**Optimization and Simulation for Ceramic Injection Mould of ZrO2 Fiber Ferrule**

Bin Lin, Meiming Zhang, Chuhan Wu and Feng Liu *Tianjin University, China* 

#### **1. Introduction**

148 Some Critical Issues for Injection Molding

Rodríguez-Senín, E.; Várez, A.; Levenfeld, B.; Torralba, J. M. & París,M. A. (2005). Processing

Stanimirović, I & Stanimirović, Z. (2010). Piezoelectric Ceramic by Powder Injection

ISBN: 978-1-4244-7198-0, Niš, Republic of Serbia, May 16-19, 2010, IEEE Stanimirović, Z & Stanimirović, I. (2010). Injection Molded Mn-Zn Ferrite Ceramics.

ISBN: 978-1-4244-7198-0, Niš, Republic of Serbia, May 16-19, 2010, IEEE Wang, S.; Li, J. F.; Wakabayashi, K.; Esashi, M. & Watanabe, R. (1999). Lost Silicon Mold

9, (August 2000), pp. 1301-1310, DOI: 10.1016/S0955-2219(99)00295-2 Yin, HQ.; Jia, CC. & Qu, XH. (2008). Micro powder injection molding—large scale

DOI: 10.1016/S0921-4534(03)00696-8

pp. 185-195, DOI:10.2298/SOS0802185Z

pp. 217-222, DOI:10.1016/ j.mseb.2010.07.031

of Mn–Zn ferrites using mould casting with acrylic thermosetting binder. *Powder Metallurgy*, 48(3), (September 2005), pp. 249-253, DOI:10.1179/174329005X64117 Skolyszewska, B.; Tokarz, W.; Przybylski, K. & Kakol, Z. (2003). Preparation and magnetic

properties of MgZn and MnZn ferrites. *Physica C*, 387(1-2), (May 2003), pp. 290-294,

Molding. *Proceedings of 27th International Conference on Microelectronics MIEL 2010*,

*Proceedings of 27th International Conference on Microelectronics MIEL 2010*,

Process for PZT Microstructures. *Adv. Mater.*, 11(10), (July 1999), pp. 873-876, DOI: 10.1002/(SICI)15214095(199907) 11:10<873::AID-ADMA873>3.0.CO;2-F Wei, W.C.J.; Wu, R.Y. & Ho, S.J. (2000). Effects of pressure parameters on alumina made by

powder injection moulding. *Journal of the European Ceramic Society*, Volume 20, Issue

production technology for micro-sized components. *Science in China Series E: Technological Sci.,* 51 (2), (Feb. 2008), pp. 121-126, DOI: 10.1007/s11431-008-0023-y Zauner, R. (2006). Micro powder injection moulding. *Microelectronic Engineering,* Volume 83, Issues 4-9, (April-September 2006), pp. 1442-1444, DOI:10.1016/j.mee.2006.01.170 Zlatkov, B. S.; Griesmayer, E.; Loibl, H.; Aleksić, O. S.; Danninger, H.; Gierl, C. & Lukić, L. S.

(2008). Recent Advances in CIM Technology. *Science of Sintering*, 40(2), (2008),

Halwax, E. (2010). Properties of MnZn ferrites prepared by powder injection molding technology. *Materials Science and Engineering B,* 175(3), (December 2010),

Zlatkov, B. S.; Mitrović, N.S.; Nikolić, M.V.; Marićić, A.M.; Danninger, H.; Aleksić, O. S. &

Fiber ferrule is a crucial part for manufacturing fiber connectors. It is fairly difficult to produce fiber ferrule because that it requires high dimension accuracy. Currently, YTZ ceramic powder is the main material used to produce fiber ferrule and Ceramic Injection Molding (CIM) is a new fabricating method capable of producing ZrO2 fiber ferrule (Fig. 1(a), Fig. 1(b)) with complex geometry and high accuracy. ZrO2 fiber ferrule quality is significantly influenced by the process conditions of CIM. Therefore, the main focus of this paper is to optimize mould structure and processing parameters based on the simulation of CIM, which promotes solid load of ceramic powder and product quality. Optimal process conditions of Ceramic Injection Molding could be determined by analyzing the simulation results. It has been found that runner cross-section shape and runner system contribute to the efficiency and filling process significantly. Hence, optimal runner cross-section shape and runner system are proposed. Reducing the gravity influence on CIM is also suggested. Moreover, optimization of cooling system could be considered an effective way to improve the dimensional precision and surface quality of ZrO2 fiber ferrule.

