**3. Methods used to create small and medium parts in MAM by factories**

Additive Manufacturing (AM) technology, in general, qualifies to build fully functional part in one process without the need for metal removal process which would waste significant amount of raw material. In addition, this process can give more flexibility to the designer in building complex geometry part. Compared to the AM method, the Traditional Manufacturing Technology (TMT) (subtractive manufacturing) has several manufacturing processes. The first level mostly deals with creating the stock material (raw material), and the next level is responsible for material removal process which usually includes several manufacturing processes to obtain the final parts. Currently, the diversification of AM method can be used with

**243**

*An Investigation of the Metal Additive Manufacturing Issues and Perspective for Solutions…*

**3.1 Powder bed fusion meal additive manufacturing (PBF-MAM) process**

variety of materials; it is possible to manufacture metallic parts with high quality

There are two main categories in MAM method: Powder Bed Fusion (PBF), which is also known as Layer Based Metallic Additive Manufacturing, and Direct Metal Deposition (DMD) [24]. PBF method is based on inert atmosphere or partial vacuum, and it produces parts layer by layer with thickness of 15–20 μm. The energy source for this MAM category is laser or electron beam which is used to fuse and bind the material (powder) on each layer. Whenever the binding of a layer will finish, the table will move down, and new layer of powder will be poured on the previous one and so forth until the part is completed. For preventing the molten (sintered) between one layer and another in substrate, there is a need to use support material which can be made in the pre-processing phase from

The Selective Laser Sintering (SLS) was the first powder-bed based AM process. This process was invented by Ross Householder in 1979 and the first material used in it was amorphous polymer powder or semi-crystalline [3]. The power source in this process was laser, and it was used to sinter (bind) the powder material. First, the model of the printed part needs to be defined by CAD design, the thickness of the layer needs to be specified, and the resulting model will be transferred to the machine software to orient the CAD model in the 3D printer software. The MAM process starts by aiming the laser on a profile representing the shape of the first layer as described by the CAD model from the base of the printed part. The laser power binds the powder layer by layer to create the final part. The new materials which could be produced by this process include ceramic and metallic alloys. The last step in this process is placing the printed part in an oven to remove the polymer (used to bind the particles), sinter the part, and improve the support material. Since this process has high production rate, it is used for rapid manufacturing or prototyping [24, 25].

Direct Metal Laser Sintering (DMLS) process was developed by Electro Optical Systems (EOS) in the 1990s. It was used purely for building metallic parts without using the polymer to bind the particles. High power laser was used to melt the metal powder in two dimensions layer by layer. This process offers printed parts with complex shape and geometry with a reasonable cost. The DMLS process utilizes a variety of metals and alloys and operates on the same concept of SLS AM process. The residual stress in product parts is an issue with this process and will be dis-

The Selective Laser Melting (SLM) additive manufacturing process is designed to fully melt the metallic powder by using high power-density laser. Therefore, it is considered more powerful and produces parts with better quality and less porosities than either SLS or DMLS processes. At the same time, it works on the same powderbed concept of both techniques. Because of high temperature of the laser source, shrinkage and thermal distortion are likely to influence the printed parts [27].

*DOI: http://dx.doi.org/10.5772/intechopen.93630*

the same material [24].

*3.1.1 Selective laser sintering*

*3.1.2 Direct metal laser sintering*

*3.1.3 Selective laser melting*

cussed in Section 6.2.1 of this chapter [26].

and complex geometry by direct and indirect AM method.

*An Investigation of the Metal Additive Manufacturing Issues and Perspective for Solutions… DOI: http://dx.doi.org/10.5772/intechopen.93630*

variety of materials; it is possible to manufacture metallic parts with high quality and complex geometry by direct and indirect AM method.

## **3.1 Powder bed fusion meal additive manufacturing (PBF-MAM) process**

There are two main categories in MAM method: Powder Bed Fusion (PBF), which is also known as Layer Based Metallic Additive Manufacturing, and Direct Metal Deposition (DMD) [24]. PBF method is based on inert atmosphere or partial vacuum, and it produces parts layer by layer with thickness of 15–20 μm. The energy source for this MAM category is laser or electron beam which is used to fuse and bind the material (powder) on each layer. Whenever the binding of a layer will finish, the table will move down, and new layer of powder will be poured on the previous one and so forth until the part is completed. For preventing the molten (sintered) between one layer and another in substrate, there is a need to use support material which can be made in the pre-processing phase from the same material [24].

#### *3.1.1 Selective laser sintering*

*Concepts, Applications and Emerging Opportunities in Industrial Engineering*

in mechanical properties of powder layer [18].

process is qualified for aerospace applications [21].

