Among automobile structural parts, air-conditioning shells are representative of more complex products. Today we will take air conditioner shell as an example to analyze design of its mold structure, which is of practical reference value for everyone.

Car air conditioner shell is core component of car air conditioner, product material is PP-TD20. Product design needs to consider multiple functional requirements for assembly, drainage, and air outlet, so its structure is relatively complicated.

 

 

At the beginning of mold design, how to divide front and rear molds is an important issue. According to conventional thinking, naturally side with more bones and columns is on back mold, side with smooth and less bones is on front mold. Because this product is a structural part, appearance requirements are not high, so side with more bones is divided into front mold, side with smooth and less bones is divided into back mold, front and back molds are treated harshly.

 

Product uses a two-point needle valve hot nozzle to feed material and directly point it on the surface of product, as shown in figure below.

 

 

Front and rear mold cores

Undercut 1 and undercut 2 are in front mold. According to general thinking, front mold lifter structure or elastic plate core can be used. This mold uses a cylinder to convert core, one cylinder controls two positions, and uses shovel base to seal.

 

 

 

Rear die slider 1 and slider 2 are structure of slider. Because of limited space, slider 2 cannot be used as a slider block. T-slot is used as a guide in design. This mechanism is suitable for occasions where slider space is small. .

Rear mold slider 3/4/5/6 is a conventional slider structure, and part of slider adopts a spring needle device to prevent product from sticking to slider.

 

There are three inverted buckles on the side of posterior mold bone, with 3 square lifters.

 

Overall rear mold

 

 

 

 

Overall front mold

 

Product diagram of LCD base is shown in Figure 1. Maximum size of product is 327.33 mm * 236.24 mm * 51.9 mm, average thickness of plastic part is 3.0 mm, material of plastic part is HIPS, shrinkage rate is 1.005, and weight of plastic part is 361.68 Grams. Technical requirements of plastic parts are that there must be no defects such as peaks, dissatisfaction with injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.

 

 

Figure 1 Product picture of LCD base
It can be seen from Figure 1 that plastic part is of a large flat shape with a partially enclosed protrusion in the middle, which is used to assemble with rear shell of liquid crystal display. There is a column position in middle convex part, which needs to design front mold slider core. This kind of mold seems to have a relatively simple structure and does not have a complicated mold structure. Due to large size of plastic parts, closed bone positions on the edge of rear mold and multiple bone positions in the middle require a reasonable design of inserts to solve processing technology problems.
When designing mold, mold processing technology must be considered. For multiple cross bone positions, the deepest part reaches 13.35mm, and width at the bottom of mold core is 1.21mm. If these bone positions are processed by machine tools, it is very difficult. If EDM is used for electrode spark processing, it is very troublesome. The most ideal processing method is professional grinder processing. For this reason, rear mold must be designed into a full-inlaid structure, see rear mold insert assembly diagram 3.
Structural method of full inlay is based on reference angle, fine frame of mold plate and two vertical sides farther from reference angle are respectively inclined at 3°~5°. Front mold is an integral mold core, and inclination is made at corresponding position of front mold core to match mold plate. Back mold is a full inlay structure, back mold core is divided into 4 pieces on the edge and one piece in the middle. This design method facilitates simultaneous processing by multiple machine tools, is widely used in large and medium-sized complex molds.
Size of plastic part is large, mold design cavity rank is 1 out 1, mold base is CI5055A100B100C120; gate sleeve 6 has an eccentric design with an eccentric angle of 15.5°. In order to improve accuracy of mold clamping, a zero degree is designed on four sides of mold base. Positioning pins are added between panel and A plate, between square iron and B plate, between square iron and bottom plate to increase rigidity of mold. Because cavity is eccentrically layout, two balance plates are designed on parting surface side, which are made of quenched steel.
Front mold slider adopts a hydraulic cylinder to pull core.
Plastic parts are ejected by a cylinder and a thimble.

 

 

 

 

 

Figure 2 Mould of LCD base

 

Figure 3 Rear mold insert assembly diagram

 

Figure 4 B board diagram