This paper presents evidence from a two-year multistage case study of an inter-organisational collaboration involving actors from universities, manufacturers and hospitals seeking to develop a prototype for digital mammography. Using ethnographic methods, the paper illustrates how developing a collaborative team with multiple experts involves an ongoing struggle to sustain creative interaction during the course of the innovation process. In particular, it focuses on how actors with different cultural drivers, derived from different disciplines and institutional backgrounds, make the transition from uncreative interaction to creative interaction as they engage in a process of knowledge sharing and knowledge integration towards the object of their collective activity. Key finding is the deployment of relational agency, a joint and more powerful form of individual agency, as a central process to manage the knowledge creation process between various experts. Management practice to foster relational agency, then, involves engaging actors to recognize and reflect on the link between motivation and object formation, enabling actors to develop tools for boundary crossing, and encouraging them to learn to work with contradictions, rather than attempt to manage those away, by constructing inclusive boundary objects.