Additive Manufacturing: State-of-the-Art, Capabilities, and Sample Applications with Cost Analysis

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Additive Manufacturing:

State-of-the-Art, Capabilities, and Sample

Applications with Cost Analysis

in Collaboration with

by

MINA ALIAKBARI

Master of Science Thesis, Production Engineering and Management,

Department of Industrial Production,

KTH

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Abstract

Additive Manufacturing – AM – which is a part of a generic term, Rapid Prototyping, comprises a family of different techniques to build 3D physical objects sequentially stacking a series of layers over each other. These techniques have been evolving over three decades with more materials available, improving the techniques as well as generating new ones. However they are all based on the same explained idea.

In this research the main AM methods followed with the opportunities of application and cost drivers is sought. For this purpose, after reviewing different processes and techniques, the application of them in diverse industry sectors is described. The influence of AM in production systems, so called Rapid Manufacturing (RM) is also discussed in terms of lean and agile concepts. Time and cost are the most important factors for the production systems to be responsive and productive respectively. Thus, case based application of RM is evaluated to clarify how AM acts in different production systems regarding these factors. To decide which method is the best, strongly depends on the case. But what has been derived from the analysis, is that however in comparison with traditional methods, AM applies more economically in one-off jobbing, yet the economy of scale exists to some extent. In fact it depends on the machine capacity utilization as well as batch size which indicates the machine volume usage.

Despite all the improvements in the last three decades, the application of AM is still not widespread. Since the demand, use, applications and materials as well as its techniques are still in a growing phase, a brighter future is seen for the upcoming customer oriented market.

Key Words: Additive Manufacturing, Rapid Manufacturing, Rapid Prototyping, Lean, Agile,

Leagile, Solid Freeform Fabrication, Tooling, Customization, Design Freedom, additive layer manufacturing,

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Sammanfattning

Additive Manufacturing – AM – som är del av en generell term, Rapid Prototyping, består av en familj olika tekniker för att bygga 3D fysiska objekt genom att sekventiellt lägga lager ovanpå varandra. Dessa tekniker har utvecklats över de senaste tre decennierna, där nya material blivit tillgängliga, teknikerna har förbättrats och nya har skapats, men i slutändan bygger de alla på en och samma idé.

Det projekt undersöks de huvudsakliga AM-metoderna, deras applikationer och kostnadsdrivare. Här görs först en litteraturstudie av olika tekniker och processer varefter deras användning inom olika industrier undersöks. Den influens AM har i produktionssystem, s.k. Rapid Manufacturing (RM), diskuteras också i förhållande till lean och agila koncept. Eftersom tid och kostnad är de viktigaste faktorerna för tillgänglighet respektive produktivitet utvärderas case-baserad användning av RM utifrån dessa faktorer för att förklara hur AM fungerar i produktionssystem.

Att besluta vilken metod som är bäst, är starkt case-baserad. Men det som framkommit från analysen är att i jämförelse med traditionella metoder, är AM mer ekonomiskt vid enstyckstillverkning, men stordriftsfördelar finns i någon utsträckning. Faktiskt det beror på maskinens kapacitetsanvändning och satsstorlek som indikerar maskinens volymanvändning. Trots alla förbättringar under de senaste tre decennierna är användandet av AM ännu inte utbrett. Eftersom efterfrågan, användning, tillämpning och material så väl som dess tekniker fortfarande befinner sig i en tillväxtfas spås en ljusare framtid för en växande kundorienterad marknad.

Nyckelord: Additive Manufacturing, Rapid Manufacturing, Rapid Prototyping, Lean, Agile,

Leagile, Solid Freeform Fabrication, Tooling, Customization, Design Freedom, additive layer manufacturing

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Acknowledgments

I would like to offer my special thanks to Mr Per Johansson and Mr Pau Mallol who inspired me with the concept and guided me in order to complete this thesis research. I also appreciate all other people who helped me in this research path.

Mina Aliakbari

Royal Institute of Technology June 2012

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Dedication

I sincerely dedicate this thesis to my father and mother who are my best teachers of love and maturity.

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1. Introduction

1.1. Definition of Concept

Additive Manufacturing (AM) is defined as the manufacturing process of building objects adding material to previous build areas, layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machining. Synonyms are additive fabrication, additive techniques, additive layer manufacturing, layered manufacturing and solid freeform fabrication. It’s also good to mention that AM includes all applications of the technology, including modeling, prototyping, pattern-making, tool-making, and the production of end-use parts in volumes of one to thousands or more. It isn’t just about prototyping as it were for almost two decades since layered manufacturing techniques started to be used.

Nowadays Rapid Prototyping (RP) on the other side comprises AM and other non-additive methods for manufacturing physical objects at usually high speed and with part features and properties that use to be aimed at some kind of testing but normally, not as a final part. Actually, the American Society for Testing and Materials (ASTM) is normalizing the AM field, i.e. creating a new 3D generic file format for it called (*.amf) to substitute STL and others (IGS, STEP…) and provide new parameters that emerging new AM machines need to exploit their capabilities (e.g. colours, so that the operator doesn’t need to pre-process the file for the Zcorp case). However, since AM is a very large subset of RP and because RP was synonym of additive or layered manufacturing since this manufacturing technique appeared, nowadays they are still used as synonyms of each other in practice. In this thesis the term AM is used.

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All the companies are looking for better responsiveness, because what is important is customer, and what is important for the customer is to get what they ask for (including function, aesthetics or competitive prices but also, for example, recyclability or energetically efficient products). Companies seek to find better methods and improvements. In the competitive market, customer-based production is what companies have in mind. That’s why a lot of researches have been done to improve and extend methods and techniques.

The first techniques for AM became available in the late 1980s. It is generally considered that the approach was born in 1987 when 3D Systems developed the Stereo-Lithography Apparatus (SLA). They were first used to produce models and prototype parts. Today, they are used for a much wider range of applications; from medical equipment to industrial products but in relatively small amount. The evolution of the methods for this technique generated new methods with improved function and material.

1.2. Problem definition

The main feature of AM methods is their flexibility in the design of a product which makes these methods responsive for almost any shape. Nevertheless the surface quality and production time and material limitations are examples of its barriers through worldwide implementation. On the other side, AM is known to be more economical when only one or few amount of a product is needed to be produced (because it doesn’t require investment e.g. for process and tooling design). This is another reason of its limited application. In this research it is investigated how AM can be improved to address any production strategy under the concepts such as production volume and cost. In other words how such parameters influence on using an AM approach in medium and large production volume. Thus, by investigating cost drivers, it is aimed to see if economy of scale exists for this technique.