Fig. 1. ZrO2 fiber ferrule; (a) Roughcast of the ZrO2 fiber ferrule; (b) Geometry of the mould.

#### **2. Optimization of runner cross-section shape**

During filling stage, the melt is firstly injected into mould cavity and this stage is accomplished as the mould cavity is fully filled by melt. Therefore, it is of great importance

Optimization and Simulation for Ceramic Injection Mould of ZrO2 Fiber Ferrule 151

*Dh D 0.9523D 0.9116D 0.8862D* 

*Dh 0.8711D 0.8642D 0.8536D 0.7090D* 

Cross-section Shapes Equivalent Diameters

2 1 <sup>1</sup> cos ( )sin(cos ) <sup>2</sup> *r x rr t x* 

*r t*

 *W* 

*x*

*r* 

Table 1. Equivalent hydraulic diameters of various runner cross-section shapes.

**A** *d*

**<sup>C</sup>**<sup>2</sup> *ab*

**<sup>D</sup>**2( ) *a bh*

**2.1 Analytical solutions of various runner cross-section shapes** 

The geometric cross-section shape determines runner efficiency.

**<sup>E</sup>**<sup>2</sup> ( arctan( )) *H H W H*

Table 2. Comparison between equivalent diameters of various runner cross-section shapes.

The main factors influencing melt flow are injection pressure, melt temperature and viscosity, mould temperature, runner cross-section area and geometric cross-section shape.

It requires the following conditions to improve runner efficiency (Pan et al., 1995). Runner resistance to the melt flow, which is normally caused by the friction between melt and inner runner surface, should be as low as possible to ensure that the melt can fully fill the mould

The heat loss should be minimal as the melt flows through runner. When the melt with high temperature flows through runner with comparatively lower temperature, melt would transfer its heat to the mould, which increases mould temperature. On the other hand, the melt temperature decreases. Also, melt viscosity increases when melt temperature becomes lower, which makes melt fluidity worse. When the temperature decreases to a certain degree, temperature distribution within inner side of melt becomes significantly inhomogeneous that causes many defects in the products. In this case, we can improve the

Crosssection

Crosssection

**B** 

cavity before solidifying.

to control melt flow pattern within mould cavity, which could promote the solid load of ceramic powder. Cooling time and many product defects like cavitations, weld line, short shot and product deformation are related to the melt flow pattern. The melt flow pattern is influenced by many factors like the dimension of runner cross-section shape and runner system arrangement. Hence, optimized runner cross-section shape and well-designed runner system would be beneficial to the Ceramic Injection Molding. In order to investigate the melt flow pattern, pressure changes, temperature, cavitations etc., we use Moldflow Plastic Insight (MPI) to simulate the melt flow pattern within the mould cavity. Also, potential defects would be predicted during this simulation. The optimal runner crosssection shape could be determined though analyzing simulation results of different runner cross-section shapes.

Runners should ensure that the melt ejected from injection machine can smoothly flow through runners and fully fill mould cavity. What is more, runners should adequately transfer pressure to all the positions of mould cavity to obtain high quality products during filling process.

Common runner cross-section shapes (Fig. 2) are circular, ladder, U-shape (combination of circular and ladder), semicircular and rectangular. It usually is recommended to use the first three runner cross-section shapes. Considering the ratio of volume to its surface area, circular cross-section shape is most suitable, with minimal pressure drop and heat loss. However, templates on both sides of circular runners need to be processed, which causes much higher cost. Furthermore, semicircles on both surfaces of those two templates of circular runners have to be aligned accurately.

Fig. 2. Common runner cross-section shapes.

Ladder runner cross-section shape requires one processed template only, which still works well. Ladder runner is commonly used in three-plate mould. Circular runner cross-section shape is rarely adopted in three-plate mould for it may be difficult to demould and cause interference between runner and sliding part of templates. Different runner cross-section shapes could be compared by hydraulic diameter (Table 1) which is the index of flow resistance. The larger the hydraulic diameter is, the lower the flow resistance is. The definition of hydraulic diameter is described as equation 1.

$$D\_h = \frac{4A}{P} \tag{1}$$

Where *Dh* is the hydraulic diameter, A is the section area and P is the perimeter.

