Injection mold molding is the most common manufacturing process for manufacturing plastic parts. The use of injection molding to make a wide variety of products varies greatly in color, size, complexity and application. The injection molding process requires the use of injection molding machines, raw materials and molds. The plastic is melted in an injection molding machine and then injected into a mold where it is cooled and solidified into final parts. The injection molding process cycle is very short, usually between 2 seconds and 2 minutes, including the following four stages:
Clamping - Before injecting material into the mold, the two halves of the mold must first be firmly closed by the clamping unit. Connect each half of the mold to the injection molding machine and slide half of the mold. The hydraulic power clamping unit pushes the mold halves together and applies sufficient force to keep the mold securely closed as the material is injected. The time required to close and clamp the mold depends on the machine - a larger machine (a machine with a larger clamping force) will take more time. This time can be estimated from the dry cycle time of the machine.
Injection - The raw plastic material, usually in pellet form, is fed into the injection molding machine and advanced through the injection molding unit. During this process, the material is melted by heat and pressure. The molten plastic is then injected very quickly into the mold and the pressure pack builds up and holds the material. The amount of material injected is called the lens. Injection time is difficult to calculate accurately due to the complexity and variation of molten plastic flowing into the mold. However, the injection time can be estimated by the injection amount, the injection pressure, and the injection power.
Cooling - The molten plastic inside the mold begins to cool once it comes into contact with the internal mold surface. As the plastic cools, it will solidify into the shape of the desired part. However, some shrinkage of the components may occur during cooling. Material packaging during the injection phase allows additional material to flow into the mold and reduce the amount of visible shrinkage. The mold cannot be opened until the required cooling time has elapsed. The cooling time can be estimated from several thermodynamic properties of the plastic and the maximum wall thickness of the part.
Squirting - After a sufficient amount of time, the cooling unit can be ejected from the mold through the eject system, and the eject system is attached to the second half of the mold. When the mold is opened, a mechanism is used to push the components out of the mold. A force must be applied to eject the part as the part shrinks and sticks to the mold during the cooling process. In order to facilitate the ejection of the component, the release agent may be sprayed onto the surface of the cavity before the material is injected. The time required to open the mold and eject the part can be estimated from the machine's drying cycle time and should include the time the part is out of the mold. Once the part is ejected, the mold can be clamped for the next injection.
After the injection cycle, some post-treatment is usually required. During cooling, the material in the mold channels will cure and adhere to the part. This excess material, as well as any flash that has occurred, must be trimmed from the part, usually using a cutter. For certain types of materials, such as thermoplastics, the scrap produced by such trimming can be recycled by placing it in a plastic grinder (also known as a regrinder or granulator), which grinds the scrap into pellets. material. Due to some reduction in material properties, the regrind must be mixed with the feedstock at a suitable regrind ratio for reuse during the injection molding process.