Car seats have a very complex structure. They consist of frames, supporting structures such as springs and beams, heating or even cooling systems, back and seat cushions, etc. The latter are made of polyurethane foams, which can possess different degrees of hardness. For example, sometimes it is desirable to use different types of foam in the middle and side parts of the cushions. Due to the complexity of the seat construction, the reactive injection moulding process is very difficult to implement. Our FOAM solver simulates the expansion process of PU foams in any geometry and offers the possibility to pre-calculate foam formation and resulting foam density in closed molds.