Review on Technical, procedural perspectives and ... · Many manufacturing challenges like accuracy...

Review on Technical, proceduralperspectives and Applications of Laser

Additive Manufacturing Process

A. Jai Krishna1, G.Shanmugasundar2,P. Jagadeeshwar3, V. Nagappan4

2Associate Professor, 1,3,4StudentDepartment of Mechanical Engineering,

Sri Sai Ram Institute of Technology,Chennai, India

[email protected]@gmail.com

June 24, 2018

AbstractLaser Additive Manufacturing has become one of the

most prominent methods of manufacturing in various fields.Laser Additive Manufacturing (LAM) works by the methodof layer by layer addition of materials over base materialusing a Laser beam and an automatic powder feed mech-anism. It does not require any additional jigs or fixturefor support or any other coolant for its operation. It al-lows designing of any intricate and complex geometric partof varying thickness and required dimensions. Now, LaserAdditive Manufacturing plays a vital role in every industry,from manufacturing of light weight components for aviationindustry to manufacturing of porous scaffolds for medicalapplication. Through this paper the LAM and its applica-tion in various fields are reviewed in technical and procedu-ral perspective.

Key Words: Laser Additive Manufacturing (LAM) ,Aviation Industry , Laser sintering, Scaffold manufacturing.

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International Journal of Pure and Applied MathematicsVolume 120 No. 6 2018, 1751-1766ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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1 INTRODUCTION

Laser additive manufacturing is a rapid manufacturing process whichuses the laser beam for the melting of the base metal and for so-lidification of the powder bed according to the given model. Itreduces the given complex 3-d model in CAD to slices for the easydeposition of the Powder material over the melt pool of the basemetal. This step by step production of the work pieces helps inthe reduction of the complex geometric shapes into simpler twodimensional manufacturing procedures. Wide Variety of applica-tions are there for LAM in various fields due to their low heatingor operating condition and faster cooling rate, due to which therewill be no change in the grain structure and hence there will beno alteration of the mechanical properties of the additive materialfrom that of the base material. They generally have complex, non-equilibrium physical and chemical nature which are material andprocess dependant. This paper reviews the role played by the LAMin various industries.

Figure 1 Laser additive manufacturing [2]

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International Journal of Pure and Applied Mathematics Special Issue

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Figure 2 Schematic diagram [2]

2 Laser Additive Manufacturing of light

weight Materials

Light weight materials are very much useful in the field of aviation.Laser additive manufacturing has more application in the field ofaviation due to its geometric freedom in manufacturing of complexgeometric work pieces LAM manufactured parts are found to be80% lesser in weight than the conventionally manufactured parts.Application of TiAl6V4 by LAM was given greater importance dueto its light weight in aviation industry.Many manufacturing challenges like accuracy and precision, surfacequality in Machining of light weight materials are faced normally.Hence, experiments were conducted in EOS 270xt and concept M2in TiAl6V4 and carbon brush re coater. A basic catalogue for var-ious complex geometric, thin walled parts and their favourable andunfavourable machining techniques was discussed in this paper bythe author. Also the explanation for the deviation in the geometries

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of the components in their unfavourable conditions was also speci-fied by the author in his publication. Hence manufacturing variouscomplex geometric work pieces used in the field of aviation wasexplained by the author. Process parameters of the experimentsconducted by the author on various complex geometric shapes aregiven below.

TABLE I Process Parameters [1]

3 LAM IN REPAIRING OF TURBO

ENGINES

Laser metal additive manufacturing not only acts as an manufac-turing techniques but also as used in repairing technique. Due toits properties like low heat input and high rate of cooling it is alsoused in the manufacturing of turbo engine components like casingand rotating vanes. LMA helps in the repairing of integrate andcomplex parts which are not repairable by conventional machiningprocesses.The first step in the process includes the layer by layer metal de-position in the melt pool layer of the, to be repaired dysfunctionalpart. Secondly the added material was inspected along with thebase metal for any deviation from their respective properties.If there is no deviation in any of their mechanical properties thenthe work piece is certified to be perfect or satisfactory. This is thework flow process in the repairing of the work components by LAM.

