Geometry- and process-dependent influences on molding shrinkage and post-shrinkage of two polymers are investigated in this thesis. The results of the molding shrinkage are compared with simulation results of Moldflow Plastics Insight 6.1 Revision 1. Boxes with different wall thicknesses are made for this purpose. The used polymers are ABS Urtal M122 (amorphous) and Hostacom BR 735 G (semi-crystalline). Changeable mold inserts allow for different combinations of the bottom and side wall thickness. Two values for each thickness are used (1 and 3 mm) which implies four different wall-thickness combinations. The simulations are performed using Midplane-, Fusion- and 3D-model meshes. The calculations are carried out with real processing parameters using default program settings and material data from the internal MPI database. The produced parts are measured optically and the measuring results are compared with the simulation results in order to evaluate the quantitative and qualitative accuracy of the calculation. A comparison between an experimental and simulated filling study is carried out. Simulation results of the packing and holding stage are compared with experimental pressure distributions. Extra chosen parts are machined mechanically by separating the box-ground from the sidewalls, removing the box-corners by milling and cutting through the box in the middle. The scope of this analysis is to release internal stresses to study the coupling of shrinkage and warpage.