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Polymer bearings:

Polymer bearings: long-lasting and costeffective alternative to metal bearings Today high-performance plastics are used in a multitude of applications from kitchen appliances to industrial environments. Bearings made from high-performance plastics are lubrication and maintenance-free and are increasingly superseding metal solutions. The “motion plastics” of igus, the plastics specialist based in Cologne, Germany, are resistant to rain, extreme temperatures and are impervious to oil and chemicals. They are also lighter and more energy-efficient as compared to metal solutions and most importantly are cost-effective. Design engineers from all over the world are now considering plastic bearings as a long-lasting and a cost-effective alternative to metal bearings. This is due to the special material properties as well as the excellent performance in motion that these high-performance plastics offer. The ability to withstand stationary stress says little about a bearing’s performance capability. The degree of wear-resistance of a bearing and how low its coefficient of friction is do not become apparent until it is used in moving applications, where wear is unavoidable. And this is exactly where the strengths of high-performance or motion plastics are. Largest combination of materials and dimensions The company, igus has been developing and producing polymer bearings for over three decades under the brand name “iglidur”. The bearings are self-lubricating and therefore maintenance-free; they can withstand enormous loads and are light in weight. The materials are developed and tested in the industry’s biggest test laboratory. In an area of around 2,750 sq. metres, more than 135 billion test movements are executed each year. The result of more than 30 years of R&D, is the largest standard range of lubrication-free polymer bearings. Around 50 materials are available, including 16 full-range materials. They are in stock in at least 113 dimensions and up to a shaft diameter of at least 50 mm in accordance with DIN ISO3547; the largest catalogue bearing has an inner diameter of 195 mm. In addition, there are many materials available in the form of bar stock, liners or for 3D printing, filament or SLS powder. Polymers enable a great deal of design freedom: with little effort, even extremely complex parts can be made or their characteristics can be significantly influenced by means of specific additives. This is precisely the core competence of igus: the optimisation of technical polymers for use in moving applications. Wear-resistant and lubrication-free MACHINE ELEMENTS About Igus Igus GmbH is a leading manufacturer of energy chain systems and polymer plain bearings. The Cologne-based family business has offices in 35 countries and employs around 2,950 people around the world. In 2015, igus generated a turnover of 552 million euros with motion plastics, plastic components for moving applications. igus operates the largest test laboratories and factories in its sector to offer customers quick turnaround times on innovative products and solutions tailored to their needs. To this end, igus has its own material development department, which is continually coming up with new iglidur materials to match specific areas of use. The individual components of the compounds are mixed homogeneously during the injection-moulding process. The excellent performance of iglidur plastic bearings derives from this homogeneous structure, whereby the basis of an iglidur bearing consists of thermoplastic polymers that ensure the bearing’s good basic resistance to wear. Fibres and filling materials increase the bearing’s load-carrying capacity. In addition, solid lubricants have been included in the material. All the components work together and result in very good sliding and abrasion properties. In contrast, rolled metal bearings have a layered structure. The inner layer is very thin and, in the event of high loads, edge pressure or vibrations, can easily be stripped off or damaged by dust particles. Moreover, the sliding layer represents a limit to the degree of possible wear. The homogeneous composition of the plastic compounds, in contrast, is considerably more robust as the wall thickness of the bearing acts as a ‘wear zone’. Unlike iglidur bearings, which made of high-performance plastics, bearings made of metal alloys have to be permanently lubricated, a disadvantage that is cost-intensive WORLD OF INDUSTRIESMOTION, DRIVE & AUTOMATION 2/2017

01 Igus bearings are developed and tested in the industry’s biggest test laboratory on 2,750 m 2 02 Igus offers the largest standard range of lubrication-free polymer bearings. Around 50 materials are available, including 16 full-range materials and also time-consuming. What’s more, lubrication with grease or oil is becoming increasingly unpopular for hygienic and ecological reasons. Sinter bearings that are commercially available also have oil lubrication incorporated into them and are therefore not dry-operating bearings. The same applies to rolling bearings, which, especially in the case of needle bearings, are often being replaced with iglidur plastic bearings for technical and economic reasons. Application in agricultural machinery sector The agricultural industry alone is a good example of the potential of plastics bearing technology from igus. The iglidur bearings that are used in agricultural machinery are extremely wear resistant and can cope with high surface and edge pressures. They are non-corrosive and resistant to impacts. Fertilizers, slurry or fuels have no effect on their ability to function. The machines can therefore be used reliably even after being out of use for a long time. Especially in agricultural environments where machines can be exposed to extreme amounts of dirt, iglidur bearings guarantee optimum functionality and long operating times. The Cologne-based company has developed special materials in the form of ‘iglidur Q2’ and ‘Q290’, which are specially suitable for typical agricultural applications involving slow pivoting at high loads. Application in the food industry In the food and packaging industry, the absence of lubrication also plays an important role in view of the strict hygienic and safety standards in these sectors. According to the regulations of the Food and Drug Administration (FDA), it must be ensured that products are not contaminated by lubricants or other substances. As a consequence, only plastics that are FDA-compliant and suitable for use with food are used in these sectors. In contrast to metals, plastics are always non-corrosive due to their organic structure and are also resistant to inorganic media, including acids, dyes and aqueous salt solutions. Plastic bearings from iglidur are being used by various manufacturers of food processing machines. The biggest advantage being that polymer bearings are not sensitive to water, penetrating through the seal during cleaning and maintenance, as the metal bearings are. The plastic machine elements, on the contrary, are characterised by a low level of water absorption and are resistant to chemicals. cases. Which material is the right one for the respective use can be quickly determined with the help of online tools such as the Product Finder, the Configurator or the Service-life Calculator. Users can click on their special requirements (“Longest service life with dry operation”, “Dirt-resistant”, “Vibration-dampening”, “Resistant to chemicals” etc.) and indicate the permissible static surface pressure and the upper and the lower operating temperatures. Cost-effecitve polymer bearings In all branches of industry, polymer bearings have been replacing metal bearings. For engineers, the wear-resistance, low coefficients of friction, the non-corrosiveness of the motion plastics and freedom from lubricants have become indispensable as they increase the service life of their machines and are also up to 40 % less expensive than metal bearings. New materials and properties are continually opening up further possible uses for polymer bearings, igus is continuing its research activities in the company’s own technical facility. Given that development in the area of shaft materials and surface treatment does not stand still, continuous tests that react to shaft changes and are aimed at a perfect matching of shafts and bearings are absolutely critical. Especially the issue of running partners illustrates the versatility of iglidur bearings, which can be used on very different shafts – and above all on cost-effective, so-called soft shafts. This is a clear advantage over many other types of bearing. In addition to the cost benefits associated with plastic bearings, the user can also utilise a non-hardened shaft and thus reduce his costs even more. It is important to choose the shaft that is best in terms of price and performance, depending on the application in question. 03 Find the right material with the igus product finder Special materials for respective application For most typical bearing applications, five standard iglidur materials are used. But at the same time the demand for specific materials used for specific applications is growing. From underwater use to high-load applications, from medical technology to the automotive industry: Igus has developed tailor-made materials for all these


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