1.3. Research scope and boundaries

Currently, diverse techniques and diverse machines of AM system are running. This research has introduced some of them which stand up for a well elaboration of this technique. However for each of them, the current available material sector and some machine-product specifications are represented, but the evaluation of the techniques based on these characteristics and analysis over their improvements are out of the scope of this project. This

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case studies.

1.4. Research methodology

The presented research is conducted as:

First it is investigated the common AM methods and techniques. Important features, advantages and disadvantages of each method are overviewed. The aim is to ease the comparison of investigated methods, for instance, in terms of material, build volume or the method itself.

Later on, the barriers and trends are introduced. The application of AM in different sectors of production (e.g. industry or consumer products) is investigated. A generic definition of Rapid Manufacturing (RM), as a capable application of AM, as well as the benefits that AM can provide for it are described, such as design freedom and process improvements.

The following part of this thesis introduces RM in more detail. Some supply chain principles is also discussed to introduce different production statuses; lean, agile and leagile. Furthermore the compatibility of RM in those statuses in addition to the benefits that it brings for them is analyzed.

The next chapter presents a basic characterization of the products, for example in terms of material or production volume. This is done to investigate AM/RM in some products to find out its benefits and limitations over production of chosen product categories. In other words, this investigation is done to show the importance of analyzing RM techniques case by case to see its applicability and/or weaknesses. This analysis is followed by an analysis over cost drivers and the performance of variable changes in the total cost of production.

Finally conclusions are provided about AM’s feasibility on production systems and aspects to make AM more feasible for conditions where now it is still not optimal is pointed out, suggesting future areas were specific research can be done to address the actual bottlenecks.

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2. Additive Manufacturing Methods

In this chapter the most widely used method of AM for plastic and metal material separately is represented, including the explanation of the techniques, material coverage, and some range of specification on machines. In some methods non-reliable data or not found records have been replaced by “-“.

2.1. Plastic Methods

2.1.1. Streolithography Apparatus (SLA)

Process:

Streolithography Apparatus (SLA) produces physical 3D objects, conceptual models or master patterns from a 3D CAD file. Support structures are either manually or automatically designed.

In this method, a controlled laser is used to cure a photopolymer resin to shape the product from a 3D CAD model. First a movable (in Z direction) table is set right under the surface of a vat filled with a photosensitive resin of the required material. The property of such a resin is that it gets hard from liquid to solid when the light of a correct color is radiated to it. SLA common resins normally require ultraviolet light, but visible light is also used for some of materials. The laser beam, then scans and hardens the material thorough the cross section of object by moving in X-Y direction.

The process is done in a sealed box to avoid the fumes to come out. Once a layer is cured, the table lowers at a distance of the defined layer thickness. Although the resin can cover the surface of the previous layer itself slowly, but to speed this process up, SLA machines use

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the next scanning. This process is repeated until the solid part is manufactured.

Stereolithography was mainly used for visual prototypes, but nowadays beside fitting models and aesthetics, it is used for functional parts as well. Best applications of SLA are:

 Aesthetic & conceptual models

 Parts requiring detail & accuracy

 Master patterns for castings and secondary processes

 Medical models.

Additionally, SLA models can be used for photo-optic stress analysis (footnote: a method which unlike mathematical methods, gives an accurate picture of stress distribution. This method is used for finding critical stress points specially in complex shape geometries where analytical methods become time-consuming and difficult to calculate) as well as dynamic vibrational analysis (footnote: the analysis over the response of the device under test against a force which is usually considered as a shaker. The amount of dynamic vibration and the points at which this oscillation is happening are extracted from this method) , which further extend engineering design capabilities.

Crisp and highly detailed products and fast delivery (ususally 2-3 days) are some benefits of SLA. The possibility of building products in large size is another notable area about this method. But on the other hand, working with liquid materials is messy and this is considered as a disadvantage. Also parts produced by SLA technique normally require a post-curing operation in a separate oven-like Post-Curing Apparatus (PCA) for complete cure and stability. In many cases, products do not have the physical, mechanical or thermal properties typically required of end use production material.

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12 Figure 1: Stereolithography

Material:

SLA uses wide range of photosensitive resins which are made of materials such as ABS-like materials, antimony-free liquid photopolymer, nanoparticle filled composites, low viscosity liquid photopolymer, Polycarbonate and ABS-like, hard plastics, polypropylene-like, polycarbonate, Polyethylene-like, Ceramic-like.

SLA 3Dsystems(ipro)

Build Size 650*750*50 mm 650 x 750 x 550 mm

Laser Power 1450 mW

Build Rate -

Layer Thickness 50 - 125 micron

Tolerance 0.025-0.05 mm

Energy Requirement 100-240 VAC, single phase

Waste Irreversible process causes in in-recyclability

Post Processing Support removal, Curing, Sanding, painting or finishing

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even colored. Some are chemical resistant, while others are water resistant or temperature tolerant. [5] [6]

Notes:

 a specific extra-large envelope size is also provided (iPro 9000XL) with build envelope of 1500 x 750 x 550 mm with accuracy of +/- 0.2mm

2.1.2. Selective Laser Sintering (SLS)

Process:

Selective Laser Sintering (SLS) is a method for plastic parts production. In this method plastic powder is kept in a cylinder in which there is a piston moving the powder bed up for each step, in order to provide the required material powder for each layer. This material is dispatched over the building table with a roller and thereafter the powder is scanned by a CO2 laser which radiates a concentrated infrared heating beam and melts the powder at the 2D cross section of the object layer. After each layer, the build table goes down in a distance of layer thickness, preparing for the next powder dispatching from the powder bed supply system. After finishing the manufacturing of the part, the object is removed and the excess powder is brushed away.

The whole process is done in a sealed box and it’s kept at a temperature just below the melting point. This will allow laser to generate only a slight increase in temperature to melt the plastic powder. This helps to speed the process up. In SLS the process is done in a nitrogen atmosphere chamber to avoid the risk of explosion when handling large amount of powder.

