Additive
Manufacturing
What is 3D Printing? Or
What is Additive Manufacturing? Or
What is Rapid Prototyping?
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3D Printing is a "general" name of "Additive Manufacturing" (AM), and uses technologies like "Computer Aided Engineering" (CAE) which includes "Computer Aided Design" (CAD) & "Computer Aided Manufacturing" (CAM) to build variety of 3-Dimensional objects layer by layer by joining or solidifying the heated polymer or metal material. This "Advance Manufacturing" method is different than traditional methods which cuts, drills and grinds away excess material from the desired object made of polymer or metal.
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"Rapid Prototyping" (RP) was the more appropriate term used in 1990s, when 3D Printing techniques were used for the production of functional or aesthetic prototypes only. After many years since the invention, the precision, repeatability, and material range has increased to the point that some of the 3D Printing processes are considered viable option for industrial low or high volume mass-production, thus considering "Additive Manufacturing" as even more suitable term for it where the material is being added together in contrast with the term "Subtractive Manufacturing" for the machining processes where the material is being removed to get to the desired object shape. The term 3D Printing is still referred only to the polymer technologies in most minds, and the term Additive Manufacturing was more likely to be used in metal-working and end use part with machines low in price or in capability compared to other terms. Some of the other terms used for this technology are Desktop Manufacturing, Rapid Manufacturing, On-demand Manufacturing & etc.
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The equipment, technologies and materials used in this Additive Manufacturing typically are very economical and are very popular in the industries such as Aerospace, Medical, Automotive, Consumer Products & many more. 3D Printing processes have reached not only in our day to day lives but in hard-to-reach locations such as military bases, International Space Station & etc. One of the other key advantages is the ability to produce very complex shapes which would be otherwise difficult & almost close to impossible to construct by other manufacturing processes, including hollow parts or internal truss structures to reduce overall weight of the objects.
How
3D Printing
Works
Steps involved in 3D Printing process are -
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Modeling -
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Computer Aided Design (CAD) software is used to create a 3D printable model with almost no digital errors, which means, errors in these 3D models can be identified and corrected before printing. CAD models are saved in "stereolithography STL" file format which stores the data based on the triangulations of the surface of the models. This file format is not tailored because of the generated large file sizes of topology optimised parts and the face that large number of surfaces are involved. On the other hand, STL file format is not used for Additive Manufacturing processes which uses additive manufacturing file format AMF, which was introduced a few years ago in 2011. This type of file format stores the information using curved triangulations of the surface of the models.
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Printing -
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Before actual printing, the STL file format must be examined for holes, normal faces, self-intersections, noise shells & manifold errors etc. Repair step in this examination fixes such problems in the original model. 3D Scanning does not produce a very good CAD model and thus it is not an effective way to start with because it is achieved by point to point mapping. Once the model is ready with no errors, it is fed to a processor software called a Slicer, which converts the model into a series of thin layers and produces a G-Code file containing instructions tailored to the printers. This G-Code file then can be loaded into 3D printing software to instruct the printer to print the object.
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Printer resolution describes layer thickness and X-Y resolution in dots per inch (dpi) or micrometers (μm). Typical layer thickness is around 100 μm (250 dpi), although some machines can print layers as thin as 16 μm (1600 dpi). X-Y resolution is comparable to that of laser printers. The particles (3D dots) are around 50 to 100 μm (510 to 250 dpi) in diameter. for that printer resolution, specifying a mesh resolution of 0.01 - 0.03 mm and a chord length ≤ 0.016 mm generate an optimal STL output file for a given model input file. Specifying higher resolution results in larger files without increase in print quality. This process can take anywhere from a few hours to a few days depending on the size and complexity of the model.
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Finishing -
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Although 3D Printers can produce the objects with maximum accuracy, in some of the other applications the accuracy is achieved by printing a slightly oversized objects in standard resolution and then removing the excess material using higher resolution process. Some printable materials allow the surface finish to be smoothed and improved using chemical vapour processes based on acetone or similar solvents. Some additive manufacturing techniques are capable of using multiple materials in the course of constructing parts. These techniques are able to print in multiple colours and colour combinations simultaneously, and would not necessarily require painting after the objects are printed & finished.
