- First, design basis
Correctness of dimensional accuracy and its associated dimensions
According to specific requirements and functions of entire product of Molded products, which kind of external quality and specific size are determined: Molded products with higher appearance quality requirements and lower dimensional accuracy such as toys and functional Molded products with strict size requirements, cameras with strict appearance and size.
Whether draft angle is reasonable.
Draft angle is directly related to release and quality of Molded products, that is whether injection can be carried out smoothly during Moulding process: draft angle has sufficient slope to match plastic product in formed parting or parting surface; whether it will affect accuracy of appearance and wall thickness dimensions;
Whether it will affect strength of a certain part of Molded products.
- Second, design process
Analysis and digestion of Molded products drawings and entities (real samples):
Geometry of article;
Dimensions, tolerances and design basis;
skills requirement;
Plastic name, brand
Surface requirement
Number of cavities and cavity arrangement:
Weight of product and injection volume of injection machine;
Projected area of product and clamping force of injection machine;
Outer dimensions of mold and effective area of mold for injection machine, (or spacing inside injection rod)
Product accuracy, color;
Whether product has a side core and a treatment method thereof;
Production batch of products;
Economic benefit (production value per mold)
After number of cavities is determined, arrangement of cavities, that is arrangement of cavities, arrangement of cavities involves size of mold, design of gating system, balance of gating system, design of core pulling (slider) mechanism, design of core and inserts, design of heat exchange system, these problems are related to selection of parting surface and gate position. Therefore, in specific design process, necessary adjustments should be made to achieve a more perfect design.
- Third, determination of parting surface
Does not affect appearance
Conducive to ensure product accuracy, Moulding process, especially the processing of cavity;
Conducive to design of gating system, exhaust system, cooling system;
Conducive to mold opening (parting, demoulding) to ensure that product is left on the side of movable mold when mold is opened;
Facilitate arrangement of metal inserts.
- Fourth, design of pouring system in application of injection moulding
Design of gating system includes selection of main flow path, shape and size of cross-section, choice of position of gate, form of gate and size of cross-section of gate. When using gate, branch is also removed. Attention should be paid to design of degasser device, de-sinking device and gate mechanism.
When designing a gating system, first select location of gate.
Choice of gate location is directly related to quality of product and smooth progress of injection process. Choice of gate location should follow following principles:
Gate position should be selected on parting surface as much as possible to facilitate cleaning of gate during processing and use of Short run injection molding;
Distance between gate location and each part of cavity should be as uniform as possible, and process should be the shortest;
Position of gate should ensure that plastic flows into cavity, and wide, thick-walled part of cavity is used to facilitate smooth flow of plastic;
Gate position shall be opened at the thickest section of plastic part;
Avoid plastics directly flowing into cavity wall, core or insert when flowing down cavity, so that plastic can flow into all parts of cavity as soon as possible, and avoid deformation of core or insert;
Try to avoid causing weld lines in product, or make weld marks appear in unimportant parts of product;
Position of gate and direction of its plastic inflow should be such that plastic can flow uniformly in the direction parallel to cavity when flowing into cavity, and facilitate discharge of gas in cavity;
Gate should be placed on the most easily removed part of product without affecting appearance of product as much as possible.
- Fifth, design of exhaust system in application of injection moulding
Exhaust system plays a vital role in ensuring quality of product.
With venting groove, venting groove is generally located at the end of cavity where cavity is filled. Depth of venting groove varies from plastic to plastic, and is basically determined by maximum allowable gap in which plastic does not generate burrs, such as ABS0. .04 is 0.02 or less with ash of 0.02 mm or less.
Use matching clearance of core insert push rod or special exhaust plug to exhaust; sometimes in order to prevent product from causing vacuum deformation when it is ejected, air pin must be provided; sometimes in order to prevent vacuum adsorption of product and Short run injection molding, an anti-vacuum adsorption element is designed.
- Sixth, design of cooling system in application of injection moulding
Design of cooling system is a relatively cumbersome task, considering cooling effect and uniformity of cooling, and influence of cooling system on the overall structure of mold.
include:
– Arrangement of cooling system and specific form of cooling system;
– Determination of specific location and size of cooling system;
– Cooling of key parts such as moving molds or inserts;
– Cooling of side slider and side core;
– Design of cooling element and selection of cooling standard Plastic injection mold components;
– Sealed structure design.
