How do plastic injection molds work.  Injection molds are commonly used tools in plastic injection processing, mainly for producing various plastic parts. Firstly, we should start with the basic steps of custom injection molding, injection mold design such as the structure of the mold, including the moving and fixed molds, followed by the role of the injection molding machine, such as heating and melting the plastic, injecting it into the mold cavity, cooling and solidifying, and finally opening the mold to remove the product.

Next, it needs to be explained in detail step by step. Firstly, the mold is installed on the injection molding machine, the fixed mold is fixed on the fixed template of the injection molding machine, and the moving mold moves the template. Then the plastic particles are heated and melted inside the barrel, and injected into the mold cavity under pressure through a screw. At this point, it is necessary to mention the pouring system of the mold, such as the main channel, diversion channel, and sprue, which guide the molten material into the mold cavity. Then comes the cooling stage, where the cooling system inside the mold solidifies the molten material, followed by moving the mold to open it, and the ejection system pushes out the product.

We also need to consider the structural composition of the mold, such as the cavity, core, pouring system, cooling system, ejection mechanism, etc. What is the function of each part. For example, the cavity determines the shape of the product, the core determines the internal structure, and the cooling system controls the cooling rate, which affects production efficiency and product quality. The ejection mechanism needs to be designed reasonably to avoid deformation of the product.

Different types of molds, such as single cavity and multi cavity molds, hot runner molds, etc. In addition, attention should be paid to the explanation of terminology, such as mold closing, injection, pressure holding, cooling, mold opening, and ejection, to ensure that users understand each step.

It is also necessary to check for any important steps that have been missed, such as the pressure holding stage, maintaining pressure after injection to prevent melt reflux and compensate for shrinkage. The control of cooling time is also important, as it affects the production cycle. In addition, the material selection of the mold, such as steel, requires high temperature and high pressure resistance, surface treatment to improve wear resistance and demolding performance.

A plastic injection mold is a tool that, in conjunction with an injection molding machine, injects molten plastic into the mold cavity, cools and solidifies to form a specific shaped product. Its working process can be divided into the following key steps:

2. Plastic melting and injection

Raw material processing: Granular plastics (such as ABS, PP, etc.) enter the injection molding machine barrel and are melted into a flowing state by a heating device (usually 180-300 ℃).
Injection process: The screw or plunger of the injection molding machine pressurizes the molten plastic and injects it into the closed cavity at high speed through the pouring system of the mold (main channel → diversion channel → gate) until it is filled.
Pressure holding stage: After the molten material is injected, the screw maintains pressure (pressure holding) to compensate for cooling shrinkage and avoid product shortage or shrinkage.

3. Cooling and solidification

Cooling system: The mold is designed with a circulating water circuit (or oil circuit) inside, which quickly lowers the temperature of the mold cavity by introducing cooling water, allowing the molten plastic to solidify and form in the mold cavity.
Time control: Cooling time determines production efficiency and product quality. If it is too short, it may cause deformation, while if it is too long, it may prolong the cycle. 

4. Mold opening and product ejection

Mold opening action: The injection molding machine drives the moving mold to retreat, opening the mold and exposing the cured product (attached to the core of the moving mold).
Top out mechanism: Devices such as top pins, top rods, or push plates inside the moving mold push products out of the core and into the collection area.
Demolding design: The surface of the mold is usually polished or demolded to avoid product adhesion. For some complex structures, lateral core pulling mechanisms such as inclined tops and sliders need to be designed.