Design Of PC Plastic Stamping Die
PC plastic die design is a key technical link in the field of plastic processing, and its design quality directly affects the precision, production efficiency and manufacturing cost of PC plastic products. PC plastic has excellent characteristics such as high strength, high temperature resistance and good impact resistance. It is widely used in high-end fields such as electronics, automobiles, and medical devices, so higher requirements are placed on its die design. In the early stage of design, it is necessary to comprehensively analyze the physical properties of PC plastics, such as melt flow rate, shrinkage, heat deformation temperature, etc. These parameters are important bases for determining mold structure, cavity size and processing technology. For example, the shrinkage rate of PC plastic is usually between 0.5% and 0.7%. During design, dimensional compensation must be performed through precise calculation to ensure that the plastic parts meet the design requirements after cooling. At the same time, PC plastics are more sensitive to temperature, and the design of the mold temperature control system needs to be accurate. Generally, the mold temperature is set at 80-120℃ to reduce the internal stress of the plastic parts and avoid defects such as cracking and deformation.
The mold structure design is the core content of PC plastic die design, and it needs to be designed according to the shape, size and production batch of the plastic parts. For simple flat PC plastic parts, a single-process die can be used, which has a simple structure and low manufacturing cost; for plastic parts with complex shapes, such as parts with holes, grooves, bosses and other features, a compound die or a progressive die is required to achieve multi-process continuous stamping and improve production efficiency. In the mold structure, the selection of the gap between the punch and the die is crucial. If the gap is too large, it will easily cause burrs on the edge of the plastic part, and if the gap is too small, it will increase mold wear and shorten the service life. Usually, the gap between the punch and the die of the PC plastic die is 5% – 10% of the thickness of the plastic part, and it is adjusted according to the actual mold test situation. In addition, the guide mechanism of the mold needs to ensure accuracy. Generally, guide pins and guide sleeves are used to guide to ensure that the punch and the die are aligned during the stamping process to avoid the phenomenon of biting the die.
The design of the feed system directly impacts how PC plastic fills the mold cavity, and thus, the quality of the molded part. Common feed methods for PC plastic die castings include side gates, pinpoint gates, and latent gates. Side gates are suitable for larger parts, ensuring uniform feed, but they leave gate marks on the part surface. Pinpoint gates are suitable for high-precision parts, resulting in minimal gate marks that are easy to remove, but they have slower feed rates and are suitable for small-batch production. Submerged gates are ideal for automated production, as the gates automatically drop out, improving production efficiency. The size and shape of the runners must also be considered when designing the feed system. Runners should be as short and thick as possible to minimize melt flow resistance and ensure uniform melt filling of the mold cavity. Furthermore, the runner surface should be polished to a Ra of 0.8μm or less to reduce friction during melt flow and prevent PC plastic degradation due to localized overheating.
The design of cooling system is an important part to ensure the quality and production efficiency of PC plastic products. The molding temperature of PC plastic is high. If the temperature distribution is uneven during the cooling process of plastic parts, internal stress and warping deformation are likely to occur. Therefore, the cooling system needs to be evenly arranged around the cavity to ensure that the cooling speed of each part of the plastic part is consistent. The diameter of the cooling water channel is usually 8-12mm, the distance between the water channel and the cavity surface is generally 15-20mm, and the spacing between the water channels is controlled at 30-50mm to ensure a good cooling effect. For cavities with complex shapes, special-shaped water channels or conformal cooling technology can be used. Advanced manufacturing technologies such as 3D printing can be used to make cooling water channels that are consistent with the shape of the cavity to improve cooling efficiency. In addition, the temperature difference between the inlet and outlet water of the cooling system should be controlled within 5°C to avoid uneven cooling of plastic parts due to excessive temperature difference. At the same time, the scale in the cooling water channel needs to be cleaned regularly to prevent blockage and affect the cooling effect.
The selection of mold materials and surface treatment have an important impact on the service life of PC plastic punching dies and the quality of plastic parts. Since PC plastic has a certain hardness and wear resistance, the mold material needs to have high strength, hardness and wear resistance. Commonly used mold materials include alloy tool steels such as Cr12MoV and SKD11. After quenching and tempering, the hardness can reach HRC58-62, which can meet the use requirements of PC plastic punching dies. For molds produced in large quantities, high-speed steel or powder metallurgy materials can be used to improve the wear resistance and service life of the mold. Mold surface treatment is also a key link. Chrome plating is usually used. The thickness of the chrome plating layer is 0.01-0.03mm, which can not only improve the wear resistance of the mold surface, but also enhance its corrosion resistance and prevent PC plastic from corroding the mold surface at high temperatures. In addition, the surface of the mold cavity needs to be finely polished to achieve a mirror effect to ensure a smooth surface of the plastic part, reduce demoulding resistance, and avoid scratches on the surface of the plastic part.
