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Radmot May 7, 2024 8:12:14 PM

Production of fasteners: metal and polymer

Fasteners are incredibly important parts – especially from the perspective of almost any bigger system. Their properties allow solid mounting of supporting elements or tight connection of the bigger object. Such parts are used in almost any industry – from automotive and construction to airplane and space. The precision of manufacturing fasteners and the selection of the right materials used for production have a strong impact on the rigidity of the systems that are connected. On top of that – can lead to significant cost optimization: manufacturing and further exploitation. 

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Types of fasteners and their applications

Fasteners are most often smaller parts (especially in the context of the system that connects). Their main goal is to connect two or more elements. Due to frequent use – these elements are manufactured in bulks with manufacturing precision adjusted to the application. 

Among the most popular fasteners it is worth mentioning: 

  • a vast variety of nuts, bolts, and machine screws – used basically in any industry, with different types of heads (from classic, 'flat' screws, to Philips and hexagonal head and star), 
  • washers, rings, rivet nuts or nuts,
  • anchors, grooves, pins,
  • simerings, o-rings, rivets,
  • hinges, brackets, hooks, chains,
  • threaded rods and other types of pins – simple (straight) and highly specialized, manufactured out of a vast variety of materials, according to the client's orders (normalized and custom).

👉 Although the list of fasteners types for industries is of course much longer – mentioned above highlight the spectrum of that type of parts. In addition – fasteners can be manufactured out of polymers (e.g. POM) and can be used in systems that require low mass and 'enough' mechanical parameters

A vast variety of applications of these connecting elements are required according to a selection of materials and well-suited fastener machining. For example – typical wood screws are manufactured out of many steel alloys, sometimes stainless or better in some additional processes (e.g. zinc coating to improve corrosion resistance). 

The manufacturing process of such screws is based on plastic forming and the main goal of the screw is to create permanent joints between elements. In most applications, screw manufacturing does not require very high tolerances but still is regulated by international and country laws. For Poland (part of the European Union) screws manufacture is regulated by the following norms: 

  • PN (Polish norm), 
  • EN (European norm), 
  • ISO (international standard). 

Such norms regulate the type, shape, and size of screw heads and threading. Other types of fasteners are highly specialized parts used in very demanding environments (for example – engine pins that connect the head and engine block). Such fasteners manufacturing process requires very high precision, which can be challenging in the production of bigger elements. 

To meet expectations for those parts and their environment manufacturers should take into consideration also possible thermal deformations and interactions with connected elements.  

In such a context the selection of the perfect material for the specialized fasteners machining can be demanding and sometimes – problematic. On top of that – there are different requirements for the wheel pins and for the engine pins, just like bridge fasteners that connect very big metal elements or parts that are responsible for sealing pressurized tanks. 


What is the cost of fastener manufacturing?

Application of the right technology in manufacturing these types of parts can translate for the quality of fasteners and the quality of the provided connection. Simple screws (eg. used for home appliance cases) are often produced in plastic machining. Forging or rolling allows the manufacture of high quantities of high-quality parts, within desired tolerances and maintaining an acceptable time of production. With increased demand for precision, the final quality of manufactured fasteners should come along. 

Such high-quality fasteners are usually machined with: 

  • CNC turning – numerically controlled technology allows the maintenance of tight tolerances and high repeatability of the whole manufacturing process. Lathes are used to turn cylindrical and threaded elements, 
  • CNC milling – allows a machine of complicated and custom fasteners or bigger connecting elements. High precision and minimal tolerances make that technology the 'go-to' for very demanding custom fastener manufacturing. 

All of the CNC-driven devices allow the manufacture of a high quantity of precise fasteners and achieve very good cost efficiency. On the other hand – single parts can be produced with traditional mills or lathes; larger series of parts should be manufactured with highly specialized CNC machines. Especially when repeatability, precision, tight tolerances, and time are important factors. Of course – such a manufacturing process requires personalized quotation that addresses matters like: 

  • selection of the right material from the material science perspective, often checked from the perspective of experienced CNC machining operators. Such analysis takes into consideration factors like clients' expectations but also the context of the system, which will be connected by an ordered fastener, 
  • selection of the right type of manufacturing, with specification in mind, 
  • selection of the best surface bettering process (if required). 

Among these reasons – the final cost of fasteners production – especially custom and complicated – can vary.

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Mentioned zinc coating of screws is one of the most popular forms of improving the mechanical parameters of the fastener's surface. Such processing should provide better protection against corrosion and atmospheric factors (e.g. salt water or acids), thus – prolonging such part life. In addition – such processes can improve the aesthetic values of parts and/or make the fasteners less visible after mounting (e.g. self-drilling screws for steel sheet mounting). 

Among the most popular forms of bettering the surface of fasteners, it is worth mentioning:

  • anodization (aluminum and titanium), zinc coating, chrome coating, and different galvanic processes, 
  • powder painting, 
  • straight painting and lacquering. 

Just like in the case of materials – the right selection of fasteners surface finishing method can provide longevity and better quality of provided connection.


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