by A Ramya · Cited by 59 — to 3D print in a wide range of materials that include thermoplastics, 3D printing as an end-use manufacturing technology is still in its infancy. But.

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PAGE – 1 ============ IJMET / p 396 International Journal of Mechanical Engineering and Technology (IJMET) Volume 7 , Issue 3 , May June 201 6 , pp. 396 409 , Article ID: IJMET_0 7 _ 03 _0 3 6 Available online at 7 &IType= 3 Journal Impact Factor (201 6 ): 9.2286 (Calculated by GISI) ISSN Print: 0976 – 6340 and ISSN Online: 0976 – 6359 © IAEME Publication 3D PRINTING TECHNOLO GIES IN VARIOUS APPLICATIONS A. Ramya Mechanical, B VRIT Hyderabad College of Engineering for W omen , Bachupally, Hyderabad – 500 090 , India Sai leela Vanapalli Mechanical, BVRIT Hyderabad College of Engineering for W omen, Bachupally , Hyderabad – 500 090 , India ABSTRACT Industrial adoption of 3D Printing has been increasing gradually from prototyping to manufacturing of low volume customized parts. The need for customized implants like tooth crowns, hearing aids, and orthopedic – replacement parts has made the life s ciences industry an early adopter of 3D Printing. Demand for low volume spare parts of vintage cars and older mod els makes 3D printing very useful in the automotive industry. It is possible to 3D print in a wide range of materials that include thermoplastics, thermoplastic compos ites, pure metals, metal alloys and ceramics. Right now, 3D printing as an end – use manuf acturing technology is still in its infancy. But in the coming decades, and in combination with synthetic biology and nanote chnology , it has the potential to radically transform many design, production and logistics processes. 3D printing encompasses a wide range of additive manufacturing technologies. Each of these builds objects in successive layers that are typically about 0.1 mm thin. In basic terms there are four categories of 3D printers. Firstly we have printers that extrude a molten or otherwise semi – liquid material. Secondly, there are printers that solidify a photo curable resin. Thirdly, there are printers that bind or fuse the granules of a powder. And finally, there are printers that stick together cut sheets of paper, plastic or metal. Key words: Stereo – lithography (SLA);Fused Deposition Modeling (FDM); Laminated Object Manufacturing (LOM); Selective Laser Sintering (SLS) & Direct Metal Laser Sintering (DMLS); Ink Jet Printing & Poly – jet printing. Cite this Article: A. Ramya and Sai leela Vanapalli, 3d Printing Technologies In Various Applications . International Journal of Mechanical Engineering and Technology , 7(3), 2016, pp. 396 409 .

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3d Printing Technologies In Various Applications IJMET /index.asp 397 1. INTRODUCTION 3D printing is an evolution of printing technologies, capable to produce or reproduce freestanding sophisticated structures in one piece. 3D Printing is one of the Additive layer fabrication processes (Vojislav et al., 2011). The 3D printing process happening inside the machine consists of two stages, (1) The direct transfer from software data to printed structures, (2) by repeatedly positioning the print head in all three directions in space in order to print layer by layer the whole object. (Lu et al., 2008) More in detail, Lu et al., (2008) mentioned how the printing process is carried out, first the design is made by a CAD system, and then the areas are printe d through a compilation of two dimensional slices representing the 3D object to consequently print layer by layer until the object is completed. The second stage of the manufacturing process can also hroughout these steps, the material is laid over a surface and by the action of a source of energy the layers are created. The source of energy and the raw materials vary depending on the used technology (Vojislav et al., 2011) [1] . 2. TECHNOLOGIES Th e technologies that can be used to build a part one layer at a time are quite varied and in different stages of development. In order to accommodate different materials, as well as improve build times or part strength, numerous technologies have emerged. S ome technologies are commercially available methods of fabricating prototypes, others are quickly becoming viable forms of production manufacturing, and newer technologies are continuously being developed. These different methods of additive fabrication ca n be classified by the type of material that is employed. 2.1. Liquid – based processes The first category of 3D printer creates object layers by selectively solidifying a liquid resin known as photopolymer that hardens when exposed to laser or other light sourc e. Some such photo polymerization 3D printers built object layers within a tank of liquid. Meanwhile others jet out a single layer of resin and use ultraviolent light to set it solid before the next layer is added. A few 3D printers based on the latter tec hnology and are able to mix several different photo polymers in the same print job, so allowing them to output objects made from multiple materials. 2.2. Powder – based processes A second and very broad category of 3D printing hardware builds object by selective ly sticking together successive layers of a very fine powder. Such powder adhesion or granular materials binding can be achieved by jetting an adhesive onto each powder layer, or by fusing powder granules together using a laser or other heat source. Yet ot her technologies melt and then fuse the granules of a powdered built material as it is deposited onto a built surface. Various forms of powder adhesion are already commonly used to 3D print in a wide range of materials. These include nylon, bio – plastics, c eramics, wax, bronze, stainless steel, cobalt chrome and titanium. 2.3. Solid – based processes There are 3D printers that create objects by extruding a molten or otherwise semi liquid material from a print head nozzle. Most commonly this involves extruding a mo lten thermoplastic that very rapidly sets after it has left the print head. Other extrusion based 3D printers manufacture objects by outputting molten metal, or by

