To respond to diverse market demands, two differentiated charging pile shell design schemes are proposed, as shown in Figure 1. Scheme 1 (gun cable type) adopts a bottom cable exit structure, while Scheme 2 (gun holder type) integrates gun holder interface below front flip cover. Except for cover, all other components of charging piles are universal parts to reduce R&D and production costs. Structural features of cover are shown in Figure 2. Gun cable type cover adopts a flat and simple design, can be equipped with an optional electricity meter window module; gun holder type cover integrates gun holder interface, flip cover hinge, and electricity meter window. The overall dimensions of both covers are uniformly 290 mm * 415 mm * 33 mm, with an average wall thickness of 3.5 mm. Exterior surface must meet high-gloss surface standard and implement MT-11000 level texture processing. Plastic part is made of PC-ASA composite material, which inherits high impact toughness of PC while also possessing UV resistance of ASA. This allows cover to maintain its toughness at low temperatures and is not easily deformed at high temperatures. It is also resistant to yellowing and cracking during long-term outdoor use. Furthermore, its good flow properties ensure moldability of thin-walled parts. Additionally, 4*φ3.2 mm through holes on the front of gun-mounted cover are perpendicular to mold opening direction, requiring a core-pulling mechanism with an inclined push rod for demolding.

 

Figure 1 Charging Pile Overall Model

 

Figure 2 Charging Pile Cover Geometric Model

Given that gun-mounted and gun-lined covers have a highly consistent overall shape (differences only exist in the central local feature area), a modular design strategy is adopted to integrate two covers into same mold system to optimize mold development costs. By replacing differentiated insert groups, co-mold production of two covers can be achieved. Compared to gun-line type, gun-base type faceplate, due to presence of a gun insertion hole and a hinged rotating shaft hole, requires an additional lifter mechanism, increasing its structural complexity. To save manufacturing costs, a single universal mold is used for both gun-line and gun-base types during mold design, allowing for production of different faceplate styles by replacing internal inserts. Since gun-base type is relatively complex, its structure is compatible with gun-line type. Therefore, mold design primarily uses gun-base type as a reference. Following will describe mold structure design of second option (gun-base type) faceplate.

As a critical external component, faceplate requires high molding quality, necessitating control of overall deformation and prohibiting obvious weld lines, flow marks, and gate marks on the surface. Mold flow analysis shows that single-gate design, due to its excessively long runner, results in a large peak injection pressure (reaching 102.6 MPa); significant temperature difference at melt flow front (approximately 40 ℃) leads to greater warpage. After optimization and analysis, injection pressure was reduced to 57.3 MPa and the overall deformation was reduced to 1.6 mm after adopting a 3-point hot runner system, as shown in Figures 3(a) to (c). Considering factors such as manufacturing cost, insert arrangement, and injection molding machine pressure, a hot runner-to-ordinary runner composite system was finally adopted, with sequential filling achieved through valve needle timing control. Use of a hot runner system can ensure that melt maintains good thermal stability during injection, ensuring that melt is always in a molten state. On the one hand, this ensures stable quality of molded plastic part; on the other hand, it can reduce injection pressure, effectively improve uniformity of melt filling, and reduce generation of flash. Gating system gate arrangement is shown in Figure 3(d), where gate G1 is transferred to bottom surface of plastic part to be molded via a side core-pulling slider; gates G2 and G3 are distributed on both sides via side core-pulling sliders. Side core-pulling mechanism is shown in Figure 3(e), which mainly consists of inclined guide pillars, core-pulling sliders, wedge blocks, and other components. Side-pull sliding block feeding method reduces machining difficulty of mold parts, optimizes layout, makes mold structure more compact, facilitates disassembly and assembly, and makes later maintenance easier. A fan-shaped gate design is adopted, with a front end size of 15 mm * 1.7 mm. To avoid problem of long weld lines caused by multiple gates and to reduce deformation of molded part, control valve pin G1 opens first, G2 and G3 are opened with a delay controlled by sequential valves, realizing sequential filling of cavity and improving surface quality of molded plastic part.

