Waste separating robot application that uses 3D printed iglide® plain bearings

ZenRobotics, a Finnish company, manufactures industrial, AI-controlled waste separation plants that provide automatic, high-quality, fast, safe waste separation worldwide. Depending on the environment, conditions for the plants are very rough - dust and other interesting surprises in the waste are the order of the day. Despite these circumstances, the plants must be able to separate waste quickly and reliably.

The new "FastPicker" plant needed plain bearings that could withstand the high torsional forces that occur during axial acceleration. The developers had the idea of 3D printed plain bearings placed 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. The great design freedom in 3D printing made it possible to adapt the geometry of the plain bearings to the grooved aluminum axis. In the next step, injection moulding tools were manufactured additively with so-called rapid tooling to take advantage of injection molding's material diversity.

Application Overview:

What was needed: plain bearings with special geometries
Manufacturing method: selective laser sintering and print2mold
Requirements: good sliding properties with aluminium as a counter partner, high abrasion resistance at high speeds, complex geometry
Material:

Industry: waste separation plants
Success from the collaboration: long service life under heavy load, significantly reduced unit costs, high design freedom

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

Solution:
Ultimately, special-geometry igus plain bearings were used. They were first made from the iglide i3 high-performance plastic using the laser sintering process in order to fit onto the grooved aluminium axis and thus stop the rotation. The company then switched to Rapid Tooling in order to use the material diversity of the injection moulding process. The Rapid Tooling or print2mold process can also reduce costs by up to 80%. The mold for injection molding can be produced within a few days and is immediately ready for use. The design freedom 3D printing offers made it ideal for the plain bearings' special geometry.

Prototypes and small batches

3D printing and print2mold have one thing in common: they are profitable from a small quantity. The production of components with machine-made injection molding tools is only cost-effective from a quantity of more than 10,000 components. 3D printing in particular can convince in the test phase of applications with its high manufacturing speed and immediate readiness for use. Depending on the component, it is ready to ship in 1 to 3 days and can be easily ordered from the online 3D printing service. ZenRobotics also used 3D-printed plain bearings for the aluminum axis with grooved profile for the first prototype. The company then chose the print2mold process, in which the injection mould is produced by 3D printing.

The decisive factors were the variety of materials and the low unit costs associated with injection molding. The final plain bearings were made of iglide J2. In this case, the print2mold component cost only a tenth of the laser sintering component (approx. €49/piece) at approx. €5/piece, and from 100 pieces onwards, the tool had also paid for itself. The tough plastic has good mechanical properties, is cost-effective and has good media resistance. In addition, the integrated solid lubricants make external lubrication of the plain bearings superfluous.

The aluminum axis with grooves is prevented from rotating by the geometry of the plain bearings.

Rapid Tooling - igus print2mold

When speed is of the essence, 3D printing is the solution for manufacturing an injection mold. Depending on the geometry, printing takes about 12-24 hours, and the tool is ready for use immediately afterwards. The print2mold process known as Rapid Tooling enables cost-effective production of advanced prototypes and small volumes. It is more profitable in quantities of up to 10,000 (no minimum quantity) than machine-produced injection molds. Wear-resistant parts can be produced with a cost reduction of up to 80%.

The quality of print2mold injection moulded parts is the same as with the conventional injection moulding process. Development processes can be greatly accelerated using the print2mold process and the material variety of regular injection moulding is also retained.