On ocean beds around the world sinking particles of residual biomass from animals and vegetation have, over time, accumulated into thick layers of sediment. For researchers these layers of sediment contain valuable information about the earth’s past climate, information that can be used to predict future climate change and to estimate natural vs. human causes of today’s global warming.The Institute of Geosciences at Stockholm University studies sediment cores that have been acquired with an apparatus called piston corer. For future coring expeditions additional piston corers are needed. However, the dimensions of the current piston corer only allow use of specially ordered polycarbonate pipes which are used as liners. This pipe is relatively expensive compared to pipes of other plastic materials and of standard dimensions. In order to lower the cost of upcoming coring expeditions a new piston corer design, that allows use of standard dimension plastic pipes as liners, is required.The process of redesigning the piston corer offers an opportunity to identify structural disadvantages and generate ideas on improvements that can be accomplished in a new construction. It also offers an opportunity to satisfy a need to increase the dimensions of the liners in order to acquire a larger volume of sediment, thereby increasing the reliability of the information gathered when examining the sediment. This thesis paper presents the process of redesigning and improving the piston corer currently used by Stockholm University. The resulting design allows use of standard dimension PVC pipes as liners. It has also been improved regarding the process of extruding liners after recovering sediment cores as well as performance and handling.