Polymer plain bearings extend to automotive uses

Although polymer plain bearings have been an established, viable alternative in the machine tool industry for many years, they are also becoming widely accepted in the automotive sector. Nowadays, there is virtually no new car on the road without plastic plain bearings. The demands on the plain bearing here include wear resistance, zero maintenance and thermal stability. Iglidur bearings from Igus possess these characteristics and can often directly replace steel backed PTFE bushes and roller bearings. They also offer a cost effective purchase and many technical benefits. Developed under the toughest conditions, they are oil, maintenance and lubrication-free, low wear, resistant to dirt and dust, corrosion free and simple to fit. Igus also has the data to precisely predict the lifetime of its bearings within a specific application. Today, there are few vehicles not equipped with Iglidur polymer plain bearings from Igus. The spectrum of applications ranges from simple seat systems to under-bonnet applications subject to high thermal stress, gearshift transmission forks, or in the exhaust gas systems of modern diesel engines. In addition to the standard range of plain bearings, Igus can offer special Iglidur materials developed for a specific application. Results obtained on test benches, specifically developed for this purpose, serve as a basis for material selection. Every year, more than 4000 tests are carried out in the Igus laboratory and more than 100 new materials are tested. Selecting the relevant Iglidur plain bearing for a specific application is always supported with empirical lifetime data. Whenever test data are not available for a particular application, Igus can carry out tests on a short-term basis. This year, Igus developed a new plain bearing material for an application with a thermoset shaft for vehicle lighting systems. This took less than 8 weeks. The prime requirement for seat systems is low cost. Igus polymer plain bearings can offer considerable cost benefits compared with metal plain bearings. Often sheet metal systems, punched holes, or widely tolerated cold extrusion metal pressings are used in seat systems. However, the bearing system must have minimum clearance in order to ensure sufficient reduction of noise. Plastic plain bearings are being used increasingly to provide this. One option is to install Iglidur polymer plain bearings to achieve a transition fit between the bearing and shaft. Following the E-coat paint process, the bearings are recalibrated by high temperatures up to 220C. A clip design will ensure a secure axial fit in metal fixings and punched parts. The properties of the car chassis directly affect the comfort of the passengers and are important for driving safety. Any materials used must be able to cope with extremely high loads and temperatures. Igus has developed a material called Iglidur Z, which can operate at pressures up to 150MPa and temperatures up to 250C. The polymer's low modulus of elasticity also provides optimum damping in the event of blows, impacts and vibration. With the introduction of new Iglidur H4 plain bearings, Igus has unveiled a material which offers a long term operating temperature of 200C and is resistant to synthetic transmission oils and fuels. In tests carried out by a major German car manufacturer, transmissions with shift forks, usually fitted with roller bearings, were retrofitted with Iglidur H4 plain bearings. Although the test drivers did not notice any significantly higher operating force, they praised the improved damping properties. Automotive steering column adjustments demand low friction values and a high degree of rigidity, despite wide housing tolerances. Slotted Iglidur J bearings enable tolerance compensation and substantially reduce the difference between static and dynamic friction. Lubricated Iglidur F bearings offer high pressure resistance and low friction values to steering systems. Glass-fibre reinforced PA or PPS materials can be used as shaft materials. Plastic-plastic bearing systems are increasingly important in the automotive sector due to cost and weight considerations. Plastic materials are preferred for their chemical resistance and the economical production of complex design parts. PA materials have been tested for reliability and efficiency in inlet manifolds for many years. Now aluminium die-cast housings, for example, in the case of throttle valves, are progressively being replaced with plastic housings. Here Iglidur plain bearings are overmoulded with PA or PPS materials at approximately 340C. A high thermal stability can be provided using Iglidur Z. Intense vibrations, abrasive dirt and high temperatures and loads mean calliper bearings must operate in extreme conditions. Iglidur H2/H4 plastic plain bearings from Igus achieve a particularly high service life due to the high resistance to alternating stress and wear. This excellent durability is standard with Iglidur materials and is achieved by the homogenous blend of base polymer, fibre reinforcement and solid lubricants. Dave Spence has been working for Igus, Northampton, for 11 years. Initially, his work focused on selling the complete Igus bearing range, but in the last few years he has become the automotive specialist for Igus UK. As Automotive Project Manager, he is now in charge of selling plastic plain bearings in the automotive sector, providing extensive technical support, from conceptual design right through to full production, whenever necessary. 'In addition to the technical benefits that plastic materials have to offer, due to their integrated lubricating capacity, we can also fall back on persuasive arguments of cost'. 'Compared with ball bearings, our Iglidur bearings are up to 90% cheaper'.