In this paper we present a collaborative 3D modeling and printing experience within a Project Based Learning (PBL) activity, carried out with two different groups of participants: pre-service teachers at the Universidad Autónoma de Madrid (Spain), and school students of Primary and Secondary level taking part in an extra-curricular activity. Students worked in groups in different projects using the software Tinkercad in different sessions, where they could design, print, verify and redesign their 3D models several times. The main objective was to analyze students' process of 3D modeling, keeping track of all the phases of the modeling cycle and evaluate the acceptance of this methodology. From the results obtained we highlight the good valuation of collaborative work in 3D modeling, the mathematical communication and threedimensional reasoning shown by students in 3D design and scaling problems, and the support for the inclusion of mathematical 3D modeling and printing activities in initial teacher training.