 

Figure 3 Gating System Design

Based on structural characteristics of plastic part, two types of fixed mold cavity plates, A and B, are configured, as shown in Figure 4(a). Cavity plate adopts an integral steel structure to enhance the overall structural rigidity; in addition, a replaceable meter insert is set to expand functionality. Moving mold part adopts an insert structure, as shown in Figure 4(b), mainly composed of a moving mold fixing plate, a moving mold core, and inserts. Its advantage is that it reduces difficulty of NC machining and facilitates later maintenance.
To enhance mold closing accuracy of moving and fixed molds, a conical positioning mechanism is adopted, achieving positioning through cooperation of fixed mold boss and moving mold groove. A 5° guide angle is set on mating surface, which improves mold closing accuracy and avoids excessive lateral wear. For easy assembly and disassembly of moving and fixed mold inserts, positioning pin holes are provided on both sides of moving and fixed mold plate insert frames. Positioning and pairing between moving and fixed mold plates and inserts are achieved through cooperation of pins of different sizes.

 

Figure 4 Design of Fixed and Moving Mold Inserts

For 4*φ3.2 mm rotating shaft holes perpendicular to mold opening direction on the front of cover of Scheme 2 (gun base model), as shown in Figure 5(a), four sets of synchronous side core pulling mechanisms are designed on fixed mold side, as shown in Figure 5(b).
Due to small size of inclined push block, forming position and inclined push rod of inclined push block are designed as an integral structure, achieving a floating connection with inclined push slider 6 through a T-slot. Inclined push slider 6 is rigidly fixed to slider mounting seat 9. Fixed mold cavity plate has oblique through holes of 4°, 8°, 6°, and 7° respectively, from top to bottom (a-d) (see Figure 5(b)). Oblique push rod passes through these holes, converting horizontal movement into a portion of vertical motion. During mold opening, spring 10 with a preload of 15 mm drives slider mounting seat 9 to move 40 mm to the left, causing moving oblique push rod 2 to perform a combined motion along oblique holes of fixed mold cavity plate 7, ultimately achieving a core-pulling distance of 2.3 mm on both sides and 3.8 mm in the middle. This scheme successfully achieves 1:17 micro-hole demolding.

 

1. Plastic part (final position) 2. Lifter pin (final position) 3. Lifter slider (final position) 4. Plastic part (initial position) 5. Lifter pin (initial position) 6. Lifter slider (initial position) 7. Fixed mold cavity plate 8. Fixed mold fixing plate 9. Slider mounting base 10. Spring 11. Fixed mold plate plate 12. Fixed mold base plate
Figure 5 Side Core-Pulling Mechanism Design

Mold cooling system has a decisive influence on molding quality of plastic parts (especially warpage control), and it is necessary to ensure a uniform three-dimensional thermal field distribution. For characteristics of flat plastic parts, a gridded three-dimensional water channel architecture based on DC channels is adopted. Moving mold system integrates 5 independent circuits, as shown in Figure 6(a). A φ12 mm main cooling ring is arranged at upper and lower ends of moving mold fixing plate to achieve base temperature control. Moving mold core adopts a three-channel parallel layout (left-middle-right, spacing (56±1) mm) to effectively suppress deformation caused by cooling differences. Moving mold insert is equipped with an L-shaped water channel (180° rotation) to achieve contour cooling. Fixed mold system is designed with 4 cooling water channels, as shown in Figure 6(b). Fixed mold cavity plate is arranged with orthogonally arranged double-circulation water channels (horizontal/vertical flow direction). Fixed mold insert is equipped with adaptive water channels to achieve local thermal management. Simulation results show that temperature difference between inlet and outlet water of system is stable within ±3 ℃, verifying effectiveness of cooling scheme, as shown in Figure 6(c).

