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Plain bearing for rotary knob in household appliances

With household appliances everything revolves around the plain bearing

For an optimal feel of the unique rotary knob, much attention has been paid to the search for the optimal material for the bearing in the new generation of household appliances.

Over 100 years ago, V-Zug set itself the task of making everyday life easier with high-quality, innovative household appliances. The company has been family-owned since it was founded in 1913 and is one of the most important employers in the canton of Zug. With state-of-the-art working methods and over 1,400 employees, the high-tech company develops and produces high-quality household appliances in Switzerland. Over 4.5 million appliances are in use throughout the country. On an area of over 60,000 square metres, V-Zug AG manufactures household appliances for the kitchen and laundry room with the highest precision and pioneering production techniques, from the basic material to the finished appliance.

Premium Swiss Quality' is applied everywhere to ensure that V-Zug appliances are particularly durable and function reliably. Reto Märchy, responsible for the development and construction of kitchen appliances at V-Zug: "Thanks to modern systems, we have been able to halve the energy consumption of every appliance in recent years. Wherever possible, we use recyclable materials and actively ensure organised disposal. Our suppliers are carefully selected - in addition to quality, environmental aspects and pricing are also taken into account."

Problem

In the first version, a brass bearing was used, but this conducted the current, which is not permitted in this application. The second version made of ceramic could also not be used due to the high costs.

Solution

With the special material iglidur® RN24, a maintenance- and lubrication-free material could be used that requires no additional grease or oil. Thanks to the good coefficient of friction and the performance, the service life requirements were exceeded threefold in the customer's test.

"The quality is right, the price is right and we were very well looked after right from the start. We were also impressed that as a 'small fish' we were treated like a giant"

Reto Märchy, Development and Design, V-Zug AG

The search for the ideal material

The first material for the mounting and functionality of this rotary knob was brass. However, as brass is conductive, it was rejected by the electronics department at V-Zug after the first tests. The designers at V-Zug then tried a ceramic solution. Although the material impressed with its hardness and precision, it was ruled out as an alternative, mainly due to its high price. The idea of testing plastic solutions was then developed with igus®. This is because V-Zug and the motion plastic specialist from Cologne have been working together for years and other demanding applications from V-Zug have already been realised with plastic plain bearing solutions from igus® in the past.

For over 30 years, igus® has been developing and manufacturing plain bearings that are used millions of times in industry. Over the years, igus® has developed a wide variety of materials with different specifications, making the bearings suitable for more and more areas of application. The spectrum ranges from economical iglidur® all-round bearings to "food-grade" bearings and bearings made of materials that are suitable for high-temperature or underwater applications. All materials have in common that they do not have to be lubricated externally with oils or greases. The iglidur® bearing materials are all made of thermoplastic materials. Embedded in them are usually fibre reinforcements to increase the compressive strength as well as solid lubricants, which optimise the wear resistance and coefficient of friction.

Household appliances from V-Zug stand for Premium Swiss Quality. To ensure that the products meet the manufacturer's requirements, high-quality components are crucial.

So V-Zug contacted igus® with the task of finding a high-quality plastic. "The challenge for us was that we have three different plastic components here and in this case we are talking about extremely small tolerances. If a plastic part is outside the tolerance, this rotary knob wobbles or jams," says Axel Ebert, contact person for the region at igus® Switzerland.

Quality from the igus laboratory

In order to guarantee the durability of its plastic products, igus® operates the largest test laboratories in the industry. On an area of 2,750 square metres, the company tests, checks and develops under real conditions, with the sole aim of providing customers with the best solution that is guaranteed to work. The extensive tests focus on tensile and shear forces, coefficient of friction, wear, abrasion and drive force under a wide range of speeds and loads. In this way, the engineers at igus® develop around 100 new plastic compounds with different specifications every year. The special material iglidur® RN24 now used by V-Zug for this control element was also developed in the Cologne laboratory. And not only that, the lubrication- and maintenance-free material used exceeds V-Zug's specifications by more than three times. "In the end, we were also able to convince V-Zug," explains Lutz Alof, CEO of igus® Switzerland. "We even set up our own testing facility for this control knob in our laboratory in Cologne. The specification from V-Zug was 40,000 cycles. With the first plastic compositions developed by our technicians, we just about reached the prescribed target. But we had to keep tinkering until we found the right mixture - and we found it. With the material we are now using, we stopped the trial after 150,000 applications."

For this application, igus developed the special material iglidur RN24, which exceeded the requirements of V-Zug three times over in the test.

"The collaboration with igus® is exemplary," summarises Reto Märchy. "The quality is right, the price is right and we were very well looked after right from the start. We were also impressed by the fact that we were treated as a 'small fish' like a giant." Lutz Alof from igus® Switzerland adds: "We don't make any internal separation into A, B or C customers. For us, a satisfied customer is the main focus. We want to find the optimum solution for every customer, and that's where all our ambition lies. We achieve this either through our continuously growing standard plain bearing programme and can supply our customers with products within 24 hours or we set up test stands in our laboratory specifically for customer projects. And if we are successful - as we were here - these are the best references for new projects."

About the products used

iglidur plain bearings