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A Short Guide on How Plastic Injection Molding Works

This guide briefly explains the process of how plastic injection molding works including a few benefits it has over other plastic manufacturing methods. Find out why you need to pick plastic injection molding for your business.


Plastics are the most commonly used material all over the world. Every year 300 million tons of plastics are produced. Many engineers and designers work hard for the development of a wide range of plastic products.

The plastic production started in the world in the early 20th century. Since then there has been much technological innovation incurred in the industry regarding plastic production and plastic creating methodologies.

Plastic market injection molding is a universally popular tool. In recent times it is proven to generate a lot of profit for the owners. Its durability, cost-festiveness, lightweight, reusability, and corrosion resistance makes it the number one plastic fabrication gadget.

Do you know injection molding is one of the top quality processes in assembling plastic article? Injection molding is one of the most widely used methods in the manufacturing of plastic products. It is accessible in both vertical and horizontal configurations. It is considered as a condemnatory pillar of the industry.

Injection molding is used to turn out the maximum number of identical plastic items. Mostly Thermoplastics, Nylon (PA), Polycarbonate (PC), Nylon, PVC, Acrylic (PMMA), Polypropylene (PP), and Polyetherimide (PEI) can be processed in injection molding.

In the plastic industry, it is used to create multiple things like a car bumper, wheelie bins, bottle caps, wire spools, toys, musical instruments, automotive parts, remote control, electronic products, chairs, mechanical parts, storage containers, and medical equipment, etc.

Image of how plastic injection molding works.

Benefits of Using Plastic Injection Molding

  • Cost Saving
  • Less labor cost
  • Multiple Finishing
  • Accurate working
  • Enhanced Strength
  • Minimize plastic waste
  • Best in mass production
  • Efficient and Resourceful
  • High-quality plastic components
  • Flexibility in material & color
  • Smooth finishing of plastic parts
  • Good Speed & Fast Production
  • Capable of using multiple plastic types

To be a top plastic producer it is significant to have knowledge of plastic manufacturing methods. The more you have a grip on technicalities and all courses of action the more you will be able to become a number one plastic manufacturer in the world.

Let’s look at the process and see how plastic injection molding works;

Scraps from plastic injection molding works.

Process of Plastic Injection Molding

Injection Molding (IM) is performed when a molten thermoplastic substance is injected into the mold. It melts the raw plastic then mold into the desired shape. The mold is comprised of two main parts, the A palate i.e. Injection mold and B plate i.e. ejector.  The melted plastic enters the mold gate and then gate bushing is sealed tightly with the nozzle of barrel molding device.

The process cycle of injection molding includes 4 stages i.e. clamping, injection, cooling, and ejection. This process gets completed in a very short time.

The plastic industry most widely uses it because of mass production functionality.  It creates complex parts at high speed and pressure. Per unit price is very low by the production with injection molding.

Parts of Injection Molding Machine

Injection molding parts include material hopper, screw-type plunger, feed zone, nozzle, heating unit, injection chamber, movable platen, stationary platen, rotating screw, barrel, clamping cylinder, and an injection ram. They all work together to hold the mold in which the shape of the plastic component is formed.

Step by Step Procedure

In the pre-processing stage, it is mandatory to plan the design, shape, color, and quality of the plastic items. Injection molding companies decide which plastic-type they will use for production.

1. Setting of Mold

In the initial step, the parts are arranged robotically or either by hand. The mold’s two halves are first required to be shut carefully by the clamping section. The hydraulic press is used in the closing down of the mold.

2. Extrusion of Plastic

The second step involves the melting of small plastic pellets that is the raw material plastic. They are expelled by an extremely hot chamber. The extrusion is done with the help of a screw tool. The injection time is needed to be estimated accurately due to the change of flow in the molten plastic placed in the mold.

3. Molding Process

Plastic molding means giving the desired shape. The plastic that has been melted is now injected into the molds. The temperature is controlled according to the requirements.

The molding procedure is highly complex. The whole process is must be performed carefully by keeping an eye on the pressure of mold clamp. Only experienced manufacture can handle the injection molding machine efficiently without any harm. Wrong timing and management could cause damage to the plastic parts.

4. Cooling & Releasing of Parts

The plastic parts are kept in the molds until it becomes cool and come into the desired solid shape. During the cooling phase, the plastic may get shrink a little bit. When required cooling time is over only then mold halves are allowed to open.

The cooling time estimation depends on the material properties of plastics which have been used in the process. The solid parts are then ejected through compressed air or by using a mechanical way. Mechanism and force are applied while taking the part out of the mold. This is how plastic injection molding works and this process can produce millions of best quality parts at rapid speed.

5. Post Processing

The runners are the pathway that is used to fill the mold cavity is automatically removed from the parts. In the end, product finishing is done for final use. The flash part is trimmed from the plastic product by using cutters.

The cycle time is processed in seconds. It produces a high volume application which is at 5000 + parts. The lead time of injection molding is 2 to 4 months. The finalized parts are then counted and weighted. Then the plastic products are shipped to different regions.

The expert team and labor force make sure that the customer gets high-quality articles. Due to mass production, injection molding fulfills the demand of customers.

In A Nut Shell,

Plastic injection molding works as the best equipment to design unique and high-quality parts at an efficient speed. It gives flexibility to plastic manufactures to make durable and complex shape products at very cost-friendly rates. Feel free to read about the latest news as well on the plastic industry today.

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