Refrigerator lock buckle is shown in Figure 1. Appearance is composed of a main shell and a derivative shell. Main shell and derivative shell are provided with multiple plug-in holes. There is an inclined wall at the center of combination of the two, and 4 inclined holes are provided on inclined wall. Holes A, B, and C are provided on the three side walls at one end of derivative shell. The overall dimensions of refrigerator lock buckle plastic part are 185 mm*77 mm*40 mm, average wall thickness is 2.5 mm, material is 10% carbon fiber modified PEEK, and shrinkage rate is 0.9%~1.2%.

 

Figure 1 Refrigerator lock buckle

Combined with structural characteristics of plastic part, maximum outer edge contour of plastic part is used as parting line to obtain main parting surface of mold, as shown in Figure 2. Parting surface P0 divides main molding parts into cavity plate insert 1 and core insert 3. Due to needs of processing and demolding, different local molding inserts are further divided from cavity plate insert 1 and core insert 3. In combination with demolding needs of plastic part holes A, B, and C, hole A insert 8, hole B insert 2, and hole C insert 12 are divided. These three inserts, combined with slider core pulling mechanism, can implement side core pulling demolding for corresponding holes. In view of demolding needs of four inclined holes, inclined hole insert 13 is designed for its side core pulling demolding. There are many plug-in holes on plastic part. If these parts are molded with integral inserts, integral inserts are difficult to process. Inserts are disassembled by disassembling inserts and then assembled in main molding parts, which can reduce difficulty of molding part processing and reduce mold manufacturing cost. For cooling of cavity, cavity plate insert 1 and core insert 3 are cooled by φ10 mm water channels respectively, and water channels are about 20 mm away from cooling surface of plastic part. A single cavity uses a single point gate to pour at geometric center of plastic part to be molded to ensure that cavity is filled. Cavity uses installation gap of insert for exhaust, and exhaust gap is 0.02 mm. Molding parts are made of S136 with a heat treatment hardness of 52~54 HRC to prevent wear and extend service life of mold.

 

Figure 2 Parting and molding part design
1. Cavity plate insert 2. Hole B insert 3. Core insert 4. Local insert 5. Local insert 6. Local insert 7. Local insert 8. Hole A insert 9. Cylindrical local insert 10. Tubular local insert 11. Local insert 12. Hole C insert 13. Oblique hole insert

Mold uses point gate casting to achieve automatic separation of runner condensate from plastic parts. Before parting surface P0 is opened, inclined hole insert 13 first completes oblique core pulling of four inclined holes with the help of opening of fixed mold side mold plate. Hole A insert 8, hole B insert 2, hole C insert 12 and slider core pulling mechanism jointly complete side core pulling of corresponding holes. After that, parting surface P0 is opened, mold push rod and push tube are pushed by injection molding machine ejector to push plastic part out of core insert 3 to achieve complete demolding.

Mold adopts a three-plate mold frame for bearing of various structural parts, as shown in Figure 3, cavity layout is 1 mold and 2 cavities. Two cavities are A1 and A2, structural parts of two are arranged in same way. They are arranged 180° rotationally symmetrically with center axis of mold as symmetry center in mold frame. Taking structural parts arrangement of A1 cavity as an example, fixed mold part is mainly arranged with cavity plate insert 1, cylindrical local insert 9, tubular local insert 10, pouring system, and four fixed mold first core pulling mechanisms M1~M4. Mechanism M1 is a locking block driven inclined slider core pulling mechanism, and M2, M3, M4 are locking block driven linear slider core pulling mechanisms, and the two have same structure. Movable mold side is mainly arranged with core insert 3, push rod 14, and push tube 15.

 

Figure 3 Mold mechanism component layout
1. Cavity plate insert 3. Core insert 14. Push rod 15. Push tube 16. Gate sleeve 17. Sealing ring 18. Sealing ring
Mechanism M1 is used to drive inclined hole insert 13 to implement inclined core pulling, mechanism M2 is used to drive hole A insert 8 to implement side core pulling, mechanism M3 is used to drive hole B insert 2 to implement side core pulling, and mechanism M4 is used to drive hole C insert 12 to implement side core pulling. For cooling of cavity plate insert 1 and core insert 3, mold is provided with cooling pipes C1 and C2. When pipes C1 and C2 pass between mold plate and molded part, leakproof sealing rings 17 and 18 must be set around water hole. Point gate is opened at geometric center of plastic part to be molded. Design of point gate and runner cross-section dimensions is shown in Figure 4. Runner cross-section adopts a U-shaped cross-section.

