**6. Conclusion**

170 Some Critical Issues for Injection Molding

Table 18 shows the temperature simulation of three different positions in different cooling system when the cycle period is 25s. Apparently, cooling efficiency of third cooling system is the best and temperature distribution of each cavity is even in the third cooling system.

Cavity Number 1 2 3 4 5 6 Maximal difference

Top 49.10 49.08 49.27 49.31 49.19 48.17 0.23 Middle 53.98 54.07 54.21 54.29 54.22 54.12 0.31 Bottom 37.74 37.75 37.99 38.02 37.91 37.81 0.28

Top 48.83 48.85 48.99 48.92 49.02 48.91 0.19 Middle 53.69 53.78 53.97 53.86 53.91 53.75 0.28 Bottom 42.82 42.80 43.04 42.96 42.91 43.01 0.24

Top 47.76 47.79 47.89 47.83 47.91 47.86 0.15 Middle 52.78 52.83 52.99 52.89 52.90 52.93 0.21 Bottom 41.88 41.90 42.07 41.98 42.01 42.03 0.19

Table 18. Temperature simulation of three different positions with different cooling system

Extreme values of temperature difference of various positions in each cavity are shown as Fig. 19 when cycle period is 25s. The extreme values of temperature difference of top, middle and bottom parts in each cavity in the third cooling system are smaller than that in

Fig. 19. Extreme values of temperature difference of various positions in each cavity when

Top Middle Bottom

Cooling system one

Cooling system Two

Cooling system three

the former two.

cycle period is 25s ( C).

when cycle period is 25s ( C).

temperature

Temperature difference

Cooling system one Cooling system two Cooling system three

Maximal temperature Minimal

Cooling system one 54.64 42.57 12.07 Cooling system two 54.37 42.30 12.07 Cooling system three 53.38 41.21 12.17 Table 17. General temperature difference of product when cycle period is 25s (°C).

Firstly, we used Moldflow to calculate pressure drop, filling time, temperature difference and clamp force of five different cross-section shapes. Outcomes demonstrate that U-shape runner has smallest pressure drop, shortest filling time, minimal temperature difference and highest efficiency. Therefore, U-shape runner is most suitable for cool-runner mould rather than circular or other kinds of runners.

Secondly, we investigated runner systems with rectangular and circular shunt respectively by orthogonal table. Also, we researched influence of mould temperature, injection temperature, screw velocity and gate dimension on products. Results show that runner system with circular shunt is most suitable for Ceramic Injection Molding. Furthermore, we considered the gravity influence on Ceramic Injection Molding and found that short shot tends to happen on the top cavity when runner diameter is 4mm. All six cavities are filled well after increasing runner diameter to 4.17 mm.

Finally, we simulated cooling efficiency of three cooling systems and results show that the third cooling system has shortest cooling cycle and best cooling efficiency, which can cool product as fast as possible. Cooling efficiency in six cavities is not the same for the cooling system arrangement and for the inlet and outlet location. Temperature extreme values of top, middle and bottom positions in each cavity in the third cooling system are smaller than that in former two cooling system.