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A. Ramya and Sai leela Vanapalli IJMET /index.asp 398 extruding chocolate or cake frosting (icing) to 3D print culinary creations. There are even 3D printers that extrude concrete or clay. 2.4. Paper based processes A final category of 3D printer is based on lamination. Here, successive layers of cut paper, metal or plastic are stuck together to build up a solid object. Where sheets of paper are used as the build material, they are cut by blade or laser and glued together. They may also be sprayed with multiple inks during the printing process to create low cost, fu ll colour 3D printed objects. [2 ] 3. TYPES OF 3D PRINTING TECHNOLOGIES 3.1. Stereo – lithography (SL A) It is the most widely used rapid prototyping technology. It can produce highly accurate and detailed polymer parts. It was the first rapid prototyping process, introduced in 1988 by 3D Systems, Inc., based on work by inventor Charles Hull. Stereo – lithog raphy is the most widely used rapid prototyping technology. Stereo – lithography builds plastic parts or objects one layer at a time by tracing a laser beam on the surface of a vat of liquid photopolymer, inside of which is a movable stage to support the par t being built. The photopolymer quickly solidifies wherever the laser beam strikes the surface of the liquid. The platform is lowered by a distance equal to the layer thickness (typically 0.003 – 0.002 in), and a subsequent layer is formed on top of the prev iously completed layers. The self – adhesive property of the material causes each succeeding layer to bond to the previous one and thus form a complete, three – dimensional object out of many layers. Objects which have overhangs or undercuts must be supported during the fabrication process by support structures. These are either manually or automatically designed with a computer program specifically developed for rapid prototyping. Once complete, the part is elevated above the vat and drained. Excess polymer is swabbed or rinsed away from the surfaces. In many cases, a final cure is given by placing the part in a UV oven. After the final cure, supports are cut off the part and surfaces are polished, sanded or otherwise finished . [ 3 ] Table 1 Capabilities of SLA M aterial type Liquid (photo polymer) Material Principally photo curing polymers which simulate polypropylene, ABS, PBT, rubber; development of ceramic – metal alloys. Maximum part size 59.00 x 29.50 x 19.70 in. Min feature size 0.004 in. Min layer thickne ss 0.0010 in. Tolerance 0.0050 in. Surface finish & Build speed Surface finish is smooth and build speed is Average Applications Rapid tooling patterns, Snap fits, Very detailed parts, Presentation models, High heat applications

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3d Printing Technologies In Various Applications IJMET /index.asp 399 ( a) Stereo l ithography (SLA) working (b) Component printed using SLA Figure 1 3.2. Fused Deposition Modeling (FDM) It was developed by Stratasys in Eden Prairie, Minnesota. In this process, a plastic or wax material is extruded through a nozzle that traces the parts cross sectional geometry layer by layer.FDM is the second most widely used rapid prototyping technology, after stereo lithography [5]. A plastic filament is unwound from a coil and supplies material to an extrusion nozzle. The nozzle is heated to melt the plastic and has a mechanism which allows the flow of the melted plastic to be turned on and off. The nozzle is mounted to an X – Y plotter type mechanism which traces out the part contours, There is a second extrusion nozzle for the support material (differ ent from the model material). As the nozzle is moved over the table in the required geometry, it deposits a thin bead of extruded plastic to form each layer. The plastic hardens immediately after being squirted from the nozzle and bonds to the layer below. The object is built on a mechanical stage which moves vertically downward layer by layer as the part is formed. The entire system is contained within a chamber which is held at

