Plastic Injection Molding

What is injection molding?

Do you already have a clue about what injection molding is? If you don’t exactly know what it is, we are going to explain everything to you in very simple language. Plastic injection molding or injection molding refers to the manufacturing process to produce customized plastic products such as plastic bottles, cell phones, containers, and everyday Essentials in a heavy quantity. All over the world, people use plastic in daily life. The process of injection blow molding makes it possible to create masses of identical plastic bottle products at affordable rates. It becomes convenient to give identical shapes and sizes of plastic products using these production methods.

Injection molding is a manufacturing technology for both small and large-scale production of identical plastic parts with good quality. In Injection Molding, polymer granules are first melted and then injected under heavy pressure into a mold. Further, the liquid plastic cools and solidifies into the required products.

The materials used in Plastic Injection Molding are thermoplastic polymers that can be colored or filled with other additives to achieve the required product. Injection molding is so popular, because of its low cost per unit on the other hand we can manufacture products on a large scale. Injection molding offers high repeatability.

Good design flexibility and it offers a wide range of varieties of products to try out. The main restrictions on Injection Molding usually come down to economics, the as high initial investment is needed when you are establishing a plant with machinery be it a small scale or large scale. The initial investment is inevitable. Also, the turn-around time from design to production is slow (at least 4 weeks) at the beginning.

What can Injection Moulding be used for?

Injection Moulding is used to make a variety of widely used products. With rapid industrialization and technology manufacturing process is improved and automated. If you look around your desk/ home, gardens, playing area, and toys, you will find a multitude of injection molded products. Products ranging from bottle tops, remote control casing, console covers, syringes, and most plastic made products.

What is plastic injection molding?

In Simple words, Plastic injection molding is the process of melting plastic materials (thermosetting/ thermoplastic polymers).

  • Firstly these plastic materials are injected at high pressure into a predesignated mold cavity.
  • Secondly, the cavity fills and solidifies to produce the final product.
  • Plastic Injection molding is the most widely used manufacturing process for the production of many plastic parts

How do injection molding companies work?

Injection molding companies have injection machines that have three primary components including the feed Hopper, heated barrel, and the screw. The plastic granules are put inside the heated barrel with the help of a Hopper. Eventually, the plastic placed inside the Hopper gets converted into raisins which are Silicon material. The same material is further melted and injected into the mold cavity through a process called injection blow molding. After the material cools down and solidifies, the final product in the form of hardened plastic takes place.

Benefits of using injection molding

  • Cost-effective

The primary advantage of using injection molding technology is to reduce the overall production cost. You just need to pay for the initial injection mold cost and then the entire process is extremely affordable. As you produce more and more parts, the price of each product reduces drastically.

  • Repeatable

Another great advantage of the plastic injection molding process is the identical appearance of the mass-produced. Each product is exactly the replica of the previous product. There are great consistency and reliability in this procedure.

Are there any disadvantages of injection molders?

The initial cost of setup and protomould is very high in the process of injection blow molding. Since one requires making a lot of effort in testing, formatting, and designing the molds, things can be slightly uncertain initially.

The proto molds are typically produced digitally on 3D printers. Later on, they are given a practical shape after checking out the feasibility of the idea.

Considerations while hiring plastic injection molding services

The idea of injection blow molding is very good until and unless you have all the experience regarding the manufacturing process. However, if you are a newcomer in the manufacturing process, these are some important considerations that you need to undertake

  • Injection mold cost

For Preparing the injection mold, you need you to make a heavy initial investment. You must choose a production technique that can provide good quality products. Determine the exact number of parts that you need to produce and then calculate the profit margin.

  • designing consideration

Clarify the exact kind of product design you expect from the company. Choosing a simpler product with a minimal number of parts would help you to reduce the cost of production.

  • Assembly

Design a product that requires minimal assembly. The process of assembling is very tiresome and can significantly induce your production cost content.

  • Key takeaways

Focus on the outcome of the product apart from planning and making the initial preparations. You should select the correct type of injection molder that can keep your cost low and the process of production optimized.

What products are made from plastic injection molding?

The process is highly versatile and can produce a wide range of products, Few such products are listed below

Plastic bottles, Electronic housings are also quite commonly manufactured with plastic injection molding

Household: Molded closures, containers, components, and drinkware are just a few of the common items that can be custom fabricated with the injection molding process.

  • Machinery and Automotive Components:
  • Mainly Injection molding is being used to produce products that are single-use, disposable items to maintain sterility, or to prevent the spread of germs or disease in the medical field.
  • Commercial Products:

    • Electrical Boxes
    • Mop Heads
    • High-end Trash and Recycling Receptacles

there are millions of different products that are being manufactured using a plastic injection molding technique

How does a plastic injection molding machine work?

