In the diverse process system of modern injection molding, injection molding with three-plate molds holds an important position due to its unique advantages. Ranging from common electronic products to high-end and exquisite packaging products, its applications are extremely extensive and have a profound impact on various plastic products in our daily lives. Next, let's explore the secrets of injection molding with three-plate molds in depth.
Three-plate molds are mainly composed of a fixed mold plate, a fixed die plate, an intermediate plate (also known as a runner plate), a moving die plate, and a moving mold plate. Compared with two-plate molds, the additional intermediate plate is a significant feature. A sprue is set between the fixed mold plate and the fixed die plate, through which the plastic melt enters the mold. The intermediate plate is mainly used to arrange the runners, distributing the plastic melt from the sprue evenly to each cavity. The cavities for forming products are installed on the moving die plate. During the injection molding process, the moving die and the fixed die close to form a closed cavity space for the filling and molding of the plastic melt.
II. Working Principle
At the start of the injection molding process, the injection molding machine heats and melts the plastic pellets and injects the melt into the sprue of the mold through a screw. The melt enters the runners of the intermediate plate from the sprue, and the runners distribute the melt evenly to each cavity according to the layout of the cavities. After the cavities are filled, through stages such as pressure holding and cooling, the products solidify and take shape within the cavities. When the mold is opened, first, the fixed mold plate and the fixed die plate separate. Due to the action of devices such as pull plates or springs, the intermediate plate maintains its relative position with the fixed die plate, and at this time, the sprue solidifies and is ejected from the sprue bushing on the fixed mold plate. Then, the fixed die plate and the intermediate plate separate, and the runner solidifies and is separated from the intermediate plate under the action of structures such as the sprue puller. Finally, the moving die plate and the intermediate plate separate, and the product is ejected from the cavity of the moving die plate through a demoulding mechanism such as ejector pins, completing the entire injection molding process.
Automatic Gate Separation: This is one of the most prominent advantages of three-plate molds. During the mold opening process, the gate can automatically separate from the product, eliminating the need for manual trimming later. This greatly improves production efficiency and also ensures the integrity of the product's appearance, avoiding surface damage to the product that may be caused by manual gate trimming.
Multi-point Gate Design: The presence of the intermediate plate allows the mold to have multiple runners, thus enabling multi-point gates. Multi-point gates can make the plastic melt fill the cavity more evenly, effectively reducing the internal stress of the product and lowering the risk of product deformation, especially suitable for large or complex-shaped plastic products.
High Appearance Quality: Thanks to the automatic gate separation and the use of multi-point gates, there will be no obvious gate marks on the surface of the product. Three-plate molds have great advantages for products with high appearance requirements, such as electronic device casings and high-end cosmetic packaging.
Electronic Equipment Field: It is often used to produce mobile phone cases, tablet computer casings, laptop computer casings, etc. These products have extremely high requirements for appearance and strict requirements for dimensional accuracy. Three-plate molds can ensure the uniform filling of the plastic melt through multi-point gates, ensuring the dimensional accuracy of the product, and the automatically separated gates will not affect the product's appearance.
Precision Instrument Components: Such as small instrument casings, optical instrument components, etc. These components not only require a smooth and flat appearance but also have strict requirements for dimensional accuracy and the internal quality of the product. The characteristics of three-plate molds can meet these needs, ensuring the high precision and quality of the product.
High-end Packaging Products: Such as high-end cosmetic packaging boxes, perfume spray bottles, etc. These products require an exquisite appearance to attract consumers. Three-plate molds can achieve a product surface without gate marks, enhancing the overall grade of the product.
Complex Mold Structure: Compared with two-plate molds, three-plate molds have an additional intermediate plate and related structures such as pull plates, springs, and sprue pullers, making the mold structure more complex, increasing the difficulty of design and manufacturing, and also raising the cost accordingly.
Increased Maintenance Difficulty: The complex structure means more components. During the use of the mold, a malfunction of any component may affect the normal operation of the entire mold, and the maintenance and repair are more difficult, requiring professional technicians to operate.
High Requirements for Injection Molding Machines: Three-plate molds have multiple actions during the mold opening process, and the injection molding machine needs to have corresponding control functions and precision to accurately control the mold opening stroke and speed at different stages, so it has high requirements for the performance of the injection molding machine.
In conclusion, injection molding with three-plate molds, due to its unique structure and principle, plays an advantageous role in multiple fields. Despite the challenges of a complex structure, difficult maintenance, and high requirements for injection molding machines, with the continuous innovation in materials science, mold manufacturing technology, and injection molding equipment, it will surely continue to be optimized and upgraded, maintain an important position in the injection molding industry, contribute to the production and manufacturing of more high-quality plastic products, and further promote the development of the injection molding processing industry.
