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How Plastic Molding Injection Works

Plastic Injection Molding in China: How It Works

By Carter Kho

Plastic items, like the ones created from plastic injection molding in China, has become one of the most common things that you would see every day. In fact, a good majority of items in your home and in your office is made out of plastic, or at least has plastic parts that help make it work. (An example of which would be the device that you are using to read this) These plastic items can include food containers, storage bins, bags, toys, utensils, kitchen items, gadgets and devices, stationary, and many more.

Indeed, plastic has become a popular material to use for the methods of manufacturing it have improved over the past few decades. Since it is a material that can be molded into any shape, people have used it to create various items. These items are created using plastic injection molding, which is an elaborate process that requires molding and heating the plastic to create an end product.

There are many people, who have become curious as to how plastic is made through these machines, as they rarely get to see it work. To give you an idea, here’s how China’s plastic injection molding machines work.


How Plastic Injection Molding in China Works

When it comes to the plastic industry, manufacturing is done using China’s plastic injection molding machines, which enable them to produce a large number of products in a shorter period of time. Instead of molding pieces individually by hand, the machine allows them to use the same mold over and over again and still get similar products.

The overall process of manufacturing may sound simple, though there are many steps that have to be done to ensure that the machine would be able to bring out a quality product. Here is how plastic injection molding in China works:

Designing the Mold

Before deciding to create a finished product, the very first process of manufacturing is to create the design first. Creating a mold requires a good amount of time and skill to pull off. This is a task assigned to design engineers, who will craft various mold designs through a computer. These people will also add texturing to enhance the details on a certain product. These include patterns, logos, matte finishes, multi-gloss finishes, gripping surface, graphics, and even layered textures.

The final mold design will be crafted through a machine, which carves out the exact dimensions of the final product. These molds are made out of steel, which is strong enough to withstand the rigors of mass production. Stress is a manufacturer’s biggest worry, as it can affect the overall quality of the product itself. It is best to make sure that there is enough space, or it has the right transitions to prevent any defects. These include unsightly seam lines, warped plastic, flashes, and even cracks.

Drafting a digital model would help them judge the right scale and shape for the mold. Maximum precision is required when doing this task, as any small error may affect the entire production of the product, leading to product recalls. Once the mold design has now been finalized, it is now time to choose which material to use in the plastic injection molding machine.

Choosing the right material

When it comes to injecting plastic into the mold, the manufacturers must make sure that they are using the right kind of plastic. Currently, there are many different kinds of plastic that are being used for manufacturing, and choosing the right one could spell the difference between a quality product or a bad one.

Companies hire chemical engineers to find the right formulas and mixtures for their products. This will allow them to experiment with various polymer materials, and choose which one fits best. These factors include durability, hardness, and color. Some polymer mixtures are fit for specific products, which means that not every plastic product would use the same kind of mixture. Choosing the right materials would ensure that anything coming out of the plastic injection molding machine would be the right product.

Frequently Used Materials:

Polyethylene – Discovered in the 1800s in Germany, polyethylene is the most widely used plastic all over the world. It is the base material of a wide majority of products that people use today, including water bottles and grocery bags. It was even used as a secret material during the Second World War due to its durability and ability to reduce radio waves.

Polyethylene Terephthalate (PET) – Also known as one of the most widely distributed types of plastic around the world, this is another kind of material that is used for plastic bags and water bottles. It is also commonly used as a fiber, known as polyester, and is used in the apparel and cloth industry. Polyester fabric is known to be highly durable, and resistant to water, which makes it a good weatherproof cover for containers and other items.

Polyvinyl Chloride (PVC) – Known for being a material used for industrial and construction purposes, PVC is a durable and cost-effective material that is highly resistant to various substances that can damage most kinds of plastics. PVC is easy to design and mold, which makes it a versatile industrial and commercial material. It can be used as a rigid and strong material, and can also be used as a soft and lightweight material.

Polyamide – This material is most commonly known as nylon and is one of the most commonly used types of plastic in the injection molding industry. Nylon is known to be highly durable and flexible. It can withstand high temperatures, and various chemicals and other substances, which makes it a popular industrial material.

With this in mind, nylon is commonly used in ropes and cords, especially ones for climbing and heavy-duty purposes, clothing, and mechanical equipment. It is even used as a substitute for certain metals in automotive parts as well.

Polypropylene – Another strong and durable type of plastic, polypropylene is known as a highly adaptable kind of material as well. It is a material that is cheap to produce, has a high melting point, and is resistant to acid. It is also one of the types of plastic that are safe for food, which makes it ideal when manufacturing food containers.

Polystyrene – Unlike other kinds of plastics, polystyrene is used in the packaging of various finished products. This kind of plastic is commonly known as Styrofoam and is used to protect various items from any form of contact that may damage it. This kind of polystyrene is known as General Purpose Polystyrene.

Acrylonitrile-Butadiene-Styrene (ABS) – Another common material used in injection molding, ABS is a type of plastic that is affordable to manufacture, durable, easy to melt, readily available, and is highly resistant to corrosive chemicals. This is one of the easiest materials to handle when using injection molding machines.

