*6.1.2 Repeatability*

*Concepts, Applications and Emerging Opportunities in Industrial Engineering*

**6.1 MAM challenges, issues, and approached solutions**

*6.1.1 Lack of knowledge of design for additive manufacturing*

approached by the author will be presented.

**approached solutions**

turbines, manipulator arm, robot arm, fins, rocket, firearms, automobile parts, impellers, fans, and medical tools. However, printing these parts by the MAM method without difficulties and issues is a challenge. This will be discussed in the next section.

**6. Metal additive manufacturing (MAM) challenges, issues, and** 

Metal Additive Manufacturing (MAM) is a process used to fabricate and repair parts that have a complex geometry or need to be functionally graded. The process can be performed by depositing multiple layers to produce the required part. Several MAM methods can be used to manufacture metallic parts. They are categorized into two types according to their method of performing (Direct Metal Deposition and Powder Bed Fusion). A successful manufacturing process depends on the deposition technique used, the parameters selected, and the materials used. Moreover, the MAM depends on deposition conditions such as temperature and protective atmosphere to determine whether cracking and oxidation of the deposited layers occurred or not. In the present study, the MAM methods are discussed and evaluated for different manufacturing parameters and deposition conditions for different metallic materials. Multiple challenges and issues encountering the MAM methods will be discussed in the next sub-sections. This study has shown that some suggested solutions can be successfully processed by MAM by using different methods. A significant number of MAM methods are being utilized these days.

Despite the ability of the MAM method in reducing the complexity of parts to simple 2D slices and machining super hard alloys, the MAM method is still suffering from several issues and challenges which are interrupting its progress. In this sub-section, these challenges and issues will be discussed, and the solution

Understanding how the materials work in MAM and how the metals are printed layer by layer to print three dimensional models are big concerns in the design for additive manufacturing. Lack of understanding the differences between plastic 3D printing and metal 3D printing can lead to parts with low quality, high defects, and high probability of failure. Skills gap in MAM method is considered an important issue. The knowledge of transferring several subtractive manufacturing processes to one metal additive manufacturing process is a big step. Selecting the appropriate metals (powder or wire) to print the parts and the appropriate process requires a significant amount of knowledge. Also, understanding the orientation of parts and adjusting the support materials in right place by using the printer software before printing is important to obtain desirable quality and characteristics. Similarly, printing high quality parts with complex geometry is also a big challenge with the MAM method, especially when printing aerospace or firearm parts. Therefore, lack of education issue can cause companies to lag or fail in performing successful MAM.

Well-trained workers or engineers and skilled workforce are necessary to diminish this problem. Building and finding capable workforce is not easy and requires

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*6.1.1.1 Proposed solution*

The MAM method is still facing a lot of variation in parts. The problem that companies encounter is to create two similar parts, then make these parts repeatedly. America Makes Company is still suffering from this problem in MAM and only 30% from the produced parts meet the specifications of the company. In addition to this problem, the MAM method is also suffering from mass production process [2].

### *6.1.2.1 Proposed solution*

The repeatability inside the MAM system can be acquired by developing the standardization of quality. A standardization should be set for the MAM process. This standardization should be developed after a massive study on every MAM process and from this study several factors, such as MAM process type, printing time, environment, used materials, part size, production rate, complexity of the part, functionality and process setting need to be discussed and assigned to standardize the process. All these factors need to be organized and assigned inside specific range which can provide the quality that is required to obtain the repeatability.

## *6.1.3 Selecting an appropriate MAM process*

Every MAM process has different strength and ability to produce specific metallic part, whether the process is Powder Bed Fusion (PBF) or Direct Energy Deposition (DED) process. Using an appropriate process in MAM method will lead to produce defect-free parts. For example, using EBM process that has a high-power source will allow to produce a thicker layer, and will lead to high production rate. However, using the EBM process to produce tiny and complex part with lot of features will be a challenge because the residual powder in each layer will be semi sintered with thicker layer that will create part with undesired quality. Therefore, complex parts can be produced successfully on a SLM or DMLS system.

#### *6.1.3.1 Proposed solution*

Making MAM process selection map is a good solution for eliminating this obstacle. This map will contain inputs and outputs. The inputs will have process parameters, such as part size, part geometry, material used, quality and mechanical properties required, and design parameters. These inputs will be analyzed and addressed, then they will be matched with each MAM process capability. Finally, the outputs will be extracted from all of that and the priority of using the MAM processes will be ordered according to their fitness for printing the required parts.

### *6.1.4 Materials issues*

Using the appropriate material (metal) for MAM is also a challenge in this process. The metals used for printing parts should match the selected 3D printing machine. MAM still faces problems in printing some metals, such as Inconel 718, Inconel 625, titanium, and tantalum. Secondly, some parts have multi-features in their design resulting in a variable mechanical properties for every feature. This will increase the probability of failure for these parts. However, it is worth mentioning that the list of metals can be used in MAM is still relatively short.

