## 3 Results and Discussion
### Moldflow Simulation
This phenomenon is expected to be a problem caused not only by the mold thickness of the injection hole part being relatively thin compared to other parts, but also the heater temperature near the lower end part is high. In addition, considering the resin hardening phenomenon as the inlet part is preferentially cured, the central part may be deformed and contracted during the curing stage. The degree of hardening around the central conductor over time must be cured at the same rate regardless of the location, so that residual stress is less likely to exist inside the manufactured spacer. Epoxy should be injected to prevent bubbles and cracks inside the manufactured spacer. To solve this problem, the simulation was conducted by changing the bottom heater (No. 7 and 8) from 115 \({}^{\circ}\)C to 130 \({}^{\circ}\)C to slow the curing of the bottom. Figure 5: Conversion properties for Condition-1, 2, 3, 4 (\(\alpha\) 70%: the curing rate of the entire spacer reaches 70%, T max: the maximum temperature inside the spacer). Figure 6: Conversion properties for Condition-5, 6, 7. As a result of the simulation, as in Condition-1, in Condition-2, curing proceeded first near the inlet, and in Condition-3, curing proceeded slowly from the vicinity of the inlet. However, the internal curing rate of the spacer at the location of heater 7 at 40 min was about 85%, and the surface was stably cured, but there was a concern that cracks may occur due to non-curing inside the spacer after deforming. As a result of the Condition-4 simulation in which heater No. 8 was set to 115 \({}^{\circ}\)C, curing at the lower end may be delayed, and thus the overall production rate may be reduced. For this reason, it was determined that Conditions-2, 3, and 4 were not suitable, and 120 \({}^{\circ}\)C was selected as the optimal temperature for the bottom heater. In the case of Conditions 5 and 6, as a result of setting the heater temperature sequentially from the upper part to the lower part, curing progressed more slowly compared to the previous conditions overall, and the curing of the lower part was delayed so that sufficient holding pressure could proceed. As a result of the Condition-7 simulation, the curing rate near the injection hole was about 95% at 40 min, and it was expected that the reaction would proceed further due to the latent heat inside the spacer and be completed even after curing was finished. In addition, it was confirmed that the curing progressed without any problems in the uncured areas that appeared in Conditions 5 and 6. Figure 8 shows the curing time and curing degree according to the mold position under the heater temperature conditions of Conditions 1 and 7. In the case of position A (black-line) with an injection hole, it is ideal for curing to occur last as the pressure for bonding is continuously maintained. In the case of Condition-1, since the curing of position A was the second fastest completed, pressurization for restoration was not applied. In the case of Condition-7, since the curing of position A occurred last compared to other positions, the possibility of bubbles and cracks occurring inside the manufactured spacer was greatly reduced by applying pressurization for maintenance. Figure 7: The degree of cure under different conditions (from Condition-1 to Condition-7). Figure 9 shows a graph of Condition-7, which is the optimal curing condition using bio-based epoxy and curing condition using petroleum-based epoxy. The curing speed of the bio-based epoxy is slightly different than that of conventional petroleum-based epoxy. However, since the overall curing tendency is very similar, it is thought that it will not be a big problem in manufacturing the GIS spacer. Figure 10 shows the experimental setup for manufacturing a GIS spacer.