The process also doesn’t need support structure, because the powder bed itself is enough to support material as the layers are build up. This saves material and finishing time. But on the other hand ittakes time for the products to cool down and be removed from the machine. Large parts with thin features may take upto 2 days to get cool.

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14 Figure 2: Selective Laser Sintering

SLS

EOS 3Dsystems (sPro)

Build Size 200*250*330 700x380x580 381 x 330 x 457 550 x 550 x 750

Laser Power 100W 30-70W 70-200W

Build Rate 0.6 to 2.5 cm3/hr - -

Layer Thickness 120 – 150 micron 0.08-0.15 mm

Tolerance ± 0.3 mm ± 0.3 mm Energy Requirement 32A, 3.5 kW 3phase 240V/12.5kW, 3phase 208V/17 kW, 3phase

Waste Powder Recyclability Powder Recyclability

Post Processing Sandblasting, surface colouring Sandblasting, surface colouring

Table 2: SLS Specifications

Material:

Alumide, Nylon (Polyamide PA2200), Glass Filled Nylon (Polyamide PA3200) PrimeCast (polystyrene based), PrimePart (Polamide based) [9] [10]

Notes:

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2.1.3. Fused Deposition modelling (FDM):

Process:

Fused Deposition modelling (FDM) is the second most AM after Stereolithography.

In this method a plastic filament, approximately 1.5mm in diameter (or in some machinery configurations plastic pellets fed from a hopper) is unwounded from a coil. This filament supplies the material to the nozzle at which it gets warmer and melts. The nozzle moves over the building table at the layer 2D geometry and relieves the extruded plastic and lets it deposit over the build table. The melted plastic gets hard immediately after depositing from the nozzle and bonds to the previous layer. Support structures are made with the same method to prevent overhangs.

The entire system is maintained at a temperature just below melting point, so it lets the nozzle to provide only a slight increase in temperature to melt the plastic filament and extrude it. This lets the process be faster and better controlled. FDM is used for functional prototypes and prototypes for form and fit testing.

See Figure 3 for a schematic illustration of the method. [11] [12] [13]

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16 FDM Fortus Dimension Build Size 356x254x254 914x610x914 203 x 203 x 305 254 x 254 x 305 Laser Power - - Build Rate 2.54 cm3/hr -

Layer Thickness 127 upto 330 micron 127 upto 330 micron

Tolerance (mm) +/- .0015 upto ± .241

Energy Requirement

230VAC, 16 A, 3phase 110-120 VAC/ 15A or 220-240

VAC/ 7A

Waste -

Post Processing Support breaking, Sanding, Pain spraying

Table 3: FDM Specifications

Material:

Several materials are available for the process including nylon, investment casting waxes, ABS plastic material, Water-soluble support materials, polycarbonate and poly(phenyl)sulfone (PPSF). ceramic and metallic materials are also under development. Model materials such as: ABS, PC, ULTEM(flame retardant high performance thermoplastic) Support materials such as: Soluble Supports (M30, M30i, PC-ABS, ABSi, ABS-ESD7(electrostatic dissipative), PC-ABS), and Breakaway Supports (PC, PC-ISO, ULTEM, PPSF) [14] [11]

Notes:

 Materialise-Online offers a build envelope of 600*500*600 mm with a range of accuracy 0.13-0.25mm

 FDM is fairly fast for small parts on the order of a few cubic milimeters, or those that have tall, thin form-factors. It can be very slow for parts with wide cross sections, however.

 Two build materials can be used, and latticework interiors are an option.

 Milling step not included and layer deposition is sometimes non-uniform so "plane" can become skewed. [14]

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2.1.4. Three Dimensional Printing (3DP):

Process:

 Z-Corp 3DP system:

3D printing (or simply 3DP) process has a cylinder for material support and a cylinder for building chamber. For each layer, a roller will spread and compress a measured amount of material powder over the building table. Instead of laser in SLS, a multichannel jetting head will deposite a liquid adhesive to bond the particles of powdered material together and shapes the 2D cross section of the object for that layer.

Once a layer is completed, the chamber goes down for the amount of defined layer thickness, getting ready for the next layer to be printed. The piston for the powder supply goes up incrementally to provide the material supply. After completion of the whole process, the final object will be removed and excess powder is brushed away leaving the green object. In this method support structures are not necessary since the powder bed can hold the overhangs. Z Corp.’s 3D printers use four colored binders: cyan, magenta, yellow and clear, to print in colors, just like a normal printer system. ZPrint software communicates color information to the printer within the slice data. [15]

3D printing’s advantage is its speed fabrication and low material cost. Z-Corp claims that its 3D printing technology is the fastest AM technique that is commercially available. Full-color 3D printing produces prototypes with the same coloring as the actual product, and the material is not toxic. On the other hand there are limitations on resolution, surface finish and available materials. Part fragility is also another issue.

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18 Figure 4: 3D Printing (ZCorp)

3DP (Z-Corp)

Build Size 236 x 185 x 127 254 x 381 x 203

Laser Power - -

Build Rate 25-50 mm3/hour

Layer Thickness 90 - 100 micron

Tolerance ± 0.2 mm

Energy Requirement 90-100V, 7.5A 100-240V, 15-7.5A

Waste powder recycling

Post Processing infiltrated

Table 4: 3DP (ZCORP) Specifications

Material:

High-performance Composites, Elastomeric Material (with rubber-like properties), Direct Casting Metal Material (a blend of foundry sand, plaster, and other additives), Investment Casting Material (a mix of cellulose, specialty fibers, and other additives), Snap-Fit Material (with plastic-like flexural properties). [15]

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 Support Structure is not necessary

 Objet 3DP system:

The Objet 3D printing process is different from that of Z-Corp. The Eden Family of Objet machines use jetting heads to lay the required amount of material, which are UV sensitive photopolymers. Just as the materials are laid on the building table, the UV light head which is integrated with other jetting heads cures the photopolymers. This means that laying and curing processes are done almost simultaneously. The jetting heads and UV light move along the 2D cross section of the object until one layer is done. Thereafter, the building tray will go down in the size of a layer thickness and the next cross section will be built.

Both model material and support material are laid on the build tray and fully cured by the UV light exposure. The support materials are removed by water jet after the object is completely manufactured. Materials are not toxic. During the process, whenever the machine is about running out of material, the material cartridges can be replace without any interruption in the process and this provides better efficiency. The integration of the liquid material inkjets and UV light head will provide better control of the material designation and alignment.