Polyoxymethylene (POM) – Known commonly as Acetal, this kind of plastic is known for its low friction, high durability, and high-temperature resistance. These qualities allow it to retain its shape after going through the molding process. Its strength makes it comparable to some of the durable metals, which makes it a lighter alternative to certain moving parts.

Polyurethane (PU) – One of the most flexible plastics available, polyurethane is a highly durable plastic that is known for its softness. This softness allows some extra grip and flexibility for various products. This can also come in liquid form, which is used in sealants, adhesives, and varnishes.

Polycarbonate – Another high impact type of plastic, polycarbonate is known for being transparent, and highly durable compared to other plastics. This helps it become resistant to different kinds of substances and high temperatures, which makes it great for construction and industrial usage. Manufacturers can also create glossy finishes by using polycarbonate and add some vivid colors for variety. The material is also scratch-resistant, which is another quality it can achieve due to its durability.

Acrylic – Another high impact type of plastic, polycarbonate is known for being transparent, and highly durable compared to other plastics. This helps it become resistant to different kinds of substances and high temperatures, which makes it great for construction and industrial usage. Manufacturers can also create glossy finishes by using polycarbonate and add some vivid colors for variety. The material is also scratch-resistant, which is another quality it can achieve due to its durability.


Before producing the final product, it is best to make sure that the plastic injection molding machine is working properly, and that the mold and polymer mixture are the right fit. Normally, pre-production molds are used to ensure that the final mold would be in the right shape, and that all necessary adjustments will be made.

It is also standard procedure to check if the parts of the machine are well-maintained, and that it is in perfect running order. This helps in keeping the work area safe from any accidents or mishaps that might occur. Being able to run tests is important, as this is a big factor on whether or not your product will be of high quality.


The building process starts off by placing the mold into the plastic injection molding machine. Once the machine starts up, it is now the time to drop down the plastic pellets into the machine. These pellets would be fed into the heater to be melted. The pellets can be fed either automatically or manually.

The melting process is done using a series of heater bands and a screw barrel. Most of the heating is done through the use of friction and high amounts of pressure (around 10,000 to 30,000 psi).

Once the pellets have been melted down, the now liquid plastic will be injected through a nozzle. The melted plastic would finally enter the mold cavity, where the plastic would cool down and harden. The mold is divided into two parts, which are attached to steel clamps called platens.

These clamps close when the plastic is injected, and then opened up once the plastic has hardened. This process can be repeated over and over, until the desired number has been reached. This process would ensure you that you would be able to produce a huge number of products, but make sure that you still have the same quality altogether.


Benefits of Plastic Injection Molding in China

In China, plastic injection molding is one of the most efficient manufacturing methods around, as you are able to produce quality products through it. However, there are more benefits that manufacturing companies will enjoy as well. Here are some of them:

  • Low scrap rates – Using a plastic injection molding machine would allow you to maximize the amount of plastic that you are using, as the machines make sure that the amount of wasted plastic during the whole production process would be minimal. This is more efficient compared to other forms of plastic production, such as 3D printing and the use of CNC machinery.
  • Cost-effective – One of the biggest benefits of using plastic injection molding in China is that you will be able to manufacture a large number of products, while spending less overall. This is due to the quality of the machine, as it is able to perform consistently, leading to significantly less errors in the final products. Labor also costs less, as you would not need as many people to run the machines during the whole process.
  • Repeatable process – Since the molds are reusable, you will be able to produce the same products over and over again without sacrificing their quality. You would be sure that you will be able to deliver the best products, as well as address the demands of the consumers at the same time.

Plastic injection molding in China has improved by leaps and bounds ever since it was first introduced in the manufacturing world. With the ability to produce high quality products with less cost; this means that the company will not only be able to be more efficient with their budget, but also make sure that they would be getting the best products available.


Where to find quality plastic products?

At Richfields Corporation Limited, you are guaranteed that you would be able to receive top of the line and high quality products, as the company ensure that their manufacturing facilities would be able to deliver.

What is Richfields?

Richfields Corporation Limited is a company that was founded in 2001. The company was organized by multiple investment groups from Hong Kong. Along with multiple investors, the company also had the support and skill from some of the most experienced plastic manufacturing personnel from China.

The company began producing its first plastic injection molds in 2004, and distributed it to various international clienteles. The company produces over 300 different kinds of molds per year for both export and use within China.

Why choose us?

Richfields Corporation Limited is a company known for its excellent customer service and our ability to be able to provide you quality products and deliver it on time. Since the manufacturing facilities are within China, this allows the company to offer competitive prices that match up with some of the world’s best. The diverse product variety also allows the company to cater to various international clients and customers. Due to its multinational nature, the company is able to establish good communications with our clienteles, which allows our network to keep growing as the years go by.

What are our products?

Richfields Corporation Limited, a molding company, offers a wide variety of products, some of which include home and safety products, along with various types of molds that can be used to create different kinds of items, such as runner molds and precision plastics. For more information about our products, you can visit this page.

Contact Us

If you have more inquiries with regards to our products and services, you can email us at ckho@richfieldsplastics.com, call us by phone (+86-769-87888726), or contact us through fax (+86-769-87909012).