Injection Molding — Setting up Manufacturing in China

Injection molding in China does take effort to set up correctly. When done right, it can add huge value to your business. Here are some top tips on setting up injection molding manufacturing in China.

This blog article was first published on www.sourcingallies.com

World War II is a dark period in history. But did you know that the great conflict that split the world into two opposing sides was also a time of opportunity, development, and progress for an emerging plastic industry? With aluminum, copper, steel, and other metals becoming precious commodity allocated solely for military use, plastics came into their own as a manufacturing material. At the same time, the fast-growing aviation and automotive industries fed the demand for inexpensive, mass-produced plastic parts and products.

Today, plastic is an essential part of our daily lives. The plastic items you come across just about anywhere are in all likelihood the product of a versatile manufacturing technique called plastic injection molding. Read on to know what the process is all about, its origin and the current state of the industry.

What is plastic injection molding?

What raw materials are used?

Thermoplastics: Thermoplastics melt when heated and harden when cooled. They can be reheated, reshaped and, therefore, remolded multiple times. Thermoplastics are recyclable. Any waste during the manufacturing process can be reused. This makes them cost-effective. Additionally, they are flexible, have a superior finish and high impact resistance (which means they are not too hard and rigid). On the flip side, thermoplastics have a lower resistance to heat and can be more expensive than thermosets.

Popular thermoplastics and their applications: Acrylonitrile butadiene styrene or ABS (computer keyboard caps), polypropylene (car fenders), polyethylene (cable insulators, skincare product containers), polyvinyl chloride or PVC (raincoats), polystyrene (food packaging) and polycarbonate (phone cases).

Thermoset plastics: Thermoset plastics harden irreversibly when heated. Compared to thermoplastics, thermosets generally have higher heat and chemical resistance, mechanical strength, and dimensional stability. However, they cannot be recycled or recast, have lower impact resistance (are more brittle) and are harder to work with, particularly during the surface finish stage.

Popular thermosets and their applications: Fiberglass (bathtubs), silicone (gaskets and seals), bakelite (buttons) and melamine (tableware).

Plastic injection molding products can be found just about anywhere

Applications

The History

1868: American inventor John Wesley Hyatt invents celluloid, the first synthetic plastic material, by mixing nitrocellulose, camphor and alcohol in a heated mold.

1872: Hyatt and his brother Isaiah patent the first plastic injection molding machine — a simple device with a plunger that injects plastic through a heated cylinder into a mold. The fledgling plastic industry, which then produced simple items such as combs and buttons, receives a big boost from this invention.

1930s: A period of growth and innovation for the plastic industry, marked by the invention of thermoplastics such as polyolefins, polystyrene, and polyvinyl chloride.

1940s: The industry expands rapidly with World War II feeding a growing demand for inexpensive, mass-produced goods. Plastic fast becomes an affordable alternative to metals and rubber, which are in short supply due to supply disruptions caused by the great war.

1946: American inventor James Watson Hendry improves on the Hyatt brothers’ invention by building a screw injection machine. This device replaces the plunger with an auger — a rotating screw-shaped device. The auger is placed in the cylinder and mixes the plastic material before injecting it into the mold. It gives the molder better control over the speed of the plastic injection. The result: better quality products. Screw injection machines are still widely used today.

1970s: Hendry develops gas-assisted injection molding, which makes it possible to produce long, hollow, and complex parts. The result is a lighter, stronger product with a better finish, made at a lower cost and with less material wasted. This period is also marked by plastic production overtaking steel production.

Made in China: The market today

Why China

  • You can find suppliers just about anywhere in China. The East and Central South regions especially have a large concentration of plastic factories. You’ll find suppliers who cater to both large-volume and small-volume orders.
  • The sheer scale of China’s manufacturing capacity means it is capable of producing all types, sizes and quantities of custom-made plastic products.
  • In line with China’s growing adoption of robot technology, many of its plastic manufacturing companies use advanced automated processes for high product consistency and production efficiency.
  • Being the world’s largest plastics producer, plastic raw material is easily available in China.
  • It is also the world’s leading producer of injection molding machines.
  • China’s transport infrastructure — with its superhighways, high-speed rail networks and ports — is among the most modern and efficient in the world and geared towards facilitating exports. As it extends its infrastructure at home, it is also providing financial assistance to neighbors such as Myanmar and Pakistan to build ports and rail terminals to service its own export hubs.
  • All of this means that China’s supply chain integration is highly superior.

If you’re thinking of sourcing plastic parts from China, here’s why it’s a good idea:

  • Prices in China are highly competitive. The overall efficiency of the manufacturing process keeps costs low and ensures that you don’t compromise on quality.
  • China suppliers have both experience and expertise. You can expect an experienced supplier to not only manufacture your goods but offer engineering support to make it a better product.
  • Sourcing from China means access to its vast resources and technologically advanced equipment.
  • There’s no need to buy your own equipment. You also save on maintenance and repair costs and workers’ salaries.

Advantages

  • Mass production with consistent measurements. It shouldn’t be a problem to produce 200,000-odd parts before the equipment requires repairs or maintenance (though the material used has a say in this).
  • Cost-efficient. As a raw material, plastic is cheaper than rubber or metals. Manufacturing and labor costs are also low, and more and more manufacturers are using automated processes that in turn further reduce manpower. Low waste rate — especially in the case of thermoplastics, which can be recycled and remolded — also helps keep manufacturing cost low.
  • Design flexibility. Plastic injection molding is perfect for producing detail-heavy and intricately shaped parts.
  • Good surface finish. Usually, very little post-production work is required, though special finishes such as a shiny look, leather-like finish or engravings are also possible.
  • Wide choice of materials and colors. Also, more than one plastic can be used simultaneously. For example, a PVC/ABS blend is intended to have the best of both materials but with few disadvantages of either.

Disadvantages

  • High initial lead time due to product conception, design, tooling, and testing. The tooling stage can take between 15 days and three months.
  • Thermoset plastics cannot be recycled.
  • Performance of recycled material is inferior compared to new material.
  • Not cost-effective for very large moldings.
  • Warpage (shape distortion during cooling) and shrinkage.

We are a China Manufacturing and Sourcing Agent with offices in the US, China and Sweden. We get the right price, quality and lead time. www.sourcingallies.com

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store