### *6.1.4.1 Proposed solution*

Using multi-material (metal) machine will solve the problem of parts with multi features. These machines can provide appropriate material for every feature in complex parts. As a result, it will fix the issue of failure in these parts. Performing this solution is not easy and needs a lot of study to get the machine structure that will be used for printing multi-materials (metals). Especially, there is one important condition; the multi-materials can be banded together to create the final parts. This solution can perform with direct deposition MAM method because the multimaterial can be melted separately and then combined, but it will be a big challenge with the powder-bed MAM method.

#### *6.1.5 Heat treatment*

The metal 3D printing is different than other types of 3D printing. In metal 3D printing, the printed metal part needs heat treatments to obtain the desired mechanical properties which meets the quality of printed parts. Since the MAM is shifting from rapid prototyping to the actual production: aerospace, firearm applications, highly customized parts, the heat treatments play a significant role in the cost and the quality of the part. Mixing different types of raw materials and creating alloys for machining, such as titanium steel, aluminum is not easy, but it can be done in MAM. However, the parts produced by MAM need heat treatments to obtain the desired mechanical properties.

### *6.1.5.1 Proposed solution*

Producing metal part in MAM method without internal stress is an issue in additive manufacturing. Some MAM machines have heat treatments in their structure. Some produced parts in MAM require more levels of heat treatment to obtain specific mechanical properties, such as the elongation to failure and the fatigue strength. Excellent vacuum furnace is required to perform the heat treatment which eliminates the oxygen from entering the machine and obtain the required temperature control and deep vacuum level. Another issue with this process might be the cost of heat treatment itself. Producing vacuum furnace with these characteristics may cost \$100 K, thus the cost of heat treatment part of titanium may reach \$600. This solution of using high maintained vacuum furnace might give high corrosion resistance with excellent strength, toughness, and low weight part of titanium alloy. Therefore, this process should be used in producing parts having important and expensive applications.

#### *6.1.6 Financial considerations*

The cost of MAM method is an issue as compared to the plastic AM. The cost of some MAM machine may reach up to \$350 k. The cost of facility and raw materials

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process.

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

(powder or wire) is also expensive. Providing the metallic powder with specific particles size for expensive metals will also add capital expenditures. In addition, with all these expenses, failures in printing the parts will push such MAM compa-

A comprehensive study regarding this financial consideration should be performed. This study will be about the investment and profit that can be obtained with transition to MAM from traditional (subtractive) manufacturing processes. A criterion should be considered about the expenses and cost of MAM and compared to the capital expenditures of subtractive manufacturing. The entire cost for structure should also be noted. Moreover, an evaluation on the throughput and type of the parts being printed should be used to make a final decision about the transition from a subtractive manufacturing process to MAM. This decision should be made between company management because it will affect the entire company's structure

The key of success for MAM is to obtain the quality and reliability required on the printed parts. Certification and regulation means assigning a customization and individualization to the additive manufactured part [2]. Certification process is considered as another challenge which manufacturing companies are suffering from in the MAM field. The MAM method without certification is a disadvantage, especially with the evaluation of the additive parts. Certification is important in the field of MAM in printing parts which requires excellent quality and reliability, such as aerospace industries, where the safety is the main

MAM part should be certified by setting methods of measurement, monitoring, and control in order to acquire the desirable quality and reliability in parts. Then, the issues in parts will be addressed and analyzed to come up with some actual solutions. Better the measurement and control methods, better the results it gives which accelerates the certification of the MAM method. The measurement method is a trigger to develop standards for addressing these MAM issues and assigning solution

Producing complex and non-homogeneous MAM parts, which contains significant numbers of different features, requires high level of inspection. By assigning inspection, the quality of additive part can be retained. The importance of the inspection is equal to the importance of the measurement which has been mentioned in the previous section. Inspection and metallurgical validation methods should be integrated with MAM parts printing. That will allow the production of highly optimized shapes. According to the current study, there is a real need to build non-traditional inspection system inherent to the MAM parts manufacturing [5]. Now, traditional nondestructive inspection methods are used in the MAM method, and these methods are not enough to detect the defect during the printing

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

nies out of business.

*6.1.6.1 Proposed solution*

including the supply chain.

requirement.

to fix them.

*6.1.7.1 Proposed solution*

*6.1.8 Inspection difficulty*

*6.1.7 Certification and regulation*

(powder or wire) is also expensive. Providing the metallic powder with specific particles size for expensive metals will also add capital expenditures. In addition, with all these expenses, failures in printing the parts will push such MAM companies out of business.
