Automobile products are mainly divided into interior parts, exterior parts, and structural parts. Interior parts are represented by dashboard, exterior parts are represented by bumper, and structural parts are represented by intake pipe. Mold structure is like playing chess, and there is no same game throughout ages. For this reason, editor has carefully sorted out 8 sets of automobile mold cases for everyone to appreciate its mold structure.

Figure below shows structure of a certain brand of automobile auxiliary instrument panel plastic parts. Material is PP-TD20, shrinkage rate is 1.011, and average wall thickness is 2.5mm. PP is base of auxiliary instrument panel cover, TD20 is a material with 20% talcum powder added to it. Purpose is to improve rigidity of auxiliary instrument panel plastic parts. Maximum size of this plastic part is 950.9×205.8×208.7mm, which is a large interior part.
Two sides of this plastic part have a unique long wavy shape, which is beautiful, but a large area of undercuts are formed on both sides, including undercuts formed by flanges and bosses. To ensure smooth demolding of plastic part, plastic part needs to be deformed to a certain angle outward before being forced out. Inner bosses of undercuts on both sides of this plastic part are also undercuts. Due to influence of plastic part space, it is impossible to design a lateral core pulling mechanism such as an inclined ejector slider. Inner undercut can only be separated from movable mold core by deforming plastic part to a certain angle outward.

 

Figure below shows parts drawing of automobile auxiliary instrument storage box. Material is ADX1056 PP-TF17, shrinkage rate is generally 1.011, and number of mold cavities is 1*1. Plastic parts are appearance parts and are one of the most important interior parts of automobiles. Size of plastic part is: 254.2*122.5*120.6mm. Characteristics of plastic part are as follows: (1) Appearance of plastic part is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects. (2) Plastic part is an interior decoration part, and appearance of plastic part needs to be leather-grained. Appearance requirements are extremely high, so appearance leather-grain surface must at least ensure that demolding angle is above 5 degrees. Fixed mold surface is treated with 400# sandpaper, and movable mold surface is treated with 320# sandpaper.

 

Figure below shows car rearview mirror base part drawing. Material is PP+GF45%, shrinkage rate is generally 1.004, plastic part is a left and right mirror part, and number of mold cavities is 1+1. Plastic part is a non-appearance part and is an internal functional part. Size of plastic part is: 185.9*113.4*75.8mm. Characteristics of plastic parts are as follows: (1) Appearance of plastic parts is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects. (2) Plastic parts are internal functional parts, and there are many deep bones in plastic parts. Exhaust is strengthened to avoid air entrapment, and deep bones are treated as inserts. (3) Appearance of plastic parts is complex, and there are 2 undercuts on outer side of plastic parts.

 

Figure below shows parts of car rearview mirror. Material is ABS, shrinkage rate is generally 1.005, plastic parts are left and right mirror parts, and number of mold cavities is 1+1. Plastic parts are appearance parts and are one of the most important exterior parts of automobiles. Size of plastic parts is: 254.2*122.5*120.6mm.
Characteristics of plastic parts are as follows: (1) Appearance of plastic parts is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects. (2) Plastic part is an exterior part. Appearance of high-end plastic part is a fine-grained part, and low-end plastic part is a painted part. Appearance requirements are extremely high. (3) Appearance of plastic part is complex, and appearance clip line requirements are extremely high. There is a large undercut on outer side of plastic part and 6 undercuts on inner side. There are many undercuts and area is large. It is a typical structure of automobile rearview mirror mold.

 

Figure below shows part drawing of automobile rearview mirror bracket. Material is ASA, shrinkage rate is generally 1.005, plastic part is a left and right mirror image part, and number of mold cavities is 1+1. Plastic part is an appearance part and is one of the most important exterior parts of automobile. Size of plastic part is: 240.1*74.9*112.5mm.
Characteristics of plastic part are as follows: (1) Appearance surface of plastic part is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects. (2) Plastic part is an exterior part. High-end plastic part has fine lines and low-end plastic part has painted parts. Appearance decoration performance requirements are high. (3) Plastic part has a complex shape and extremely high requirements for appearance clip line. There are two large-area undercuts on outer side of plastic part and two undercuts on inner side. There are many undercuts and area is large. This is a typical structure of automobile rearview mirror mold.
Inner side of plastic part is undercut in direction of fixed and movable mold ejection. Conventional design is to use an oblique push block core pulling structure. For this type of rearview mirror plastic part, according to characteristics of plastic part, it can be forced out and then manually taken out to break plastic part out. Premise is that there must be space for manual breaking out and there must be space for swinging when plastic part is taken out. If this mold uses an oblique push block structure, it cannot solve problem of undercut ejection, so a push block structure is used.