On the other hand, using UV technology and liquid photopolymers makes this method have waste material because of the polymerization. So the cured material cannot be reused.

See Table 5 for specifications of the process. [18] [19] [20]

3DP (Objet)

Build Size 250x 250x 200 490*390*200

Laser Power -

Build Rate 20mm3/h

Layer Thickness 16/30 micron

Tolerance 0.1-0.3

Energy Requirement 110-240 V, 1.5 kW, single phase

Waste Irreversible process cause in in-recyclability

Post Processing Support removal

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Transparent material, Opaque material, rubber like flexible material, ABS-like, polypropylene-like , rubber-like, High temperature resistance material, acrylic-based polymer. [21]

2.2. Metal Methods

2.2.1. Direct Metal Laser Sintering (DMLS)

Process:

Direct Metal Laser Sintering (DMLS) is one of AM techniques for metals. The same process of common AM methods happens here. In each step recoater, which is like a blade that dispatches material powder, sweeps a layer of powder. This metal powder is sintered before the build tray goes down in a defined size of layer thickness. Then the recoater dispatches new layer of material, making the next layer to be sintered.

Along with layered manufacturing of part, support structure is also built depending on th e shape of product. The more complex the component is, the more economical is the technique. Reduction in assembly time and increase in reliability by combining several parts and manufacturing them in one go, elaborates the savings from this method. It also offers the traceability by self labeling the products.

See Table 6 for specifications of the process. [22] [23] DMLS Build Size 250 x 250 x 215mm 250 x 250 x 325mm Laser Power 200W 400W Build Rate 2 - 4 mm3/s 2 – 8 mm3/s Layer Thickness 20 - 80 μm Tolerance +/- 0.1 mm Energy Requirement -

Waste 98% of unused powder is recycled

Post Processing support removal, shot peening,polishing, heat treating

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Stainless Steel , Maraging Steel, Cobalt Chrome Alloy, Aluminium Alloy, Titanium Alloy [24] [3]

Notes:

 Multimaterial opportunity exist.

2.2.2. Selective Laser Melting (SLM)

Process:

Selective Laser Melting (SLM) is an AM method that uses high powered laser to melt metallic powders together to shape the product from a 3D CAD data. Renishaw, the founder of this technique, uses a high powered ytterbium fibre laser to fuse metal powders. the same idea of AM happens. The recoater sweeps a layer of fine material powder and makes it ready for the laser to fuse them according to the 2D cross section of each layer under a tightly controlled inert atmosphere. When the part is made completely, it goes for the required heat treatment and post processing.

Typical applications for laser melting technology are functional testing of production quality prototypes, manufacturing of organic or highly complex geometries, low volume manufacturing of complex metal parts in specialist materials.

See Table 7 for specifications of the process. [25] [26] SLM Build Size 125 x 125 x 125 mm 250 x 250 x 300 mm Laser Power 100-200W 200-400W Build Rate 4 - 16 mm3/s Layer Thickness 20 – 100 µm Tolerance +/- 0.05 Energy Requirement 230 V 1 PH, 16 A

Waste 95% of the material is re-usable after refinement

Post Processing -

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22 Material:

Stainless steel 316L and 17-4PH, H13 tool steel, aluminium Al-Si-12, titanium CP, Ti-6Al-4V and Ti-6Al-7Nb, cobalt-chrome (ASTM75), inconel 718 and 625 [26] [25]

2.2.3. Electron Beam Melting (EBM)

Process:

Electron Beam Melting (EBM) technology builds fully dense parts from metal powder. The metal powder is melted by an electron beam (power of up to 3kW) and so the technology uses high energy to provide high melting capacity and productivity. Parts are free from residual stresses and distortions. The required temperature is specific for different alloys, and the electron beam maintains that temperature. Then for each layer, the beam melts contours of the 2D shape of part and finally the balk; i.e. the surface area within the contours.

Building parts at elevated temperatures results in stress-relieved products with good material properties. Also the process occurs in a vacuum space to maintain the chemical specification of the powder material. Arcam, the owner of EBM patent, claims that their machines provide parts with excellent properties for strength, elasticity, fatigue, chemical composition, and microstructure.

See Table 8 for specifications of the process. [27] EBM

Build Size 200x200x180 mm 200x200x350 mm

Laser Power 50–3000 W

Build Rate 45-66 mm3/s

Layer Thickness 50 micron

Tolerance +/- 0.2 mm

Energy Requirement 3 x 400 V, 32 A, 7kW

Waste 95% recovery of unmelted powder

Post Processing Support removal, Grit blasting

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Released Materials (which are basic common materials with detail defined properties by Arcam Company):

 Titanium Ti6Al4V

 Titanium Ti6Al4V ELI

 Titanium Grade 2

 Cobalt-Chrome, ASTM F75

Additional Materials (which are not as specified as released materials, but have been used in cases successfully)

 Titanium aluminide

 Inconel (625 & 718)

 Stainless steel (e.g. 17-4)

 Tool steel (e.g. H13)

 Aluminium (e.g. 6061)

 Hard metals (e.g. NiWC)

 Copper (e.g. GRCop-84)

 Beryllium (e.g. AlBeMet)

 Amorphous metals

 Niobium

 Invar [27]

Notes:

 Comparatively to SLM and DMLS, EBM has a generally superior build rate because of its higher energy density and scanning method. [27]

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2.2.4. EasyCLAD

Process:

EasyCLAD uses a nozzle at which the metallic powders are injected and concentrated at center end point of it where a laser beam is placed. The laser beam fuses the powder and creates a dense and uniform deposite of metal. The process is protected by a neutral gas to prevent oxidation. That makes the metallurgical properties of products good in comparison to forging and casting.

Manufacturing functional parts, repair worn part, work on machined part, multi material with powder mixing are the advantages of using this technology.

