The art of 3-D printing has attracted mechanical designers specially in automotive and aviation industry because it has revolutionized model prototyping. As far as vehicle design is concerned, this industry was the first to espouse 3D modeling for generating template models of vehicle body and engine parts. The simplest way to describe 3D modeling is that a digital input file results in a physical three dimensional object using a computer controlled mechanism. From modeling point of view it is the formation of an object by addition of different horizontally sliced cross sections of the actual object, combined to generate the final entity and due to this addition principle it is also known as additive manufacturing.

How it Works?
The process of 3D printing starts with making a digital file depicting the characteristics of the real or some imaginary object using computer aided design software or by using the object scanner which create a detailed image of the real object. The source can be a high resolution digital camera or some other devices also called 3D scanners which employ the technologies like modulated light or volumetric scanning etc to provide the digital copy of the real object. As the object is segmented horizontally into different layers, this file is basically composed of hundreds of sub files with each file containing a 2D information of a particular layer. This layer wise information is fed to the printer machine which manufactures each layer and adds the next on the previous one thus constituting a final 3D object. The typical file format for the digital file of the model is known as STL(stereolightography) which is first check for any bugs in a process known as repair process. In the next step a G-code file is prepared which contains layer wise information of the object and is prepared by a slicer software. This G-code file is finally printed in the form of a 3D object.

Technology Aspects of 3D Printing
The techniques that different 3D printing systems employ differ in the type of technology they adopt. The distinguishing factor is the way layers of the actual model are prepared. Few processes have been reported to use melting or softening material for generating layers and among other well known and commonly adopted methods include selective layer sintering and fused deposition modeling. In  2010, the American Society for Testing and Materials (ASTM) classified 3D printing into seven major categories. For sake of brevity only those would be mentioned upon which additive manufacturing industry majorly rely on.

Vat Photopolymerization Technique
As the name implies, this process incorporates photopolymer resins in a vessel and layers are hardened by using a source of ultraviolet rays. Each cross section of the actual object is traced on the liquid resin surface which adds to the previous layer being mapped through the same mechanism and elevator platform ascends or descends to produce next subsequent layer until all the last layer is reached.

Binder Jetting
A powdered material used as a base is combined in conjunction with a liquid binder in this process. This technique was first presented by Massachusetts Institute of technology in the decade of 1990 to 2000, and is still widely used in 3D printing process. Each layer is coated with the powdered material and the binder material is bombarded using the jet nozzle that follows the pattern of provided digital information of each layer. This is how the complete 3d model is constructed.

Fused deposition modeling and selective laser sintering
Fused deposition modeling (FDM) is mainly used in material extrusion and selective laser sintering (SLS) is employed in the powder bed fusion method of additive manufacturing. In material extrusion technique, metallic or composite material is provided from a wounded coil which is electronically unwrapped and applied from a nozzle which in turn is heated to shape the material in desired format. In the powder bed fusion process a high intensity laser is projected on the material to be shaped into a 3D object. It can be a metal, glass or any other material. The laser injection is controlled through a computer program which correctly accomplishes the manufacturing of each cross section of the required model.

Sheet lamination, material jetting and direct energy deposition are some other types of processes alternatively applied depending upon the application and feasibility of the outcome.

Aviation, automotive, healthcare and architecture are the ultimate beneficiaries of the additive manufacturing. Rapid prototyping has revolutionized the automotive and aviation industry where 3D modeling helps both in analysis and production of new systems. Healthcare department is utilizing 3D implants and prosthetics which has improved quality of health care to an extent never experienced before. The pace at which this industry is growing and the novelty that 3D printing has introduced, it is predicted that additive manufacturing will affect almost all the fields of daily life including trade and commerce in near future.

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