Figure 1 shows central water outlet part of bathroom faucet, which is an internal functional part. Difficulty of this plastic part is inner hole area shown in Figure 1 A-A. Inner hole cannot be demolded on mold by slider core pulling, because shape is abnormal, and it cannot be demolded by arc core pulling structure. Wall thickness of plastic part is 2.46 mm. After analysis, plastic part is divided into three parts without changing shape and inner hole size of plastic part, as shown in Figure 2, which is divided into upper cover, main body, and welding body. Figure 2 A-A shows that upper cover and main body are accurately positioned through concave-convex stop position. External dimensions and inner hole dimensions of plastic part have not been changed. This split allows special-shaped tube to be demolded smoothly when mold is opened through moving and fixed molds.

 

Figure 1 Water outlet part of center of bathroom faucet

 

Figure 2 Plastic parts disassembly 1. Upper cover 2. Main body 3. Welded body

Point gate injection molding is used for upper cover and main body. Finally, upper cover and main body are combined, welding body is formed by point gate injection molding. Assemble upper cover, main body, and welded body into a whole to obtain final product, as shown in Figure 3. Pouring point position is analyzed and verified by MoldFlow software, and will not be described in detail.

 

Figure 3 Point gate location

Three different plastic parts are formed in a pair of molds. Mold structure is different from conventional mold structure. Three parts need to be formed separately each time mold is opened and closed. Therefore, core part of movable mold needs to be switched to realize different molding of plastic parts. Figure 4 shows structure of movable core mold. Main parts and components include: runner switching mechanism, fixed mold core, movable mold core, cylinder, cylinder connecting block, ejection mechanism, anti-dropping mechanism, ejector mechanism, etc.

 

Figure 4 Mould structure
1. Runner switching mechanism 2. Fixed model core 3. Moving model core 4. Cylinder 5. Cylinder connecting block 6. Push-out mechanism 7. Anti-dropping mechanism 8. Ejector mechanism

Fig. 5 shows different position states of movable mold core, and Fig. 5(a) shows position state 1 of movable mold core. Main body of aⅠ-cavity molding is left in moving mold core after mold is opened to prepare for next step of forming welded body. Upper cover is formed in bⅡ cavity. When mold is opened, upper cover is fixed on fixed mold core due to effect of anti-dropping mechanism, preparing for next step of forming welded body. Function of cⅢ cavity is to form a welded body after main body of upper cover is assembled. Welded body is finished product, ejection mechanism is pushed out by ejector rod, and d cavity is not formed.

 

Figure 5 Position of movable mold core
1. Fixed mold core 2. Cylinder connecting block 3. Moving mold core 4. Anti-falling mechanism 5. Push-out mechanism 6. Push-out mechanism 7. Push-out mechanism 8. Push-out mechanism
Cylinder is connected to movable model core through cylinder connecting block. Due to pushing action of cylinder, movable model core position state 1 is switched to position state 2, as shown in Figure 5(b). At this time, a-cavity is not formed, function of bⅠ-cavity is to form a welded body after upper cover body is assembled, ejection mechanism is pushed out by ejector rod, and cII-cavity forms upper cover. Main body of dⅢ cavity is left on movable mold core after mold is opened to prepare for next step of forming welded body.
Position state of movable mold core is sequentially switched to state 1 and state 2 through cylinder control, and cycle is like this.

Anti-dropping mechanism is shown in Figure 6, push rod and reset rod are fixed on push rod fixing plate with a cover plate and screws. Spring acts on push rod fixing plate. When mold is opened, spring will push push rod fixing plate and push push rod. After mold is opened, because upper cover is designed with an anti-dropping positioning column, upper cover will be fixed to fixed mold core to prepare for next action. Function of reset lever is to return anti-dropping structure to closed state when mold is closed.

 

Figure 6 Anti-dropping mechanism
1. Reset lever 2. Push rod fixing plate 3. Push plate 4. Push rod 5. Cover plate 6. Spring
Figure 7 shows ejection mechanism. Push rod, reset rod, spring are fixed on push rod fixing plate with a cover plate and screws. Ejection mechanism is pushed by ejector rod, and push rod is pushed to push molded plastic part out of movable mold core to complete demolding of plastic part. Function of spring and reset lever is to ensure that ejection mechanism can return to mold clamping state after ejection action is over.

 

Figure 7 Launch agency
1. Reset lever 2. Push rod fixing plate 3. Push plate 4. Spring 5. Push rod

Runner switching mechanism is installed on fixed mold runner plate to control pouring of different movable mold core positions, as shown in Figure 8. Cylinder is fixed on fixed mold runner plate through cylinder fixing plate, sliding plate is pushed to move back and forth through cylinder connecting rod. Runner switch is installed on sliding plate and follows reciprocating movement of sliding plate to make runner switch in different positions. Different positions of flow channel switch can control connection and closing of flow channel. As shown in Figure 9, combined use of multiple flow channel switches can realize connection and closing of flow channel to achieve required functions. Each position state of runner switch corresponds to each mold clamping state.

Figure 8 Runner switching mechanism

1. Cylinder 2. Cylinder fixing plate 3. Cylinder connecting rod 4. Gate sleeve 5. Press block 6. Pull rod 7. Slide 8. Runner plate 9. Press block 10. Fixed mold runner plate 11. Runner switch

 

Figure 9 Flow channel closed and connected state

Through cooperation of flow channel switching mechanism and moving core, molded plastic part is shown in Figure 10, each mold opening and closing action circulates in turn. Since it is formed on a pair of molds, upper cover and main body can cooperate well, final welding effect is also better, production efficiency of plastic parts is higher, which meets requirements of customers.

 

Figure 10 Molded plastic parts