See Figure 5 for a schematic illustration of the method. [28]

Figure 5: EasyClad

EasyCLAD

Build Size 400 x 350 x 200 1500 x 800 x 800

Laser Power 300 - 500W 750 - 4000W

Build Rate up to 85 mm3/s

Tolerance +/- 0.1-0.5

Energy Requirement 400VAC, 3phase , 17.3 kW

Waste Recycling of the powder

Post Processing polishing, blasting, micro shotpeening

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All kinds of metallic material can be atomized as powder grains. Like: TA6V, TiSn Alloy, INCO 718, INCO 625, Stellite 6, 12, 21, 25, Tool Steel, Waspalloy, Hatfield steel, ... [28]

2.2.5. Laser Consolidation (LC)

Process:

Laser Consolidation (LC) uses a nozzle for its laser and a nozzle for material feed. This technique requires a solid base (called substrate) to build the part on it. A consolidated laser is used to creat a molten pool as the metallic powder is fed to it by the other nozzle at the same time. The first layer is made creating a molten material as laser and powder injection nozzle move along the cross section of the object. The molten material solidifies rapidly as the nozzles move away.

Products manufactured by LC are fully dense and free from cracks as they are fully melted. Good dimentional accuracy and mechanical properties are the benefits of using this technology. [29]

See Figure 6 for a schematic illustration of the method. [30]

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26 Laser Consolidation Build Size 500*500*500 Laser Power 20 to 300 W Build Rate - Layer Thickness - Tolerance +/- 0.05 Energy Requirement -

Waste Using 99.5% of materials

Post Processing finishing

Table 10; Laser Consolidation Specifications

Material:

Laser Consolidation adds high strength alloy (super alloy) features or tool steel on inexpensive metals, reduces expensive alloy use. [30]

Notes:

 multimaterial possibility exist.

2.2.6. LaserCusing

Process:

The term LaserCusing comes from CONCEPT for the letter C and the word FUSING. It says that the process uses fusion and complete melting to creat parts. The process is owned by Concept-Laser Co.

The principle is familiar; a metal powder surface is dispatched over the build table. The laser fuses the cross section of the required layer and the process repeats until the final product is completed. Concept-Laser Co. clarifies that the special thing about LaserCusing machines is the stochastic exposure strategy in line with the “island principle”. The segments of each cross section in an individual layer are called “islands”. They are made in succession which result in reduction in part’s inert stresses.

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and for mass production tooling.

See Figure 7 for a schematic illustration of the method. [31] [32] [33]

Figure 7: LaserCusing LaserCusing Build Size 250*250*280 Laser Power 200 Build Rate 0.5 – 5.5 mm3/s Layer Thickness 20 - 80 µm Tolerance +/- 0.05

Energy Requirement 400VAC, 3phase, 22.1 kW

Waste 100% compatible for re-use

Post Processing Micro blasting

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28 Material:

High-grade steels, Hot-work steels, Stainless hot-work steels, Aluminium alloys, Nickel-base alloys, Titanium alloys, Pure titanium, Cobalt-chromium alloys, Precious-metal alloys. [31] [32] [33]

2.2.7. Laser Engineered Net Shaping (LENS)

Process:

Laser Engineering Net Shaping (LENS) uses a high power (500W to 4kW) laser to fuse powder metals and shape a dense product. It has a closed-loop process control to ensure the accuracy of part manufacturing.

The metal powder is fed to the correct position over a substrate by means of one or more feeders. The powder is deposited either by gravity or by pressure of an inert gas. The laser on the other hand focuses a beam and creats a pool on the substrate or the previous layer. The metal powder is absorbed into the molten pool. As the laser and powder feeder move along the cross section of the object, the first layer is made. The whole process is done in a sealed argon filled box to maintain the oxygen level in less than 10 parts per million (ppm) to have the parts clean and prevent against oxidation.

The LENS technique has the possibility of using composite powder mixture. high cooling/solidification rate is another advantage. On the other hand, severe overhangs are an issue because of a lack of a different material for support structures.

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29 Figure 8: Laser Engineering Net Shaping

LENS

Build Size 300 x 300 x 300 900 x 1500 x 900

Laser Power 500W 1000W

Build Rate 5 mm3/s upto 60 mm3/s

Tolerance ± 0.125 mm

Energy Requirement -

Waste 80% powder utilization

Post Processing -

Table 12: LENS Specifications

Material:

variety of metals including titanium, nickel-base super alloys, cobalt, Inconel, stainless steels and tool steels. [34] [35]

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30 Notes:

 Direct Metal Deposition (DMD) is the same technology (See Figure 9). A difference is in the building capacity that in DMD passes 2meters. But the structure is quite the same, so it’s not explained in detail in this report. [37] [38]

Figure 9: Direct Metal Deposition

2.2.8. Digital Part Materialization (ProMetal)

Process:

The process of Digital part Materialization is the same as 3DP (Z-Corp). The difference is that here the approach is used for metallic and some non-plastic powders. So this technique works with metal powders and a chemical binder to shape the product.

For sand parts, first the sand powder is spread over the table, and then a binder catalyst is dispatches over the sand. When the binder is injected over the binder catalyst from a print head jet (based on the cross section shape), a polymerization happens between the binder and the catalyst and as a result the sand particles bond together. So the curing process i s done with no need of heating. The process is repeated layer by layer until the object is built. The excess sand is removed from the part and it’s ready to be used for casting or other functions. For metal parts, it’s a bit different. After the metal powder is dispatched over the build table, the print head jets the binder selectively over the metal powder surface based on the cross section of the object. The layer dries and the process is repeated until final product is completed. The excess metal powder is removed, but the part is so fragile, known as “green

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state”. It should go for a sintering process where the binder is burned and metal particles are melted and hardened. It gets 60% dense and it usually goes for an infiltration process to get full density.

For glass parts, the process is the same as metal parts, but it doesn’t need the infiltration process.

Less waste and patternless sand casting possibilities together with the possibility of complex internal geometry availability are the benefits of this method. However, the time consuming post processing (specially for the metal and glass parts) are the weaknesses of it.

See Table 13 for specifications of the process. [39]

Digital Part Materialization

sand metal Build Size 1800 x 1000 x 700 750 x 400 x 400 Laser Power Build Rate 16500 to 30000 mm3/s 2000 mm3 /s

Layer Thickness 280 to 500 micron

Tolerance +/- 0.125

Energy Requirement 400 V / 3 phases, 5 kW

Waste -

Post Processing -

Table 13: Digital Part materialization Specifications

Material:

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2.2.9. Other Methods

There are number of other methods and there are new ones generating. Although the concept is the same, but they combine different technologies and generate different part specifications as a result.

