As production equipment is often designed and built by equipment suppliers rather than made in-house, a collaborative buyer-supplier-relationship could be utilized in order to create robust solutions and enhance innovative ideas. The purpose with this paper is to explore critical user-supplier collaboration activities throughout the different lifecycle stages of the production equipment development. The purpose is accomplished by a literature review and a case study including more than 30 semi-structured interviews at four companies. The challenges vary depending on equipment life cycle phase and user/supplier perspective. A life cycle model with eight stages is proposed including critical interconnected activities for each stage.