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Figure 3 Cross section of groove wall reconditioned by LMD [2]

Figure 4 LMD machine for repairing genuine aero enginecomponents. [2]

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4 Additive Manufacturing and Laser Sin-

tering

There are three typical processes like Laser Sintering, Laser meltingand laser metal deposition being developed to satisfy the demandsof cost effective fabrication of end use metallic components.

Figure 5 classification of various processes based on laser materialinteraction. [3]

Laser sintering is the process wherein layer by layer spreadingand deposition of the powder material which is subsequently fol-lowed by laser sintering. This process consists of a laser, an auto-matic powder feeder, a computer for the controlling of the process.Lasers like CO2, 54Nd-YAG, 56 disc lasers etc. The choice of thelasers mainly depends upon the powder type. The process proce-dures are:

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• The substrate for fabrication is clamped or fixed on the plat-form and is then leveled.

• Then inert gas is later fed into the sealed building chamberto act as protective agent and to reduce the interior oxygencontent.

• Later by layering mechanism, loose powder is deposited for athickness of 100mm.

• Laser beam scans the powder bed in order to form layer wiseprofiles according to the CAD data

• The above procedures are repeated and building of the com-ponents occurs in a layer by layer manner.

Figure 6 Schematic diagram of LS apparatus [3]

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5 Additive Manufacturing of Medical

Implants

Medical implants and scaffolds were designed by digital methodsand was fabricates by Laser additive manufacturing. Porous arti-ficial femur and vessel scaffolds was designed and was obtained byusing selective laser melting of powdered titanium alloy material.The cross section of the tissue was first obtained by the CT scanand was later converted and exported as Dicom file format. Laterthe design was customized in ProE and the 3D model was importedinto the additive manufacturing system. Ytterbium fiber laser witha wavelength of 1090 nm, a galvanometer and a F-theta lens witha focal distance of 163 nm were used. The powder dispenser plat-form was raised up and a flexible brush spreads the powders on thebuilt platform. From the machine control system the X and theY movements of the laser beam to heat the powder are controlled.The machine repeats the above steps to fabricate a scaffold layerby layer.

Figure 7 Schematic Diagram of LAM in Scaffold manufacturing [5]

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Laser assisted bio printing consists of two horizontal coplanarglass slides of same and equal thickness. The glass slide which isto be placed above is coated a thin layer of a material which ab-sorb allows laser to pass through it i.e. a laser absorbing material.The upper glass slides also coated with the bio material which isto be printed. The bio material is in the form of sol which is nongelled form of precursor of hydrogen within which cells are embed-ded in. The top slide which is also called the donor slide is mountedupside down with small distance in micron level up to 500micronmeter above the second slide. The second slide is also called theacceptor slide. The laser is passed through the donor slide into thelaser absorbing layer. The laser absorbing layer absorbs the pho-tons and generates plasma within picoseconds. By laser irradiationthe plasma is further heated. Due to rise in temperature the ab-sorption layer is thereby evaporated in the focal point of the lasercreating a vapor bubble. The bubble expands, but the expansioninto the half space is resisted is lower in the perpendicular direc-tion of the surface since the amount of the hydrogen gel is smallwhen compared to the lateral direction. Hence the vapor bubbleconsists of an elongated shape. Due to expansion the inner pressureis lesser than the atmospheric pressure. This causes the bubble tocollapse just within few micro seconds after the laser pulse. As thebubble collapse due to surface tension and inertia, the sol presentin the forefront of the bubble moves on, forming a sol jet which isfed by the sol flow. Sol flows as a jet in the direction of the loweracceptor glass slide. Because of the limited supply or due to theless availability of the reservoir of sol, syringing from the area onthe donor glass slide, with 200 micro meters in diameter, the jetof the sol disrupts after few micro seconds. The sol hence remainsas a micro droplet in the slide. By moving the glass slide with re-spect to the laser any kind of desired structure or pattern can begenerated on the acceptor slide 3-d patterns can also be generatedby layer by layer printing. Laser of different kinds like infra redlaser of 1064-nm wavelength, UV lasers with 193 nm and 355 nm.Hence replacement of tissues and organs, and their interaction withother cell or organs and their action with surroundings can easilyunderstand using Printed 3d cell models.

