A research based approach lead us to the ultimate fixing...
Proprietary Spida Features:
Admax is our proprietary treatment that has been specially developed to increase the bond strength of Spida fixings. This is no average surface treatment. Months of R&D have gone into developing a process that creates surface deformation to depths of around 20 microns. That is up to five times more than other fixing treatments. It maximises Spida’s surface area, surface energy and wicking properties, helping to achieve an unbeatable bond.
Our advanced Admax technology not only deforms the surface but also creates microscopic undercuts, significantly increasing the mechanical strength of the bond. On our carbon steel fixings we use an advanced electroplating technique to protect and further increase the size of the undercuts.
Reduced contact with substrate
Without Admax the base of a fixing could make contact with the substrate. Admax reduced the potential contact area from about 1cm2 down to a few microns. This is because only the microscopic 'peaks’ of the undulations will make contact with the substrate. The rest of the surface will fill with adhesive further increasing the strength of the bond.
Minimum bondline thickness
The 20 micron deep undulations ensure a minimum bond-line thickness around the edge of concave bases and the bottom of flat based fixings.
Reduction in air voids
The Admax surface treatment is designed in such a way that helps the adhesive spread across the surface of fastener without leaving air voids.
Not just a surface treatment
Admax treatment makes the metal denser, harder and therefore stronger and also reduces fatigue crack nucleation.
Spida bases have a 'castellated' circumference. This interlocks with the adhesive or binding polymer increasing torsional resistance. The edge of the base is where mechanical advantage is greatest and therefore the best location for this anti-torsion feature.
As well as improving torsional resistance the castellations improve the rheology of adhesive as it protrudes from the edge of the base which also improves it's peel and cleavage strength.
Spida Fixings are designed to hold in place a threaded fastener that can be loaded up to its ISO breaking point without damaging the fastener, bond, substrate or the component connected to the fixing.
The 'parabolic elasticity' of Spida’s patented concave shaped base means that forces are not 'point loaded' into the centre of the fastener, instead they are dissipated across the entire base and beyond.
Stresses in the centre of the base are attenuated because there is space for more adhesive in the centre. Optimal tensile strength is also provided by a parabolic base, as this is the shape that a flat plate forms naturally when pulled in the centre.
This prevents premature adhesive or cohesive failure in the centre of the base and reduces the forces applied to the fastener, substrate and connected component, which means you can use less fasteners for the same job. Just think what that means for your product’s weight, cost and manufacture time.
Curing adhesive bonded fixings
We offer a range of fixings for different applications. Our fixings with flat bases are designed for welding and certain specialist adhesives (e.g. acrylics) that require minimal bond line. However our more popular concave bases are better for most applications including bonding with epoxy adhesives.
Whether installing a bonded fixing by hand or using a jig there is a natural tendency for installers to press ‘hard’ when positioning it. This results in adhesive being squashed out from under the base leaving only a thin layer. Our research has shown that when using an exothermic adhesive (i.e. adhesives that cure by creating their own heat when mixed) such as epoxy, this thin layer does not usually reach ‘peak exotherm’ (i.e. optimal temperature) under real life conditions and therefore the bond is not fully cured. This is why we developed Spida fixings with concave bases that retain the optimal depth of adhesive under them.
A balanced footing
Our concave base shape self-levels the fixing by forcing it to land level to the substrate even when loaded with a viscous adhesive. This is because the concavity retains a space for the adhesive whilst the edge of the base levels the fixing. This is one reason why we recommend our concave bases for exothermic adhesives such as epoxy. Retaining a similar level of adhesive under a flat base would make it difficult to ensure perpendicularity. The slightest deviation and the adhesive may not spread out evenly under the base leaving an area with less or zero adhesive, which will weakening the bond. We therefore only recommend our flat bases for welding and non-exothermic adhesives such as acrylics that require a minimal bond line depth of adhesive.
Also, if a concave base is accidentally overloaded with adhesive this can be more easily wiped away from the edges as the fixing is not ‘floating’ on a pool of adhesive like with flat based fixings.
The shape of the base also affects the polymer chains (i.e. molecular structure) in the adhesive. When the adhesive under a flat base is squashed very thin the polymer chains align parallel to the substrate. Our concave bases allow space for more polymer chains to form at right angles to the substrate helping it to resist tensile, peel, shear and cleavage loads.
A real life example of polymer chain alignment is seen in a plastic shopping bag. Due to the way the bag is made the polymer chains are aligned in the direction of the handle, this makes it strong enough to hold by the handle but weak if you try to stretch the bag sideways (perpendicular to the polymer chains). With a fixing that needs to resist forces from multiple directions it is important that polymer chain alignment is avoided. This is why we only recommend our flat based fixings for welding and specialist adhesives such as acrylic that require minimal bond line depth.
We use the best possible metals and finishes for our fasteners.
Our high tensile carbon steel products are made from Manganese Boron (20MnB4). This is a premium steel ideal for fasteners as characterised by its consistent mechanical properties, homogeneous structure, minimal dimensional tolerances and ease of use in cold forging and welding without cracking or necking. The bases of our carbon steel fasteners are made from CR4 which is ideal for progression pressing.
We also offer marine grade 316L stainless steel fixings. 316L contains additional molybdenum providing enhanced resistance to corrosion and it’s low carbon content offers additional resistant to grain boundary carbide precipitation. Additionally its non-magnetic austenitic structure gives excellent toughness particularly at cryogenic temperatures.
Our stainless steel fixings are passivated to improve their corrosion resistance.
Our mild steel fixings can be zinc clear heavy trivalent plated, this forms a 8-14 micron thick layer that provides corrosion resistance of 72hr of salt spray resistance to white rust (corrosion of the Zinc plating) and 240hr to red rust (corrosion of the Iron itself). For even better protection our mild steel fixings can be zinc-nickel plated, this forms an 8 micron layer that provides corrosion resistance of 768Hrs to red rust.
Our passivation and plating is done by the top suppliers in Europe to ensure that we achieve the highest standard finish for our fixings.
Not all metals are the same. The crystalline microstructure within metals is influenced by the way it is manufactured and treated.
We cold forge our fasteners and progression press our bases which enhances and aligns the metallic grain flow to provide superior strength. We also roll the threads onto our fasteners (rather than cutting, chasing or grinding them) which further improves the grain flow.
On top of this, our carbon steel fixings are heat treated to resistance class 8.8 to increase their tensile strength and hardness.
Funded by the UK government and guided by Southampton University we spent 2 years designing the perfect fixing. We approached the design work from the ground up, iterating through radical new designs and testing each before landing on the final product. By using finite element analysis (or FEA for short) we could simulate how our designs would respond to real world stresses. Prototypes were then subject to extensive testing in our unique custom built testing equipment and finally in real life applications.
Designing out the weak points
The weakest point of any male threaded fastener is just below the last thread. Our studs compensate for this by retaining as much material as possible at this point and gently tapering into the base. The optimised grain flow in this area also improves its strength. These factors allow more load to be passed through to the base.
A better weld
The larger 35mm and 53mm Spida bases are fed onto the stud head and then autogenously welded from behind ensuring that as much of the two parts as possible are joined. This makes it impossible to pull the stud off the base or push it through, which means that our fixings can withstand forces up to the ISO breaking point of the thread.
From our rolled threads to our advanced welding machines our manufacturing processes and quality checks ensure that every fixing attains a high degree of geometric accuracy. This not only allows you to construct products with more precision but it also reduces the chance of fixing failure by reducing point loading and uneven bonding.