Some other methods are Ultrasonic Consolidation (UC) which is based on ultrasonic welding of the metal foils. This is one of the hybrid technologies that combine additive and subtractive methods by joining metal sheets and contour milling respectively. Ultrasonic oscilation together with pressure welds the metal sheets, and then a CNC mill will shape the required countor of cross section. Foils of Al-Cu alloy, Ni-base alloy, Inconel, Al alloy can be used for this method. [40] [41]

Another method is Ion Fusion Formation (IFF) which is DMD-like process but it uses a plasma welding torch that generates very hot ionized gas to melt the deposited metal. One advantage of this method has been recognized as the possibility of having coating application in build process. [42]

The Laminated Object Manufacturing (LOM) from Helisys Inc. and many other methods are developed and under development. But in this project has not concentrated on them.

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3. Capabilities and Opportunities

3.1. Overview

Additive Manufacturing has been used initially for prototyping. In fact it was the first and successful area of application for AM which made it categorized in Rapid Prototyping concept. Prototypes which were used for visual understanding or presentation models were later used for testing operations also, and current application of this technology is heading more and more towards part production, besides prototyping.

The main barriers, which are challenges that prevent AM to be used for part manufacturing widely or vast its market, are:

- material,

- cost (of production due to materials, machines…) and - surface roughness and accuracy

There are a lot of concerns about material improvements (e.g. in Loughborough University) and the range of materials which could be used for AM is growing. But it is still a challenge. While there is opportunity for new kind of materials, mixture of materials (for instance in EasyClad and Laser Consolidation Technologies) and better microstructures of materials, there exist problems concerning material tolerability in terms of weight, temperature and force. However, every year there are a new group of materials introduced for AM and refinements of the properties. A concern in this area is to create a standard for material. Standard material will later allow for Finite Element Method (FEM) which is a part of Product Lifecycle where virtual tests are executed. Standard material will also make the end

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user trust the product built by AM method. ASTM International prepares two meetings per year to review the progress of this standard establishment.

The cost of producing parts is high if AM is used for large quantity of products, at least by now. With better materials, faster machines this problem can be solved or mitigated. This technology works better than conventional methods if a small batch is going to be produced. Because the cost of making a one off product with conventional machines will need tooling which is the main cost, AM can take this responsibility since it does not need tooling thanks to its layer by layer manufacturing method. It also beats traditional manufacturing methods when the part geometry is complex or even impossible to build with classical techniques. But when it is a mass production, the cost of tooling becomes inconsiderable. However it is assumed [43] that with the market going toward customization and more innovative products with shorter life cycle, and with less RM labour cost this problem may become less than an issue in future. [44]

An issue of the AM techniques is surface roughness and accuracy that is not sufficient for part production unless some kind of post-processing is added to the manufacturing chain (sanding, pinning… or even machining). However some companies like EOS claims that customers can use the product after simply a shot pinning process. But generally, the need to have some finishing processes after making the product by AM, will result in an increase in cycle time and cost. But hybrid machines can solve the problem. As an example the Ja panese Matsuura LUMEX Avance 25 which combines metal sintering with subtractive milling process after every single layer if needed, was introduced at Euromold 2011 (an event related to AM techniques). This machine gets benefits of machining accuracy and surface roughness and flexibility of additive manufacturing. [45]

These three main challenges which AM technology is facing will become solved with better machines with faster and more accurate lasers which combining with better material can overcome the current problems and barriers. Despite, producing end use products (considered to be the largest application of AM in future) is more challenging than just prototyping (Figure 10). So it surely takes time to become fully accepted in industry as a new generation of production. [46]

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T. Wohlers (RapidTech 2009) claims that although the cost of product coming out of AM is higher than conventional methods, this higher cost can be justified by sooner delivery of product to costumer, design flexibility and immediate customization. In addition, expensive operations, time consuming processes, or labor intensive methods are now more comfortable with AM. In the following sections, some aspects of new applications of AM are presented.

3.2. Direct part manufacturing

Direct part manufacturing using AM is far from displacing mass production, but it is compatible in some special kind of industries such as in:

- ear hearing aids, - medical implants, - dental equipment, and

- furniture, fashion products and footwear

Such industries are good market for AM since they don’t need high amount of products, because they are normally customized to specific consumers.

On the other hand, the production of parts using AM is expected to far surpass the current scale of rapid prototyping. According to T. Wohlers [44] the ratio of prototypes to production parts is typically 1:1000 or much greater.

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- Part consolidation

- Reduction/elimination of tooling

Part consolidation reduces assembly, tooling, inventory, waste and inspection costs with AM’s high flexibility in geometric complexity design which defines the main advantages of direct part manufacturing. Part consolidation will also increase the opportunity of making more complex parts while Reduction in assembly and sub assembly means less labor and less cycle time.

Reduction of tooling eliminates the design considerations and economics of part manufacturing which are the restrictions of conventional production. So the possibility of design will become restricted only to design tool (CAD) limitations.

However, having AM as part production methods brings out new aspects for designers, like considering:

- minimum wall thickness, - achievable tolerances and - preferred build orientation.

They can also think “outside of the box” because of new design freedom.

To have AM as production system one must also consider build speed and capacity in conjunction with machine price. To have AM more viable in production area, these aspects should be improved. [44]

3.2.1. Consumer products

In the area of consumer products, furniture, lightning, office accessories, fashion products, jewellery, art and gifts are in attention of AM market.

Consumer related AM brings out the opportunity for consumers to design their own desired products or to buy custom and edited products, and designers to quickly step in market after making their prototypes.

Currently there are some opportunities regarding online ordering for parts from customers. They will define their products using a CAD system. Some user-friendly design support tools are developed, e.g. Google SketchUp, FreeForm from Sensable, and Spore Creature Creator

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system needs training and not all the people are used to work with such systems.

A number of user-friendly design support tools have been developed but there is no guarantee that the designed shape would be produced. On the other hand if the product is going to be so complex, then it may need professionals to design it because they have lots of internal parts and need engineering ability to make them. Some design toolkits, however rare, but exist. For example Rapid Shell Modeling software for hearing aid design from Materialise have capabilities like automatic placement of components, interactive previews, and automatic quality checks and use a model either coming from a consumer or from a 3D scanner.

Examples are consumer designed products are pasta boxes (by Billy Zelsnack) and headphone wrappers (by Eric Weinhoffer) which are ordered by consumers who designed them for their everyday comfort. Development of comfortable and easy-to-use 3D modelling systems could turn two billion Internet users into potential AM customers in this way.