Equivalent hydraulic diameters of various runner cross-section shapes are compared in Table 2.

to control melt flow pattern within mould cavity, which could promote the solid load of ceramic powder. Cooling time and many product defects like cavitations, weld line, short shot and product deformation are related to the melt flow pattern. The melt flow pattern is influenced by many factors like the dimension of runner cross-section shape and runner system arrangement. Hence, optimized runner cross-section shape and well-designed runner system would be beneficial to the Ceramic Injection Molding. In order to investigate the melt flow pattern, pressure changes, temperature, cavitations etc., we use Moldflow Plastic Insight (MPI) to simulate the melt flow pattern within the mould cavity. Also, potential defects would be predicted during this simulation. The optimal runner crosssection shape could be determined though analyzing simulation results of different runner

Runners should ensure that the melt ejected from injection machine can smoothly flow through runners and fully fill mould cavity. What is more, runners should adequately transfer pressure to all the positions of mould cavity to obtain high quality products during

Common runner cross-section shapes (Fig. 2) are circular, ladder, U-shape (combination of circular and ladder), semicircular and rectangular. It usually is recommended to use the first three runner cross-section shapes. Considering the ratio of volume to its surface area, circular cross-section shape is most suitable, with minimal pressure drop and heat loss. However, templates on both sides of circular runners need to be processed, which causes much higher cost. Furthermore, semicircles on both surfaces of those two templates of

Circular Ladder U-shape Semicircular Rectangular

Ladder runner cross-section shape requires one processed template only, which still works well. Ladder runner is commonly used in three-plate mould. Circular runner cross-section shape is rarely adopted in three-plate mould for it may be difficult to demould and cause interference between runner and sliding part of templates. Different runner cross-section shapes could be compared by hydraulic diameter (Table 1) which is the index of flow resistance. The larger the hydraulic diameter is, the lower the flow resistance is. The

> 4 *h <sup>A</sup> <sup>D</sup>*

Equivalent hydraulic diameters of various runner cross-section shapes are compared in

Where *Dh* is the hydraulic diameter, A is the section area and P is the perimeter.

*<sup>P</sup>* (1)

cross-section shapes.

circular runners have to be aligned accurately.

Fig. 2. Common runner cross-section shapes.

definition of hydraulic diameter is described as equation 1.

filling process.

Table 2.


Table 1. Equivalent hydraulic diameters of various runner cross-section shapes.


Table 2. Comparison between equivalent diameters of various runner cross-section shapes.

#### **2.1 Analytical solutions of various runner cross-section shapes**

The main factors influencing melt flow are injection pressure, melt temperature and viscosity, mould temperature, runner cross-section area and geometric cross-section shape. The geometric cross-section shape determines runner efficiency.

It requires the following conditions to improve runner efficiency (Pan et al., 1995). Runner resistance to the melt flow, which is normally caused by the friction between melt and inner runner surface, should be as low as possible to ensure that the melt can fully fill the mould cavity before solidifying.

The heat loss should be minimal as the melt flows through runner. When the melt with high temperature flows through runner with comparatively lower temperature, melt would transfer its heat to the mould, which increases mould temperature. On the other hand, the melt temperature decreases. Also, melt viscosity increases when melt temperature becomes lower, which makes melt fluidity worse. When the temperature decreases to a certain degree, temperature distribution within inner side of melt becomes significantly inhomogeneous that causes many defects in the products. In this case, we can improve the

Optimization and Simulation for Ceramic Injection Mould of ZrO2 Fiber Ferrule 153

machine. This is the main advantage of rectangular runner. However, it is rather difficult to demould for rectangular runner without demoulding inclination. Therefore, we usually use

Width of the runner *D* 1.13 1.60 1.00 1.07 1.12

with unit length *<sup>V</sup>* 12.57 16.83 16.00 16.04 14.61

The efficiency of circular runner is highest and its runner volume to its unit length is minimal. Decreasing runner volume can promote the utilization of raw materials and save energy. However, if the circular runner is used in the cold-runner mould, circular runner needs to be divided into two semicircular runners on the parting surfaces of cover half and moving half respectively. These two semicircular runners have to be exactly the same. Therefore, it would be very difficult to manufacture mould with circular runners. Usually, the circular runners are used in the hot-runner mould rather than in the cool-runner mould. Apparently, with the same cross-section shape area, efficiency of U-shape runner is highest compared with that of semicircular and ladder runners. The width of U-shape runner is smaller than that of circular runner. With the same efficiency and length (unit length), the volume of U-shape is minimal among the semicircular, ladder and U-shape runners and next to that of circular runner. Therefore, U-shape is most suitable in the cool-runner mould. Semicircular runner is not the perfect approach for its minimal efficiency and largest width

