Instrument panel body product is shown in Figure 1. Maximum size of product is 343.40 mm * 167.13 mm * 48.01 mm, average thickness of plastic part is 2.00 mm, material of plastic part is PP TD40, shrinkage rate is 1.010, and weight of plastic part is 208.88 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, underfilling of injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, etc.

 

Figure 1 Product diagram of dashboard body
Instrument panel body is internal bracket of instrument panel of a Japanese car. It can be seen from Figure 1 that structure of plastic part is a flat and complex shell, movable and fixed molds have many bone positions and column positions, etc., size is relatively large, and mold is a large mold. Material of plastic part is PP TD40, and material is added with calcium carbonate filler, mainly to increase the rigidity and fatigue resistance of plastic part, play role of shock absorption and shock absorption.
Due to large size of plastic parts, mold design cavity ranking is 1 cavity, injection molding machine is 220 tons of Nissan, specifications of 220 tons of JSW injection molding machine are shown in Figure 5, mold design drawing is shown in Figure 2, and mold design specification is shown in Figure 4.
Mold design style book is an important document for commodity mold design. It stipulates number of mold cavities, way of plastic injection, brand grade of mold core steel and standard parts, mold life, injection molding machine model and injection cycle, etc., which are basis for mold design. The most common terms of Japanese molds are briefly introduced as follows:
Matching meeting-mold review meeting; hooking-demolding angle; mold force-clamping force; gold mold-mold; model see this-test pattern Product
Inch method-----size; tip R------spherical surface of sprue sleeve;
Mold review meeting is also called mold meeting meeting in Japanese companies. Review product, mold structure problems and improvement countermeasures, determine mold parting surface, ejection method and gate, all review content should be marked with red and blue pencils or pencils in product drawing, written in mold specification book. After review is completed, fill in relevant review record, stamp on drawing, and sign for confirmation by both parties.
Guide pin and sleeve of mold are primary positioning of entire mold. Because there is a gap of 0.01-0.03mm between guide pin and hole of guide sleeve, for large molds, it is obviously not enough to rely on guide post and guide sleeve to locate. Four conical positioning parts are designed on four sides of mold base. Three-level positioning refers to precise positioning of design tiger's mouth on mold core, which mainly protects precise positioning of inserting surface of mold. Instrument panel body mold is designed with two three-level positioning systems. The first is positioning of tiger's mouth around guide post and guide sleeve of mold base, second is design of tiger's mouth positioning at four corners of front and rear mold cores of mold. Design of so many positioning is mainly due to fact that instrument panel body mold is a large mold, and there is an eccentric design configuration of mold core, so it is very important to design effective positioning and guidance. In order to balance clamping force, a balance block is designed on parting surface 5.
Exhaust of large injection molds is very important. For export molds, exhaust must be analyzed in advance, focusing on areas that are prone to trapping, design exhaust on mold drawing. Vent groove should also be ground on the edge of insert to facilitate injection molding and filling.

 

Due to large size of plastic parts, cavity is ranked 1 cavity eccentrically. Mold base is standard mold base CH5565, front and rear mold cores are positioned and locked by squeezing blocks. Positioning pins are added between movable mold B plate, square iron, and bottom plate to maintain rigidity of mold. Area of plastic parts is large and process of molten plastic is long, so design of gating system is very critical. Considering that there are many bones and holes in plastic parts, there are many factors that affect flow of molten plastic, and filling resistance is relatively large. Therefore, gating system is designed with a 3-point latent gate to feed glue, and gate position is on same side of plastic part. Runner pull pin is designed with a tapered pull pin, which is convenient for manipulator to grab nozzle material. See enlarged view of runner system in Figure 2 of mold design.
Ejection system of plastic parts adopts thimble and cylinder to eject. In order to make ejection system smooth, some innovative designs have been made. Middle support guide post 13 is designed, which is guided by a graphite middle support. Top of middle support guide post 13 is fixed on the back of B board with a positioning pin, bottom is fixed on bottom plate of movable mold with screws. This design of center support guide post has the best guiding performance, overcomes disadvantage of traditional center support guide post and thimble plate of poor verticality. At the same time, middle support guide post 13 can also function as a support head. For convenience of mold installation, M10 threaded holes are designed on the end of back pin to facilitate tightening of ejector plate. At the same time, a limit screw 17 is designed on ejector plate, top of supporting head 11 and supporting head 12 are designed with positioning pins. All thimble uses Japanese MISUMI high-speed steel thimble SKH51.
Cooling system design of mold is shown in Figure 3. Front and rear molds are designed with direct water and ponds, which effectively ensure cooling effect.

 

Total number of mold parts is more than 40 and number is nearly 100, so reasonable identification of parts is particularly important for design and production. First of all, according to role of each part in mold, parts can be divided into 4 categories: mold plate type, cavity type, structural part type and standard part type. Mold plate constitutes matrix of mold, cavity is core of mold, structural parts and standard parts are auxiliary parts of mold. Drawing number of parts is based on this, and it is represented by 3 Arabic numerals. After confirming coding rules of part drawing numbers, parts of same type can be set on different layers during 3D parting. Drawing numbers are arranged clockwise or counterclockwise in sequence on assembly drawing:
1) Mold plate is arranged in the order of M1, M2, M3... from fixed mold fixed plate to movable mold fixed plate;
2) Cavity parts (fixed molds) are arranged in the order of V1, V2, V3...;
3) Core parts (movable molds) are arranged in the order of C1, C2, C3...;
4) Slider parts are arranged in the order of S1, S2, S3...;
5) Inclined roof parts are arranged in the order of L1, L2, L3...;
6) Auxiliary parts of fixed mold are arranged in the order of A1, A2, A3...;
7) Auxiliary parts of movable mold are arranged in the order of B1, B2, B3...;
Specific meaning of part number is: the first letter indicates category of part, following number is sequence number of part. Such classification drawing numbers are easy to compile and can achieve purpose of classification management and classification processing of parts. In specific mold design, it is necessary to ensure that 2D drawing of mold is consistent with part drawing number of 3D drawing, drawing is consistent with actual mold part, it is written on mold part when necessary to facilitate future maintenance and replacement of mold part.
When mold is changed, number of parts will change. For modified parts, add A, B, C, D... after drawing number to indicate different versions, and for newly added parts, write new drawing numbers according to rules. All new and revised drawings must update drawing date on drawings to facilitate production management.

 

 

 

 

 

Figure 3 Water transport arrangement diagram of dynamic and fixed model