People can also buy the customized products with some modification and edition options. FigurePrints company makes the avatars from game characters and have gained a good market in this area so that customers can have their orders of avatars in colors. FigurePrints gets the data information of avatars which are normally stored in 3D file format in games, to produce the products by 3D printing.

A big potential users of AM machines are new entrepreneurs who have innovative ideas in mind and want to show up in market. These people are mostly concerned about the viability of the material and the surface finish that the system provides for them. They will buy an AM machine when they get sure that the machine will represent what they want so that they can quickly get into market. So depending on their product complexity, material and required accuracy they decide to work with what kind of machine. Wider range of material or lower cost of machine or improvement in machine features will vast this market.

Another challenge in this area is that consumer products using AM machines are limited to be small due to the small production volume and cost of production that this technique has by now. [44]

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3.2.2. Industrial Products

Here some examples of use of AM part production in some industries are represented:

 Aerospace: several parts for satellites are made by AM methods like laser sintering. LENS technique’s most common application is for direct part manufacturing for Aerospace.

 Automotive industry: many assemblies such as audio/video assembly or headrest assembly and engine control units are made by companies that use AM.

 Machinery industry: reduction in weight is in consideration. Using light weight material by AM to produce drag chain links for mining industry is an example.

 Medical industry: custom-made products in is often a necessity; e.g. cranial plates, artificial jaws.

 Manufacturing industry: jigs and fixtures, templates, gauges, drill guides are types of manufacturing tools which are normally expensive because they are customized and are produced in a small number of items. In this area, AM has gained a good attention and is successful in that. [44]

3.2.3. Tooling

A big market that AM has started as its initiation for direct part manufacturing is tooling. Currently many methods such as DMLS, SLS, SLM, EBM, ProMetal, LENS, DMD, and UC are commercially available for direct tooling and metal parts. In addition to jigs, fixtures and gauges, another area is tooling such as dies and patterns for casting. For example, almost any type of AM methods can produce patterns for investment castings. For complex shapes, AM patterns bring out a huge saving in time and cost in comparison to machining. According to research the number of companies which adapted their systems to use AM patterns for casting had an increase from 5% to 95% in the last decade.

There are two categories of using AM in tooling:

- Indirect approach: includes patterns which are used to make dies and molds (master patterns).

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These are like patterns’ indirect assist in tooling. Patterns used in silicon rubber tooling, epoxy-based composite tooling, spray metal tooling and many other methods are usually made by AM.

For direct tooling approach, EOS, ProMetal, 3D Systems, and ZCorp have offered systems that are capable of creating molds directly. However they haven’t gone through sand casting except ProMetal. Also POM and EOS systems produce dies for die casting, but because of required pressure and temperature in die casting, it seems improbable that AM will replace machined tooling in this area in the near future unless a new generation of materials is developed for.

One advantage of using AM for direct tooling is that it will reduce the number of steps required to make the tooling; i.e. to produce dies directly will reduce the time of creating molds and dies because there is no need of making pattern. It also increases geometric inaccuracy compared to pattern-based process.

Another advantage of using AM for tooling in dies is that because of its rougher surface in comparison to machined parts, it’s better for cooling systems in dies. The rougher surface in cooling channels increases the heat transfer which is called conformal cooling.

On the other hand, Optomec and POM have used AM to produce direct molds and dies with copper cores. Copper is highly thermally conductive and so it better transfers out the heat. The outer side is made of thermally resistant hard material. Thus it’s good to construct dies in this way for a better thermal management.

The strength and weaknesses of conventional machining such as CNC machines and AM machines for tooling should be considered for any case. It should be decided based on complexity, surface quality, allowed design changes, material and time to market.

Sometimes maybe a hybrid solution is useful, when inserts can be produced by AM and the other parts with CNC machines. In this way we can take advantage of both systems. For example a most common way of using hybrid system is to use DMLS for production of cores and using CNC for cavity part. However in this case also a challenge is the incompatibility of the tolerance of two systems, normally the accuracy of AM machines are not the same as conventional machining. Also material properties used by two systems differ (which clarifies

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the need for standardization). So, one should consider this in the design of the hybrid system. [44]

3.3 Rapid Manufacturing

A widely accepted definition for Rapid Manufacturing (RM) is generated by Neil Hopkinson at Loughborough University. He defined it as “The use of a CAD-based automated additive manufacturing process to construct parts that are used directly as finished products or components”. Therefore, as it is mentioned in the previous subchapter, producing consumer products, tooling, or industrial products are all included in the RM area, if they are produced directly from an AM method. [47]

RM has been considered as one of the most exciting methods for 21th century which is progressing fast. The wide range of market that it covers consist of aerospace, automotive, medical, healthcare and consumer products such as furniture and shoes.

Despite all the examples provided before, there is still more progress and development to be done for RM to be used widespread.

3.3.1. Design freedom

The major driver for using RM is in design area since it offers the capacity of producing parts with unlimited geometry complexity. Conventional manufacturing’s cost is highly dependent to the geometry complexity. RM however is not only independent to complexity, but also is capable of production of every shape.

Lower cost combined with design freedom will benefit both manufacturer and customer which mean better customer satisfaction.

Currently, designers should be well familiar with the design constraints and geometry feasibility considering all the production steps (manufacturing but also assembly, maintenance, disposal…), which is called Design for Manufacturing and Assembly (DFMA). DFMA puts a step before designing level, at which manufacturing requirements and constraints are represented to designer so that he can design the required product in a way that it won’t be hard to manufacture. But with the help of RM the only limitation is the designer’s imagination and the design tools. So Design-for-Manufacturing is shifted to Manufacturing-for-Design using RM.

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and thus will remove the barriers such as wall thickness limitations, sharp corner avoidance, need for ejection pins.

In addition, RM will make it possible to create features which are not possible by conventional method or it requires high-cost tooling complexities and set ups. These features include blind holes and undercuts.

Moreover, there is no necessity of considering split lines especially in comparison to injection molding which needs experience to place such features and sometimes it is not possible. RM will hide the constraints of Design for Assembly in the area at which it reduces the number of parts which are going to be assembles. In other words it is able to manufacture sub-parts consolidated in only one part. It also reduces the time of assembly by integrating assembly process with sub-products’ production.

