This thesis reports on a development project of a Lessons Learned knowledge management system. Lessons Learned (LL) is a knowledge sharing method that takes advantage of useful knowledge from previous or on-going project events in order to be reused in on-going or following project activities. Product Development (PD) is an area particularly of particular interest when it comes to sharing lessons learned. In a early design phase, in fact, various experts have to share what they know about the hardware and its services to create a successful product concept. This knowledge takes often the form of lessons learned, that is the form of recommendations that are specific and measurable. These lessons, however, are very seldom formalized in a way that can be readily used across the organizational boundaries by the product development. Most of this knowledge is usually tacit and in general difficult to formalize and share. Accordingly, there is a need to establish a structured Lesson Learned System (LLS) that takes into consideration all obstacles in conveying knowledge amongst different people. This involves giving guidelines on how to structure the LL in different cross-functional development activities. The development of the LLS kicked off with the analysis of the user needs and the identification of relevant requirements. The definition of the requirements list was aided by a generic knowledge lifecycle derived from the literature and composed by five different steps: collecting, verifying, storing, disseminating and reusing LL. In the concept development phase a strong emphasis has been given to the concept of “lightweight” knowledge sharing technologies. The guiding principles and mechanism of Web 2.0 have been considered particularly interesting to enhance the level of interaction between the system users and to leverage the way the system is populated, maintained, updated and validated across the company. Eventually, the thesis presents the results of the prototyping phase. A LLS mock-up has been developed and tested both with researchers and practitioners working in the laser welding domain, as well as with in design sessions with students. The lessons learned system detailed specifications as well as the feedback from the validation activities have to be considered the main results of this master work.