Table 4 shows the parameters of various cross-section shapes with the same area ( 4 *S*

Circular Diameter *D* (*2r*) 4

Runners Cross-section shapes Parameters Values (*mm*)

semicircular Diameter *D* (*2r*), height (*t*) *D*=5.65; *t*=2.825

U-shape Width (*W*), height(*H*) *W*=3.98; *H*=3.71

line(*a*), height(*h*)

Rectangular Width (*a*), height (*b*) *a*=*b*=3.54

Ladder Upper line (*b*), lower

Table 4. Parameters of various cross-section shapes.

Semicircular runner

Rectangular runner

0.282 0.244 0.250 0.250 0.262

Ladder runner

U-shape runner

> ).

*b*=3.8; *a*=3.3; *h*=3.534

gate with rectangular cross-section in practice.

Runners Circular

Efficiency of the runner

Volume of the runner

and volume.

**2.2 Modeling and mesh generation** 

runner

Table 3. Comparison between the analytical solutions of various runners.

injection pressure moderately. However, it would affect clamp if injection pressure becomes too high.

For improving runner efficiency, many measurements could be adopted during designing and manufacturing stages. Firstly, the area of runner cross-section shape can be increased, which decreases the resistance to melt flow. However, it would waste energy and raw materials if the area of runner cross-section shape becomes oversize. Secondly, the contact area between runner and melt could be diminished by decreasing periphery length of runner cross-section shape. Thirdly, runner layout should be simple and its length should be minimal. Finally, the runner surface roughness can be decreased. Normally, Ra is between 0.8 and 1.8*m* . Also, mould temperature needs to be controlled within certain range.

Projected area of runner on the parting surface should be minimal. The injection area actually is decreased if we decrease projected area, which diminishes the opening force of mould. In this way, we can adequately use the clamp force of injection machine to clamp the mould.

The smaller the runner volume is the better. This would improve utilization ratio of raw materials and save energy. The runner volume with fixed length would become smaller as the runner cross-section shape area decreases. Hence, the runner cross-section shape area should not be oversize.

Runners with advantages mentioned above can be considered to have high efficiency. And runner efficiency is expressed by equation 2.

$$
\eta = \frac{S}{L \bullet I} \tag{2}
$$

where is runner efficiency, S is runner cross-section shape area, L is peripheral length of runner cross-section shape, *l* is runner length and *L l* is runner lateral area.

Equation 2 illustrates that runner efficiency is equal to the ratio of runner cross-section shape area to its lateral area. Also, the runner lateral area is equal to the peripheral length of runner cross-section shape multiplied by runner length. Therefore, increasing the runner cross-section shape area, decreasing the peripheral length of runner cross-section shape and reducing the runner length all can improve runner efficiency. In this paper, runner efficiency refers to the runner efficiency when runner length is unit length ( 1 *l* ). Its value is equal to the ratio of runner cross-section shape area to its peripheral length (equation 3).

$$
\eta = \frac{S}{L} \tag{3}
$$

Runner efficiency is influenced by its cross-section shape area and peripheral length. Therefore, runner efficiency is related to its geometric parameters of cross-section shape.

We compare various runners under the same conditions (Table 3). In the Table 3, is runner efficiency and D is runner width. Cross-section shape areas of different runners are the same ( <sup>2</sup> *s mm* 1 ) when calculating and D. V is the runner volume when runner length is unit length and efficiency is 1 ( 1 ). According to Table 3, the width of rectangular runner is minimal. Dimension of runner projection on the parting surface would be decreased if we reduce the width, which improves the mode-locking of the injection

injection pressure moderately. However, it would affect clamp if injection pressure becomes

For improving runner efficiency, many measurements could be adopted during designing and manufacturing stages. Firstly, the area of runner cross-section shape can be increased, which decreases the resistance to melt flow. However, it would waste energy and raw materials if the area of runner cross-section shape becomes oversize. Secondly, the contact area between runner and melt could be diminished by decreasing periphery length of runner cross-section shape. Thirdly, runner layout should be simple and its length should be minimal. Finally, the runner surface roughness can be decreased. Normally, Ra is between

*m* . Also, mould temperature needs to be controlled within certain range.

