¿Qué tienen en común los productores de leche que protestan y el sector de la construcción de máquinas agrarias? Ambos están sometidos a la presión económica. Por consecuente, las inversiones en la técnica agraria deben conducir a mejoras significativas a costes relativamente bajos. En el ejemplo que sigue, los Cojinetes (en esta aplicación Cojinetes especiales) de polímeros tribologicamente optimizados aseguran una conexión continua en un componente estándar que es el elemento central de la máquina. Desde hace varios años, los Cojinetes de plástico hacen sus pruebas en el rudo trabajo del campo.
The company AGCO Feucht GmbH (at that time still Fella-Werke GmbH) has already been designing implements for tractors for more than 90 years. These include mowers, hay rakes and swathers. The swather works by using eight, ten or twelve tine arms to rake together stalk material that has already been mown or spread out to form a swathe. All swathers made by this supplier work exclusively using rotary technology, i.e. exploit the benefit of high area performance. Supporting the prongs is one of the tasks of the complex control system and is the machine's most important function. Two plain bearings are fitted to each prong. If damage occurs here, the rotary swather stops, which must not happen under any circumstances during harvest time.
During the high season in summer, agricultural harvesting machines have to work smoothly for many hours a day for a few weeks. The external stresses are extremely high. The transport of the stalk material over the ground, as well as the contact of the prongs with the ground or the approach to obstacles such as bushes, hedges and stones, primarily generates radial forces. To avoid damage to the plain bearings in these situations, they must be shock-resistant and very tough. Then there is the dust and dirt, and finally the high-pressure cleaning. Harsh operation conditions and long service life with possible corrosion of the steel parts place very high demands on the plastic plain bearings.
Lastly, the machine builder aimed to find a compact and affordable solution.
Tribo-optimised polymer plain bearings made of the special material iglidur G have been used as plain bearings for ten years now. These are economical all-round bearings which - free of lubricants and maintenance - among other things prove their strengths in simple pivoting and rotating movements, with very high loads as well as with high dirt requirements.
Since the introduction of volume production, the system has been working smoothly. The anti-rotation feature ensures a completely firm fit of the bushing in its housing. The benefits pay off for the manufacturer of agricultural machines: the amount of wear has been significantly reduced in comparison to plain bearings made of metal and less noise is generated when the equipment is in operation. Furthermore, the economic efficiency is good, since, among other things, the finishing of the housing hole for the plain bearings in the aluminium bearing tube is completely unnecessary. Thus, the plastic bearing with the conical outer side was simply adapted to the conical design of the housing hole. This also applies to the conical mounting holes of the aluminium bearing tubes, which are screwed to the tapers of the gyroscopic bells.
It quickly became clear to the company that costs could be saved with plastic. In the beginning, we turned the plastic bushings ourselves and later injection-moulded. Since the choice of material was not right, the result was not right either. The extensive igus® product range, which includes standard and customised parts, quickly provided a suitable solution. Having been tested thousands of times under everyday conditions in the igus® laboratory, the high level of abrasion resistance and the dry-operation properties of the polymer plain bearings immediately revealed their worth in real-life agricultural applications.