 

Figure below shows automobile rearview mirror rotation axis part drawing. Material is ABS, shrinkage rate is generally 1.005, plastic part is a left and right mirror image part, and number of mold cavities is 1+1. Plastic part is an appearance part and is one of the most important exterior parts of a car. Size of plastic part is: 164.1*89.5*114.9mm. Characteristics of plastic part are as follows: (1) Appearance surface of plastic part is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects. (2) Plastic part is an exterior part. Appearance of high-end plastic part is a fine-grained part, and low-end is a spray-painted part. Appearance decoration performance requirements are high. (3) Appearance of plastic part is complex and appearance clip line requirements are extremely high. There are 3 large-area undercuts on the outer side of plastic part and 1 undercut on inner side. Undercuts are large in area and are a typical structure of automobile rearview mirror mold.

 

Figure below shows car instrument storage box parts diagram. Material is PPC, shrinkage rate is generally 1.012, and number of mold cavities is 1*1. Plastic part is an interior part and is one of the most important interior parts of a car. Size of plastic part is: 362.9*274.6*457.5mm.
Characteristics and design points of plastic part are as follows: (1) Appearance of plastic part is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects.
(2) Plastic part is an interior part, and appearance of plastic part needs to be leather-grained. Appearance requirements are extremely high, so appearance leather-grained surface must at least ensure that demolding angle is above 5 degrees. Fixed mold surface is treated with 400# sandpaper, and movable mold surface is treated with 320# sandpaper.
(3) Shape of plastic part is complex, and appearance clamping line requirements are high. There are three large undercuts on outer side of plastic part, namely S1, S2, and S3. Among them, S3 needs to be made into a tunnel core pull due to limitation of plastic part structure. Tunnel core pull mechanism is key structure of this mold design. Undercut S4 on inner side of plastic part adopts "lifter + inclined push rod" core pull structure.
(4) Before designing mold, check mold draft of A surface (i.e., appearance surface) of plastic part: especially whether area that needs to be etched reaches allowable slope; insertion slope requirement for automotive plastic parts is 7º, both fixed and movable molds must be tested; high-polished plastic parts are 5º.

 

(5) Check large and small end dimensions of all ribs on plastic part: large end cannot be greater than 1/3 of corresponding main wall thickness, otherwise shrinkage marks will appear on the surface; small end cannot be less than 0.6MM, which is not conducive to processing and injection molding.

Figure below shows car map bag parts diagram. Material is PP-M20, shrinkage rate is 1.010, and number of mold cavities is 1+1. Plastic part is an interior decoration part and is one of the most important interior decoration parts of a car. Size of plastic part is: 612.2*258.6*116.9mm.
Characteristics and design points of plastic part are as follows:
(1) Appearance of plastic part is not allowed to have spots, gate marks, shrinkage depressions, weld marks, flash and other defects.

(2) Plastic part is an interior decoration part and is a typical low-pressure injection molded plastic part.

(3) Shape of plastic part is complex and appearance clip line requirements are high. Since plastic part is formed by low-pressure injection molding technology, plastic part is different from general mold when it is split. It is necessary to raise parting surface and adopt a large angle insertion method instead of banging. Purpose of this is to facilitate separation of cloth on plastic part from mold and to facilitate cutting of cloth after injection molding.
Due to this mold splitting method, a slider needs to be designed at the bottom of side wall of this plastic part below PL parting line, so undercut 1 adopts indirect core pulling method of "cylinder + slider + shovel base". (See partial enlarged view C for details) Undercuts 2 and 3 on inside of plastic part both adopt "lifter + inclined push rod" lateral core pulling mechanism.

(4) Since appearance of plastic part is covered with cloth, under molding conditions, slight shrinkage and top whitening of plastic part are acceptable.

(5) Since plastic part is molded by low-pressure injection molding technology, a special low-pressure injection molding machine is required, and molding conditions are strict.