Large Injection Mould

1. Structural types of large injection molds
1. Flat structure
Flat structure means that mold plate and movable mold plate are connected by a flat plate, which is suitable for injection molding machines with a locking force of less than 1,500 tons, a mold size of less than 15 square meters, and injection molded parts with small product sizes.
2.Box structure
Box structure means that mold plate and movable mold plate are connected by a box, which is suitable for large injection molding machines with locking forces from 1,500 to 5,000 tons, products with a mold size of 13-40 square meters, and injection molded parts with larger product sizes.
3. Composite structure
Composite structure refers to adding boosting mechanism, moving diaphragm, forming diaphragm and other components to flat or box structure, so that mold has more functions and is suitable for production of high-precision and complex injection molded parts. .
2. Design points of large injection molds
1. Mold plate design
Mold plate is main part of mold. Mold plate specifications and arrangement should be designed according to product size and production scale. During design process, factors such as reinforcing ribs, cooling holes, contact surfaces, and parallelism of mold plate also need to be considered.
2. Guide post and guide sleeve design
Guide posts and guide bushings are important components that play a positioning role in mold. Their design requirements are highly stringent, factors such as number, size, and arrangement of guide posts, as well as smoothness, sealing, and matching of guide posts with guide posts need to be considered. .
3.Mold cavity and cooling system design
Mold cavity and cooling system are core components that determine product quality and production efficiency. During design process, factors such as machining accuracy of mold cavity, thermal runaway issues, bubble prevention, and surface finish need to be considered. At the same time, a reasonable cooling system needs to be designed to ensure product quality and rapid cooling.
4. Ejection mechanism design
Ejection mechanism is a component used to eject injection molded parts from mold cavity. Design must consider factors such as ejection amount, ejection method, and ejection position to ensure shape integrity and surface quality of product.
5. Mold processing process design
Mold processing technology is an important link in determining quality and life of mold. Factors such as processing sequence, processing method, processing accuracy, processing surface finish, heat treatment, etc. need to be considered to ensure quality and life of mold.
3 Precautions for processing large injection molds
Optimization of process includes many aspects such as pouring system, molded part size, material selection and manufacturing, mold structure and action characteristics. According to structural characteristics of large injection molds and some practical problems often encountered, pouring system, size and material selection of mold are often targeted for optimization.
1. Gating system
Since flow ratio (L/£) of plastic melt in large molds is large, whether design of gating system is reasonable will directly affect loss of melt pressure and temperature, filling process, pressure maintaining and filling, and parts. Many aspects such as internal stress and weld marks will also affect internal and external quality of product, stiffness and strength of mold. Therefore, gating system often becomes main target for optimization of large injection molds. In gating system, it mainly includes optimization of number and location of gates, size and shape of runner, etc.
1.2 Mold size
Generally speaking, for large injection molds, its strength is not a big problem, main problem is its stiffness, rigid deformation will cause mold deformation and even damage to mold. Therefore, key parts of mold and stressed components (such as cavity side walls, core pads, etc.) must be strictly scientifically calculated, and corresponding simulation analysis can also be performed if conditions permit.
1.3 Mold materials
In addition to specific requirements of part and its processability, selection of mold materials must also consider its mechanical properties. Generally speaking, due to complex structure of large injection molds, stress state of mold parts is also relatively complex. During use of many large molds, fractures or cracks of formed parts often occur, which has a great relationship with selection of materials and their heat treatment.

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