versatile new adhesives ideal for all metal bonding applications such as

Adhesive tapes are also used to connect metal parts. They are probably the easiest method to apply but lack sufficient permanence for most applications.