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A. Ramya and Sai leela Vanapalli IJMET /index.asp 400 a temperature just below the melting point of the plastic. Support structures are automatically generated for overhanging geometries and are later removed by breaking them away from the object. A water – soluble support material is also available for ABS parts. A range of materials are available including ABS, polyamide, polycarbonate , polyethylene, polypropylene, and investment casting wax . [ 4 ] Table 2 Capabilities of FDM Material type Solid (Filaments) Material Thermoplastics such as ABS, Polycarbonate, and Poly – phenylsulfone; Elastomers Maximum part size 36.00 x 24.00 x 36.00 in. Min feature size 0.005 in. Min layer thickness 0.0050 in. Tolerance 0.0050 in. Surface finish & Build speed Surface finish is rough and build speed is slow Applications Rapid tooling patterns, Small detailed parts, Presentation models, Patient and foo d applications, High heat applications ( a) Fused Deposition Modeling (FDM) (b) Component printed using FDM Figure 2

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3d Printing Technologies In Various Applications IJMET /index.asp 401 3.3. Laminated Object Manufacturing (LOM) The first commercial Laminated Object Manufacturing (LOM) system was shipped in 19 91. LOM was developed by Helisys of Torrance, CA. The main components of the system are a feed mechanism that advances a sheet over a build platform, a heated roller to apply pressure to bond the sheet to the layer below, and a laser to cut the outline of the part in each sheet layer. Parts are produced by stacking, bonding, and cutting layers of adhesive – coated sheet material on top of the previous one. A laser cuts the outline of the part into each layer. After each cut is completed, the platform lowers b y a depth equal to the sheet thickness (typically 0.002 – 0.020 in), and another sheet is advanced on top of the previously deposited layers. The platform then rises slightly and the heated roller applies pressure to bond the new layer. The laser cuts the ou tline and the process is repeated until the part is completed. After a layer is cut, the extra material remains in place to s upport the part during build. [ 5 ] Table 3 Capabilities of LOM Material type Paper, plastics (Sheets) Material Thermoplastics such as PVC; Paper; Composites Maximum part size 32.00 x 22.00 x 20.00 in. Min feature size 0.008 in. Min layer thickness 0.0020 in. Tolerance 0.0040 in. Surface finish & Build speed Surface finish is rough and build speed is fast Applications Less deta iled parts, Rapid tooling patterns ( a) Laminated Object Manufacturing (LOM ) (b) Component printed using LOM Fig ure 3

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3d Printing Technologies In Various Applications IJMET /index.asp 403 (b) Component printed using SLS Fig ure 4 3.5. Direct Metal Laser Sintering (DMLS) It was developed jointly by Rapid Product Innovations (RPI) and EOS GmbH, starting in 1994, as the first commercial rapid prototyping method to produce metal parts in a single process. With DMLS, metal powder (20 micron diameter), free of binder or fluxing agent, is completely melted by the scanning of a high power laser beam to build the part with properties of the original material. E liminating the polymer binder avoids the burn – off and infiltration steps, and produces a 95% dense steel part compared to roughly 70% density with Selective Laser Sintering (SLS). An additional benefit of the DMLS process compared to SLS is higher detail r esolution due to the use of thinner layers, enabled by a smaller powder diameter. This capability allows for more intricate part shapes. Material options that are currently offered include alloy steel, stainless steel, tool steel, aluminum, bronze, cobalt – chrome, and titanium. In addition to functional prototypes, DMLS is often used to produce rapid tooling, medical implants, and aerospace parts for high heat applications. The DMLS process can be performed by two different methods, powder deposition and pow der bed, which differ in the way each layer of powder is applied. In the powder deposition method, the metal powder is contained in a hopper that melts the powder and deposits a thin layer onto the build platform. In the powder bed method (shown in fig.5 ( a)), the powder dispenser piston raises the powder supply and then a re – coater arm distributes a layer of powder onto the powder bed. A laser then sinters the layer of powder metal. In both methods, after a layer is built the build piston lowers the build platform and the next layer of powder is applied. The powder deposition method offers the advantage of using more than one material, each in its own hopper. The powder bed method is limited to only one material bu t offers faster build speeds. [6 ]

