# Sustainable Manufacturing Decisions through the Optimization of Printing Parameters in 3D Printing
## 5 Conclusions  
In this study, we identified the optimal printing parameters of the dimensional accuracy (W, OW, OL, and T), carbon dioxide emissions, and three printing costs in delta-type FFF-3D printers through several single-objective and multiobjective optimizations. The printing parameters are the fan rate, printing speed, nozzle temperature, build plate temperature, and layer thickness. The following conclusions could be drawn from this research:  
1. The optimal parameters of single objectives were obtained using the S/N ratio and average effect plot. They are as follows: A1B3C3D2E1 in W; A1B3C3D2E1 in OW; A1B3C3D2E3 in OL; A2B3C1D1E3 in T; A1B1C3D3E1 in carbon dioxide emissions; A2B2C2D2(3)E1 in material cost; A2B1C2D2E1 in labor cost; and A1B1C3D3E1 in electricity cost. The optimal parameters of dimension W were the same as those of dimension OW, and only the layer thickness was different from dimension OL. Under the optimal parameters of dimension W, the difference could be improved by reducing the layer thickness. In addition, reducing the layer thickness and increasing the nozzle/build plate temperature must be implemented together to optimize dimension T. However, a higher temperature can result in higher carbon dioxide emissions and electricity costs, which can be eliminated by increasing the printing speed and lowering the build plate temperature. 2. The contribution and impact of each factor in different single-objective optimizations can be obtained using ANOVA. The dimensional accuracy of W, material cost, and labor cost are most significantly affected by the layer thickness. Although delta-type machines are suitable for high-speed printing, mechanism movement errors can affect the accuracy of printed parts, causing such errors to have the highest significance with regard to OW, OL, and T. The carbon dioxide emissions and electricity costs are most significantly affected by the build plate temperature. 3. Five objectives, namely the dimensional accuracy, carbon emissions, and three printing costs, could be optimized using a desirability analysis. In addition, through the desirability analysis and weights, different optimal printing parameters could be determined under the same multiple objectives. They are as follows: A1B3C1D1E3 in dimensional accuracy; A1B3C1D2E2 in dimensional accuracy and carbon dioxide emissions; A2B2C2D3E1 in three printing costs; A2B3C1D1E2 in dimensional accuracy and three printing costs; and A1(2)B3C1D2E2 in dimensional accuracy, carbon dioxide emissions, and three printing costs. The optimal printing parameters of the dimensional accuracy, carbon dioxide emissions, and three printing costs could be obtained in three different groups. This method is suitable for finding the optimal parameters with different weightings under multiple objectives. The optimal printing parameters for the dimensional accuracy and carbon dioxide emissions are the same as the majority for the dimensional accuracy, carbon dioxide emissions, and three printing costs. This means that the same set of printing parameters can be balanced across multiobjective optimizations, even if there are different weights in the objectives. Therefore, the best solution to achieve the full goal in terms of dimensional accuracy is to only moderately reduce the build plate temperature and layer thickness values without minimizing them. The surface roughness and mechanical properties are also important elements for evaluating printing quality. In future works, we aim to try to obtain optimized parameters of the surface roughness and tensile properties of printed objects through the S/N ratio and mean effects plot. In addition, we aim to add goals that affect environmental impacts so as to establish a more comprehensive relationship between printing quality and sustainable manufacturing.