Inner outer shell of door component is divided into two plastic parts, see 3D diagram. Maximum outer dimension of product is 266.26.0 mm * 152.93 mm; average glue thickness of plastic parts is 3.00 mm, plastic parts material is FPP ATX799HF, and shrinkage rate is 1.009. Technical requirements for plastic parts are that there must be no defects such as peaks, underfilling, flow lines, pores, warping deformation, silver streaks, cold materials, jet lines, etc. and they must comply with ROSH environmental requirements.

 

Figure 1 3D diagram of inner shell mold of door component

 

Figure 2 Diagram of needle valve hot runner
As can be seen from Figure 3, plastic part is a flat closed shell, and mold design cavity ranking is 1+1. Due to large size of plastic part, mold is a large mold. Since customer is in North America, customary standard for mold design is DME standard. Accordingly, both mold base and mold standard parts need to be in imperial format. Mold base of this set of molds is 38"*21" in imperial size. In addition, because mold is a hot runner mold, shape of mold base is quite different from domestic standard mold base.

 

Figure 3 Parting surface diagram

 

Figure 4 Water transportation system design
Outer surfaces of the two plastic parts are both appearance surfaces and gates cannot be designed. Gate design on the side of plastic part will also affect appearance. For European and American customers, designing horn gates is the best choice. Design of horn gate is shown in Figure 5. Requirements for pouring system of European and American molds are to automatically cut off nozzle in mold, fully automatic injection molding production, no release agent is allowed, product and nozzle material can fall freely or be grabbed by a robot, a hot runner is used when glue needs to be fed on the top of product. Due to expensive labor costs in Europe and United States, it is generally not allowed to design mold structures that require manual trimming of nozzles. Therefore, sub-gate and cowhorn gate can automatically cut off water outlet when ejected, and are widely used. Location of horn gate is shown in 3D diagram. In the past, due to difficulty in processing horn gate insert, horn gate insert was divided into two halves to facilitate processing. At present, with maturity of 3D printing technology, application of integral horn inserts is gradually popularized.
Cooling system of front and rear molds adopts straight-through water transportation and parallel circuit design to increase cooling water flow rate and heat exchange efficiency. Cooling water transport design is shown in Figure 4. Distance between any two water carriers is 2" to facilitate even cooling.

 

Figure 5 Gate and ejection system diagram

 

Figure 6 Guide column exhaust design and dustproof plate
Rigidity issue of large molds is a very important issue, especially for molds with needle valve hot runner systems. In mold design, it is necessary to reduce scope of disassembly and assembly required when repairing or replacing a certain part. Especially when replacing wearing parts, scope of disassembly and assembly should be reduced as much as possible. During dismantling process of hot runner mold, if there is no problem with hot runner system itself and only mold insert needs to be removed, there is no need to disassemble hot runner system. Design four fixed mold plate positioning pins, diameter should be above Φ30, and matching with mold plate should be H7/g6. Their length should exceed tip of hot nozzle, which can protect tip of hot nozzle from being damaged during assembly. When mold is assembled and disassembled for maintenance, you only need to remove fixed mold fixing bolts. Hot runner system is fixed on three mold plates on top surface and does not need to be disassembled, which makes mold maintenance convenient. Although this design adds a hot nozzle fixing plate and increases cost of mold, due to its ease of maintenance, cost savings greatly exceed cost of mold plate and is worthy of promotion. Connection of needle valve hot runner system mold plate is shown in Figure 8.

 

Figure 7 Large sloping roof structure design
Figure 6 shows an example of designing a protective plate to prevent manipulator from accidentally dropping flow channel condensate into push plate, causing an accident. Protective plate is usually made of 5 mm thick PMMA board and fixed on the side of movable mold with 4 countersunk screws. Signal wire of travel switch can pass through protective plate. When push plate is pushed out, edge of push plate and protective plate should be kept away from each other to prevent friction.
Large plastic parts for automobiles, air conditioners and large medical equipment often have large lifters. There are many design structures for large sloping roofs, and most of them in Europe and United States use structure shown in Figure 7. Inclined ejector rod is round and is designed with a guide sleeve, a pressing block is used to position and lock guide sleeve.

 

Figure 8 Connection of needle valve hot runner system mold plate