The computer animation and visualisation techniques allow the acquisition of important information which can aid the designer in correcting and controlling the product from early conceptual design phase to the final assembly design stage. The computer assembly animation of a mechanical product is shown utilising a commercial CAD system. By utilising appropriately some features of the CAD system, a general trajectory can be assigned for each mating product component that allows us to analyse either the local and global product assemblability/disassemblability or to analyze feasible disassembling trajectories which guarantee that no collisions happen. An application regarding a mechanical assembly product is illustrated.