[16]. Jun Du et al. developed and tested newly proposed AM method based on Metal Fused Coating Additive Manufacturing (MFCAM). This method is a combination of Fused Metal Coating and Laser Surface melting (bed-based process). They used small parts of 7075 aluminum alloy to prove the experimental work [17]. Christoph et al. developed a computational model to study the critical influence of powder cohesiveness on powder recoating process. Researchers focus on the relationship between the powder particle size and powder layer quality. Small parts of Ti-6Al-4 V were used in this study. As results from this study, decreasing the particle size (increase cohesiveness) will decrease the powder layer quality with highly non-uniform surface profile. In addition, the particle size plays the main role

Lawrence et al. reviewed the development of droplet 3D printing (Droplet Additive Manufacturing). This process was used in producing large and small sized parts for three decades. They discussed the issues regarding process optimization, product structure and properties influenced by oxidation. Their investigation ended up with the conclusion that using the Droplet 3D printing process can change the structure of product, thereby reducing the weight, cost, and increasing strength [19]. Mercado et al. studied the stability and microstructure of large sized parts of nickel-base metal matrix produced by building Plasma Transferred Arc Additive Manufacturing (PTAAM) system; this process can build high scale 3D printed parts. Their study concluded that the PTAAM system has capability to build 3D printed part on nickel-base metal matrix with tungsten carbide wear resistance [20]. Yoozbashizadeh et al. developed new Novel AM method to fabricate medium sized bronze-aluminum parts with Ceramic. This process has been performed by combining Thermal Decomposition for Salt (TDS) method with Powder Bed AM (PBAM) to produce Metal Matrix Composite (MMC). Ceramic particles have been created from TDS, and then combined with bronze-aluminum to create MMC. This

Livescu et al. faced challenges of AM tantalum represented by high melting temperature via utilizing Direct Metal Laser Sintering (DMLS) method. Deposition parameters such as deposition speed and building direction have been analyzed as significant factors to influence on Grain morphology, grain size, crystallographic, and deposition porosity. The authors' results showed that the obtained structure was columnar along the building direction. The deposition condition (speed) has significant effect on microstructural variation. The strip width has the main influence on grain growth [22]. Thao Le et al. tried to combine additive and subtractive strategies to manufacture new part (final part) from end of life part (existing part) by using several additive and subtractive manufacturing processes. They obtained good mechanical properties in final parts. The methodology of combining additive and subtractive manufacturing can be applied by generating process plan for both of them [23].

**3. Methods used to create small and medium parts in MAM by factories**

Additive Manufacturing (AM) technology, in general, qualifies to build fully functional part in one process without the need for metal removal process which would waste significant amount of raw material. In addition, this process can give more flexibility to the designer in building complex geometry part. Compared to the AM method, the Traditional Manufacturing Technology (TMT) (subtractive manufacturing) has several manufacturing processes. The first level mostly deals with creating the stock material (raw material), and the next level is responsible for material removal process which usually includes several manufacturing processes to obtain the final parts. Currently, the diversification of AM method can be used with

**242**

The Selective Laser Sintering (SLS) was the first powder-bed based AM process. This process was invented by Ross Householder in 1979 and the first material used in it was amorphous polymer powder or semi-crystalline [3]. The power source in this process was laser, and it was used to sinter (bind) the powder material. First, the model of the printed part needs to be defined by CAD design, the thickness of the layer needs to be specified, and the resulting model will be transferred to the machine software to orient the CAD model in the 3D printer software. The MAM process starts by aiming the laser on a profile representing the shape of the first layer as described by the CAD model from the base of the printed part. The laser power binds the powder layer by layer to create the final part. The new materials which could be produced by this process include ceramic and metallic alloys. The last step in this process is placing the printed part in an oven to remove the polymer (used to bind the particles), sinter the part, and improve the support material. Since this process has high production rate, it is used for rapid manufacturing or prototyping [24, 25].

### *3.1.2 Direct metal laser sintering*

Direct Metal Laser Sintering (DMLS) process was developed by Electro Optical Systems (EOS) in the 1990s. It was used purely for building metallic parts without using the polymer to bind the particles. High power laser was used to melt the metal powder in two dimensions layer by layer. This process offers printed parts with complex shape and geometry with a reasonable cost. The DMLS process utilizes a variety of metals and alloys and operates on the same concept of SLS AM process. The residual stress in product parts is an issue with this process and will be discussed in Section 6.2.1 of this chapter [26].

#### *3.1.3 Selective laser melting*

The Selective Laser Melting (SLM) additive manufacturing process is designed to fully melt the metallic powder by using high power-density laser. Therefore, it is considered more powerful and produces parts with better quality and less porosities than either SLS or DMLS processes. At the same time, it works on the same powderbed concept of both techniques. Because of high temperature of the laser source, shrinkage and thermal distortion are likely to influence the printed parts [27].
