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FEATURE SPRINGS & SHOCK ABSORBERS A WAVE OF SPRING APPLICATIONS
From medical products such as surgical instruments and
wearable medical technology, to electric bicycles, designers are reaping the benefits of wave springs, as Simon Ward, technical manager at TFC, an AFC Industries company, explains
A
variety of medical products – including surgical instruments, medical devices, wearable medical technology and orthopaedic equipment – feature springs. They are commonly used as return springs for function buttons, where they can provide the necessary force to restore a button to its original position; and to maintain electrical contact or compensate for assembly tolerances. Wave springs are being used due to their
space-saving advantages – while they require less than half the space of a coil spring, wave springs deliver the same spring force with a smaller operating height. The compact design of a wave spring is particularly valuable in situations with tight space constraints, so they are used in handheld instruments, tools and wearable devices – in situations where designers are
seeking to create lightweight, compact and well- balanced products. They have been used in the design of insulin pens, and in surgical and dental tools that use high speed precision bearings. When selecting a wave spring for medical
applications, there are a few factors to consider. One option is the Crest-to-Crest wave spring, which is suitable for applications requiring lower spring rates. For applications involving short deflections and low to medium forces, a single-turn wave spring can provide precise and reliable performance. Linear springs may be a suitable choice if a straight load bearing system is required. However, it’s important to note that engineers
cannot simply interchange coil springs with wave springs without considering their distinct characteristics. When a load is applied, wave springs flatten to provide upward force, whereas coil springs twist during compression, causing the force to deviate from the axis. Consulting with a wave spring expert can provide valuable guidance when integrating the appropriate spring into your medical device. Wave springs are manufactured in several
different forms, and with a range of spring characteristics. If off-the-shelf options do not fit the size and environmental resistance requirements needed, spring specialists can design custom wave springs. This involves tailoring the number of turns or waves, material and size to meet the specific product needs. There are a range of materials available that are ISO 13485:2016 certified,
50 DESIGN SOLUTIONS DECEMBER/JANUARY 2024
suitable for different environmental conditions. Popular materials for wave springs in
medical applications include 302 and 316 stainless steel, which can withstand the higher temperatures applied during cleaning and sterilisation processes, without any compromise to spring properties.
SPRINGS FOR E-BIKES With fuel prices remaining high, cycling has seen interest spike, with many turning to it as a cheaper alternative to driving. E-bikes are the most natural replacement for driving short distances. Two million electric bikes are sold in Germany every year, according to data from the Bicycle Association. In the UK, however, only 165,000 e-bikes are purchased each year. The Bicycle Association’s executive director,
Steve Garidis, said: “It’s clear looking at the sales data – particularly comparing the UK with European countries like Germany and France – that we risk being left behind here. However, e-bikes clearly have huge potential, which could be unlocked here in the UK.” Growing the e-bike market requires
manufacturers to effectively design appealing products, manufacture them efficiently and scale up e-bike production profitably. In e-bikes, springs and retaining rings can be used in drive technology, wheel hubs and braking systems, as well as throughout the structural framework. Wave springs provide solutions to design and manufacturing problems by compensating for tolerances,
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