Projected area of runner on the parting surface should be minimal. The injection area actually is decreased if we decrease projected area, which diminishes the opening force of mould. In this way, we can adequately use the clamp force of injection machine to clamp the mould.

The smaller the runner volume is the better. This would improve utilization ratio of raw materials and save energy. The runner volume with fixed length would become smaller as the runner cross-section shape area decreases. Hence, the runner cross-section shape area

Runners with advantages mentioned above can be considered to have high efficiency. And

*S L l*

Equation 2 illustrates that runner efficiency is equal to the ratio of runner cross-section shape area to its lateral area. Also, the runner lateral area is equal to the peripheral length of runner cross-section shape multiplied by runner length. Therefore, increasing the runner cross-section shape area, decreasing the peripheral length of runner cross-section shape and reducing the runner length all can improve runner efficiency. In this paper, runner efficiency refers to the runner efficiency when runner length is unit length ( 1 *l* ). Its value is equal to the ratio of runner cross-section shape area to its peripheral length (equation 3).

> *S L*

Runner efficiency is influenced by its cross-section shape area and peripheral length. Therefore, runner efficiency is related to its geometric parameters of cross-section shape. We compare various runners under the same conditions (Table 3). In the Table 3,

runner efficiency and D is runner width. Cross-section shape areas of different runners are

rectangular runner is minimal. Dimension of runner projection on the parting surface would be decreased if we reduce the width, which improves the mode-locking of the injection

is runner efficiency, S is runner cross-section shape area, L is peripheral length of

(2)

(3)

and D. V is the runner volume when runner

). According to Table 3, the width of

is

runner cross-section shape, *l* is runner length and *L l* is runner lateral area.

too high.

0.8 and 1.8

where  should not be oversize.

runner efficiency is expressed by equation 2.

the same ( <sup>2</sup> *s mm* 1 ) when calculating

length is unit length and efficiency is 1 ( 1

machine. This is the main advantage of rectangular runner. However, it is rather difficult to demould for rectangular runner without demoulding inclination. Therefore, we usually use gate with rectangular cross-section in practice.


Table 3. Comparison between the analytical solutions of various runners.

The efficiency of circular runner is highest and its runner volume to its unit length is minimal. Decreasing runner volume can promote the utilization of raw materials and save energy. However, if the circular runner is used in the cold-runner mould, circular runner needs to be divided into two semicircular runners on the parting surfaces of cover half and moving half respectively. These two semicircular runners have to be exactly the same. Therefore, it would be very difficult to manufacture mould with circular runners. Usually, the circular runners are used in the hot-runner mould rather than in the cool-runner mould.

Apparently, with the same cross-section shape area, efficiency of U-shape runner is highest compared with that of semicircular and ladder runners. The width of U-shape runner is smaller than that of circular runner. With the same efficiency and length (unit length), the volume of U-shape is minimal among the semicircular, ladder and U-shape runners and next to that of circular runner. Therefore, U-shape is most suitable in the cool-runner mould. Semicircular runner is not the perfect approach for its minimal efficiency and largest width and volume.

### **2.2 Modeling and mesh generation**

Table 4 shows the parameters of various cross-section shapes with the same area ( 4 *S* ).


Table 4. Parameters of various cross-section shapes.

Optimization and Simulation for Ceramic Injection Mould of ZrO2 Fiber Ferrule 155

During these simulations, injection temperature is 140 C and mould temperature is 60 C. Injection time, pressure and velocity are controlled by program. The simulation outcomes of

Circular Semicircular Rectangular Ladder U-shape

Filling time (s)

A Circular 96.492 0.1847 7.3 1.8128 B Semicircular 105.177 0.1868 10.3 1.8277 C Rectangular 103.587 0.1860 8.7 1.7344 D Ladder 103.668 0.1858 8.6 1.7811 E U-shape 100.792 0.1854 8.1 1.8101

Temperature difference (°C)

Clamp force (ton)

Fig. 5. Filling time simulation.

