What is Injection Molding?

In the manufacturing world, if there is a manufacturing process that is specifically designed to produce large quantities of parts, injection molding technology should be at the top of the list. Injection molding is widely used in modern manufacturing due to its efficiency, versatility, and outstanding results in the mass production of high-quality parts.  

If you are an aspiring person who is interested in injection molding technology or just entering the manufacturing industry, then this article on injection molding will benefit you a lot. In this blog, we will explore the complexity of injection molding, its principles, processes, materials, applications, and more.  

Injection molding is a manufacturing process that creates parts by injecting molten material into a mold. It is a special molding process that is neither additive manufacturing nor subtractive processing.   

Injection molding technology has great advantages in the production of various parts. Whether it is used to produce complex small parts or large parts. Therefore, it is widely used in the manufacture of parts in industries such as automobiles, consumer goods, and medical devices.

What is the principle of injection molding?  

The core principle of injection molding is to inject molten thermoplastic or thermosetting material into a precisely designed mold cavity to make it into the desired part shape.   

After a special process, when the material cools and solidifies, the mold is opened and the finished part is ejected. This process can achieve high productivity of injection molded parts while maintaining consistent quality and dimensional accuracy.  

What is the specific process of injection molding?  

Injection molding is a complex process. The specific injection molding process can usually be divided into the following key steps:  

1. Material preparation: pour the original plastic particles into the hopper. This step is the preparation before the injection molding begins. After the material is fed into the hopper of the injection molding machine, the mold must be closed in time, therefore, this process is also called "mold closing".  

2. Melting: As the screw of the injection molding machine rotates, the heat of the work is transferred to the barrel, and then the plastic particles in the barrel are gradually heated to a melted state until it is completely turned into molten material. This step is considered complete.  

3. Injection: The molten plastic is injected into the mold under high pressure. In this process, when the molten plastic reaches the end of the barrel, the gate (which controls the injection of the plastic) will close and the screw will move backward. This will suck in a certain amount of plastic and build up pressure in the reciprocating screw in preparation for injection.  

At the same time, the two halves of the mold are closed together and maintained under high pressure, which is called clamping pressure. The gate will open only when the injection pressure and clamping pressure reach the predetermined value under the joint action of the injection tool and the screw. At this time, the screw moves forward so that the molten plastic can be fed into the mold.  

4. Cooling: The material cools and solidifies in the mold. The specific cooling time depends on the type of raw material and the complexity of the custom injection molded part. Under normal circumstances, this "holding time" ranges from a few seconds to a few minutes.  

5. Ejection: Open the mold and eject the finished part. When the cooled injection molded part ends the cooling time, the ejector plate or ejector pin in the injection molding machine will eject the injection molded part from a specific tool. Then it falls onto the conveyor belt or compartment next to the machine and proceeds to the next process.  

6. Trimming: Remove all excess material (commonly known as burrs, burrs), such as gates and runners.  

What are the common types of injection molding processes?  

There are many types of injection molding processes, including:  

· Standard injection molding: The most common form, used for thermoplastics.  

· Gas-assisted injection molding: It uses high-pressure nitrogen to inject when the plastic is filled into the cavity to push the molten plastic to continue to fill the cavity, and replaces the plastic pressure holding process with gas pressure holding. ‌ Not only that, it can also use gas to create hollow parts in parts to reduce material usage.  

· Injection blow molding: The injection blow molding process is to first inject the molten plastic into the injection mold by the injection machine to form a tube blank, and then form it on a hollow punch with micropores on the four walls; then move it to the blow mold while it is hot; then close the mold and pass compressed air from the pipe of the core rod to inflate the tube blank and make it close to the wall of the mold cavity; finally, after pressure holding and cooling, the compressed air is released, the mold is opened, and the plastic part is taken out. Used to make hollow objects such as bottles.  

· Multiple injection molding: Multiple injection molding is a method of processing injection molded parts. By setting multiple cavities and injection heads in the injection mold, injection molding operations at different positions can be achieved. ‌   

This method is usually used to produce products with complex structures. By controlling the injection molding process of each cavity separately, each part can be accurately molded. ‌  

· Insert molding: The pre-prepared inserts of different materials are placed in the mold, and then resin or molten material is injected to make it bonded with the insert to form an integrated product. ‌‌  

What materials can be injection molded?  

Injection molding can accommodate a variety of materials, the most common of which include:  

· Thermoplastics: such as polyethylene (PE), polypropylene (PP), and polystyrene (PS).  

· Thermosets: including epoxy resins and phenolic resins.  

· Elastomers: flexible materials like rubber, such as the well-known TPE or TPR materials.  

· Composites: materials that combine plastics with fibers or other materials to enhance strength and durability.  

What are the applications of injection molding?  

Injection molding is used in many industries, including:  

· Automotive: used for components such as dashboards, bumpers, and interior parts.  

· Consumer products: such as toys, kitchen utensils, and household items.  

· Medical devices: production of syringes, instrument housings, and other key components.  

· Electronics: used for housings, connectors, and various electronic parts.  

Do you provide injection molding services?

At RT, we provide injection molding services to our customers. These services usually include custom mold material selection injection molded part manufacturing and quality control to ensure that the final product meets the required specifications.   

If you need injection molding processing services, please upload your design files and our experienced quotation engineers will provide you with a free quotation service. On the other hand, if you want to know the progress of your project, you can communicate one-on-one through our business team.  

Summary

Injection molding is an efficient manufacturing process that plays a vital role in producing a large number of products in various industries. Its ability to create complex shapes with high precision and consistency is an invaluable technology in modern manufacturing. In the end, whether you are looking for custom parts or large-scale production, RT injection molding can provide you with a tailor-made solution.