What is Injection Moulding

Plastic Injection moulding

Injection moulding (or Injection Molding) is a manufacturing technology for producing products from plastics. Injecting the molten plastic resin at high pressure into an injection mould, which the mold is made according to the desired part shape, the part shape was created by designer using some CAD design software ( such as UG, Solidworks etc), The mould is made by a mould company (or moldmaker) from metal material or aluminum, and precision-machined to form the features of the desired part by some high technical machines like CNC machine, EDM machine, lather machine, grinding machine, wire-cutting machine, etc, step by step to make final mould cavity base on exactly desired part shape and size, which we called an injection mould. Injection moulding is very widely used for producing a variety of plastic products, from the smallest component to the big bumpers of cars. It is the most common technology to produce molding products on the world today, with some commonly made products including food containers, bucket, storage bins, house cooking equipment, outdoor furniture, automotive components, medical components, molding toys, more and more.



If you want to run your business with injection moulding, below some basic information you may need to know

  • 1 Types of Injection Molding
  • 2 Injection molding equipment
    • 2.1 Injection molding machine
      • 2.1.1 Horizontal or vertical machines
      • 2.1.2 Clamping unit
    • 2.2 Injection mold
  • 3 Injection molding process
    • 3.1 Injection Molding Cycle
    • 3.2 Molding trial
    • 3.3 Molding defects

Types of Injection Molding

Basically 7 types of injection moulding process as below

Injection molding equipment

Injection molding machine

Injection molding machine, American normally called injection press (or press), press our custom made injection mold in the machine. Injection machine is rated by tonnage, which indicates the amount of clamping force that the press can generate. This clamping force keeps the mold closed during the injection molding process. There are Various specifications of injection molding machines from less than 5 tons to 6000 tons, or even bigger.

Horizontal or vertical machines

There are normally two types of injection molding machines, Horizontal & vertical molding machines,

Which means molding machines fasten the mold in either a horizontal or vertical position. The majority is horizontally injection molding machines but vertical machines are used in some niche applications such as insert molding or some special molding process requirement, there are some injection machines can produce two colors, three or four colors molded parts at one step, we call double shot injection molding machine or 2K injection molding machine (more color will be 3K or 4K),

Clamping unit

Machines are classified primarily by the type of driving systems they use: hydraulic, electric, or hybrid. Hydraulic presses have historically been the only option available to molders until Nissei introduced the first all-electric machine in 1983. The electric press, also known as Electric Machine Technology (EMT), reduces operation costs by cutting energy consumption and also addresses some of the environmental concerns surrounding the hydraulic press. Electric presses have been shown to be quieter, faster, and have higher accuracy, however, the machines are more expensive. Hybrid injection molding machines take advantage of the best features of both hydraulic and electric systems. Hydraulic machines are the predominant type in most of the world, with the exception of Japan.

Injection Mold

Simply explain the injection mold is custom made of desired part shape by cutting the steel or aluminum, and produce the mold that can be used in the injection molding machine, which we called injection mould or plastic injection mold, go to https://www.plasticmold.net/injection-mold/ to know more about injection mold, but to make injection mould actually is not easy, you need to have a professional team (mold maker, mold designer) and mold manufacturing equipment like CNC machines, EDM machines, wire-cutting machines, etc

Injection Mouding process

Injection Molding Cycle Time

The basic injection cycle time is including Mold close – injection carriage forward –plastics filling time – metering – carriage retracts – holding pressure – cooling time – mold open – eject part(s)

The mold is closed shut by the injection molding machine, and the melted plastics is forced by the pressure of the injection screw to inject into the mold. The cooling channels then assist in cooling the mold and the liquid plastics become solid into the desired plastic part. The cooling system is one of the most important part in the mold, inappropriate cooling can result in distorted molding product and the cycle time will be increased, this will increase the injection molding cost as well.

Injection MoldingMolding trial

When the injection mold has been made by moldmaker, the first thing we need to do the mold trial, this is the only way to check the mold quality if made according to our requirement, to trial the mold we normally fill the plastics the mold step by step, use short shot filling at the first and increase the material weight little by little until the mold is 95 to 99% full. After meeting this status a small amount of holding pressure will be added and holding time increased until gate freeze off has been occurred, then holding pressure is increased until the molding part is free of sink marks and part weight has been stables. Once the part is good enough and has passed any specific technical tests, a machine parameter sheet need to be recorded for massive production in the future.

Molding defects

Injection moulding is a complex technology and problems may happen every time. A new custom made of an injection mold has some issue is normal, to fix the mold we need to test the mold several times (normally 3 or 4 times) and finally all of the issues are solved completely.

If you want to know more please go to our other injection moding post, if you are looking for injection molding service, you are welcome to send us your requirement for a quotation.