**3.1 Layout of runner system**

156 Some Critical Issues for Injection Molding

Injection pressure is an important, technical parameter of injection molding. It should not be too high or it may be hard to demould and cause raw edges on the product surface. What is more, the melt would not be able to fully fill mould cavity if the injection pressure is too high. Therefore, a suitable injection pressure is very necessary. Improving the injection pressure can improve the melt compression ratio and dimension accuracy (Liu et al., 2002). Runners with

Runner Circular Semicircular Rectangular Ladder U-shape

Filling time ranking 1 5 4 3 2

difference ranking 1 5 4 3 2 Clamp force ranking 4 5 1 2 3 Processability Hard Easy Easy Easy Easy

Suitable Unsuitable Rarely use in

material Easy Easy Hard Easy Easy

According to Table 7, circular runner has minimal pressure drop, shortest filling time and smallest temperature difference, which means that it has the highest efficiency. On the other

Compared with semicircular and ladder runners, U-shape runner has smallest pressure drop, shortest filling time, minimal temperature difference and highest efficiency. Therefore,

During Ceramic Injection Molding stage, raw materials within staff canister firstly are heated to become melt which is driven quickly by the piston or screw into the closed cavity. Then, the melt within mould cavity compressed by mould and cools down to become product. The main concern of Ceramic Injection Molding is that the products should meet the quality requirement. Also, the solid load of ceramic powder, which is related to the

The conventional methodology optimizing process parameters requires experts use the trial and error method basing on their experience and professional knowledge. As the development of CAE technology, it becomes increasingly important to industry, especially to improve product quality and decrease cost etc. We combine CAE experiment and DOE

**3. Layout of runner system and optimization of technical parameters** 

1 5 3 4 2

practice Perfect Most suitable

for cold runner

different cross-section shapes are compared under the same conditions (Table 7).

Cross-section shape

Pressure drop ranking

Temperature

Removing the cold

Comprehensive evaluation

Table 7. Comparison between runners.

hand, rectangular runner has the smallest clamp force.

product quality, should be as high as possible.

runner with U-shape cross-section shape is the best choice.

The mould is composed of two templates with six cavities and common arrangement of multi-cavity system is radiated runner system. Melt can only be poured into the cavity through gates on both sides of mould for there is a fairly small hole in the axial center of products. Runner systems with rectangular and circular shunt are showed as Fig. 8 (Zhang, 2005, 2007).

Fig. 8. Two runner systems; (a) Runner system with rectangular shunt; (b) Runner system with circular shunt.
