Injection moulding is one of the most important technologies for the production of technical plastics parts. An increasing demand of moulds each time more complex and efficient needed exists. Simultaneously the time available for their design and manufacture is shorter, this enhancing the role of the design phase. For the design of the ejection systems, data related to the involved forces is necessary. In order to understand the particularities of the friction phenomena in the interface polymer/mould (steel), it is necessary to understand the replication process. Due to the very different nature of the materials involved (steel and polymers), different optical techniques were used to achieve a qualitative and a quantitative characterization of the surfaces involved.