## 4 Discussion  
In this study, a decision flow chart is proposed for the market evaluation of aluminum AM methods. To verify the accuracy of this flowchart as well as consider the printability of parts in high-voltage products, a case study is selected. GIS-ELK-04/145 kV is considered as a case study, and the proposed flowchart is applied to every aluminum component of this product. The results show that there are significant restrictions and challenges due to the replacement of CM methods with AM technologies. These challenges include high requirements of electrical and mechanical properties, threading and sealing areas in the majority of parts, and large and heavy parts without the possibility of significant re-design and weight optimization. Additional post-processing and heat treatment will reduce the benefit of AM methods because of the increase in supply chain management risks. Moreover, most aluminum parts in GIS products for small to medium-sized parts are made of aluminum 6061 and 6063 with high mechanical properties and proper electrical conductivity. However, the available AM methods are focused on Al-Si-Mg alloys (high Si percentage) with lower mechanical properties and lower electrical conductivity because of powder with laser-induced. In addition, the long process of standardization for some unique parts is ignored. The proper testing and qualification of products is one of the most important tasks when applying additive manufacturing in the high-voltage industry. As mentioned earlier, the high electrical conductivity of metals is a must in most HV applications; therefore, in the selection of proper 3D printing technology, such material properties must be verified. In addition, the quality of the printed microstructure must be high without internal cracks and voids, minimizing the potential failure of the part during normal operation. Such robust and reliable function of the product must be assured for even more than 20 years. This means that long-term aging tests of the printed parts (e.g., creep behavior) should be performed. Currently, HV engineering has no standard procedures indicating how the printed components should be qualified. The most reliable procedure in Hitachi Energy is standard tests (type tests) for specific products. Since these tests and related certifications are costly and time-consuming, in the future, the development of standardization procedures will be required. Some sectors, including aerospace and automotive, have already established various consortia aiming at the development of such standards. Here, ASTM organization plays an essential role in establishing its Additive Manufacturing Center of Excellence (AM CoE) and, together with academics, industry, and government, is carrying out research and development to accelerate the development and adoption of 3D printing technology [16]. Such agreements are an essential part of the adoption of AM for energy sectors. Another challenge in considering AM as a manufacturing method is cost. A cost comparison between AM and CM methods for some candidate parts shows the significantly higher cost of AM methods for series production. However, AM can bring huge benefits for spare parts management and prototyping. Short lead time, order-on-demand, and cost savings are the benefits of using AM for service units and technology centers. AM methods can be a suitable case to prevent engineers from manufacturing an expensive mold for one spare part or prototype. Besides lead time, even from the cost point of view, if an aluminum part with the current manufacturing method of casting + machining is less than 12-13 kg, it is beneficial to print the spare part or prototype instead of manufacturing the mold. The presented study focused mainly on the application of 3D printing for manufacturing aluminum parts/ spare parts in GIS products; thus, for most of the components, the same design was used as that in traditional manufacturing.