Paper Title (use style: paper title)

3D PRINTING

Sumit

2311228

ECE Department

Ambala College of Engineering and Applied Research

Ambala

sumitharish95@gmail.com

Abstract3-D printing is a unique technology in the realm of CNC. Often this technology is referred to as Rapid Prototyping as its functional use is often one of (relatively) quickly producing a physical object from a CAD design model. This object can be used to test form, fit, and function prior to building the object in its real material, which likely costs more in time and material stock to produce. As a prototype, this object is fully (exceptions below) workable and functions to test both visual and engineering specifications, as well as completeness, correctness, and overall design integrity. The production approach is so simple that it is almost not even worth consideration. Take your 3D model, run it through some software, and hit Go. A few hours later, its done.FDM is one of many so-called Rapid Prototyping techniques, but they all fall under one larger conceptual umbrella. They all operate by deconstructing geometry into distinct layers, then building up those layers one-by-one, depositing material on top of material discreetly to slowly build a 3D form. The process is distinctively additive, especially as compared with the subtractive processes we have and will explore with the laser and 3-axis milling and routing.

I. Introduction

3D printing is a form of additive manufacturing technology where a three dimensional object is created by laying down successive layers of material. It is also known as rapid prototyping, is a mechanized method whereby 3D objects are quickly made on a reasonably sized machine connected to a computer containing blueprints for the object. The 3D printing concept of custom manufacturing is exciting to nearly everyone. This revolutionary method for creating 3D models with the use of inkjet technology saves time and cost by eliminating the need to design; print and glue together separate model parts. Now, we can create a complete model in a single process using 3D printing. The basic principles include materials cartridges, flexibility of output, and translation of code into a visible pattern. 3D printing is a form of additive manufacturing technology where a three dimensional object is created by laying down successive layers of material. It is also known as rapid prototyping, is a mechanized method whereby 3D objects are quickly made on a reasonably sized machine connected to a computer containing blueprints for the object. The 3D printing concept of custom manufacturing is exciting to nearly everyone. This revolutionary method for creating 3D models with the use of inkjet technology saves time and cost by eliminating the need to design; print and glue together separate model parts. Now, we can create a complete model in a single process using 3D printing. The basic principles include materials cartridges, flexibility of output, and translation of code into a visible pattern.

II. General principlesA. Modeling

3D printable models may be created with acomputer aided design(CAD) package or via a3D scanneror via a plain digital camera andphotogrammetrysoftware. The manual modeling process of preparing geometric data for 3D computer graphics is similar to plastic arts such as sculpting. 3D scanning is a process of analysing and collecting digital data on the shape and appearance of a real object. Based on this data, three-dimensional models of the scanned object can then be produced. Regardless of the 3D modelling software used, the 3D model (often in .skp, .dae, .3ds or some other format) then needs to be converted to either a.STL or a .OBJ format, to allow the printing (a.k.a. "CAM") software to be able to read it.

Figure 2.1: 3D model slicing

B. Printing

Before printing a 3D model from anSTLfile, it must first be examined for "manifold errors", this step being called the "fixup". Especially STL's that have been produced from a model obtained through3D scanningoften have many manifold errors in them that need to be fixed. Examples of manifold errors are surfaces that do not connect, gaps in the models. Examples of software that can be used to fix these errors arenetfabbandMeshmixer, or even Cura, or Slic3r.

Once that's done, the .STL file needs to be processed by a piece of software called a "slicer" which converts the model into a series of thin layers and produces aG-code filecontaining instructions tailored to a specific type of 3D printer (FDM printers). This G-code file can then be printed with3D printing clientsoftware (which loads the G-code, and uses it to instruct the 3D printer during the 3D printing process). It should be noted here that often, the client software and the slicer are combined into one software program in practice. Several open source slicer programs exist, including Skeinforge, Slic3r, and Cura as well as closed source programs including Simplify3D and KISSlicer.

C. Finishing

Though the printer-produced resolution is sufficient for many applications, printing a slightly oversized version of the desired object in standard resolution and then removing materialwith a higher-resolution subtractive process can achieve greater precision. Some printable polymers allow the surface finish to be smoothed and improved using chemical vapour processes.

Some additive manufacturing techniques are capable of using multiple materials in the course of constructing parts. These techniques are able to print in multiple colors and color combinations simultaneously, and would not necessarily require painting. Some printing techniques require internal supports to be built for overhanging features during construction. These supports must be mechanically removed or dissolved upon completion of the print. All of the commercialized metal 3-D printers involve cutting the metal component off of the metal substrate after deposition. A new process for theGMAW3-D printing allows for substrate surface modifications to removealuminumcomponents manually with a hammer.