Fig. 6. Temperature difference simulation.

Fig. 7. Clamp force simulation.

Cross-section shape

Serial number

various runner cross-section shapes are shown as Table 6.

Pressure drop (MPa)

Table 6. Analytical parameters of various runner cross-section shapes.

#### **2.3 Feedstock rheology**

Compositions of ZrO2 feedstock are filler (solid paraffin), adhesive (vinyl acetate polymer) and lubricant (stearic acid). These compositions are shown as Table 5 (Wenjea et al., 1999) and the relationship between viscosity and shear rate is shown as Fig. 3.


Table 5. Compositions of ZrO2 feedstock.

Fig. 3. Relationship between viscosity and shear rate.

#### **2.4 Simulation outcomes**

Pressure drop, filling time, temperature difference and clamp force determines the product quality and these are important parameters of injection machine. In this paper, we use the parameters mentioned above to discuss simulation outcomes of various cross-section shapes (Fig. 4, Fig. 5, Fig. 6, Fig. 7).

Fig. 4. Pressure drop simulation.

Fig. 5. Filling time simulation.

Compositions of ZrO2 feedstock are filler (solid paraffin), adhesive (vinyl acetate polymer) and lubricant (stearic acid). These compositions are shown as Table 5 (Wenjea et al., 1999)

(SA)

solid paraffin(PW) Vinyl acetate polymer

and the relationship between viscosity and shear rate is shown as Fig. 3.

Zirconia (PSZ) stearic acid

Mass fraction (%) 86.7 0.9 7.0 5.4 Volume fraction (%) 50.0 3.3 28.0 18.7

Pressure drop, filling time, temperature difference and clamp force determines the product quality and these are important parameters of injection machine. In this paper, we use the parameters mentioned above to discuss simulation outcomes of various cross-section shapes

**2.3 Feedstock rheology** 

Table 5. Compositions of ZrO2 feedstock.

Fig. 3. Relationship between viscosity and shear rate.

**2.4 Simulation outcomes** 

(Fig. 4, Fig. 5, Fig. 6, Fig. 7).

Fig. 4. Pressure drop simulation.

Fig. 6. Temperature difference simulation.

Fig. 7. Clamp force simulation.

During these simulations, injection temperature is 140 C and mould temperature is 60 C. Injection time, pressure and velocity are controlled by program. The simulation outcomes of various runner cross-section shapes are shown as Table 6.


Table 6. Analytical parameters of various runner cross-section shapes.

Optimization and Simulation for Ceramic Injection Mould of ZrO2 Fiber Ferrule 157

methodology to get the best parameter combination based on the range analysis of orthogonal experiment. Also, the conclusion could be tested by the CAE comparison

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,

(a) (b)

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

Injection molding CAE technology uses finite element methodology, finite difference methodology and boundary element methodology to analyze the flow, dwell and cooling stage. It can calculate stress distribution within product and mould to predict product quality. Also, it can analyze the influences of process conditions, material parameters and mould structure on the products for the purpose of optimizing mould structure and process

Experiment design method (DOE) is mainly used to acquire the experimental data and analyze the experimental data and results scientifically. The main DOE application is the orthogonal experiment which designs the experiment based on data orthogonality (Yang et al., 2004). There are many distinct advantages of orthogonal experiment. Firstly, it can select a small number of experimental conditions, which are representative, from a large number of experimental conditions. Secondly, the best experimental conditions and manufacture process could be determined by analyzing experimental outcomes with those representative conditions. Finally, it would be much easier to process the data based on the orthogonal

Orthogonal table is the most important, basic tool and orthogonal experiments can easily calculate the effect of each condition on the results and display them by tables. Then, we can determine the best parameters after range analysis and comparison. All the calculations are done by tables and the whole processes are rather easy. Therefore, DOE is able to shorten the cycle of developing and designing new products, which is necessary to the manufacture and

experiments.

2005, 2007).

with circular shunt.

parameters.

experiment.

**3.2 Orthogonal experiment methodology** 

**3.1 Layout of runner system** 

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


Table 7. Comparison between runners.

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 hand, rectangular runner has the smallest clamp force.

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

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

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 product quality, should be as high as possible.

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 methodology to get the best parameter combination based on the range analysis of orthogonal experiment. Also, the conclusion could be tested by the CAE comparison experiments.