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Figure 8 Stroboscopic images of the printing process between glassslides [7]

Figure 9 Scaffold manufactured by LAM[5]

6 Investigation of the Correlation be-

tween Plasma Electron Temperature

and Quality of Laser Additive Manu-

facturing Process

Aim of the experiment is to detect fluctuation of temperature inplasma. Experiment based on Coaxial based power feed directmetal deposition, Ytterbium doped fiber laser, a GTV PF 2/2power feeder. Beam Diameter 600nm.Argon was used as shield-ing gas and delivery gas. 3 variables changed during process laserpower, scanning speeding gas. Increase in power increases temper-ature due increase heat input per unit time. When speed increases

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temperature increase but decrease. Shielding gas is important fac-tor in forming quality.

Figure 10 Variation of powder flow rate with repect totemperature.[6]

7 Application of LAM in dental

Additive Manufacturing by Selective Laser Meltiing The RealizerDesktop Machine and its application for the Dental Industry. TheSelective Laser Melting is playing a significant role in aerospace anddental fields with the addition of desktop machine it has evolvedits use in dental market and shows improvisation in metal dentaldevices. The Selective Laser Melting was introduced in 2009 whichwas initially used in small scale industries for the manufacturingof small parts of their necessity but later it evolved its applicationin dental and aerospace industries. The powder used for SelectiveLaser Melting must possess good mechanical properties and should

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dense such that its finds in application in crafts. the main appli-cation of Selective Laser Melting process is to create a fully denseproduct, basically the Selective Laser Melting process is the LaserWelding process. So it includes all the complications of weldingsuch as shrinkage, crack, distrotion, and surface hardening to avoidthese complications there are certain crietrias to be followed, theprocess must be carried out under shielding gas. And the optimalbeam diameter must be in the range of 0.2-0.4 micrometer and thelayer thickness must not exceed 30micrometer. The Desktop ma-chine consists of a sealed build chamber containing the powder feedand handling system, the round process chamber with the movablebuild platform, the leveling system, the laser window and a micro-scope for visual. Inspection during the build the Desktop Machineis basically used for making small but different parts for small com-panies.The dental craft Enterprises renders service for the dentists.But it is seen that it had made several consumers to face a lot ofproblems. Thus there is a scope for the development in the field ofdental craft enterprises. The dental craft enterprises has extendedits service in the field of dental crowns and bridges. The SelectiveLaser Machining process is one of the key technology in manufac-turing. Dental crown and bridges. since Selective Laser Machin-ing process is basically Laser Welding it has its own disadvantagessuch as distortion,cracks etc., to avoid these the diameter of thelaser beam must be optimized for each product. For better under-standing of how the dental crown and bridges are manufactured thelaser beam travels around the boundaries of the tooth thus fillingit and making it a physical area. but it is a challenging task tocreate a dental crown not only dense but also without microporesand cracks. The obtained product can be checked for its conicalangle by placing it in between the two conical snags. The Selec-tive Laser Machining process has not only improvised in the fieldof dental but also in Milling and Casting but it more challengingthan manufacturing of dental crowns and bridges.

8 CONCLUSION

The layer by layer addition of materials by LAM process helps indesigning various intricate and complicate parts of different geo-

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metric dimensions in various fields. Laser additive manufacturingof light weight components in aviation industry . LAM is used forreparing turbo engines. Reduce environmental impact for manu-facturing sustainability. It does not require any coolant or jigs andfixtures for manufacturing hard to manufacture complex geometricwork pieces. Hence, it results in the manufacturing of innovativegoods and improves the supply chain management by quickeningthe manufacturing process and decreasing the product rejectionsdueing inspections. The workpieces manufactured through LAMwas found to be working with efficiency without any change in themechanical, chemical properties of the base metal. But the maindrawback of this process is that the health hazard and its impactto the environment was not evaluated till and calculating its im-pact with its duty cycle is tedious process which has to be done toprevent any other future problems. Hence, LAM is a process whichwill be creating a revolution in manufacturing in all fields includingmedical to aviation, from printing jet components to printing ofa living cell. Laser Additive manufacturing is said to create thirdindustrial revolution in every fields of manufacturing and inven-tions and advancements are made day by day in Laser AdditiveManufacturing.

References

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[12] Luke Scime, Jack Beuth. Anomaly detection and classificationin a laser powder bed additive manufacturing process usinga trained computer vision algorithm. Additive Manufacturing,2018.

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