First, the design basis
The accuracy of the dimensional accuracy and its associated dimensions.
According to the specific requirements and functions of the whole product of plastic products, which kind of external quality and specific size are determined: plastic products with higher appearance quality requirements and lower dimensional accuracy, such as toys; functional plastic products, size requirements Strict; plastic products that require strict appearance and size, such as cameras.
Whether the draft is reasonable.
The draft angle is directly related to the release and quality of the plastic products, that is, whether the injection can be carried out smoothly during the injection process: the draft angle is sufficient; the slope should be in the form of the part or the part of the molded part of the plastic product. Adaptation; whether it will affect the accuracy of appearance and wall thickness dimensions;
Whether it will affect the strength of a certain part of the plastic product.
Second, the design process
Analysis and digestion of plastic product drawings and entities (real samples):
a, the geometry of the product; B, dimensions, tolerances and design basis;
C, technical requirements; D, plastic name, brand E, surface requirements
Number of cavities and cavity arrangement:
a, the weight of the product and the injection volume of the injection machine; B, the projected area of ​​the product and the clamping force of the injection machine;
C. The outer dimensions of the mold and the effective area of ​​the mold for the injection machine, (or the spacing inside the injection rod)
D, product accuracy, color; E, product with or without side core and its processing method;
F, production batch of products; G, economic benefit (production value per mold)
After the number of cavities is determined, the arrangement of the cavities, that is, the arrangement of the cavity positions, the arrangement of the cavities involves the size of the mold, the design of the gating system, the balance of the gating system, the design of the core pulling (slider) mechanism, and the inserts. With the design of the core and the design of the heat exchange system, these problems are related to the selection of the parting surface and the gate position. Therefore, in the specific design process, the necessary adjustments should be made to achieve a more perfect design.
Third, the determination of the parting surface
Does not affect the appearance;
Conducive to ensure product accuracy, mold processing, especially the processing of the cavity;
Conducive to the design of the gating system, exhaust system, cooling system;
Conducive to mold opening (parting, demoulding) to ensure that the product is left on the side of the movable mold when the mold is opened;
Facilitate the arrangement of metal inserts.
Fourth, the design of the pouring system
The design of the gating system includes the selection of the main flow path, the shape and size of the cross-section, the choice of the position of the gate, the form of the gate and the size of the cross-section of the gate. When using the gate, the branch is also removed. Attention should be paid to the design of the de-gate device and the de-sinking device.
When designing the gating system, first select the location of the gate.
The choice of gate location is directly related to the quality of the product and the smooth progress of the injection process. The choice of gate location should follow the following principles:
1 The position of the gate should be selected on the parting surface as much as possible to facilitate the cleaning of the gate during the processing and use of the mold;
2 The distance between the gate position and each part of the cavity should be as uniform as possible, and the process should be the shortest;
3 The position of the gate should ensure that the plastic flows into the cavity, and the cavity is wide and thick, so that the plastic can flow smoothly;
4 The gate position should be opened at the thickest part of the plastic part;
5 to avoid the plastic straight into the cavity wall, core or insert when flowing down the cavity, so that the plastic can flow into all parts of the cavity as soon as possible, and avoid deformation of the core or insert;
6 Try to avoid causing weld lines in the product, or make the weld marks appear in the unimportant parts of the product;
7 The position of the gate and the direction of its plastic inflow should be such that the plastic can flow uniformly in the direction parallel to the cavity when flowing into the cavity, and facilitate the discharge of gas in the cavity;
8 The gate should be placed on the most easily removed part of the product, while not affecting the appearance of the product as much as possible.
Fifth, the design of the exhaust system
The exhaust system plays a vital role in ensuring the quality of the product.
a. Using the exhaust groove, the exhaust groove is generally located at the portion where the cavity is finally filled. The depth of the exhaust groove varies depending on the plastic, and is basically determined by the maximum allowable gap in which the plastic does not generate a flash. For example, aBS0.04 is 0.02 or less with ash of 0.02 mm or less.
B. Exhaust by the matching clearance of the core insert push rod or the special exhaust plug;
C. Sometimes, in order to prevent the product from causing vacuum deformation when it is ejected, a gas pin must be provided;
D. Sometimes, in order to prevent vacuum adsorption of the product and the mold, an anti-vacuum adsorption element is designed.
Sixth, the design of the cooling system
The design of the cooling system is a relatively cumbersome task, that is, considering the cooling effect and the uniformity of cooling, and considering the influence of the cooling system on the overall structure of the mold.
The arrangement of the cooling system and the specific form of the cooling system;
Determination of the specific location and size of the cooling system;
Cooling of key parts such as moving molds or inserts;
Cooling of the side slider and the side core;
Design of the cooling element and selection of cooling standard components;
Sealed structure design.
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