Choosing the right method to assemble parts for your application

Pros and cons of mechanical fastening, welding and structural adhesives for creating part assemblies.
Jacob Meyer
Choosing the right method to assemble parts for your application

Very rarely are components made from one single piece. Most industrial components need to be assembled in various forms to make the final part. Here are some considerations to think about before picking your assembly method while designing a new part.

Mechanical Fastening: Mechanical fasteners are one of the most widely used methods assembling parts. The ease and availability of fasteners available, the tools as well as trained people in assembly and disassembly of parts makes this the most popular way to assemble parts. However, mechanical fasteners often lead to stress concentrations at the point of fastening. It also requires designing to accommodate the fasteners, including holes to accommodate the fasteners, which might change the aesthetics of the joint. Mechanical fasteners generally can be removed, making the end of the life-cycle management of parts easier. At the end of service, parts can be separated and recycled appropriately by taking apart the mechanical fasteners. 

Welding: Traditionally used in the case of metals, welding is a very established method in the industry. Welding generally involves melting of the base material and using the fusion of the molten material leading to joining. Welding has advantages using similar materials as the bonding substrates, reducing mismatch stresses. An earlier study by the Boeing Company indicated that a labor savings of up to 61% could be afforded by implementation of a welding approach as compared to a bolting approach [1]. Welding is also used in the area of thermoplastics, where two thermoplastic parts are brought close to the melt temperature and are joined together during cool down.  

Structural Adhesives: Structural adhesives are used widely in the industry to join parts. The ease of use, no need of drilling holes as in case of mechanical fasteners and the specialized equipment required compared to welding makes it one of the most desirable ways of putting parts together. As well, parts bonded using structural adhesives are more aesthetically appealing and require minimal post processing compared to mechanical fasteners or welding. There are a lot of options available in the industry for structural adhesives ranging from acrylics, urethanes, cyanoacrylates or epoxies. The choice of the structural adhesive for a given application depends on the substrates, the service temperature of the parts, other environmental factors the part is going to be exposed to like UV, moisture or heat and other considerations like fatigue, vibration damping or solvent resistance. Conventionally, once bonded, structural adhesives cannot be debonded and then later reused without removing the cured adhesive. 

ATSP has developed a new class of structural adhesives termed “Self-Bond™” that provides all the conventional advantages of a structural adhesive while being able to go through multiple bond-debond cycles by virtue of bond exchange reactions intrinsic to the resin chemistry [2]. This allows for a new way of designing parts where assemblies can be easily created from older components. Additional advantages of the Self-Bond™ adhesive system include include wide-area application such as powder coating, rapid bonding time, infinite and touch-safe/non-tacky open time, and an entirely solid-state process. Bonding times of a minute or less can be achieved by resistive and inductive methods.

For more information on Self-Bond visit,
[1] Tavares, Sérgio Manuel Oliveira. "Design and advanced manufacturing of aircraft structures using friction stir welding." (2011).
[2] Meyer, Jacob L., et. al. "Reversible Bonding of Aromatic Thermosetting Copolyesters for In‐Space Assembly." Macromolecular Materials and Engineering 304, no. 4 (2019).