Designing the front door for a vending machine

I worked on this project when I was working for the product consultancy Kinneir Dufort. The goal for the client, Mars Drinks, was to integrate a digital screen at the front door of a vending machine.

The Context

While working at the product design consultancy Kinneir Dufort, I collaborated with Mars Drinks on the redesign of their vending machine interface.
The goal was to integrate a digital touchscreen into the machine’s front door to guide users through the drink selection process and display system status or fault information to maintenance staff.

The Challenge

The existing machines relied on static buttons and unclear instructions, leading to confusion and inconsistent user experiences across markets.

The key challenges were to:

  • Design a clear, intuitive digital interface within the constraints of the physical machine.

  • Improve usability and accessibility for a wide range of users.

  • Ensure the design worked effectively across multiple languages and cultural contexts (UK, Germany, France).

User testing the interaction with the screen and the buttons

The Process

I began by mapping the end-to-end user journey, from initial interaction to drink collection and error handling.
After defining the critical touchpoints, I designed interactive prototypes that simulated the full-scale experience using a large-screen TV to match the real dimensions of the vending machine.

We conducted usability testing across three markets — the UK, Germany, and France — to evaluate both the interface and physical interactions.

The research revealed that while users responded positively to the new touchscreen guidance, confusion remained around the physical buttons on the machine. Based on this feedback, I redesigned the button layout and labelling to improve clarity and reduce user error.

Outcomes

Improved user understanding of machine operation through a clear, guided touchscreen interface.

  1. Reduced user confusion by redesigning button labels and layout for clarity.

  2. Positive feedback across markets, validating the design’s cross-cultural usability.

  3. Enhanced accessibility and user satisfaction through simplified visual and physical interactions.

  4. Prototype findings directly informed the production design for Mars Drinks’ next-generation machines.