**1. Introduction**

Additive manufacturing (AM), also referred to as solid freeform fabrication, rapid prototyping and three-dimensional (3D) printing, is ostensibly a transformative manufacturing technique that will play a vital role in the next Industrial Revolution. AM entails the fabrication of 3D structures with both geometrical complexities and spatial resolution beyond the capacity of traditional fabrication techniques. The ubiquity of AM, from the automotive and aerospace industry, to tissue engineering and drug delivery, unequivocally demonstrates the rising appeal of the technology. From a research perspective, AM allows for rapid prototyping and integration with other technologies, that again, seldom observed in traditional routes.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Furthermore, there are several polymeric AM technologies available for purchase by consumers that will allow manufacturing of goods to be achieved at home. However, despite the vast progression made, the technology is still in its infancy. Therefore, to make AM an essential instrument, further research is needed, including new material formulations.

Rheology is a necessity for all polymer fabrication techniques. The characterisation can deliver extensive and reliable material information. The data is subsequently correlated to the process to maximise productivity. Rheology will further be a key component as new materials are formulated to advance the versatility of AM. In spite of this, rheology remains an underutilised tool. Thus, a chapter into how rheology can be utilised to help maximise AM efficiency is warranted. The chapter presents two of the commonly-used AM techniques in the field of polymers: fused deposition modelling (FDM) and stereolithography (SLA); and demonstrates the necessity of rheology thereto. As detailed herein, both technologies form 3D structures through disparate means, and albeit different, rheology is still an indispensable tool for both technologies. The chapter will conclude with a brief description of other AM techniques and how rheology is still relevant.
