The right connections

Louise Davis

Louise Smyth reports on the latest news from the fasteners sector

In engineering design, fasteners can often turn out to be the single component that takes an idea from concept to reality.

As such, their value should not be underestimated. And in recent years, as things such as composite materials have evolved so too have fastening solutions.

Today it’s a surprisingly fast-moving sector. Here we present a roundup of the latest news from those at the forefront of fastenings.

Fasteners on Mars

One fastening expert was recently commissioned to supply high-strength blind rivets for the ground-penetrating radar system on NASA’s 2020 Mars Exploration Rover.

TR Fastenings Norway received this commission from the Norwegian Defence Research Establishment (FFI), which won a bid with NASA to design and build the Mars Rover’s Radar Imager.

The radar, known as RIMFAX (Radar Imager for Mars’ Subsurface Exploration), is one of seven scientific instruments on the Exploration Rover that should help establish whether it’s feasible to sustain human life on the Red Planet.

The sophisticated radar imager consists of an electronics box mounted inside the Rover and an ultra-wideband slot antenna mounted on the rear of the vehicle.

The rivets help ensure the structural integrity of the radar’s antenna, which is constructed to aerospace standards from lightweight aluminium sheet metal and assembled from several complex shaped parts. These components will be exposed for years to the hostile conditions of a planet famous for its extreme dust storms and temperatures as low as minus 125°C.

The currently operational Rover, Opportunity, landed on Mars in 2004 for a planned mission of 90 Martian days (92.4 Earth days) but is still in service.

The new Mars Exploration Rover will roam Mars’ rocky terrain searching for a wide range of rocks and soils that hold clues to past water activity on the planet. RIMFAX’s ground-penetrating radar will send radio frequency electromagnetic waves into the ground to a depth of up to 10m and then detect the reflected signal as a function of time to reveal the subsurface structure and composition.

Ground-penetrating radar has the capability to reveal subsurface terrains such as lava flows, buried channels, and polar ice cap stratigraphy.

Jan-Erik Storsve of TR Fastenings Norway comments: “It’s incredible to think of those fasteners being used in outer space! We are extremely proud to be involved in the next Mars mission and everyone at TR is looking forward to the launch with great excitement.”

Meeting the need for threaded fasteners

Each manufacturing industry has its own requirements, but all use threaded fasteners – nuts, bolts, screws and washers. Challenge Europe strives to address these varying applications with technical expertise that can save manufacturers’ time, money and concerns about quality. Industries such as electronics, medical, agricultural, general machinery, instrumentation, marine, and building, all benefit from their careful consideration of the presented specification and supply of quality fasteners.

Each application is different of course as MD Kevin Moorcroft explains: “In many applications the requirement is fairly straightforward and can often be met by a standard item, however it is also quite common to require a higher spec material or different length, different head form, unusual thread length or non-standard finish. That is where we come in to help identify what is needed and to supply at a competitive price. Where something more custom is needed then we can deal with that too; as we can with a range of fastener associated products or, where a threaded system is not suitable, then we can provide a riveting solution.”

Standard products include socket shoulder screws, machine screws, self-drilling screws and hex-headed high tensile bolts. Smaller sizes of many fasteners particularly suit the electronics industry and a range of plastic plugs protect products in transit from ingress of foreign bodies. Korrex plastic nut caps are ideal for outdoor protection.

Moorcroft also highlights the need to choose the right material for your application. “The material choice is the most important first step but often just as important is the choice of finish – we offer chemi-black on mild steel, stayblack on stainless steel, zinc plated, chrome plated and nickel plated as standard finishes on many of our fixings.

“We work with design engineers and buyers in all industries to optimise choices and minimise costs so we can ensure highest quality and quickest assembly times for each product.”

Making (very small) waves

As important as material choice is, size is also a critical factor in many fastening applications. The designers at Smalley have acknowledged that as engineers around the world design smaller and smaller assemblies, they have started to ask ‘where can I find the compact components to support my designs?’

Smalley devised the answer to this question with its newly expanded Crest-to-Crest Wave Spring Series. Smalley’s popular C (imperial) and CM (metric) Series have been expanded; standard sizes are now available from stock down to .188” and 5mm in diameter.

“We were the originator of the Crest-to-Crest Wave Spring,” states Darryl McBride, Smalley’s director of engineering. “I was amazed when I saw our springs coiled up to 12ft in diameter, what surprised me even more was how much engineering went into designing smaller. Our expanded spring series will open up possibilities for designers in the medical, computer and robotics industries, where wave springs couldn’t fit before,” states McBride.

The light idea

As well as the trend for ever smaller fastening solutions, a great many applications are demanding lighter components too.

