Rear outer drum is an important component of a drum washing machine, typically made of polypropylene (PP) + 20% glass fiber. Due to undercuts around outer wall, structure is complex and requires four-sided slider core-pulling for molding, as shown in Figure 1. In Figure 1, points I and II are motor mounting posts, with undercuts in both horizontal and vertical directions, requiring core-pulling in two directions, as shown in Figure 2. This structure cannot be molded using conventional slider core-pulling. An innovative design incorporates a special inclined push structure within slider, enabling successful core-pulling in both directions.

 

Figure 1: Rear Outer Drum Structure

 

Figure 2: Core-Pulling Direction

Composite core-pulling mechanisms come in various forms, such as composite inclined slider secondary core-pulling mechanisms, composite half-slider mechanisms, outer wall half-slider mechanisms, and outer wall undercut demolding sub-mechanisms. This section introduces a composite core-pulling mechanism with an in-slider inclined push.

Rear wall of outer cylinder has multiple undercuts, requiring a slider core-pulling mechanism on all four sides, as shown in Figure 3. In Figure 3, top-side slider 3 and bottom-side slider 1, due to their long core-pulling distance (110 mm), use a hydraulic cylinder piston rod to drive core-pulling mechanism. Operating-side slider 2 and non-operating-side slider 4 use a slanted guide post core-pulling mechanism.

 

Figure 3 Slider Layout
1. Bottom-side slider 2. Operating-side slider 3. Top-side slider 4. Non-operating-side slider
Based on above analysis, motor mounting post in the bottom-side slider 1 requires core-pulling in two directions. While hydraulic cylinder piston rod drives slider to pull core, slanted push structure built into slider completes core-pulling action in one direction first. Then, bottom-side slider 1 continues to move to complete core-pulling in the other direction. Composition of bottom-side slider 1 core-pulling mechanism is shown in Figure 4. In Figure 4, driving force of bottom-side slider 1 is provided by hydraulic cylinder 4. Hydraulic cylinder and slider are connected through hydraulic cylinder connector 5. After slider reaches set position, a signal is provided by limit switch 3. When slider moves, it is guided by slider pressure plate 7. Inclined push structure 2 is built into ground-side slider 1. Slider and inclined push structure move sequentially, cooperating to complete core-pulling action in two directions.

 

Figure 4 Ground-side slider assembly
1. Ground-side slider 2. Inclined push structure 3. Limit switch 4. Hydraulic cylinder 5. Hydraulic cylinder connector 6. Wear-resistant plate 7. Slider pressure plate

Inclined push core-pulling structure, as shown in Figure 5, mainly consists of a fixed block 2, a limiting block 3, an inclined push rod 5, and a guide block 6. Guide block 6 is fixed to inclined push rod 5 by a pin and can slide within square groove of fixed block 2. Limiting block 3 is fixed to ground-side slider by screws 4. When slider moves, it drives inclined push structure to complete core-pulling action. As shown in Figure 1, vertical undercut at motor mounting post is 24 mm. Core-pulling distance is generally 2-3 mm larger than undercut, therefore core-pulling distance H is 26 mm, and inclined push angle is 25°, as shown in Figure 6. Calculations show that distance inclined push structure moves within slider is S = H/sin25° = 61.52 mm, and horizontal distance is L = H/tan25° = 55.75 mm.

 

Figure 5: Components of inclined push structure
1. Water nozzle connector 2. Fixing block 3. Limiting block 4. Screw 5. Inclined push rod 6. Guide block

 

Figure 6: Core pulling distance

Ground-side slider composite core pulling mechanism is shown in Figure 7, and actual mold is shown in Figure 8. Since it needs to complete core pulling in two directions, operation process is complex. Specific working process is as follows:

 

Figure 7: Ground-side slider composite core pulling mechanism
1. Ground-side slider 2. Fixing block 3. Limiting block 4. Hydraulic cylinder 5. Inclined push rod 6. Guide block

 

Figure 8: Actual mold
(1) Mold closing and injection, followed by pressure holding and cooling, then mold opening to the set position.
(2) Piston rod of hydraulic cylinder 4 retracts, driving ground-side slider 1 to move in -X direction. Simultaneously, slider's movement drives built-in inclined push rod 5. Due to its positional limitations, inclined push rod 5 can initially only move in Y direction within groove of fixed block 2, with no displacement in X direction. When inclined push structure moves 26 mm in Y direction, it completely exits Y-direction undercut of molded plastic part at motor fixing post. At this point, slider moves 55.75 mm in X direction, and D-side of limiting block 3 touches E-side of inclined push structure.
(3) When slider moves 55.75 mm in X direction, guide block 6 also moves to B-side position of fixed block 2. As slider continues to move in X direction under action of hydraulic cylinder piston rod, limiting block 3 fixed on slider drags inclined push structure and slider to move another 54.25 mm until they completely exit X-direction undercut. This successfully completes core-pulling action in both directions of plastic part.
(4) After core-pulling action is completed, molded plastic part is ejected by push rod set on mold.
(5) During mold closing, hydraulic cylinder piston rod extends outward, driving ground-side slider 1 and inclined push rod 5 to move together 54.25 mm in X direction. At this time, guide block 6 touches C surface of fixed block 2, preventing inclined push rod 5 from continuing to move in X direction. It can only move in Y direction under action of slider's inclined surface.
(6) When ground-side slider 1 continues to move 55.75 mm in X direction, inclined push rod 5 moves 26 mm in Y direction, completing core-pulling reset in both directions.
(7) After core-pulling mechanism resets, mold closing and injection are performed, entering next molding cycle.