Understand the Basics of Injection Molding

Injection molding is a common manufacturing process in the manufacturing industry, which is used to mass-produce injection molded parts. Design plays a vital role in injection molding because it directly affects the function and manufacturing of the final product. This article will introduce the basic principles of injection molding in detail, basic design principles process processes, etc.

The basic principle of injection molding

Injection molding is sending granular or powdered plastic raw materials into the heating cylinder of the injection machine and melting the plastic into a flowing state by heating. Then, the molten plastic is then injected into the closed mold cavity at high pressure. Finally in the mold, the plastic is cooled and set to form the desired shape.

Basic design principles of injection molding

Opening direction and parting line：

First, determine the mold opening direction and parting line of the injection product to ensure that the use of the core-pulling slider mechanism is reduced. The stiffeners, fasteners, protrusions, and other structures of the product should be designed as much as possible in the same direction as the opening mold.

Draft angel:

Properly deserter slope can avoid problems such as hair hair and top injuries. The slope of the smooth surface of the smooth surface should be ≥0.5 degrees, the surface of the fine leather pattern is greater than 1 degree, and the surface of the coarse leather pattern is greater than 1.5 degrees.

Product wall thickness:

Plastic generally has a wall thickness of 0.5-4mm. Unexpected wall thickness can cause problems such as surface shrinkage, pores, and melting marks.

Reinforcement:

Reasonable use of reinforcing bars can increase the rigidity of products and reduce deformation. The thickness of the reinforcement bar must be ≤(0.5 ~ 0.7)T product wall thickness, and the slope of one side should be greater than 1.5° to avoid jacking‌.

Rounded corners:

A reasonably rounded corner can avoid stress concentration, resulting in product cracking or mold cavities. The choice of rounded corners should also be considered as the processing process of the mold. For example, the cavity can be processed directly with R blade milling to avoid low -efficiency electricity processing.

The design of the hole:

The shape of the hole is generally round. We need to align the axis of the hole with the direction of the mold opening. A large-length hole should be set with caprices, and the long diameter ratio of the blind hole should not exceed. The distance between the edge of the hole and the product is generally greater than the size of the hole diameter.

The process of injection molding

1. Raw material preparation:

First, you need to prepare plastic raw materials, which are generally supplied in a granular or powder-like form.

2. Feed and warm up:

We add the plastic raw materials to the hopper of the injection molding machine and then preheat the raw materials. The purpose of preheating is to heat the raw material to the appropriate temperature to ensure that it can flow adequately and fill the mold during injection molding.

3. Shooting and injection:

When the raw material preheats the temperature required, the injection molding machine begins to perform shooting and injection operations. The injection material is the preheated plastic raw material injected into the nozzle of the injection molding machine through the screw propulsion device. And then the plastic raw material is injected into the mold through the high-pressure injection system to fully fill all the cavities and empty cavities of the mold.

4. Keep and cool the pressure:

After the injection molding is completed, it is necessary to maintain a certain pressure to ensure that the plastic raw materials are fully solidified, and the required part shape is formed in the mold. Subsequently, cooling is needed, usually cooling through the cooling water or air in the injection mold to cool the plastic parts to solidify and get the final hardness and strength.

5. Model opening and feeding:

When the plastic parts are completely cooled, the injection molding mold will be opened, and the feeding device will be taken out of the mold from the mold.

6. Cooling and frost:

Finally, the completed plastic parts are placed on the cooling table to cool naturally to ensure that there are no residual calories on the surface, and defrost treatment is performed when needed.

Through the above process, plastic raw materials are finally processed into the required plastic products.

Conclusion

Injecting and molding parts are usually used in automotive accessories, medical devices, home appliances, and general consumer electronics products. By understanding the basic knowledge of injection molding, manufacturers can optimize injection molding technology, improve quality, reduce defects, and improve production efficiency. DMTC has a complete technical team. By continuously improving the process to adapt to the development trends and updates, we are always at the forefront of injection technology and meet the requirements of various industries for the production of plastic parts.

Common questions and answers

Comparison of injection molding and 3D printing