The injection molding machine consists of 4 major parts. Before we go in detail about each part, let us look at the Molding machine parts. With a clear diagram, it will be easier to understands how each part will play a role in making the final product.

  1. The Base

  2. The Hopper

  3. The Barrel

  4. Clamping Unit.

1)Base :

The base is used as a container and supports all injection molding machine parts. it’s on-base itself the entire molding machine will stand and operates. Inside the base containers, you can fit the electronic controllers and other inbuilt components which are essential to run the molding machine.

The electronic controllers on the molding machine will reside in the base. With outer display, you can regulate a range of heaters, hydraulics, and sensors, as well as the injection pressure.

2) Hopper:

Thermoplastic materials are fed to molders in the form of small pellets. The hopper looks like a funnel. It sits on top of the injection molding machine. The hopper holds these pellets. The pellets are gravity-fed from the hopper through the hopper throat into the barrel and screw assembly

3) The Barrel:

Injection molding machine barrel

The barrel is a screw-like structure which crushes thermoplastic pellets and injects into the molds cavity. It is heated by the electric heater bands

4) Clamping Unit.

Its’s clamping unit is responsible to close the mold with moving platen which takes half of the mold. The clamping unit holds mold closed under pressure during shot and cooling. After a while, it opens the mold so that the workpiece can be knock-outed from the mold. There are mainly four different kinds of clamping systems in injection molding machine:

  • Hydraulic clamping system
  • Mechanical clamping system
  • Hydromechanical clamping system
  • Electric clamping system

Below an example of a Hydraulic clamping system is shown.

injection molding machine clamping unit

What is the injection molding process?

The process of injection molding is divided into 6 parts.

  1. Clamping

  2. Injection

  3. . Dwelling

  4. Cooling

  5. Mold opening

  6. Removal of molded products


Before the material is put inside the mold, the outer shell, or as we call it the mold must be secured with the help of a clamping unit. Both the molds are attached to the injection molding machine and one unit of it is made slippery. The clamps are hydraulically empowered in which the unit gives the pressure to each have the mold together so that there is sufficient force generated to keep two halves intact during the injection of the material. A larger machine requires more time in securing the clamp to close the mold.


With the help of the injection unit, the plastic granules are inserted within the injection molding machine to take the manufacturing process further. The material is converted into liquefied form with the help of pressure and heat. This liquefied plastic material is eventually injected within the mold at a rapid speed. The pressure build-up helps during holding up of the material. Whatever amount of material/injection is inserted within the mold is technically known as the shot. It is very difficult to calculate the overall injection time because the complexity and the flow of molten material vary from time to time.

Thermoplastic is the material used by most of the injection molding companies because it quickly and falls. Polythene, polypropylene, and polycarbonate is the most commonly used injection Material at a global level. It is cost-effective, valuable, and produces minimal wastage.

To put it in simple words, injection uses plastic in the form of pellets that are put inside the Hopper towards the top of the injection unit. There is a cylinder that is fed with plastic pallets. The pellets are strongly heated and melted to form liquid raisin. The same Cylinder has a motorized screw that creates a homogeneous mixture by mixing everything till the end. After there is sufficient material within the cylinder that reaches the end of the screw, the actual process begins.


Dwelling refers to a phase in which a small pause is taken during the injection procedure. After the liquid raisin is injected into the mold, the pressure creation takes place to make sure that the entire mold cavity has no leftover spaces.


The process of solidification of the molten material to create the actual shape or the desired object is known as cooling. Some shrinkage can take place during the cooling process. It is very difficult to identify the exact amount of shrinkage taking place in the molten material. You cannot open the mold until and unless it has completely solidified. There is a sufficient amount of time required for the cooling to take place. Water is the most commonly used coolant by the maximum of the injection machines.

5)Mold opening

The final step that ensures the completion of the process includes the ejection of the molded products. The ejector rod and the pins are removed to open the mold

6)Removal of molded products

The machine cycle ends after the process is complete and the robots separate the usable parts from the runner. In several cases, runners are recycled and powdered to reduce environmental impact and production costs. The usable parts are separated and packed for shipping and assembly. The process of injection molding helps in the generation of high-quality three-dimensional parts that are perfect for the automotive, toy, and packaging industry.

What plastic is used for injection molding?


The process of injection molding is not that complicated if you can actualize the overall process. No doubt It requires a very solid understanding of machinery, Chemicals, and procedure. But once you can manage to create a perfect proto mold, everything automatically goes ahead smoothly flows with the flow. Injection molding may seem like a complex one, but it’s the most common manufacturing method because of its capability and efficiency to produce a plethora of everyday items. Injection molding is one of the most cost-effective ways to build both functional prototypes and end-use products.

Leave a comment

Your email address will not be published. Required fields are marked *