3.3.2. Mass Customization

The less the batch size, the more effective is RM. Although the range of batch size is increasing year by year, but still in comparison to conventional systems, RM is well serving products of one or few but with high details and high profit per product unit. Using Conventional methods for production in low volume will require a high cost of tooling, set up, etc. But if RM is used for such end use products, then it will be more efficient to produce. An era, in which RM has taken place in some companies, is body fitting products. Especially in car manufacturing, this area has been under consideration, but it was so expensive because of labour cost and tool cost since products should be configured for each customer and it will make different product, in this case car seats, from customer to customer. So, highly mass-individualized products cannot be produced conveniently with non-additive methods. These boundaries made such products far from public eye because they were considered as highly customized and expensive products. But with the help of RM producing such products which are ergonomically friendly with body can be widely provided. Mass customization is decided to be done in automotive industry, car seats, for MG Rover Group. [47]

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3.3.3. Added functionality

Additional functionality in a product will help it to be more advantageous in use. Including porosity in parts produced for medical implants to improve cell-ingress possibility or have porous parts to have less weight are some examples of added functionality. RM with its additive layer technology can make it possible.

One market sector which is so capable of using RM but is not conquered so much is textile. With the help of this technique new styles of garments can be produced which are innovative both in texture and garment body fitting structures. This will lead to have more functional garments. However there are some problems in using the new method for this area. Some problems include RM systems’ resolution and 3D data generation incapability. Loughborough University has used SLS technology to make fabrics however. But still there should be more investigations on smart textile production. [47]

The on-going potential includes multiple weaving, assembled garments, textiles with built in functionalities.

3.3.4. Process improvements

RM provides the opportunity of having distributed manufacturing. This possibility will let the manufacturer to make the product more near to customer, so that the packaging, transportation, and lead time will be decreased thanks to the decentralization of the production system.

An example in this area is the pierce of RM in game industry where the customer is widely distributed. Customer will order the character of the game that he wants and manufacturer can produce the same product in multiple locations being protected from the single source production system. In single source production the company will face a lot of investment having same tooling and instrument in different places; but since RM does not require any tooling, it is free from such a risk.

Another thing to be mentioned is that the need for a huge initial investment most of the times prevents new products to enter the market. With the help of RM there is no need of consideration for tooling or moulds. In other words, it not only removes the need for tooling,

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tool producers, etc. this will make this technology a disruptive system for other methods. [48]

3.3.5. Environmental drivers

RM normally uses less energy than conventional systems such as heavy presses, injection motors and melting systems. This less energy usage make this method of manufacturing competitive since these days there is always speaking about energy limitations.

Another area at which RM can benefit is waste. It is obvious that RM produce less, if any, waste because it uses additive methods instead of subtractive methods. The ration of input material to output product material usage is so high in machining processes. Although in some methods there exists waste generation in terms of support material and used powder, many other methods are more than 95% material efficient in terms of reusability or recyclability.

As it is mentioned previously, distributed manufacturing will result in less packaging and transportation which will be translated to less haulage. This makes this method to a more environmentally friendly method since the cost of fuel and natural resources is increasing. As it’s discussed on better functionality of the products manufactured by RM, another advantage is gained which is defined as the term optimized product. An optimized product can be lower weight product or better featured product. Either way it will result in reduction of energy and natural resources consumption. [48]

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4. Rapid Manufacturing in Supply Chain

4.1. RM Overview

Rapid Manufacturing (RM), as it is defined before is a method to use Additive Manufacturing (AM) for end use products. But RM is not the only application of AM (sometimes called Additive Layer Manufacturing processes). Another application is for prototyping.

As it’s mentioned in chapter 3 the initial concept of RM started from Rapid Prototyping (RP). In RP, the purpose is to quickly make, to use as a conceptual model, test the functionality or any other processes that include first released product evaluations. For prototypes which are going to be used as a sample part or to test a function, it is not economical to put cost on making moulds or manufacture it with common methods of manufacturing. These methods are not economical, but RP not only saves money to build a testing part, but also makes it possible to make any part with any design. In addition RP does not only use AM, it may also use other rapid methods such as High Speed Milling.

The main advantage of RP is its ability for one-off jobbing. It is expensive to manufacture and set-up traditional production tooling and moulds to produce a prototype, especially if it is revealed that the proposed product is not functional and needs redesign, it becomes a high risk investment. By means of RP the problem of time and money wastage can be mitigated considerably. However some prototypes do not have the accuracy or functionality of end use appliance. It of course depends on the desired accuracy and requirements of product.

While the advantages of RP were taking place in production units, another concept started to appear: Additive Manufacturing. It uses 3D CAD models as an input and produces the product layer by layer. So AM is included in RP, but it is not the same, since RP does not

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traditionally used to refer to prototyping using AM techniques although that is currently changing in the direction of clearly differentiating the terms RP and AM.

AM is generally suitable for production of functional end use parts in small volumes/quantitites, as mentioned in chapter 3; but it is just a technique, and a technique can be used either in design of experimental models, or in end-use product manufacturing. This means that one application of the AM is in prototyping, namely Rapid Prototyping, while the other application of it is in production line, namely Rapid Manufacturing.

RM is the application of AM in fabrication, so it shapes the system of production based on Additive Layer Manufacturing. This is the maturity of this concept up to now and it is growing more and more to take place in many industries; aerospace, health, casting, etc. the application of it has been discussed in subchapter 3.2.

The main advantages of RM, is that it directly makes the product from a 3D data model with additive methods and their advantages (regarding to material waste, flexibility, speed….). So if the advantages can become compatible to production systems and disadvantages become solved by supporting methods, then what will be the barrier for its application? Of course everything depends on product type and required features. Sometimes RM doesn’t offer required product lifetime and sometimes it doesn’t bring out the required accuracy. There should always be evaluation of pros and cons, product by product.

4.2. Supply Chain Principles

A supply chain starts from raw material supplier to customer and involves all the people and machines with information and activities among them. To explain the concept regarding managing of the chain of production, the following concepts are explained.

Lean Concept in production:

Lean production is defined as “an adoption of mass production in which workers and work cells are made more flexible and efficient by adopting methods that reduce waste in all forms”. [49] Hobbs [50] mentions the production of the “one unit at a time” to eliminate delays such as queue time in lean concept. The reduction of waste in time, space and cost with better configuration of the man-machine system and resource designation is the main

Additive Manufacturing: State-of-the-Art, Capabilities, and Sample Applications with Cost Analysis