**2. Literature review**

Additive Manufacturing (AM) was employed for the first time in 1987, through use of a stereolithography (SLA) system to build the first three-dimensional model (solidifying a thin light-sensitive layers liquid polymer by using ultraviolet [UV] rays) [3]. Starting in 2017, manufacturing companies focus began orienting manufacturing processes in a new direction; these companies started to depend on AM methods to produce parts. AM methods have grown over the last year, becoming the key area of interest for many such companies [4]. However, the main focus of this literature review related to the MAM method for producing small and medium metallic parts and asking what the main issues and challenges facing this process are.

This concerns frameworks for selecting the right MAM process, adjusting support material, building direction, geometry (complexity) of the part, and printing orientation. Some of these challenges can interrupt the process itself and cause other issues (such as defects in the final manufactured product, including: porosity, variation in mechanical properties, microstructure evolution, residual stress, and crystalline phase heat accumulative and thermal behavior). Inspection difficulties in MAM have been investigated, with the conclusion that inspection ability and metallurgical validation of highly optimized shape must be integrated with product design and process parameter during and after the CAD design [5]. Several challenges facing MAM methods have been investigated, such as financial consideration, certification and regulation, repeatability, and skills gap. Some suggestions have been made to eliminate these challenges and this researcher discusses further potential solutions for these challenges [6]. Serena et al., studied the difficulties and challenges to be facing when designing for metal additive manufacturing in Selective Laser Melting Additive Manufacturing (SLM AM) process for producing professional sport equipment (medium size cam component). These difficulties, such as functionality, manufacturability, assembly, and printability. All of these difficulties should be considered in the designing of metal additive manufacturing. They present many suggestions to enhance the redesign and printability the cam system [7].

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along the building direction [15].

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

Chergui et al. studied the schedule problem and nesting in production of MAM method by developing mathematical model in Python with a heuristic approach. The heuristic approach has been explained step-by-step as a result, improving the scheduling and nesting problems [8]. Bradley et al. created a seven degree-of-freedom, dual-arm hydraulic by using the SLM method for subsea use. Researchers have described the hydraulic system and how they created the titanium manipulators for Naval research. They have also discussed lessons learned throughout the project and process (design) changes for the future [9]. For particle size, heat treatment, shape analysis, and hardness testing, microstructural analysis in MAM, several solutions

Li et al. have discussed the residual stress issue in printing metal parts due to rapid heating rate, rapid solidification with high cooling, and melting back the layers that previously melted. They used Powder Bed Fusion (PBF) and Direct Energy Deposition (DED). This work was performed on small and complex geometry parts of nickel based super alloys, titanium alloys, and stainless. The results showed there is a connection between the residual stress and microstructure: the residual stress has been measured in both as-build metal part and post-processed [11]. Reza Molaei and Ali Fatemi have reviewed the main factors that influence fatigue behavior in producing metal parts. In this review, they have collected some multiaxial fatigue data for Selective Laser Melting (SLM), which is based on Powder Bed Fusion (PBF). They used titanium alloy (Ti-6Al-4 V) as metal powder for printing small

In terms of energy consumption in MAM, and how it affects the quality of parts produced by MAM methods, ZY Liu et al. have studied the effect of energy consumption on microstructure and mechanical properties. Researchers have also used different types of metallic parts to perform investigations on both the machine and the process levels. On the machine level, they have studied the high-energy tool, control system, and cooling system whereas on the process consumption level, they have investigated energy flow distribution [12]. Bintao et al. reviewed the defects occurred in Wire Arc Additive Manufacturing (WAAM) related to microstructure and mechanical properties (deformation, porosity, and cracking) for high scaled fabricated components and high deposition rate. They used different size of metallic parts for different alloy types (Titanium Alloy, Aluminum Alloy and steel, Nickel based super alloy, and other alloys). Researchers concluded that WAAM is still facing many challenges in producing different materials. The WAAM needs to perform sustainable system in a reasonable time frame. There is a need to produce defect free products by using WAAM. Finally, they suggested ways to improve quality of the product [13]. Filippo et al. developed a methodology for cooling system (impinging air jet) in WAAM process to prevent heat accumulation which increases the workpiece average temperature and consequently affects the WP quality. They used small parts of Fe alloys in their study. Their results showed that the impinging air jet can prevent the heat accumulation on part produced by WAAM [14]. Bintao et al. used in-situ temperature measurement method to analyze the heat accumulation and thermal behavior in Gas Tungsten Wire Arc Additive Manufacturing (GT-WAAM) process. They used medium sized titanium alloy (Ti6Al4V) parts. The result shows that the microstructural morphology, crystalline phase, mechanical properties and fracture feature have been changed when the heat accumulation was

Xuxiao Li and Wenda Tan built a numerical model to investigate the threedimensional grain structure in Direct Laser Deposition (DLD) for stainless steel 304 material. They enhanced the three-dimensional grain structure by using nucleation mechanism. The investigation showed that the nucleation mechanism used in this research could play a role in modifying grain structure in MAM method

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

have been presented, discussed and applied [10].

sized parts [1].

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

Chergui et al. studied the schedule problem and nesting in production of MAM method by developing mathematical model in Python with a heuristic approach. The heuristic approach has been explained step-by-step as a result, improving the scheduling and nesting problems [8]. Bradley et al. created a seven degree-of-freedom, dual-arm hydraulic by using the SLM method for subsea use. Researchers have described the hydraulic system and how they created the titanium manipulators for Naval research. They have also discussed lessons learned throughout the project and process (design) changes for the future [9]. For particle size, heat treatment, shape analysis, and hardness testing, microstructural analysis in MAM, several solutions have been presented, discussed and applied [10].