III. 3d printing processes

Several different 3D printing processes have been invented since the late 1970s. The printers were originally large, expensive, and highly limited in what they could produce. A large number of additive processes are now available. The main differences between processes are in the way layers are deposited to create parts and in the materials that are used. Some methods melt or soften material to produce the layers, e.g.selective laser melting(SLM) ordirect metal laser sintering(DMLS),selective laser sintering(SLS),fused deposition modeling(FDM),or fused filament fabrication (FFF), while others cure liquid materials using different sophisticated technologies, e.g.stereolithography(SLA). Withlaminated object manufacturing(LOM), thin layers are cut to shape and joined together (e.g. paper, polymer, and metal). Each method has its own advantages and drawbacks, which is why some companies consequently offer a choice between powder and polymer for the material used to build the object.Other companies sometimes use standard, off-the-shelf business paper as the build material to produce a durable prototype. The main considerations in choosing a machine are generally speed, cost of the 3D printer, cost of the printed prototype, cost and choice of materials, and color capabilities. Printers that work directly with metals are expensive. In some cases, however, less expensive printers can be used to make a mould, which is then used to make metal parts.

A. Fused deposition modelling

Fused deposition modeling (FDM) was developed byS. Scott Crumpin the late 1980s and was commercialized in 1990 byStratasys.After the patent on this technology expired, a large open-source development community developed and both commercial andDIYvariants utilizing this type of 3D printer appeared. As a result, the price of this technology has dropped by two orders of magnitude since its creation. In fused deposition modeling the model or part is produced by extruding small beads of material which harden immediately to form layers. Athermoplasticfilament or metal wire that is wound on a coil is unreeled to supply material to anextrusionnozzle head. The nozzle head heats the material and turns the flow on and off. Typicallystepper motorsorservo motorsare employed to move the extrusion head and adjust the flow. The head can be moved in both horizontal and vertical directions, and control of the mechanism is typically done by acomputer-aided manufacturing(CAM) software package running on a microcontroller.

Figure 3.1: Fused deposition modeling: 1 nozzle ejecting molten plastic, 2 deposited material (modeled part), 3 controlled movable table

B. Selective Laser Sintering (SLS)

Selective Laser Sintering(SLS) is anadditive manufacturing(AM) technique that uses alaseras the power source tosinterpowdered material (typicallymetal), aiming the laserautomaticallyat points in space defined by a3D model, binding the material together to create a solid structure. It is similar todirect metal laser sintering(DMLS); the two are instantiations of the same concept but differ in technical details.Selective laser melting(SLM) uses a comparable concept, but in SLM the material is fully melted rather than sintered,allowing different properties (crystal structure,porosity, and so on). SLS (as well as the other mentioned AM techniques) is a relatively new technology that so far has mainly been used forrapid prototypingand forlow-volume productionof component parts. Production roles are expanding as thecommercializationof AM technology improves.

An additive manufacturing layer technology, SLS involves the use of a high powerlaser(for example, acarbon dioxide laser) to fuse small particles ofplastic,metal,ceramic, orglasspowders into a mass that has a desired three-dimensional shape. The laser selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of the part (for example from aCADfile or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed. Because finished part density depends on peak laser power, rather than laser duration, a SLS machine typically uses apulsed laser. The SLS machine preheats the bulk powder material in the powder bed somewhat below its melting point, to make it easier for the laser to raise the temperature of the selected regions the rest of the way to the melting point. Unlike some other additive manufacturing processes, such asstereolithography(SLA) andfused deposition modeling(FDM).

Figure 3.2: Selective laser sintering process

C. Stereolithography

Stereolithography(SLAorSL; also known asoptical fabrication,photo-solidification,solid free-form fabrication, solid imagingandResin printing) is anadditive manufacturingor3D printingtechnology used for producingmodels,prototypes,patterns, and production parts up one layer at a time by curing a photo-reactive resin with a UV laser or another similar power source.

The term stereolithography was coined in 1986 byCharles (Chuck) W. Hull,[2]who patented it as a method and apparatus for making solid objects by successively "printing" thin layers of anultravioletcurable material one on top of the other. Hull's patent described a concentrated beam of ultraviolet light focused onto the surface of a vat filled with liquidphotopolymer. The light beam draws the object onto the surface of the liquid layer by layer, and using polymerization or cross-linking to create a solid, a complex process which requires automation. Stereolithography is an additive manufacturing process which employs a vat of liquid ultravioletcurablephotopolymer"resin" and an ultravioletlaserto build parts' layers one at a time. For each layer, the laser beam traces a cross-section of the part pattern on the surface of the liquid resin. Exposure to the ultraviolet laser light cures and solidifies the pattern traced on the resin and joins it to the layer below.

