This study aims at presenting the process of machine design and agricultural implements by means of a reference model, formulated with the purpose of explaining the development activities of new products, serving as a guideline to coach human resources and to assist in formalizing the process in small and medium-sized businesses (SMB), i.e. up to 500 employees. The methodology used included the process modeling, carried out from case studies in the SMB, and the study of reference models in literature. The modeling formalism used was based on the IDEF0 standard, which identifies the dimensions required for the model detailing: input information; activities; tasks; knowledge domains; mechanisms; controls and information produced. These dimensions were organized in spreadsheets and graphs. As a result, a reference model with 27 activities and 71 tasks was obtained, distributed over four phases of the design process. The evaluation of the model was carried out by the companies participating in the case studies and by experts, who concluded that the model explains the actions needed to develop new products in SMB.