Li et al. have discussed the residual stress issue in printing metal parts due to rapid heating rate, rapid solidification with high cooling, and melting back the layers that previously melted. They used Powder Bed Fusion (PBF) and Direct Energy Deposition (DED). This work was performed on small and complex geometry parts of nickel based super alloys, titanium alloys, and stainless. The results showed there is a connection between the residual stress and microstructure: the residual stress has been measured in both as-build metal part and post-processed [11]. Reza Molaei and Ali Fatemi have reviewed the main factors that influence fatigue behavior in producing metal parts. In this review, they have collected some multiaxial fatigue data for Selective Laser Melting (SLM), which is based on Powder Bed Fusion (PBF). They used titanium alloy (Ti-6Al-4 V) as metal powder for printing small sized parts [1].

In terms of energy consumption in MAM, and how it affects the quality of parts produced by MAM methods, ZY Liu et al. have studied the effect of energy consumption on microstructure and mechanical properties. Researchers have also used different types of metallic parts to perform investigations on both the machine and the process levels. On the machine level, they have studied the high-energy tool, control system, and cooling system whereas on the process consumption level, they have investigated energy flow distribution [12]. Bintao et al. reviewed the defects occurred in Wire Arc Additive Manufacturing (WAAM) related to microstructure and mechanical properties (deformation, porosity, and cracking) for high scaled fabricated components and high deposition rate. They used different size of metallic parts for different alloy types (Titanium Alloy, Aluminum Alloy and steel, Nickel based super alloy, and other alloys). Researchers concluded that WAAM is still facing many challenges in producing different materials. The WAAM needs to perform sustainable system in a reasonable time frame. There is a need to produce defect free products by using WAAM. Finally, they suggested ways to improve quality of the product [13]. Filippo et al. developed a methodology for cooling system (impinging air jet) in WAAM process to prevent heat accumulation which increases the workpiece average temperature and consequently affects the WP quality. They used small parts of Fe alloys in their study. Their results showed that the impinging air jet can prevent the heat accumulation on part produced by WAAM [14]. Bintao et al. used in-situ temperature measurement method to analyze the heat accumulation and thermal behavior in Gas Tungsten Wire Arc Additive Manufacturing (GT-WAAM) process. They used medium sized titanium alloy (Ti6Al4V) parts. The result shows that the microstructural morphology, crystalline phase, mechanical properties and fracture feature have been changed when the heat accumulation was along the building direction [15].

Xuxiao Li and Wenda Tan built a numerical model to investigate the threedimensional grain structure in Direct Laser Deposition (DLD) for stainless steel 304 material. They enhanced the three-dimensional grain structure by using nucleation mechanism. The investigation showed that the nucleation mechanism used in this research could play a role in modifying grain structure in MAM method

*Concepts, Applications and Emerging Opportunities in Industrial Engineering*

MAM processes, in the production of small and medium size parts.

and asking what the main issues and challenges facing this process are.

suggestions to enhance the redesign and printability the cam system [7].

lieu of a single knowledgeable worker.

**2. Literature review**

AM is the current and dominant future manufacturing method [1]. AM processes are considered easier as compare to subtractive processes represented by machining and other manufacturing types. This is because of producing a part through one AM process is more effortless than producing the same part through several subtractive manufacturing processes (such casting then machining). Subtractive manufacturing processes often require millions of dollars, while using AM processes can offer the same manufactured parts at a fraction of the cost, and in less than half the time [2]. In addition, manufacturing the part in one process eliminates the need for several skilled workers (which subtractive manufacturing requires), in

AM is the future face of the industry, not just in manufacturing field—printing technology has even been used to construct buildings in recent years. However, the MAM process for producing small and medium size metallic parts also present difficulties and issues. These difficulties may be inherent to the MAM process itself, such as selecting the right MAM process, adjusting support materials, building direction, geometry (complexity) of the part, and printing orientation. All these difficulties might lead to some issues and defects in MAM products, such as porosity, variation in mechanical properties, microstructure evolution, residual stress, fatigue, and crystalline phase and more. In the next section a recent comprehensive literature review is presented to explain the main issues and difficulties facing

Additive Manufacturing (AM) was employed for the first time in 1987, through use of a stereolithography (SLA) system to build the first three-dimensional model (solidifying a thin light-sensitive layers liquid polymer by using ultraviolet [UV] rays) [3]. Starting in 2017, manufacturing companies focus began orienting manufacturing processes in a new direction; these companies started to depend on AM methods to produce parts. AM methods have grown over the last year, becoming the key area of interest for many such companies [4]. However, the main focus of this literature review related to the MAM method for producing small and medium metallic parts—

This concerns frameworks for selecting the right MAM process, adjusting support material, building direction, geometry (complexity) of the part, and printing orientation. Some of these challenges can interrupt the process itself and cause other issues (such as defects in the final manufactured product, including: porosity, variation in mechanical properties, microstructure evolution, residual stress, and crystalline phase heat accumulative and thermal behavior). Inspection difficulties in MAM have been investigated, with the conclusion that inspection ability and metallurgical validation of highly optimized shape must be integrated with product design and process parameter during and after the CAD design [5]. Several challenges facing MAM methods have been investigated, such as financial consideration, certification and regulation, repeatability, and skills gap. Some suggestions have been made to eliminate these challenges and this researcher discusses further potential solutions for these challenges [6]. Serena et al., studied the difficulties and challenges to be facing when designing for metal additive manufacturing in Selective Laser Melting Additive Manufacturing (SLM AM) process for producing professional sport equipment (medium size cam component). These difficulties, such as functionality, manufacturability, assembly, and printability. All of these difficulties should be considered in the designing of metal additive manufacturing. They present many

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[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 in mechanical properties of powder layer [18].

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 process is qualified for aerospace applications [21].

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].
