Fused Deposition Modelling (FDM) of thermoplastic materials such as Polylactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS) is a rising rapid manufacturing process within the engineering and design industry. This paper takes an off the shelf consumer 3D printer, a MakerBot Replicator 2 (in conjunction with manually written custom G codes), and adapts the already known FDM technology to allow for Multi-Layered Infill Structures (MLIS). These novel structures are produced by laying down material in the X and Y axes (as normal) whilst adjusting the print bed in the z direction to form continuous 3D structures. By this method it is possible to create multiple layers simultaneously, giving parts an added element of strength in the Z-axis in comparison to traditional FDM components. Additionally, by controlling the internal structure of printed parts, the MLIS system offers the additional possibility of mimicking complex structures such as bone for medical device fabrication.