Intake pipe bracket is an important accessory in a car engine. Product is shown in Figure 1. Maximum external dimension of product is 270.00 mm * 242.50 mm * 118.00 mm, average thickness of plastic part is 2.65 mm, material of plastic part is PP-T40, shrinkage rate is 1.010, and weight of plastic part is 408.10 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.

 

Figure 1 Product map of intake pipe bracket
Air intake pipe bracket product is a complex product with an inclined tube in the shape, and it is necessary to design inclined slider core pull. There is a round hole and 2 screw columns on outer side of tube wall of inclined tube, and inclined slider core pulling is also required. When pulling core of inclined slider at these two places, junction between outer bottom of round tube and body of plastic part also needs to be included in core pulling of slider. There is R at end edge of pipe wall inside plastic part, where R must be formed from inside of plastic part, therefore, a sloped top needs to be designed here. 3D drawing of mold design is shown in Figure 2.

 

Figure 2 3D drawing of mold

 

Figure 3 Parting plane diagram
Material of plastic parts is 40% calcium carbonate filled PP material. Calcium carbonate is a commonly used inorganic filler. It has advantages of low price, easy to use, easy surface treatment, easy color adjustment, and less wear to equipment. It is widely used in PP materials.
Addition of calcium carbonate to pp mainly plays following roles:
Calcium carbonate plays a skeleton role in plastics, which can improve dimensional stability of plastic products, improve hardness and rigidity of plastic products. Addition of calcium carbonate can change rheological properties of plastics, also help in processing and shaping of plastics. It can not only improve hardness of product, but also improve surface gloss and surface smoothness of product. It can also reduce shrinkage rate, linear expansion coefficient and creep properties of plastic products, and improve heat resistance of plastic products. Reduce cost of plastic products, price of ordinary calcium carbonate is far lower than price of plastic, addition of calcium carbonate will reduce cost of plastic products. Calcium carbonate is added to automobile engine parts to improve impact resistance, absorb shock, and reduce noise.

 

Figure 4 3D drawing of the back mold
Size of plastic parts is large, coupled with inclined slider core pulling in two directions, so mold is bulky, mold cavity ranking is 1 cavity, and mold base is a standard mold base DCH6570 A200 B130 C195 GP500 EGP ∅30 ( 4X), mold is positioned so that one slider is facing sky side and the other slider is facing the non-operating side. In the plan view of front and rear molds, four sides of plastic part are vertical, but cylindrical shape of core pulling is not vertical to shape. When mold is designed and ranked, a slider needs to be positioned in vertical direction, that is, sky side. This will tilt plastic part in plane. A basic principle of mold design is that for slider core pulling, at most one direction of inclination can be designed, and sliders inclined in two directions cannot be designed. Because sliding block inclined in two directions will bring great inconvenience to mold design, processing and inspection, it should be avoided as much as possible. Two inclined positioning blocks are designed on the edge of mold. There is insufficient space on both sides of slider, and slider core is not designed.
Positions of two oblique core-pulling sliders are staggered. In the process of mold clamping and mold opening, two sliders need to move in sequence. Therefore, two inclined sliders are controlled by oil cylinders. Inclined surface of slider is locked with A plate, and a wear-resistant plate is designed on inclined surface. Inclined guide rails at the bottom of slider are all inlaid design. Fixing method of oil cylinder needs to be paid attention to. Piston rod of oil cylinder cannot be screwed directly on slider seat. Correct way is to screw piston on joint, and then clamp joint in T-slot of slider seat.
Gating system adopts glue feeding method of turning from a small nozzle to a large nozzle. Gate is designed as a side gate, and glue is fed from a side gate at the edge of plastic part.
Ejection of plastic parts adopts inclined ejector and ejector pin ejection. Sloping roof is a sloping roof with a T-shaped groove structure.
Front and rear molds of mold are designed for cooling in pool. Slider is designed with a water-carrying circuit with direct water-carrying cooling to ensure effective injection molding.

 

Figure 5 Collision between lifter and slider