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Which Setting Principles Should Be Followed When Designing Injection Molds?
May 30, 2018

First, design basis

    Correctness of dimensional accuracy and its related dimensions

    According to the specific requirements and functions of the entire product of the plastic product, the external quality and specific dimensions are determined: the plastic products with high appearance quality and low dimensional accuracy, such as toys, functional plastic products, and size requirements Strict; appearance and size require very strict plastic products, such as cameras.

 

    Is the draft angle reasonable?

    The draft angle is directly related to the demoulding and quality of the plastic products, that is, whether the injection process can be performed smoothly during the injection process: the draft angle is sufficient; the slope must be matched with the plastic product in the forming mold or parting surface. Adaptation; whether it will affect the accuracy of the appearance and thickness of the wall; whether it will affect the strength of a certain part of the plastic products.

 

    Second, the design process

    Analysis and digestion of plastic products drawings and entities (samples):

 

    The geometric shape of the product;

 

    Dimensions, tolerances, and design criteria

 

    skills requirement;

 

    Plastic name, brand name

 

    Surface requirements

 

    Number of cavities and cavities:

 

    Product weight and injection volume of the injection machine;

 

    The projected area of the product and the clamping force of the injection machine;

 

    Dimensions of the mold and the effective area of the injection molding machine mounting mold (or the distance between the injection rods in the injection machine)

 

    Product accuracy, color;

 

    Products with or without sideshaft core and its processing methods;

 

    Product production volume;

 

    Economic benefits (production value per die)

    After the number of cavities is determined, the arrangement of the cavities is performed, that is, the placement of the cavities. The arranging of the cavities involves the size of the mold, the design of the pouring system, the balance of the pouring system, the design of the core pulling (slider) mechanism, and inserts The design of the core and the design of the heat exchange system are related to the selection of the parting surface and the location of the gate. Therefore, during the specific design process, necessary adjustments must be made to achieve a relatively perfect design.

 

    Third, the determination of the profile

 

    Does not affect the appearance

 

    Help to ensure product accuracy, mold processing, especially the cavity processing;

 

    Conducive to the design of the pouring system, exhaust system, cooling system;

 

    Is conducive to mold opening (parting, mold release) to ensure that in the mold opening, leaving the product on the side of the moving mold;

 

    Easy to arrange metal inserts.

 

    Fourth, gating system design

    The design of the gating system includes the selection of the main flow path, the determination of the shape and size of the runner section, the position of the gate, the shape of the gate, and the determination of the size of the gate section. When the gate is used, it is necessary to ensure the separation of the runner. Attention should be paid to the design of the deglacial device, the dewatering device, and the sprue mechanism.

 

    When designing the gating system, the first step is to choose the location of the gate.

 

    The choice of the gate location is directly related to the product molding quality and the smooth progress of the injection process. The selection of the gate location should follow the following principles:

 

    The position of the gate should be selected on the parting surface as much as possible to facilitate the cleaning of the gate during mold processing and use;

 

    The distance from the gate to each part of the cavity should be as consistent as possible, and the process flow should be the shortest;

 

    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;

 

    The location of the gate should be set at the thickest section of the plastic part;

 

    To prevent the plastic from punching cavity walls, cores or inserts when flowing down the cavity, so that the plastic can flow into various parts of the cavity as soon as possible, and avoid deformation of the core or the insert;

 

    Try to avoid making welding marks on the products, or to make weld marks on the unimportant parts of the products.

 

    The position of the gate and the direction of its plastic inflow should allow the plastic to flow in evenly along the direction parallel to the cavity when it flows into the cavity, and is beneficial to the discharge of gas in the cavity;

 

    The gate should be set 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

 

    Exhaust systems play a crucial role in ensuring the quality of the molded products.

 

    With the exhaust groove, the exhaust groove is generally provided at the portion where the cavity is filled at the end. The depth of the exhaust groove varies depending on the plastic, and is basically determined by the maximum allowable clearance for the plastic to produce no flash, such as ABS0. .04 with less than 0.02mm muddy steel 0.02 or less.

 

    The use of core plug push rod, etc. with the clearance or exhaust plug exhaust; sometimes in order to prevent product vacuum deformation caused by ejection, must set the gas pin; sometimes in order to prevent the product and the model of a vacuum adsorption, and design protection Vacuum adsorption element.

 

    Six, cooling system design

 The design of the cooling system is a relatively cumbersome work, that is to consider the cooling effect and the uniformity of the cooling, but also to consider the cooling system on the overall structure of the mold.

 

    include:

    The arrangement of the cooling system and the specific form of the cooling system;

    The specific location and size of the cooling system;

    Key parts such as cooling of moving molds or inserts;

    Side slider and side core cooling;

    Cooling element design and selection of cooling standard elements;

    Sealed structure design.