**7. Summary and conclusion**

In this chapter, a review on design for additive manufacturing was conducted to address and answer some concerns about Metal Additive Manufacturing (MAM). These concerns were related to challenges, issues, and defects which are prevalent in MAM method in factories while printing small and medium sized parts. Explanations about the printing procedures and materials are also discussed in this chapter. Moreover, potential approach and solutions are inferred by the author to diminish these problems. Comprehensive literature review was developed from a recent research paper to address and understand these manufacturing obstacles. The MAM method is divided into two main processes: PBF and DED. These processes were explained in detail by the author.

The main obstacles which the MAM methods encounter are categorized into two types: challenges (difficulties) and defects. Several obstacles have been explained in this chapter, such as repeatability, material issue, schedule, certification, heat treatment, and inspection. Also, several defects which obstruct high quality and reliability, such as fatigue, stress analysis, porosity, heat accumulation, delaminating, and cracks were listed and discussed. For every challenge and defect, a potential solution was suggested and discussed by the author. Some of these suggested solutions need to be tested and validated on actual metal three-dimensional printing processes. Other suggested solutions, such as inspection and orientation, should be implemented by visiting manufacturing companies and making local study on to solve the problems.

However, based on the literature review and analysis, DED processes, especially WAAM, have more defects and challenges than PBF processes. Some of these challenges and defects are common in three-dimensional printing, a fast-growing manufacturing process. More study and analysis are required to fix these obstacles and make MAM method smooth. Such concurrent failures can induce huge losses in industries and force them out of business. Therefore, future studies can eliminate these failures and yield higher production rate and profits.
