## 3 Results and Discussion
### Production Time and Cost Analyses  
The actual production time for fabricating specimens with different support structures remained the same (32 min) in this research. The production time refers to the actual fabrication time excluding the required post-processing time, and it is calculated based on print speed and build path length. In this paper, the print speed selected for different specimens is the same; and the total length of the build path is similar. That's the main reasons why production time remains the same for specimens studied in this paper. In practice, specimens with more complex structures will require longer post-processing time, which is not considered in this research. The estimated production costs for different specimens are slightly different for specimens studied in this research. The detailed cost calculation results are shown in Table 5. It can be observed from the table that all specimens have the same fixed cost and indirect cost, because each fabrication requires the same machine setup and maintenance, and the same consumption of consumables (such as compressed air, Argon gas, and filters). The direct material cost, on the other hand, is contributed by the material price and the consumption of materials of parts as well as the support structures; the direct material cost for different specimens remain similar because these specimens have the same weights of the parts and similar weights of the support structures. This means that the production cost of a specific specimen remains the same when different support structures are used but these structures have the same weight (assuming other factors remain the same such as the values of process parameters), indicating promising opportunities to perform cost-aware support structure design. Figure 8: The SEM micrographs of the IN718 parts fabricated on top of different support structures: (**a**) AT53G80, (**b**) CT53G80, (**c**) PT53G80, (**d**) AT 33G80, (**e**) AT80G80, (**f**) AT33G100, and (**g**) AT60G100. It can also be observed from Table 5 that different specimens have similar cost distributions among three cost components: fixed cost, indirect cost, and direct cost. As example of cost distribution among different cost components is shown in Figure 10 for specimen AT53G80. The cost calculation results in Figure 10 show that the fixed cost has the largest contribution at 84.17%, the direct cost is around 15.55% of the total cost, and the material-related direct cost is only less than 1% of the total cost. This indicates that in AM practices, despite the fact that raw material powders seem to be expensive, the material cost can be neglected compared to other consumables and machine setup and maintenance. In addition, the cost distributions among the main part and the support structure are shown in Figure 11. Among samples with different support structure types and geometry, their contribution to the total cost is similar, ranging from 24.06% (AT33G100) to 35.78% (AT80G80). The reason for this difference is mainly due to the support structure geometry (both thickness and gap). In addition, samples AT53G80, CT53G80, and PT53G80 demonstrate similar cost performance, indicating that the support structure type (angled, cone, and pin) does not evidently alter the cost contributions between the main part and the support structure.