Construction and agricultural machines are constantly in use under difficult environmental conditions. Always out in the open, they have to cope with changing temperatures and constant dust and dirt pollution. Especially for the moving machine components it is a great challenge to be in operation for many years without failure in order to fully meet the manufacturers' requirements. For example, iglidur plastic plain bearings from the motion plastics specialist igus, whose products have been used in the foot pedals of the company Sensata for many years.
"The environmental conditions are difficult: dust, humidity, temperature changes, aggressive cleaning agents and exposure to diesel or fertilizer". This is how Michael Stoffers, Engineering Manager Mechanic Design at Sensata Technologies GmbH, describes the environmental conditions in the driver's cabins of agricultural and construction machinery. The company's products are used here. With 22,000 employees, Sensata is one of the leading manufacturers of sensors and man-machine interface products such as example, Motorcycle handles, joysticks, operating units for construction and agricultural machinery, cranes and lifting platforms or even foot pedals Foot pedals in particular must be able to withstand extreme stress from foreign matter and moisture. "In places the pedals are even a few centimetres deep in the gravel," explains Michael Stoffers.
In use for over 10 years - plastic bearings from igus ensure smooth movements in foot pedals from Sensata.
The pedals are used in construction and agricultural machinery. The bearings often have to struggle a lot with dust and dirt. Added to this are environmental parameters such as aggressive cleaning agents, fluctuating temperatures and humidity.
Plain bearings made of iglidur J are resistant to media and offer a very good coefficient of friction for pivoting movements. The pedals have been successfully tested by the customer and have survived five million operations. Since it is maintenance-free and lubrication-free, dust and dirt from the environment do not settle. They are easy to clean and can also be completely rinsed.
Despite these conditions, it is of course essential for the used components to ensure reliable operation to users. Above all, moving parts such as foot pedals must always move smoothly. For this reason, Sensata has relied on iglidur plain bearings from igus for many years. "Our customers, manufacturers of agricultural and construction machinery, demand long-term reliability and durability," Michael Stoffers clarifies. "The entire unit has to last throughout the time promised by us. “
Unlike metal bearings, the plastic bearings from igus do not have to be lubricated with oils or greases. Due to microscopic abrasion, the solid lubricants homogeneously distributed within the bearing are released and deposited on the shaft, whereby a lubricating effect is achieved. The iglidur compounds consist of these solid lubricants as well as special technical thermoplastics and reinforcing fibres. Depending on the composition, there are different iglidur materials, which are optimised for very different requirements such as an especially high surface pressure or resistance to temperature fluctuations and chemicals. As conventional lubricants are not used, dirt and dust cannot stick to the bearing points, which is also an important argument in favour of the igus plain bearings.
Plain bearings made of the material iglidur J have been used in the company's foot pedals for over ten years. This is considered to be a cost-effective but at the same time very versatile endurance runner, which is very wear-resistant on various shafts. This is a great advantage, as the counter partner here is a plastic shaft, which is rather unusual. "Normally the heat development can be a challenge with this pairing," explains Benjamin Neumann, the Technical Sales Consultant in charge at igus. "However, this can be neglected in this application due to the low rotational speed. “
The durability of the iglidur J plain bearings has also been impressively proven by igus and Sensata. "We successfully tested the pedals with millions of actuations to ensure years of trouble-free operation," recalls Michael Stoffers. Here the plastic plain bearings demonstrate a further strength: "Sintered bearings require high rotational speeds in order to achieve a lubricating effect," explains Benjamin Neumann from igus. "The oil film necessary to ensure that sintered bearings function effectively does not work in the case of pivoting movement or slow rotations. " In contrast, the homogeneous structure of the iglidur plain bearings ensures that the incorporated solid lubricants are always available regardless of the type and speed of movement. This ensures optimum coefficients of friction and wear over the entire service life. In addition to the significantly lower price, another decisive advantage was that the plastic bearings require less installation space than sintered bearings due to their thinner walls.
Sensata has been satisfied with the plain bearings from igus for years now. The plastics specialist has also carried out tests specifically for this application in the past. And that was when the only complaint so far occurred: "A customer had the problem that the foot pedal could no longer move properly," recalls Michael Stoffers. Some research was then carried out and the application was also simulated at igus. "In the end, however, it turned out that the customer's pedals were cleaned with very aggressive chlorine cleaner. This corroded the aluminium, causing it to swell at the bearing point and compress the bearing. " Apart from this case, there has not been a single complaint in over ten years about the plain bearings in the foot pedals - despite the adverse conditions.
The absence of external lubricants means that no dirt or dust adheres to the bearings, which could potentially impair movement.
Put to the acid test - several tests of the foot pedals were successfully completed at Sensata that covered the required five million operations.
Michael Stoffers, Engineering Manager Mechanic Design, Sensata Technologies GmbH (right), together with Benjamin Neumann, Technical Sales Consultant, igus GmbH.