Considerations in Plastic Mold Design

Emphasis on Design of Inlet Channels for Plastic Moulded Products

The inlet should be located in the thicker part of the product to ensure smooth and complete mold filling. It should be placed where it does not affect the appearance and function of the product as much as possible, and the pull rod can be placed at the edge or bottom of the product in the cold cavity near the gate to facilitate the demolding of the flow path, large or flat products. It is recommended to use multi-point feeding to prevent product warping, deformation, and missing materials. Its position should be chosen at the shortest place during plastic molding to reduce pressure loss, facilitate the exhaust of plastic moulded products, and avoid opening the gate near slender cores. This can prevent the material flow directly impacting the core of the mold, causing deformation, misalignment, or bending.

The size of the gate is determined by the size, geometry, structure, and plastic type of the product, which can be modified according to the test conditions of plastic moulded products. The seam line caused by the gate position and its impact on the appearance and function of the product can be judged through mold flow analysis or experience, and it can be solved by increasing the cold cavity. When a mold has multiple cavities, the same product uses symmetrical pouring method.

Precautions for Designing Plastic Moulded Products

• When developing or trial-producing new products, some users often focus only on the initial R&D of the product and neglect communication with the mold manufacturing unit. After the preliminary design of the product design scheme is determined, it can ensure that the designed product has a good molding process and will not modify the stereotyped design due to the difficulty of parts processing, so that the mold makers can make preparations in advance to prevent hasty considerations that may affect the schedule.

• According to the different requirements of physical and chemical properties, material of components, dimensional accuracy, mechanical strength, surface finish, service life, and economy, different types of plastic moulded products are selected for molding, and strict requirements are made for mold materials and molding processes. High-precision molds need to be processed by high-precision CNC machine tools. Some components have special requirements in the molding process. Advanced technologies such as gas-assisted molding, hot runner, and nitrogen cylinder should be used in the mold.

• Generally, large stamping molds need to consider whether the machine tool has an edging mechanism, a multi-station progressive die, etc. When choosing a cooperative manufacturer, you must understand its processing capabilities. You cannot just look at the hardware equipment, but also combine its management level, processing experience, and technical strength. For the same set of molds, the quotes of different manufacturers are sometimes very different. Users must weigh them comprehensively based on their own needs.

• Even if you have qualified plastic moulded products, you may not be able to produce qualified products in batches. This is mainly related to machine tool selection, molding process, and technical quality of operators. Good molds need good molding processes, preferably through coordination, and try to avoid multi-party cooperation.