Purpose � The purpose of this paper is to describe the framework of conceptual design support tool (CDST) developed to assist designers during conceptual design process. The premise of the study is that, by combining human creativity with computer capabilities, it is possible to perform conceptual design process more efficiently than solely manual design. The study aims to show how conceptual design knowledge can be captured from experienced designers and kept in the computer system for later use and how the developed tool assists designers by handling some of the repetitive and time�consuming tasks. Design/methodology/approach � A conceptual design process model, which integrates systematic design approach with knowledge�based system, is proposed. Based on this model, a CDST, which consists of function library, alternative concepts database, different modules for conceptual design activities, and a knowledge�based system is developed. The alternative concepts database is built based on design reuse philosophy. Furthermore, the tool is designed to accept and save new concepts from the user through its knowledge acquisition module without modifying the source code. The CDST is developed using public domain open source programming environments namely CLIPS, Python, wxPython, and PyCLIPS. Findings � Through its graphical user interface, CDST assists designers in performing the conceptual design process such as functional modelling, using standard vocabularies of functions, generating concepts and displaying on morphology chart, concept combination, and concept evaluation. The functionality and interaction between the user and the CDST is demonstrated with an example. Research limitations/implications � Currently, the alternative concepts database consists of concepts from subsea process equipment design and few general mechanical designs. The database can be enhanced by adding more concepts through the knowledge acquisition module provided. Practical implications The tool can be used as a knowledge management system in industry by capturing expertise knowledge and to train novice designers. It augments designer's knowledge by providing concepts from past designs. Originality/value � The research output from this paper can be valuable resource in industry to support designers with computers. The research represents one of the attempts to develop domain independent conceptual design tool that can acquire new concepts throughout its lifetime. © 2011, Emerald Group Publishing Limited