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A. Ramya and Sai leela Vanapalli IJMET /index.asp 404 Table 5 C apabilities of DMLS Material type Powder (Metal) Material Ferrous metals such as Steel alloys, Stainless steel, Tool steel; Non – ferrous metals such as Aluminum, Bronze, Cobalt – chrome, Titanium; Ceramics Maximum part size 10.00 x 10.00 x 8.70 in. Min fea ture size 0.005 in. Min layer thickness 0.0010 in. Tolerance 0.0100 in. Surface finish & Build speed Surface finish is average and build speed is fast Applications Rapid tooling, High heat applications, Medical implants, Aerospace parts ( a) Direct Metal Laser Sintering (DMLS) (b) Component printed using DMLS Fig ure 5 3.6. Ink Jet Printing This method uses a single jet each for a plastic build material and a wax – like support material, which are held in a melted liquid state in reservoirs. The l iquids are fed to individual jetting heads which squirt tiny droplets of the materials as they are moved in X – Y fashion in the required pattern to form a layer of the object. The materials

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3d Printing Technologies In Various Applications IJMET /index.asp 405 harden by rapidly dropping in temperature as they are deposited. Af ter an entire layer of the object is formed by jetting, a milling head is passed over the layer to make it a uniform thickness. Particles are vacuumed away and are captured in a filter. The process is repeated to form the entire object. After the object is completed, the wax support material is either melted or dissolved away. The most outstanding characteristic of the Solid – scape system is the ability to produce extremely fine resolution and surface finishes, essentially equivalent to CNC machines. The tec hnique is very slow for large objects. Materials selection is very limited. Other manufacturers use considerably different inkjet techniques, but all rely on squirting a build material in a liquid or melted state which cools or otherwise hardens to form a solid on impact. 3D Systems produces an inkjet machine called the Thermo – Jet Modeler (TM) which utilizes several hundred nozzles in a wide head configuration. It uses a hair – like matrix of build material to provide support for overhangs which can be easily brushed off once the object is complete. This machine is much faster than the Solid – scape approach, but doesn’t offer as good a surface finish or resolution. [3 ] Table 6 Capabilities of Ink jet printing Material type Liquid Material Acrylic based thermo polymeric Plastic, Natural and Synthetic Waxes, Fatty Esters Maximum part size 12.00 x 6.00 x 6.00 in. Min feature size 0.005 in. Min layer thickness 0.0005 in. Tolerance 0.0010 in. Surface finish & Build speed Surface finish is very smooth and build speed is slow Applications Very detailed parts, Rapid tooling patterns, Jewelry and fine items, Medical devices ( a) Inkjet Printing

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A. Ramya and Sai leela Vanapalli IJMET /index.asp 406 (b) Jig and fixture Fig ure 6 3.6. Poly – Jet 3D printing Objet Geometries Ltd., an Isra eli company, introduced its first machine based on Poly – Jet technology in early 2000. It is a potentially promising replacement for stereo – lithography. Poly jet process is very similar to the ink jet printing done on paper but in this process, instead of j etting drops of ink onto paper, the printer jets layers of liquid polymer onto a tray and then the UV rays instantly cure the model. The process is based on photopolymers, but uses a wide area inkjet head to layer wise deposit both build and support materi als. It subsequently completely cures each layer after it is deposited with a UV flood lamp mounted on the print head. The support material, which is also a photopolymer, is removed by washing it away with pressurized water in a secondary operation. The ad vantage of poly – jet systems over SLA systems is that the resins come in cartridge form (no vat of liquid photopolymer), the machines are clean, quiet and office friendly. There is less post processing cleanup on parts. Disadvantages are that the print head s are relatively expensive and need to be replaced regularly, adding to maintenance costs . [3] Table 7 Capabilities of Poly – jet printing Material type Liquid (photo polymer) Material Photopolymer resin Maximum part size 19.30 x 15.40 x 7.90 in. Min fea ture size 0.006 in. Min layer thickness 0.0006 in. Tolerance 0.0010 in. Surface finish & Build speed Surface finish is smooth and build speed is fast Applications Very detailed parts, Rapid tooling patterns, Presentation models, Jewelry and fine items

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