Maintenance-free operation in a fully automated street barista system

• What was required: Bearing for the dispensing unit
• Requirements: Maintenance-free, permanently low breakaway torque, jerk-free, hygienic and corrosion-free, suitable for use in the food industry
• Area of application: Vending machinery

In collaboration with Rothweiler Feinwerkmechanik, MyAppCafé has developed a fully automatic vending machine that prepares customised coffee creations in seconds. Thanks to a special milk system, 650 coffee portions can be prepared without refilling. Customers can place their orders on site via a touchscreen or simply via an app: They select their desired creation, can top it off with their own motif made from milk foam and pay directly without cash. When they arrive at the vending machine, they hold their smartphone up to a reader and a few seconds later their self-created coffee is served. They can also send their own creation as a code to partners and friends via messenger.
The first machine has been in operation in the Postgalerie Karlsruhe since August 2020, with another in Sindelfingen, and there are numerous enquiries, including from abroad. In future, it will certainly also be found on the street, in train stations and at airports.

In addition to the interface problems, the output systems and their bearing support were a particular system design challenge. One of the two most important bearing selection criteria was that they require no maintenance, since "we cannot completely rule out fluids, coffee grounds or other substances getting into the bearings over the course of years. The warm-cold cycle can also cause condensation or steam, which can affect the bearing. The concept also lends itself to output systems for other food items. We don't know how a standard ball bearing would eventually react. So we were looking for a solution that would cover all scenarios reliably," says Dirk G. Rothweiler. The second decisive bearing selection criterion was low breakaway torque over the long term. "This is especially important at low start-up speeds. Our servomotors start up very slowly, accelerate slightly and then brake carefully again before coming to a complete stop." The bearings should translate the rotary movement with as little loss of force as possible.

Ready-to-install iglidur 04 series slewing ring bearings are ideal for this application. Their design is based on dry-operating, maintenance-free sliding elements made of iglidur J material in combination with rings made of anodised aluminium. The sliding elements in this series are preloaded to ensure zero play throughout their entire service life. The iglidur J material is characterised by extremely low coefficients of friction in dry operation and very low stick-slip tendencies. It is also resistant to common cleaning agents used in the food industry and has low moisture absorption, allowing it to be used in wet or humid environments.

The bearings have a long service life. Thanks to extensive testing in the igus test laboratory, with load figures in the millions and precisely tailored to the customer's operating conditions, this can be calculated precisely in the online tool.