• • • ELECTRICAL EQUIPMENT • • •
ELECTRICAL RELIABILITY STARTS AT ASSEMBLY: WHY FASTENING
ACCURACY NOW MATTERS MORE IN HIGH-DENSITY SYSTEMS
BY ALEXANDER HALE, PRODUCT MANAGER, DESOUTTER
n electrical equipment manufacturing, assembly determines how electrical, thermal and mechanical behaviours interact once a system is in operation. At fastening interfaces in particular, small deviations in clamping force or seating condition can alter contact resistance and, over time, influence overall system stability.
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While electrical designs are typically engineered for defined parameters, such as current density, thermal rise, creepage and clearance, these assumptions depend on one critical condition: stable and repeatable physical interfaces. When joint conditions vary, electrical behaviour becomes less predictable. Contact pressure and the real area of metal-to-metal contact determines contact resistance, so small changes at the interface can show up as local heat exactly where the system is least able to dissipate it. Elevated contact resistance, inconsistent clamping force or poor seating can introduce localised heating and voltage instability, which may accelerate degradation under sustained load.
When mechanical variation
becomes an electrical issue A fastening operation in electrical assembly does more than secure components together. It shapes interface pressure, influences conductivity at the interface and determines how a joint responds to vibration and thermal cycling.
As equipment becomes more power dense, these effects are amplified. Higher currents are increasingly carried through smaller physical footprints, meaning that even minor variations in resistance can have a disproportionate impact on heat generation and performance stability. At the same time, miniaturisation is tightening mechanical tolerances. Assembly conditions that
14 ELECTRICAL ENGINEERING • APRIL 2026
were previously absorbed within broader design margins are now far more likely to influence long- term reliability. In this context, the quality of the fastening process becomes a direct input into electrical performance rather than a secondary mechanical consideration.
The limits of manual assembly Despite these sensitivities, many electrical manufacturing processes still rely on manual input at critical fastening stages. Variability can be introduced before tightening even begins, through issues such as incorrect fastener selection, misalignment or inconsistent seating of components. Torque is often used as the control variable in production, yet friction and surface condition influence the relationship between torque and clamp load.
Even when a tightening operation passes the set limits, the torque angle curve can still show abnormal joint behaviour, so DeMeter, Desoutter’s manufacturing data analytics software for tightening and drilling, applies real-time curve analytics with AI-led classification and alerts plus capability indicators to help teams spot drift early and strengthen traceability. These factors are often not visible during assembly and may pass end-of-line inspection without detection. However, under electrical load, vibration or thermal cycling, they can manifest as changes in contact resistance and joint stability.
Alongside this, traceability expectations are increasing across the sector. It is no longer sufficient to demonstrate that assemblies meet specification at the point of inspection; manufacturers must also demonstrate that processes are controlled, repeatable and supported by reliable production data. Manual steps at critical interfaces make consistent process data significantly more difficult to achieve.
Bringing control to
the fastening interface In response, electrical equipment manufacturers are increasingly focusing automation on the interfaces where mechanical, electrical and
thermal behaviours converge. Fastening represents one of the most critical of these points because it directly determines the integrity of electrical joints. Automated screw-feeding systems help address a key source of variation in this process. By delivering screws in a controlled and repeatable manner, they reduce reliance on manual handling and mitigate common assembly issues such as misfeeds, incorrect presentation and inconsistent seating prior to tightening. Desoutter’s RAPID screw feeding system supports this approach by automating screw delivery to the tightening tool. This ensures consistent component presentation and reduces operator-dependent variation, particularly in high-throughput environments or assemblies with restricted access.
In compact electrical products, where fastener size and accessibility already increase process sensitivity, stable screw presentation becomes especially important. Even small inconsistencies at this stage can influence how a joint seats, with downstream effects on contact behaviour and electrical stability. Crucially, improved consistency at the feeding stage also strengthens downstream process control. When screw delivery is stable and repeatable, tightening data becomes more reliable, supporting traceability requirements and enabling better verification of assembly quality in safety- critical applications.
As electrical equipment continues to evolve towards higher power density, greater miniaturisation and wider deployment across critical infrastructure, performance is increasingly shaped by the precision of assembly rather than design intent alone. Fastening is not the only factor in electrical assembly, but it is a key interface where mechanical variation can directly translate into electrical and thermal consequences. In this environment, controlling the fastening process becomes a prerequisite for consistent system reliability.
https://www.desouttertools.com/en-gb
electricalengineeringmagazine.co.uk
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