kitchen with Rational kitchen device

RATIONAL - Series launch for a new product family in the professional kitchen

Machines, Industrial technology

RATIONAL AG from Landsberg has been developing combi steamers and multifunctional kitchen appliances for over 40 years, making it the world market leader. As a long-standing development partner, BUSSE Design+Engineering was commissioned with the design development for the new appliance family.

With the goal of developing a new industrial design and user interface design for the new generation of the iCombi Pro, iCombi Classic and iVario, an exciting development process began that lasted several years. BUSSE Design+Engineering accompanied the development from the very beginning and was able to apply its extensive expertise in product development. In keeping with the holistic UX720° approach, industrial design and UI/UX design worked closely together during the development in order to extract the maximum ease of use for users.

Industrial Design

The task was to create a completely new and modern look, yet still tie in with RATIONAL's tradition.

After many years of partnership with RATIONAL, BUSSE Design+Engineering had gained a great deal of experience in the development and design of RATIONAL's products. Nevertheless, this new development was rolled up from the bottom up. The employees of BUSSE Design+Engineering started with a large-scale market research, visited trade fairs and took part in cooking events organized by RATIONAL.

In the subsequent, very intensive creative phase, BUSSE Design+Engineering developed various design strategies, all of which reinterpreted RATIONAL's established key design features.

The most important elements of the RATIONAL design were also the requirements for the product of the future: the soft radius in the front, the dynamic lines on the control panel and the glass cutout in the door, were to be transformed into a contemporary design. For a more modern look and also to make cleaning easier, there was a desire to enlarge the glass surfaces and eliminate height differences in the material transitions. A major technical challenge was the flush design of the fronts with their clean lines and precise gap dimensions.

This laid the foundation for the new series. In the subsequent detailing phase, the key design elements were adapted to the very different appliance sizes and types.

The various development stages were visualized throughout the entire project period in our company using both high-quality photorealistic renderings of CAD data and a wide variety of 1:1 models and prototypes produced in-house at BUSSE Design+Engineering. In addition to 3D animations, new technologies such as virtual reality and augmented reality were also used.

The result of the development and design work is impressive:

The straight lines of the design are deliberately interrupted by purposefully placed radii and chamfers. On the one hand, these formal elements represent the bridge to the earlier series, on the other hand they serve to deliberately break up the hardness of the otherwise stringent straight lines.

A special design feature of the combi steamers is the generous glass surface of the door. On the table-top units, it extends over the entire height of the door and provides an excellent view into the cooking chamber and of the food being prepared inside. The door handle has also been adapted to the new, tighter lines and reflects the dynamic lines of the door in the metal insert.

All units are equipped with the control panel in the family design. The control panel stands out from the overall picture thanks to its discreet color scheme and picks up on the lines of the door cutout.

For precise settings or quick confirmations, the control wheel, as a historical operating element, has been integrated into the design at the bottom of the control panel.

The hand shower is also used across a wide range of appliance types. Both the design and the sophisticated function and ergonomics of the hand shower are particularly striking. The water jet can be varied to master all conceivable applications in everyday commercial kitchens. At the same time, the clear, unobtrusive design integrates effortlessly into all the appliance fronts of the new series.

The visual design for the iCombi Pro and iVario

The visual redesign for the user interface of the two appliance series ran parallel to the industrial design development. The aim was to create a simple and intuitive operating concept supported by a visual design that was in keeping with the RATIONAL brand and deliberately differentiated from competitor products. At the same time, the history had to be preserved in order to ensure a smooth changeover for existing users of the system, despite a completely new development of the HMI.

The screen contents of the mockups and click prototypes from the operating concept phase served as the basis for the interface design. A 10.2" color display with glass touch function was selected for the future HMI.

To give the series a new visual face, it was important to test different design directions.

The very different concepts, ranging from conventional to unusual, were presented to the Executive Board and the RATIONAL project team and then evaluated. From this intensive design phase, design features from the different concepts were worked out and defined. These elements formed the basis for the further development of the user interface.

In an iterative process, the main screens were then designed and presented and discussed in regular meetings. After the final presentation and approval of the board for the visual design, the transfer to the other screens from the user concept followed. All global design features were defined and described in a comprehensive style guide.

