Fasteners and Sealing
4 Alistair Rae looks at some recent developments that are helping designers to reduce the cost and lead time for custom fasteners.
4 Alistair Rae se penche sur des développements récents qui aident les designers à réduire les coûts et le délai de réalisation pour les attaches sur devis.
4 Alistair Rae beschäftigt sich mit neuen Entwicklungen, die Designern helfen, die Kosten und Lieferzeiten für kundenspezifische Halterungen zu reduzieren.
Cutting the cost and time associated with custom fasteners
T
here are thousands of different standard fasteners available. For threaded fasteners alone, if you consider the possible combinations of different thread forms (with many
offered in standard, course and fine pitches), lengths, head styles, materials and finishes, the extent of standard product portfolio soon becomes very large. However, there are various reasons why an alternative head form or non-standard length might be required, and it can be beneficial to incorporate location lugs, integral washers, O-ring grooves or other geometric features. Sometimes the ‘fastener’ can be redesigned so as to additionally perform the functions of another component. Fastener manufacturers have been highly
innovative in recent years, taking advantage of the important role their products can play in reducing bills of materials and assembly time, as well as providing reliable joints in adverse operating conditions. One example of this is Arnold Umformtechnik’s screws that benefit from a patented Mathread dog point. These are designed to prevent the screws from being cross-threaded during insertion, which might otherwise result in increased cycle times and damaged assemblies, and a risk of injuries to operatives. As the threads of the patented Mathread dog point come into contact with the female thread, they begin to cam over the female thread, thereby ensuring that the two thread helices align correctly every time without fail (Fig. 1). Compared with alternative solutions to this
cross-threading problem, screws with Mathread dog point are claimed to be shorter, lighter and can be used in more applications. With innovative features like this available on standard fasteners, the message to designer engineers is that they should not hold back from asking fastener manufacturers to create new products to solve specific assembly problems.
Customised fasteners
Companies such as Non Standard Socket Screws (NSSS) can cater for much of industry’s requirements for customised fasteners, with manufacturing facilities that include double-blow hot forging presses, CNC (computer numerical control) turning and milling machines, grinding machines and thread rolling machines, as well as on-site heat treatment. Parts can be manufactured in various grades
of steel, alloys, brass, aluminium, titanium and other exotic materials. For applications requiring enhanced resistance to corrosion, NSSS offers a comprehensive range of surface treatments, such as zinc plating, Geomet, Dacromet, Delta, galvanising and Xylan fluoropolymer coatings. In addition, fasteners can be supplied with a
dry threadlocking adhesive pre-applied to a portion of the thread so that potentially messy liquid threadlockers do not need to be applied during the assembly process.
Rapid prototyping
Fig. 1. Arnold Umformtechnik’s Mathread dog point ensures that the male and female threads are self-aligning so that the threads cannot become crossed during assembly.
Arnold Umformtechnik, which is part of the Würth Group, is finding that customers are increasingly making use of its Fastener Express service for rapid prototyping complex non-standard fasteners and small precision parts (Fig. 2). According to the company, prototype components can be supplied in one-quarter of the usual time and at a quarter of the cost of producing prototypes using conventional processes. Because the rapid prototyping process is so different to Arnold Umformtechnik’s usual work, the company has formed a specialist team to ensure that orders are progressed quickly. First, the proposed design is assessed to ensure that it is technically feasible. Three-dimensional CAD data is then processed so that a suitably sized blank can be machined on automatic lathes and machining centres. If any other processes are necessary, such as heat treatment or electroplating, these can be completed in-house.
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