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  1 CHAPTER 1 3DIMENSIONAL PRINTING 1.1   INTRODUCTION 3D printing or additive manufacturing (AM) is any of various processes for making a three-dimensional object of almost any shape from a 3D model or other electronic data source primarily through additive processes in which successive layers of material are laid down under computer control. A 3D printer is a type of industrial robot. Early AM equipment and materials were developed in the 1980s.In 1984, Chuck Hull of 3D Systems Corporation, invented a process known as stereolithography employing UV lasers to cure  photopolymers. Hull also developed the STL file format widely accepted by 3D printing software, as well as the digital slicing and infill strategies common to many processes today. Also during the 1980s, the metal sintering forms of AM were being developed (such as selective laser sintering and direct metal laser sintering), although they were not yet called 3D printing or AM at the time. In 1990, the  plastic extrusion technology most widely associated with the term 3D printing was commercialized  by Stratasys under the name  fused deposition modeling   (FDM). In 1995, Z Corporation commercialized an MIT-developed additive process under the trademark 3D printing   (3DP), referring at that time to a proprietary process inkjet deposition of liquid binder on powder. AM technologies found applications starting in the 1980s in product development, data visualization, rapid prototyping, and specialized manufacturing. Their expansion into production (job production, mass production, and distributed manufacturing) has been under development in the decades since. Industrial production roles within the metalworking industries [5]  achieved significant scale for the first time in the early 2010s. Since the start of the 21st century there has been a large growth in the sales of AM machines, and their price has dropped substantially.According to Wohlers Associates, a consultancy, the market for 3D printers and services was worth $2.2 billion worldwide in 2012, up 29% from 2011. Applications are many, including architecture, construction (AEC), industrial design, automotive, aerospace, military, engineering, dental and medical industries, biotech (human tissue replacement), fashion, footwear, jewelry, eyewear, education, geographic information systems, food, and many other fields. In 2005, a rapidly expanding hobbyist and home-use market was established with the inauguration of the open-source RepRap and Fab@Home projects. Virtually all home-use 3D printers released to-date have their technical roots in the on-going RepRap Project and associated open-source software initiatives.In distributed manufacturing, one study has found   3D printing could become a mass market  product enabling consumers to save money associated with purchasing common household objects.For example, instead of going to a store to buy an object made in a factory by injection molding (such as a measuring cup or a funnel), a person might instead print it at home from a downloaded  2 1.2 History of 3d printing 3D printing was developed by Charles Hull, the founder of 3D Systems in 1984. Mr. Hull, born May 12, 1939, was an inventor of over 60 U.S. patents in the fields of ion optics and rapid prototyping. In his patent for the ―Apparatus for Production of Three - Dimensional Objects by stereo lithography‖, issued on March 11, 1986, he defined stereo lithography as a method and apparatus for making solid objects by successively ―printing‖ thin layers of the ultraviolet curable material one on top of the other. Originally called Stereolithography, in the early years the technological development of the 3d printer systems by 3D System using the Stereolithography technique was in parallel development to Fused Deposition Modeling (FDM), invented in 1988 by Scott Crump, the founder of Stratasys. In 1993 Massachusetts Institute of Technology (MIT) added to the developm ent of this field by patenting ―3 Dimensional Printing techniques‖ based on modifications of 2D printer technologies, which was then licensed to Z Corporation for development of their 3DP printers. In the year 1996 the world saw the first major release of 3d printers by Z Corp, Stratasys, and 3D Systems. At this time the use of 3d printer nomenclature became more widespread. In the course of further development over the next decade printer technology developed in respect to resolution and software capability, culminating in 2005 with the launch of the Spectrum Z510, the first high definition The next year, in 2006, a breakthrough open source printing project, named Reprap, was developed in England. The rep-rap was capable of manufacturing various plastic parts, roughly 50% of itself. The first version of the Reprap, the Darwin, was released in 2008. In continued development of Reprap  printers the next model developed was the Mendel. The Mendel succeeded the Darwin in efficiency using a varient triangular core structure as opposed to the square frame of the Darwin. Following the Mendel several different research projects took the rep-rap in new directions, one of those directions  being the Huxley, another the Prusa (a simpler streamlined rep rap offering), and others including mini-mendel systems. Concurrent development of extruder technology has allowed for the modification of most Reprap commercial printers, and with the capability of self-replication, these  printers are an effective means to generate additional copies and 3d printing capability.    3 Fig 1.1 (An ORDbot Quantum 3D printer)  4 CHAPTER 2 TERMINOLOGY Early AM equipment and materials were developed in the 1980s.[3] In 1984, Chuck Hull of 3D Systems Corporation,[4] invented a process known as stereolithography, in which layers are added by curing photopolymers with UV lasers. Hull defined the process as a system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed. [5][6] He also developed the STL (STereoLithography) file format widely accepted by 3D printing software as well as the digital slicing and infill strategies common to many processes today. The term 3D printing srcinally referred to a process employing standard and custom inkjet print heads. The technology used  by most 3D printers to date  —  especially hobbyist and consumer-oriented models  —  is fused deposition modeling, a special application of plastic extrusion. AM processes for metal sintering or melting (such as selective laser sintering, direct metal laser sintering, and selective laser melting) usually went by their own individual names in the 1980s and 1990s. Nearly all metalworking production at the time was by casting, fabrication, stamping, and machining; even though plenty of automation was applied to those technologies (such as by robot welding and CNC), the idea of a tool or head moving through a 3D work envelope transforming a mass of raw material into a desired shape layer by layer was associated by most people only with processes that removed metal (rather than adding it), such as CNC milling, CNC EDM, and many others. The umbrella term additive manufacturing gained wider currency in the decade of the 2000s[7] as the various additive processes matured and it became clear that soon metal removal would no longer be the sole occupant of the aforementioned paradigm. It was during this decade that the term subtractive manufacturing appeared as a retronym for the large family of machining processes with metal removal as their common theme. However, at the time, the term 3D printing still referred only to the polymer technologies in most minds, and the term AM was likelier to be used in metalworking contexts than among polymer/inkjet/stereolithography enthusiasts. By the early 2010s, the terms 3D printing and additive manufacturing developed senses in which they were synonymous umbrella terms for all AM technologies. Although this was a departure from their earlier technically narrower senses, it reflects the simple fact that the technologies all share the common theme of sequential-layer material addition/joining throughout a 3D work envelope under automated control. (Other terms that have appeared, which are usually used as AM synonyms (although sometimes as hypernyms), have been desktop manufacturing, rapid manufacturing [as the logical production-level successor to rapid prototyping], and on-demand manufacturing [which echoes on-demand printing in the 2D sense of printing].) The 2010s were the first decade in which metal parts such as engine brackets[8] and large nuts[9] would be grown (either before or instead of machining) in  job production rather than obligately being machined from bar stock or plate. The term subtractive has
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