Special attention was paid to the icons during the visual redevelopment. Historically, there were a large number of different and sometimes complex icons. BUSSE Design+Engineering succeeded here in achieving stylistic standardization and also in defining an individual and illustrative design. Furthermore, icons that were familiar and familiar to end customers in particular were sensitively revised and transferred to the new icon world.

In addition to the visual design, BUSSE Design+Engineering was also able to convince in the interaction design. Detailed interaction sequences were defined for various operating situations, and wizard animations were created. Animated device renderings provide users with visual assistance to interact with the device in the best possible way.

The user interface, designed in dark mode, gives the RATIONAL brand with the iCombi Pro and iVario a high-quality appearance with recognition value.

In keeping with the holistic product development approach of BUSSE Design+Engineering, the design language of the appliance design was also adopted in the user interface. Thus you will find

z. For example, the shape of the control panel and the glass pane is reflected in the main screen. The structured and self-explanatory user interface is characterized by clearly defined interaction elements with an individual and country-independent icon language.

iCombi Classic

In the course of the UI development, the interface for the iCombi Classic was also redesigned in line with the iCombi Pro.

While the former series device still had a 7-segment display, the iCombi Classic now features a much larger 4.3-inch TFT display with 6 function keys. To ensure consistent operation across the devices, the new icons from the icon world of the iCombi Pro were transferred to the hardware conditions of the iCombi Classic.

Launch of the product family

The result is convincing all along the line - a new development for a complete product family with an industrial design that corresponds to the RATIONAL brand as well as a self-explanatory and visually appealing visual design.

We are very pleased about the nomination for the UX Design Award 2020 in the category "Product" and are looking forward to the award ceremony in September 2020.

For BUSSE Design+Engineering, the design development for the three device series was a very exciting task.

We are delighted about the joint, constructive and long-standing collaboration and would like to thank RATIONAL for the trust they have placed in us.

Various Rational kitchen appliances
iCombi Pro from the front
iCombi Pro various display screens
iCombi Pro Display

Our skills

Product design

User interface design

Your contact person
Sven Schaarschmidt, Senior Industrial Designer
Sven Schaarschmidt, Senior Industrial Designer

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UI/UX Design


„BUSSE is our design game-changer for snow groomers! Their UI/UX team elevates not only icons and layout but the entire user experience to a new level. Clear operation turns every ride into a pleasure. Reliable from development to series production, BUSSE is by our side. Their interface, based on precise product research, simplifies operation. Flexible, forward-thinking, and reliable – BUSSE is our satisfaction guarantee!"



"BUSSE has been the perfect partner for us to develop new and innovative ideas for over fifteen years. BUSSE offers a very high level of professionalism and a first-class understanding of the brand. The team has completely internalized the high standards of our projects and with exceptional creativity, as well as full dedication, has helped us to set new trends. Many of our bestsellers bear BUSSE hallmarks."


Britax Römer

„Child seats are not only visually complex but also technically demanding. Our longstanding partnership with BUSSE turns development into a creative experience. Design sprints and a versatile selection matrix relieve engineers, minimize time-consuming iterations. We appreciate BUSSE for their timely implementations despite limited resources. The collaboration is not only effective but also truly enjoyable!"



"We were particularly impressed by the enthusiasm and technical creativity of the Busse employees. The atmosphere in the project was characterized by professional looseness and great agility. We turned an idea into a finished product in 4 months!"



„We discovered BUSSE Design+Engineering through online research. Contacting them for a functional model led to a contract for a technical redesign. Due to our concept changes, Redesign II was initiated and realized in a prototype, earning a golden award at the 2019 Ambiente trade fair. BUSSE executed the project with precision, on schedule, and with excellent craftsmanship. We look forward to future collaboration with BUSSE."



„The collaboration with the entire project team was always goal-oriented, constructive and pleasant in terms of communication. Mr. Timm and his project team always kept the functional and safety requirements in mind and understood what is also important to us in product development: can-do mentality, agile mindset as well as flexibility and efficiency in all project situations."



"With BUSSE as a sparring partner, we were able to successfully work out a brand-defining design for our latest products that was appropriate for the target group. BUSSE understood our internal company processes very well and was therefore able to deliver optimal results. Deadlines were always met, you can rely on BUSSE. Anytime again!"



"We were positively surprised by the collaboration with BUSSE in that the focus was not solely on the appearance of our product, but rather on the interplay of economical manufacturing solutions, optimized ergonomics and a functional design. The result now impresses with a coherent, unprecedented design concept."