New aluminium versions of SI threaded inserts from PennEngineering have stepped up to introduce lead-free and lightweight alternatives to brass counterparts. They also offer ideal solutions to eliminate potential environmental and recycling issues while contributing to overall lighter assemblies.

The aluminium option – approximately 70% lighter than brass equivalents – can be specified for all types of SI inserts and augments the standard line of brass and corrosion-resistant lead-free stainless steel products. All provide durable and reusable metal threads in plastics to accept mating hardware and subsequently allow for access to an assembly whenever required.

Applications for SI threaded inserts include plastic enclosures or components for the consumer electronics, medical, automotive, aerospace, transportation, and recreational industries, among many others.

Whether manufactured from aluminium, stainless steel, or brass, the SI product line for plastic assemblies includes ultrasonic/heat staking inserts for installation ultrasonically or with a thermal press, moulded-in types installed during the moulding process, and press-in types installed by pressing the insert into a pre-moulded or drilled hole.

All install permanently and, unlike fixed and unyielding joining methods (such as adhesives or rivets), the inserts ultimately offer the capability to disassemble and re-attach plastic components easily and quickly without damaging the threads, compromising attachment integrity, or otherwise adversely impacting an assembly.

SI threaded inserts have been engineered in a variety of designs and lengths – including micro fastener versions with threads as small as M1 – and can be supplied in unified or metric thread sizes.

On the latch

New advances are also being made to improve on fastenings such as latches. In one example, a new shutter cam latch from Southco has been designed to prevent accidental opening.

The drop bushing feature of the E5 Shutter Cam Latch adds additional security by preventing the cam from rotating open in high vibration applications.

The latch is designed with a spring-loaded bushing that covers the driver recess. To actuate the latch, the bushing must be manually depressed. In the event that the latch is not entirely closed, the bushing remains in the depressed position, providing a visual indication that the latch is unsecured.

The E5’s bushing is designed with a longer travel distance, providing enhanced security. With its flush, low profile design, the E5 Shutter Cam Latch provides a clean appearance, minimising dust and debris collection that may affect operation. The E5 Shutter Cam Latch also meets NEMA 4 and IP65 standards for water and dust protection, as well as EN61373, the shock and vibration standard for railway applications.

The range delivers robust, vibration-resistant fastening, features a variety of grip lengths and is available in numerous head style options for added security. Additionally, the new latch features the same panel hole prep as the standard series and is available with a separate latch and cam assembly to promote modular use.

Southco’s Loc Tieu comments: “With its spring-loaded bushing and visual indicator feature, our newest E5 Cam Latch is designed to keep doors and panels affected by excessive vibration securely closed. It satisfies industry regulations for water and dust ingress protection, making it an ideal solution for high traffic areas such as floor panelling and enclosures in transportation and HVAC applications.”

Next-gen harsh environment connector

The recently introduced HEC ‘harsh environment connector’ from Binder is now available in a 12-pole version.

Known as series 696 the HEC connector is protected to IP68, IP69k, withstands high-pressure washing, has excellent resistance to UV, temperature fluctuations, acid rain, salt spray, ozone and other pollutants.

Ideal for agricultural, construction, process engineering, water purification and recycling equipment, traffic and signalling systems and similar applications, the HEC range has a secure, fast, three-point bayonet locking system while a robust coding mechanism prevents incorrect orientation and provides over 1,000 mating cycles. 

The connector uses a variety of crimp contacts to achieve a secure vibration proof termination.

The new version has 12 silver-plated crimp contacts rated to 5A and 250V to complement the existing eight-pole hybrid version with four signal contacts and 3 +PE both of which can accommodate a variety of wire gauges.

Hermetic connectors get certified

From Esterline Connection Technologies, Souriau's range of hermetic 38999 connectors has successfully obtained QPL certification from the DLA. The hermetic 38999 connector range is intermateable and interchangeable with standard MIL-DTL-38999 connectors. These hermetic connectors can be mounted in four different ways (screw, jam nut, weld and solder) according to the type of use.

The qualified versions include 45 layouts and cover many configurations from 3 to 128 contacts with sizes ranging from 22 to 8AWG.

The hermetic receptacles follow stringent quality control procedures and include helium leak testing to ensure leakage rates of less than 10-7 atm.cm3/s. The connectors are suitable for critical aerospace environments. Hermetic 8D connectors are used on many types of equipment where airtight seals are a key factor in protecting electronics from fluid or gas ingress.

"Our hermetic 38999 connectors are used on many types of safety-critical components, from pressure sensors, temperature sensors, speed sensors, and vibration sensors, to landing gear actuators and flight control components" says Samuel Tournier, product manager for hermetic connectors. "They ensure that these highly critical components operate properly and safely."

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