*6.1.6.1 Proposed solution*

*Concepts, Applications and Emerging Opportunities in Industrial Engineering*

that the list of metals can be used in MAM is still relatively short.

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

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

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

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.

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

*6.1.4 Materials issues*

*6.1.4.1 Proposed solution*

*6.1.5 Heat treatment*

*6.1.5.1 Proposed solution*

*6.1.6 Financial considerations*

with the powder-bed MAM method.

to obtain the desired mechanical properties.

**248**

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 including the supply chain.