 

Figure 6 Cooling System Design

Core function of ejection mechanism is to achieve safe separation of plastic part from cavity. Its design affects plastic part yield and production efficiency. Due to shrinkage rate (0.6%-0.8%) of PC-ASA material, plastic part in mold experiences strong clamping forces, necessitating a well-planned ejection system. For 290 mm * 415 mm flat plate structure, uneven ejection force distribution can cause warping and whitening defects at ejection area. Therefore, a three-level zoned ejection system is designed in mold: ① Basic ejection unit: A φ5 mm ejector array is arranged in deep groove area around cap surface, with φ8 mm reinforcing ejectors on both sides of screw holes. An 8*φ12 mm main ejector frame is used in the bottom area to form basic demolding frame; ② Deformation resistance enhancement unit: Nine sets of ejector-block units cover projected surface of plastic part, achieving stress balance across the entire area by doubling contact area; ③ Runner separation unit: Two*φ6 mm runner ejectors are set in each gate area, completing demolding together with main body. Mold ejection mechanism is shown in Figure 7. Simulation verification shows that maximum ejection stress during plastic part ejection drops to 22 MPa, which is less than 30% of yield strength of PC-ASA material, effectively eliminating risk of whitening at ejection area.

 

Figure 7 Ejection Mechanism

Gun-shaped faceplate mold adopts a single-cavity hot runner structure with external dimensions of 750 mm * 700 mm * 714 mm, as shown in Figure 8. Its working process is based on F direction as reference axis. Mold working process is as follows:
(1) Injection Molding. Injection molding machine pushes mold to close. Under pressure of injection molding machine, melt enters mold cavity through hot runner insert 21, runner insert 34, and gate, filling the entire cavity and completing pressure holding-cooling-solidification process cycle.
(2) Mold Opening and Core Pulling. When injection is completed and mold opens, injection molding machine slider drives moving mold to move in F direction. Moving mold plate 7 and fixed mold plate 18 separate along parting surface. Inclined push rod 35, driven by inclined push slider 16, completes lateral core pulling of through hole of plastic part. Synchronous core-pulling slider 26 and slider insert 27 achieve lateral displacement under guidance of inclined guide post 25, completing external core-pulling of gate area. At this time, core-pulling slider 26 and slider insert 27 remain at moving mold plate 7.
(3) Ejection of plastic part. Injection molding machine pull rod drives connecting block 28, pushing ejector plate 3 and ejector fixing plate 4 in linkage, so that lifter 6 + ejector block 10 and ejector 29 work together to achieve smooth demolding of plastic part driven by moving mold core 11.
(4) Mechanism reset. During reset, connecting block 28 drives moving mold to reset, while reset spring 5 ensures precise return of ejector system (ejector fixing plate 4, ejector plate 3, and ejector 29, etc.).
(5) Mold closing. Each motion unit re-meshes at parting surface, and after dynamic calibration, returns to its initial state, completing injection closed loop and waiting for next injection cycle.

 

1. Lifting ring 2. Moving mold base plate 3. Ejector plate 4. Ejector rod fixing plate 5. Return spring 6. Lifter rod 7. Moving mold plate 8. Moving mold fixing plate 9. Positioning wedge 10. Ejector block 11. Moving mold core 12. Plastic part 13. Fixed mold cavity plate 14. Gun nozzle insert 15. Fixed mold fixing plate 16. Lifter slider 17. Slider mounting seat 18. Fixed mold plate 19. Fixed mold base plate 20. Positioning ring 21. Hot runner insert 22. Spacer block 23. Limiting post 24. Wedge block 25. Angled guide post 26. Core-pulling slider 27. Slider insert 28. Connecting block 29. Ejector rod 30. Guide sleeve seat 31. Guide sleeve 33. Screw 34. Runner insert 35. Lifter rod 36. Fastening screw
Figure 8. Mold Structure

Mold production machine uses a 1000 kN injection molding machine. Plastic part material is Kingfa JH960-6010, and plastic part undergoes texturing treatment. Injection molding machine barrel temperature is set to 240℃, hot runner temperature is set to 230℃, and mold temperature is set to 60℃. During holding pressure stage, injection pressure is reduced to 80% of injection pressure, and holding pressure time is set to 10s; after holding pressure ends, it drops from 80% to 0 for 2s, completing injection molding of plastic part.
Production verification shows that molded plastic part, as shown in Figure 9, has a good appearance, with no obvious shrinkage marks, flash, weld lines, or other molding defects. Pass rate is high, meeting needs of mass production.

 

Figure 9. Actual Molded Plastic Part (Gun Mount)