The versatility of the injection moulding process can be increased by combining multiple polymers in one product. The multi-component injection moulding process (MCIM) offers the possibility to inject two or three materials sequentially or simultaneously into a mould to make products that consist of e.g. a layered structure. For a successful application of this technique for geometrically complex products or multiple materials, the material distribution in the product has to be predicted In this paper numerical tools are described for calculating the positions of material particles during the flow in the mould cavity. These tools make it possible to solve the inverse problem of predicting the injection sequence in MCIM given a required material distribution in the product. The simulations are validated using experimental results of a co-injected strip with stiffener ribs. Furthermore the effect of a bifurcation of the midsurface on the material distribution is investigated numerically using a simplified model based on the local mass balance.