Discussion on injection molding of the hottest sha

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Brief discussion on injection molding of shampoo bottle cap (Part 1)

[Key words] three plate mold; Automatic stripping; Out of mold distance parting; Abstract: Taking the common shampoo bottle cap of haifeisi as an example, it further explains the importance of having bold, flexible and broad thinking ability when the distance from its head is equal to or less than twice the diameter in the concept of mold design

1 product structure and process analysis

(1) product name: Head & shoulders shampoo bottle cap is shown in Figure 1 (Figure omitted)

(2) product material and appearance analysis

shampoo bottle cap belongs to appearance product, and the appearance requirements are relatively strict:

① appearance gloss

② material: pp+gf20% (light blue), shrinkage: 1.5%

polypropylene (PP) is a crystalline plastic with excellent fluidity and low hygroscopicity. Melting and cracking may occur. The mold temperature should not be too high (80 ℃ ~ 90 ℃), and the cooling speed is fast. Therefore, the pouring system and cooling system should dissipate heat slowly; Its molding shrinkage range is large, the shrinkage rate is large, and it is prone to shrinkage, dents, deformation, and strong directionality. During injection, the molding temperature should be strictly controlled. The directionality is obvious when the material temperature is low, especially when the low and medium super cable has reached a cooperation agreement with Jiangnan graphene Research Institute, Xi'an Jiaotong University, Changzhou No.6 element material technology Co., Ltd. It is more obvious when the temperature is high and the mold temperature is lower than 50 ℃, the plastic parts are not shiny, and it is easy to produce poor fusion Flow mark; When the mold temperature is higher than 90 ℃, it is easy to warp and deform; The wall thickness of plastic parts shall be uniform, and notches and sharp corners shall be avoided to prevent stress concentration during forming. The mold shall be designed with sufficient exhaust

the molding wall thickness of polypropylene (PP) material shall not be less than 0.85mm

the molding wall thickness of the product is less than 0.85mm. In order to increase the strength of the product, it needs to be modified and added with GF15%

(3) analysis of product molding structure

the molding wall thickness of this product is relatively thin (0.80mm), which is prone to warpage and deformation during molding; The fit between the small cover nozzle and the large cover opening should be tight and should not be loose; When forming the folding part of the small cover, it should not be too thin or too thick. It should have enough folding resistance and easy folding. The arc of the rubber elastic piece should not be too long. It should be ensured that after the small cover is buckled, the surface is not arched and fits well

it is difficult to form the internal structure of the product:

① the overall position of the internal structure will determine the appearance of the bottle cap and body after assembly with the bottle body

② the connection between the internal structure and the bottle mouth is thin, and the diameter and height should ensure that it can stretch into the bottle mouth and expand the inner wall after assembly, which plays a sealing role, so that shampoo cannot flow out of the bottle cap

③ the shampoo bottle cap is locked on the outer rib of the bottle mouth with expansibility (inner rib), and the inner rib of the shampoo bottle cap should not be demoulded after forming

④ the symmetrical part of the circular wall where the inner rib of the bottle cap is located has an opening, which plays the role of elastic expansion of the circular wall when the bottle cap is locked, and the inner rib of the bottle cap is difficult to process on the mold core (there is a bulge at the face of the core cylinder)

(4) determine the mold structure

① in order to ensure the appearance of the product, the form of direct dispensing port of three plate mold with glue feeding at the center of the top surface of the product (small coverage) is adopted

② when the bottle cap is formed, the small cap is open, and the core of the small cap must be installed on the a template. In this way, the small cap must first be removed from the fixed mold when the mold is opened, so as to ensure that the folded part of the small cap is not damaged and connected with the large cap; The mold must have reliable non-metallic materials, which play an important role in environmental protection, comfort and beauty of the automobile. The fixed mold ejection structure is fixed mold ejection

③ considering the forming factors, one mold with four cavities is adopted, and the gate plate and parting are required. The gate of this mold is designed to fall off automatically. The mold needs to have a distance parting device for the parting surface of the gate plate for distance parting

④ optimal design of dynamic mold ejection system inclined ejection principle (i.e. core inclined ejection demoulding)

the shape of the shampoo bottle cap is roughly oval, the molding wall thickness is thin, and the bottle cap has internal ribs, which is small. Forced demoulding requires a large demoulding force. According to the inclined top principle, the demoulding method of the dynamic mold is designed as the core inclined ejection, the ejection force is large and reliable, and the structure of the dynamic mold ejection system is simple

2 mold structure and its working process

(1) mold structure

① according to the characteristics of polypropylene (PP) with fast cooling speed, the gating system and cooling system should dissipate heat slowly, and the molding of the fixed mold part of the mold is less, so the fixed mold part of the mold will not be equipped with a cooling system

② this mold pouring system will not be designed with hot runner, because polypropylene (PP) is sensitive to temperature, so the temperature should not be controlled

③ because polypropylene (PP) is sensitive to temperature, there should not be too many mold heaters (heating rods), which should be installed in the mold. The full LCD numerical control should set the required parameters to better control the mold temperature, but it should not be too close to the mold cavity

(2) design and analysis of molded parts

① cavity design

the cavity is the main part of the outer surface of the molded product. The product has strict requirements on the outer surface of the molded product. Considering the large production volume of the product, in order to improve the strength and stiffness of the mold, the cavity is easy to process and replace, so the cavity adopts the integral insert type, and the material adopts imported P20

② core design

core is the main part of the internal surface and structure of molded products. There are many cores of this product, especially the fixed mold, which brings certain difficulties to the assembly accuracy of the mold. Many core parts will bring difficulties to the manufacturing accuracy when repairing the mold and replacing parts in the future

an important part of the mold design: using the moving model core to slide out and demould

③ design points of fixed mold ejection

there are two types of fixed mold ejection: in mold and out of mold:

a. the ejection force outside the mold is large (generally using pneumatic devices, when the ejection part of plastic parts is large), and the pneumatic ejection speed is fast, which is consistent with the speed of mold opening. (to be continued)

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