After the pattern has been traced, the SLA's elevator platform descends by a distance equal to the thickness of a single layer, typically 0.05mm to 0.15mm (0.002in to 0.006in). Then, a resin-filled blade sweeps across the cross section of the part, re-coating it with fresh material. On this new liquid surface, the subsequent layer pattern is traced, joining the previous layer. A complete3-Dpart is formed by this process. After being built, parts are immersed in a chemical bath in order to be cleaned of excess resin and are subsequently cured in an ultraviolet oven.

Figure 3.3: Stereolithography apparatus

IV. Applications1) Automobiles

In early 2014, the Swedishsupercarmanufacturer,Koenigsegg, announced the One, a supercar that utilises many components that were 3D printed. In the limited run of vehicles Koenigsegg produces, the One:1 has side-mirror internals, air ducts, titanium exhaust components, and even complete turbocharger assembles that have been 3D printed as part of the manufacturing process.

2) ConstructionAn additional use being developed isbuilding printing, or using 3D printing to build buildings.This could allow faster construction for lower costs, and has been investigated for construction of off-Earth habitats.For example, the Sinterhab project is researching a lunar base constructed by 3D printing using lunar regolithas a base material. Instead of adding a binding agent to the regolith, researchers are experimenting with microwavesinteringto create solid blocks from the raw material.3) FirearmsIn 2012, the US-based groupDefense Distributeddisclosed plans to "[design] a working plasticgunthat could be downloaded and reproduced by anybody with a 3D printer."Defense Distributed has also designed a 3D printable AR-15 type riflelower receiver(capable of lasting more than 650 rounds) and a 30 round M16 magazine The AR-15 has multiple receivers (both an upper and lower receiver), but the legally controlled part is the one that is serialised (the lower, in the AR-15's case). Soon after Defense Distributed succeeded in designing the first working blueprint to produce a plastic gun with a 3D printer in May 2013, theUnited States Department of Statedemanded that they remove the instructions from their website.After Defense Distributed released their plans, questions were raised regarding the effects that 3D printing and widespread consumer-levelCNCmachiningmay have ongun controleffectiveness.4) Medical3D printing has been used to print patient specific implant and device for medical use. Successful operations include a titaniumpelvisimplanted into a British patient, titanium lowerjawtransplanted to a Belgian patient,and a plastictrachealsplint for an American infant.The hearing aid and dental industries are expected to be the biggest area of future development using the custom 3D printing technology.In March 2014, surgeons in Swansea used 3D printed parts to rebuild the face of a motorcyclist who had been seriously injured in a road accident.Research is also being conducted on methods to bio-print replacements for lost tissue due to arthritis and cancer.5) SpaceIn September 2014,SpaceXdelivered the first zero-gravity 3-D printer to theInternational Space Station(ISS). On December 19, 2014,NASAemailed CAD drawings for a socket wrench to astronauts aboard the ISS, who then printed the tool using its 3-D printer. Applications for space offer the ability to print broken parts or tools on-site, as opposed to using rockets to bring along pre-manufactured items for space missions to human colonies on the moon, Mars, or elsewhere.The European Space Agency plans to deliver its new Portable On-Board 3D Printer (POP3D for short) to the International Space Station by June 2015, making it the second 3D printer in space.6) Education and research

3D printing and open source RepRap 3D printers in particular, are the latest technology making inroads into the classroom.3D printing allows students to create prototypes of items without the use of expensive tooling required in subtractive methods. Students design and produce actual models they can hold.s

V. Conclusion

3d printing is a relatively new technology. There are no restrictions on the industry. By using this technology, we can significantly decrease the product development cycle and overall costs in making a product. Additive manufacturing, starting with today's infancy period, requires manufacturing firms to be flexible,ever-improvingusers of all available technologies to remain competitive. Advocates of additive manufacturing also predict that this arc of technological development will counterglobalisation, as end users will do much of their own manufacturing rather than engage in trade to buy products from other people and corporations.The real integration of the newer additive technologies into commercial production, however, is more a matter of complementing traditional subtractive methods rather than displacing them entirely.

Acknowledgement

The author would like to express his thanks to Prof. Ashok Kumar, Dean Academics and Head, ECE Department and Management of Ambala College of Engineering and Applied Research, Ambala for their encouragement and support during this work.

References

[1] http://en.wikipedia.org/wiki/3D_printing#Impact

[2] http://www.theengineer.co.uk/in-depth/the-big-story/the-rise-of-additive-manufacturing/1002560.article

[3] http://www.pcmag.com/slideshow_viewer/0,3253,l=293816&a=289174&po=1,00.aspx

[4] http://www.economist.com/news/united-states/21571910-regulatory-and-legal-challenges-posed-3d-printing-gun-parts-ready-print-fire

[5] http://edition.cnn.com/2013/07/31/tech/study-at-home-3-d-printing-could-save-consumers-thousands/index.html

[6] http://www.kurzweilai.net/3d-printing-multi-material-objects-in-minutes-instead-of-hours-to-minutes