Tech up, cost Down - low unit costs and a longer service life of plain bearings with 3D printing and injection moulding

• What was needed: plain bearings with special geometry
• Manufacturing process: selective laser sintering and injection moulding
• Requirements: good sliding properties with the mating partner aluminium, high abrasion resistance at high speeds, complex geometry
• Material: iglidur i3 (laser sintering) and iglidur J2
• Industry: waste separation plants
• Success through cooperation: long service life despite high loads, significantly reduced unit costs, high degree of design freedom

The application at a glance:
The Finnish company ZenRobotics manufactures industrial, AI-controlled waste separation systems that ensure automatic, high-quality, fast and safe waste separation worldwide. Depending on the environment, the conditions for the systems are very harsh - dust and other interesting surprises in the waste are daily occurrences. Despite these conditions, the systems must be able to separate waste quickly and reliably. For the new "FastPicker" system, plain bearings were needed that could withstand the high torsional forces that arise during axial acceleration. The developers came up with 3D-printed plain bearings that are mounted on aluminium axes with a grooved profile to prevent rotation. The plain bearings can withstand linear speeds of 3m/s with radial and axial accelerations. Thanks to the high degree of design freedom in 3D printing, it was possible to adapt the geometry of the plain bearings to the grooved aluminium axis. The next step involved manufacturing an injection-moulding tool to use the material diversity of injection moulding.

During the test phase of a new "FastPicker" waste sorting system from ZenRobotics in Finland, it quickly became clear that classic plain bearings cannot withstand the torsional forces during axial acceleration if the centre of mass is not at the centre of the moving axis. Initially, the rotation was to be stopped by stopper elements. However, these quickly failed due to the heavy load. In addition to the stopper elements, standard plain bearings from the igus range were initially used to withstand the radial and axial acceleration.

In the end, igus plain bearings with a special geometry were used. They were first produced from the high-performance plastic iglidur i3 via laser sintering. That way, they fit onto the grooved aluminium axis and thus stopped rotation. After that, an injection mould was produced according to the special geometry so that it was possible to use the material variety of injection moulding. This means that a cost reduction of up to 80% can be achieved.

3D printing and injection moulding often differ in terms of their cost-effectiveness: 3D printing often pays off from a small number of units. The production of components with machine-made injection moulds is only worthwhile from a quantity of more than 10,000 components. 3D printing in particular scores points in the test phase of applications with its high production speed and immediate readiness for use. Depending on the design, parts are ready to ship in one to three days and can be easily ordered in the online 3D printing service. For its prototype, ZenRobotics also used 3D-printed plain bearings for the aluminium axis with a grooved profile. The company then decided to produce the components in larger quantities via injection moulding. The decisive factors were the variety of materials and the low unit costs associated with injection moulding. The final plain bearings were manufactured from iglidur J2. At around €5/piece, the injection-moulded component cost only a tenth of the SLS part (approx. €49/piece) and the tool paid off after 100 pieces. The robust plastic has good mechanical specifications, is cost-effective and offers good media resistance. In addition, the integrated solid lubricants make external lubrication of the plain bearings superfluous.