In West Africa countries, the design of food-processing equipment requires better user integration throughout each phase of the design process. Usually, there is often a break in user integration, with users only being consulted at the launching of the project during the need analysis phase and then at the end during prototype testing in real conditions. During the interim period, the design team works alone, with the significant risk of taking decisions in place of the users. To promote better user integration, the whole design process, we propose a new tool to provide better understanding of the conventional process and therefore the need, and a methodological framework: COSU Method. COSU method comprises four scenarios which are objects and are used as interface with the users.