 

Figure 4 Design of gate and runner cross-section dimensions

Mold frame mold plate includes parts 19~22 and parts 24~26, as shown in Figure 5. Under joint control of short tie rod 35, long tie rod 31 and clamping buckle 30, mold frame opens mold in order of P1→P2→P3, and closing order is opposite.

 

Figure 5 Installation of mechanism M1 and M3
1. Cavity plate insert 2. Hole B insert 3. Core insert 13. Inclined hole insert 19. Fixed mold base plate 20. Stripper plate 21. Fixed mold plate 22. Locking block 23. Pressure strip 24. M3 slider 25. Moving mold plate 26. Pad 27. Push rod fixing plate 28. Push plate 29. Moving mold base plate 30. Locking buckle 31. Long pull rod 32. Limit block 33. Locking block 34. Spring 35. Short pull rod 36. Spring
Components of mechanism M1 mainly include inclined hole insert 13, locking block 33, limit block 32, and spring 34. When mold is opened at P1 and P2, fixed mold plate 21 carries inclined hole insert 13 downward (inclined hole insert 13 is designed as a slider), locking block 33 forces inclined hole insert 13 to pull core according to F1 through guide convex edge above it, so as to realize the first core pulling and demolding of four inclined holes of plastic part. When resetting, locking block 33 pushes inclined hole insert 13 to reset and locks it during injection. Spring 34 plays the role of auxiliary drive reset.
Components of mechanism M3 include locking block 22, pressure strip 23, M3 slider 24, spring 36. Similar to mechanism M1, it is also a fixed mold core-pulling mechanism. When mold is opened on P1 and P2 surfaces, locking block 22 drives M3 slider 24 and hole B insert 2 to perform side core-pulling. When resetting and closing, locking block 22 drives M3 slider 24 to reset and lock it during injection. Push tube 15 is installed on push plate 28 and is pressed by push rod fixing plate 27. Center rod is installed on movable mold base plate 29 and locked with a pressure plate.
Mechanisms M2 and M4 are installed as shown in Figure 6. Fixed mold core is also pulled first by locking block driving slider. Due to existence of mechanisms M2, M3, and M4, when closing mold, in order to prevent push rod 14 and push tube 15 from interfering with slider head, reset spring 38 must be used on reset rod 39 to push push plate 28 to reset first, and push plate 28 must be provided with a guide mechanism push plate guide column 40 for motion guidance.

 

Figure 6 Installation of mechanism M2 and M4
1. Cavity plate insert 3. Core insert 8. Hole A insert 12. Hole C insert 21. Fixed plate 25. Moving plate 28. Push plate 37. Pull rod 38. Reset spring 39. Reset rod 40. Push plate guide pin

As shown in Figures 5 and 6, mold is installed on injection molding machine. After mold cavity completes filling, pressure holding, cooling and other processes, mold is opened. Slider of injection molding machine drives movable mold to retreat, mold P1 surface opens, and sliders of mechanisms M1~M4 are driven at the same time to start core pulling. Runner condensate is pulled off at point gate, and plastic part is separated from runner condensate. Then, movable mold continues to move downward, mold P2 surface opens, runner condensate is automatically demolded, and core pulling action of four mechanisms is completed. As movable mold continues to retreat, mold P3 surface opens, plastic part is ejected from cavity plate insert 1, and remains on core insert 3. After movable mold retreats to a certain position, push plate 28 is supported by injection molding machine ejector, and movable mold plate 25 continues to retreat. Plastic part remains on push rod 14 and push tube 15, and is separated from core insert 3. Finally, it automatically falls off from push rod 14 and push tube 15, and complete demolding is achieved. When resetting, action process is opposite to mold opening process.