Injection mold base design
Injection mold frame design is a fundamental step in mold design, directly affecting the mold’s overall performance, service life, and manufacturing cost. Factors such as the product’s size, shape, production batch, and injection molding machine parameters must be comprehensively considered during the design process. The mold frame’s overall structure must possess sufficient strength and rigidity to withstand the injection pressure and clamping force during the injection molding process and prevent deformation during long-term use. Typically, the thickness of the mold frame’s main components, such as the movable and fixed platens, is calculated based on the cavity layout and stress conditions. For large molds or high-pressure injection molding applications, additional support columns are required to enhance the platen’s load-bearing capacity and prevent bending due to excessive stress.
The design of the mold base’s guide mechanism is key to ensuring the accuracy of mold opening and closing. The guide mechanism typically consists of guide pins and guide sleeves, and their layout and precision requirements must be strictly controlled. The guide pins and guide sleeves should be evenly distributed at the four corners or edges of the mold base to ensure balanced guidance. Large mold bases generally use four guide pins, while small mold bases can use two, but sufficient guide length must be ensured. The fit accuracy of the guide pins and guide sleeves is typically H7/h6, and the clearance should be uniform to ensure smooth opening and closing of the mold and avoid jamming. The guide pin head should be designed with a conical or spherical shape to facilitate smooth insertion into the guide sleeve during mold closing. The guide pin length should be sufficient to remain partially within the guide sleeve when the mold is fully opened to prevent separation.
The mold base’s template design must balance installation performance and processability. The fixed and movable templates are the primary components for mounting the cavity and core. Their flatness and parallelism must be highly precise, typically within 0.01mm/100mm, to ensure a tight seal during mold closing and prevent melt overflow. The templates require various mounting holes, screw holes, and pin holes for securing molded components, guide mechanisms, and ejection mechanisms. The positional and dimensional accuracy of these holes must be strictly controlled to ensure accurate assembly of all components. The template material selection depends on the mold’s intended use. For standard molds, medium-carbon steels such as 45 steel or S50C can be used after quenching and tempering. For high-precision, long-life molds, alloy tool steels such as P20 and 718H should be selected and surface-hardened to enhance wear resistance and hardness.
The mold frame’s ejection mechanism requires a well-designed installation space. This mechanism ejects the product from the core or cavity after mold opening, primarily between the movable mold base plate and the movable mold plate. Depending on the type of ejection mechanism (e.g., push rod, push tube, or ejector plate), sufficient space must be reserved during design to ensure unimpeded movement. The ejection mechanism’s guidance and positioning must also be considered in the mold frame design. Guide pins and sleeves can be incorporated to ensure a smooth ejection process and prevent deformation of the ejection mechanism due to uneven force. Furthermore, the ejection stroke must be calculated to ensure complete release of the product from the core. This stroke is generally 2-5 mm greater than the maximum height of the product.
The matching design between the mold frame and the injection molding machine cannot be ignored. The overall dimensions of the mold frame must match the tie rod spacing of the injection molding machine to ensure that the mold can be smoothly installed on the injection molding machine. The positioning holes and mounting screw holes on the fixed mold base plate and the movable mold base plate must correspond to the fixed mold plate and the movable mold plate of the injection molding machine to ensure that the mold is accurately positioned and firmly fixed on the injection molding machine. The maximum and minimum thicknesses of the mold frame must be within the allowable range of the injection molding machine, otherwise it will affect the clamping force and mold opening stroke of the injection molding machine. In addition, the size of the main runner bushing of the mold frame must match the nozzle of the injection molding machine to ensure that the molten material can smoothly enter the mold cavity. In the final stage of mold frame design, a comprehensive check is required, including strength check, rigidity check and motion interference check, to ensure that the mold frame design meets production requirements and provide reliable protection for the normal operation of the mold.
