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What Setting Principles Should Be Followed In The Design Of Injection Mold?
Mar 05, 2019

I. design basis

The accuracy of dimension and its relative dimension

According to the specific requirements and functions of the whole product of plastic products to determine its external quality and specific size belongs to which kind: appearance quality requirements are higher, the size accuracy requirements are lower plastic products, such as toys; Functional plastic products, strict size requirements; Plastic products, such as cameras, that are strictly required in appearance and size.

Whether the stripper slope is reasonable.

Demoulding slope is directly related to the demoulding and quality of plastic products, that is, the injection process, whether the injection can be carried out smoothly: demoulding slope is enough; Slope to plastic products in the molding of the parting or parting surface; Whether it will affect the accuracy of appearance and wall thickness size;

Whether it will affect the strength of a part of plastic products.

Ii. Design procedures

Analysis and digestion of plastic product drawing and solid (solid sample) :

The geometry of the product;

Dimensions, tolerances and design benchmarks;

Technical requirements;

Name and brand of plastic

Surface requirements

Cavity number and cavity arrangement:

Product weight and injection volume of injection machine;

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

Mold size and the effective area of the injection machine installation mold, (or the distance between the pull rod of the injection machine)

Product precision, color;

Whether the products have side shaft cores and their treatment methods;

Batch production of products;

Economic benefits (production value per mold)

Cavity number was determined, and then to the arrangement of cavity, the cavity position arrangement, cavity arrangement involves the mould size, the design of gating system, the balance of gating system, the design of the core-pulling slider) institutions, insert, and the design of the core, the design of the heat exchange system, these problems and parting surface and the selection of gate location, so in the process of the specific design, to make the necessary adjustments, in order to achieve more perfect design.

Iii. Determination of the parting surface

It doesn't affect the appearance

To ensure the accuracy of products, mold processing, especially cavity processing;

It is conducive to the design of pouring system, exhaust system and cooling system.

It is conducive to die opening (parting, demoulding) to ensure that the products are left on the side of the moving die when the die is being opened;

Facilitate the arrangement of metal blocks.

Iv. Design of pouring system

The design of the pouring system includes the selection of the main flow channel, the determination of the shape and size of the runner section, the choice of the location of the gate, the gate form and the determination of the gate section size.

When designing a gating system, the location of the gate is first selected.

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

Gate location should be selected on the parting surface as far as possible, so as to facilitate mold processing and use of the gate cleaning;

The distance between the gate position and each part of the cavity should be consistent as far as possible, and the flow of the tool should be the shortest.

The location of the gate should ensure that plastic flow into the cavity, the cavity in the wide, thick wall parts, so as to facilitate the smooth plastic flow;

Gate position should be opened at the thickest section of plastic parts;

Avoid direct injection of plastic into the cavity wall, core or insert when flowing down the cavity, so that plastic can flow into all parts of the cavity as soon as possible, and avoid deformation of the core or insert;

Try to avoid the products to produce welding marks, or make the welding marks in the product is not important parts;

Gate position and plastic inflow direction, should make the plastic flow into the cavity, along the parallel direction of the cavity uniform inflow, and conducive to the discharge of gas in the cavity;

The gate should be placed on the part of the product that is easiest to remove without affecting the appearance of the product as much as possible.

V. design of exhaust system

Exhaust system plays an important role in ensuring the forming quality of products.

Using the exhaust slot, the exhaust slot is generally located at the part where the cavity is filled at the end. The depth of the exhaust slot varies with different plastics, and is basically determined by the maximum clearance allowed by the plastic without flanging, for example, ABS0.04 is below 0.02mm of plaster and 0.02 of steel.

Use the fitting clearance of core insert push rod or special exhaust plug to exhaust; Sometimes in order to prevent products in the ejection caused by vacuum deformation, gas pin must be set; Sometimes anti-vacuum adsorption components are designed to prevent vacuum adsorption of products and modules.

Vi. Design of cooling system

The design of the cooling system is a complicated work, which should consider the cooling effect and the uniformity of cooling, and the influence of 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;

Determination of the specific location and size of the cooling system;

Key parts such as moving mold or insert cooling;

Cooling of side sliders and side cores;

Design of cooling elements and selection of cooling standard elements;

Sealing structure design.