Reliable storage of boot lids under extreme temperatures

ITW Highland UK was looking for a durable and reliable solution for the bearing of boot lids. During various tests, two main problems emerged that were associated with high demands on the bearing. Firstly, they were looking for a long-lasting solution that could withstand at least 30,000 cycles even under adverse environmental conditions, primarily characterised by dust and salt water. A previous solution only managed 10,000 movements. The holes for the housings are made in 47 3.5 mm steel, creating burrs that cut into the bushings until they are completely destroyed. This problem was temporarily solved by gluing in the bearing. In addition to endurance tests, other requirements such as total moisture absorption, stiffness, lateral displacement and behaviour under prolonged static load must also be met. For further tests, the customer sent the vehicles together with the installed bearing solution to climate chambers to simulate cold and hot desert conditions for around eight weeks. A second requirement was the bearing support. The previous bearings fell out of the housing during the assembly process. Although this problem was solved by improvised gluing of the housing into the holes, this was not a sensible and economical process for assembly line production. The car manufacturer was therefore looking for an optimised solution that would meet the high requirements and be easy to install.

The decision was finally made to take a closer look at the potential of plastic plain bearings. The customer had already dealt with polymers as a material, whereby one of the main problems was the electrical conductivity. With iglidur® bearings made of the material iglidur® RN89, the customer finally found the optimum solution for his application. The bearings can be painted electrostatically (e-coating), since the assembly has good conductivity. After it was decided to install samples, the bearings showed an absorption of 20 Newton in the application, whereby this value was reduced to 8 Newton after the e-coating process without a significant loss of stiffness. The bearings were tested at -40 °C and showed only a minimal build-up of torque.
The iglidur® bearings stop the rotation in the housing and hold firmly in the intended hole without having to be glued. The costs for the new bearing solution are even slightly lower than the steel bearings, resulting in considerable savings potential.