The structure of the injection mold must be selected rationally. Based on the plastic part's drawings and technical requirements, appropriate molding methods and equipment should be evaluated and selected. Taking the factory's machining capabilities into account, a structural design proposal should be formulated. Relevant parties should be consulted and the design discussed to ensure the mold structure is rational, reliable in quality, and convenient to operate. If necessary, requests to modify the plastic part drawings may be made to suit mold design and manufacturing needs, but such changes require the client's approval before implementation.
The dimensions of the mold's molding components must be calculated accurately. Molding components directly determine the shape, dimensions, and surface quality of the plastic part; they are critical and require special attention. The "average shrinkage rate" method is generally used to calculate component dimensions. For high-precision parts requiring controlled mold-adjustment allowances, the "tolerance zone" method may be used. For large, precision parts, the "analogy" method is preferred-calculating based on measured shrinkage rates in different directions-to account for factors that are difficult to model theoretically.
The mold design should facilitate ease of manufacturing. Designs should aim for ease of fabrication and cost-effectiveness. For complex molding components, one must consider whether to use standard machining or specialized processing methods. Issues such as assembly procedures following specialized processing must be addressed during the design phase. Additionally, sufficient allowance for mold adjustment (trimming) after the initial trial run must be incorporated.
The mold design should ensure high efficiency, safety, and reliability. This requirement encompasses many aspects of the design, such as an effective gating system, secure mold locking, efficient temperature control, and a flexible, reliable ejection mechanism.
Mold components should be wear-resistant and durable. The durability of individual components affects the service life of the entire mold; therefore, specific requirements regarding materials, machining methods, and heat treatment must be established. Components such as ejector pins are prone to jamming, bending, or breaking-failures that account for a significant portion of overall mold malfunctions. In this regard, consideration should also be given to ease of adjustment and replacement, while ensuring that the service life of the components is compatible with that of the injection mold.
The injection mold structure must be adapted to the molding characteristics of the plastic material. When designing the mold, it is essential to fully understand the molding characteristics of the plastic and accommodate them as much as possible; this is a crucial step in obtaining high-quality plastic parts.