The sleek aluminum casings of iPhones have become ubiquitous in our lives, but you may not be aware that Apple once introduced a line of iPhone 5C with plastic casings.

Every day, we often use a variety of plastic products, and most of these products are created using plastic injection molding technology. Have you ever wondered how the process of making the casing for the iPhone 5C or these plastic products takes place? Let’s explore the history of the injection molding process – the art of shaping plastic.

It all began over 150 years ago in 1872 when brothers John and Isaiah Hyatt were granted a patent for a device that heated and injected celluloid plastic into a mold made of plaster of Paris. Celluloid was the world’s first synthetic plastic, replacing expensive materials like horn and ivory in the production of jewelry and toys. By the 1950s-1960s, this technology expanded its applications to various industries such as electronics, automotive, and household goods. The development of computers and digital control in the 1970s-1980s further popularized and modernized this technology.

From its early days of development to the present, plastic injection molding technology has become an integral part of the manufacturing process for a diverse range of goods. With the advancement of plastic materials and technology, creating unique and intricate products has become easier than ever.

Injection molding is a mass production technology for creating identical plastic products by shaping them with intricately crafted molds. Materials such as synthetic plastics are melted before being injected into the molds and cooled to achieve the desired shape. This process is called injection molding because it resembles injecting a liquid substance through a syringe.

Injection Molding Process

This process is relatively short, typically ranging from 2 seconds to 2 minutes, and consists of four stages.

Clamping

Before delving into the plastic injection process, two molds are clamped together. The molds have shapes and dimensions corresponding to the final product we are creating. In this step, the molds play a role in holding the product securely and ensuring that there is no plastic leakage during the injection process.

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Injection

After the molds have been securely clamped, the plastic is fed into the plastic injection machine. The high-temperature injection machine melts the plastic into a liquid state. This melting process makes the plastic easily flow into the molds, shaping the final product.

Cooling

After the plastic has been injected into the molds, the cooling process begins. Cooling solidifies the plastic, ensuring that the product maintains the desired shape and structure. The cooling time can vary depending on the type of plastic and the size of the product.

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Ejection

Once the product has sufficiently cooled and reached a stable hardness, the molds open. An ejection system pushes the product out of the molds. The final product is then retrieved and undergoes quality inspection before moving on to the finishing and packaging stage.

Different types of plastics commonly used in injection molding

All types of thermoplastics can be used in injection molding. Some types of silicone and other rigid plastics are also employed in the plastic injection molding process. Common plastic materials used in plastic injection molding include:

Polypropylene (PP): ~38% of the total global production output
ABS: ~27% of the total global production output
Polyethylene (PE): ~15% of the total global production output
Polystyrene (PS): ~8% of the total global production output.

Even when considering all other manufacturing technologies, plastic injection molding with these four plastic materials accounts for over 40% of the total plastic components produced globally each year.

In the example of plastic molding technology products

In our surrounding life, we can encounter numerous plastic products. From simple educational tools such as rulers and pens to complex items like tables, chairs, computers, automotive parts, motorcycles, airplanes, etc., are all made of plastic. These products come in various colors and shapes, enhancing the beauty and convenience of our lives.

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Packaging

In the kitchen of every household, we often see plastic food containers. They are made from polyethylene (PE) or polypropylene (PP), helping to preserve food and providing convenience for storing various sizes of meals. These containers come at a very affordable cost, ranging from a few thousand to a few tens of thousands of Vietnamese dong.

Electronic Devices

The protective casing for most everyday consumer electronic devices is mass-produced using injection molding technology. ABS and polystyrene (PS) are two preferred types of plastics due to their excellent impact resistance and good electrical insulation properties.

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Children's Toys

Currently, there are two types of plastics approved for use in the production of toys for young children: ABS (Acrylonitrile Butadiene Styrene) and PP (Polypropylene).

The advantages of PP plastic include high durability, rigidity, non-flexibility, and being odorless, tasteless, and non-toxic. On the other hand, ABS plastic is very rigid, tough but not brittle, capable of withstanding impacts as well as heat at low temperatures.

PP plastic is more widely used today in the mid-range price segment for manufacturing plastic toys, while ABS plastic is employed to create toys at a slightly higher price point.

Automobile and Motorcycle Spare Parts

Cars and motorcycles are everyday means of transportation that we are all familiar with. Most plastic components in the interior of a car are produced through injection molding. The three most common types of injection-molded plastics used in the automotive industry are Polypropylene (PP) for non-critical parts, PVC for its good weather resistance, and ABS for its high impact resistance.

More than half of the plastic parts in a car are made from one of these plastics, including bumpers, interior components, and dashboards.

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Medical Devices

Various materials with antibacterial properties and compatibility with the human body are used in the plastic injection molding technology in the medical industry. For example, Medical Grade Silicone is one of the most common materials. However, silicone is a thermosetting plastic, requiring special machinery and control processes, making it more costly to manufacture compared to other materials.

For medical devices with less stringent production requirements, other plastics such as ABS, polypropylene (PP), and polyethylene (PE) can be used.

Plastic Injection Molding at CNCTech
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CNCTech offers injection molding service and specializes in various plastic molds for Motorcycles, Telecom Equipment, Home Appliances, IoT Devices, and other OEM Applications. We run nearly 150 presses with capacities from 75 to 450 tons in northern and southern facilities.

Our shops routinely handle technical grade resins including ABS, ASA, HIPS, PC, PBT, PMMA, PA, POM, and TPEE. The granules often come with flame retardant additives, and at times, reinforcement fibers.

Following are complementary services we’re building around our end-to-end manufacturing solution for plastic molded parts:

Threaded inserts installation (ultrasonic or thermal heat)
  • Machining (routing)
  • Silk printing and pad printing
  • Protective film application
  • Assembly and packaging
  • Spray painting and plating (by our local partners)