Maintenance-free operation in a fully automated street barista system

• What was needed: Bearings for the output unit
  
• Requirements: No maintenance, continuously low breakaway torque, no jerking, hygienic properties with no corrosion, food application suitability
• Application area: Vending machinery

In cooperation with Rothweiler Feinwerkmechanik, MyAppCafé has developed a fully automatic coffee robot that prepares customised coffee creations in seconds. A special milk system allows 650 coffee portions to be prepared without a refill. Customers can place their orders at the machine, using its touchscreen, or with an app that enables them to select their creation, top it with their own milk foam motif, and pay directly and cashlessly. When he arrives at the machine, the customer holds his smartphone to its reading unit and a few seconds later receives his own coffee creation. He can also send his creation by Messenger as a code to partners and friends.
The first system has been in operation in Karlsruhe's Postgalerie since August 2020, there is another in Sindelfingen, and there are numerous international queries. In the future, it will certainly also be found on the street and in train stations and airports.

"Our coffee machine can produce 120 cups per hour; a trained barista can manage only 20 cups of this quality in the same time," says Bora Yelkenkayalar, managing director of technology at MyAppCafé.

Problem

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.

Solution

Ready-to-install iglidur 04-series slewing ring bearings are ideal for this application. The design is based on dry-operating, maintenance-free sliding elements made of iglidur J materials in combination with rings made of anodised aluminium. The sliding elements of this series are pre-loaded, so there is no haptic clearance over the entire service life. iglidur J features very low coefficients of friction in dry operation and a very low stick-slip tendency. It is also resistant to common cleaning agents 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 which can be calculated exactly in the online tool thanks to extensive tests in the igus test laboratory, with millions of loads, precisely matched to the customer's operating conditions. 

The system's output unit: igus iglidur PRT-04-60 slewing ring bearings are the central element.

In a box measuring around nine square meters, a robot prepares and serves a wide variety of coffee creations.

The MyAppCafé app enables users to combine features to generate their own coffee creations topped with a unique motif.