What is Injection Molding

Injection molding is a common plastic processing technology, the principle is to heat the plastic particles to melt, through the injection machine will melt the plastic into the mold, under a certain pressure and temperature cooling and solidification, and ultimately formed the desired plastic products process.

Injection Molding


High productivity, relatively low cost, ability to produce complex parts and products, wide choice of materials, and automation.


Such as large investment in equipment, high initial cost, and high requirements for precision of molds and equipment.

Common types of plastic injection molding

  • Conventional Injection Molding
  • Two-Color Injection Molding
  • High-Speed Injection Molding
  • Precision Injection Molding
  • Gas-Assisted Injection Molding
  • Large Part Injection Molding
  • Thin-Wall Injection Molding
  • Micro Injection Molding
  • Compound Injection Molding
  • Hot Runner Injection Molding

Conventional injection molding is suitable for the production of various specifications, shapes and materials of plastic products, such as plastic tableware, home appliance shells and so on.

Two-color injection molding is suitable for the production of complex plastic products requiring multi-color or multi-material combinations, such as automotive interiors.

High-speed injection molding is suitable for the production of high-volume, simple structure of plastic products, such as bottle caps.

What are the main raw materials used in the injection molding process?

The main raw materials used in the injection molding process are thermoplastics and thermosets. These plastics become soft at high temperatures, can be shaped in a mold, and cure to form when cooled. The following are some of the common raw materials:

Injection Molding materials

Polystyrene (PS)

PS is a colorless, transparent, glossy granule with good optical and electrical properties that is easy to mold and process and color.

Polypropylene (PP)

PP is a colorless, transparent or somewhat glossy granular material, also known as 100 folds of soft rubber, is a crystalline plastic.PP has good flow and molding properties, excellent heat resistance, can be sterilized by boiling at 100 degrees Celsius.

Nylon (PA)

PA is an engineering plastic composed of polyamide resins. Nylon has high crystallinity, high mechanical strength, good toughness, abrasion resistance, corrosion resistance, heat resistance, non-toxic, and excellent electrical properties.

Polyoxymethylene (POM)

POM is also known as race steel material, is a kind of engineering plastics.POM has a high degree of crystalline structure, excellent mechanical properties, good abrasion resistance and self-lubricating properties, good dimensional stability, can manufacture precision parts.

ABS (Acrylonitrile Butadiene Styrene)

ABS plastic belongs to a high-strength modified polystyrene, composed of three compounds of acrylonitrile, butadiene and styrene in a certain ratio.ABS plastic has high strength, strong impact resistance, good creep resistance, the surface can be plated, and can be co-mingled with other plastics and rubbers to improve performance.

Polycarbonate (PC)

PC, also known as bulletproof glass, is a non-toxic, tasteless, odorless transparent material with good impact resistance and heat resistance.

Polybutylene terephthalate (PBT)

PBT is an engineering plastic with good mechanical properties and heat resistance, commonly used in electronic and electrical components.

Polymethylmethacrylate (PMMA)

PMMA is a thermoplastic with excellent transparency, chemical stability and weather resistance, and is commonly used to make high-quality decorations and parts.

The choice of plastic raw material depends on the needs of the end product, including factors such as desired physical properties, chemical stability, heat resistance, cold resistance, color, and transparency. Cost-effectiveness and environmental impact also need to be considered when selecting raw materials for injection molding.

What are the unique advantages of injection molding over other plastics processing methods?

Highly efficient and automated production

The injection molding process allows for highly automated production, from raw material preparation, injection, mold opening and closing, and product removal, all of which can be automated, which gives the injection molding process a high degree of productivity and production speed, and enables it to meet the needs of mass production.

High precision and consistency

The injection molding process can achieve high precision products, the size and shape of the mold cavity determines the size and shape of the product, so the consistency of the product is very high. This is of great importance in industrial production fields where the consistency of product size and performance is highly demanded.

Wide material applicability

The injection molding process can be applied to a wide range of plastic materials, including thermoplastics, thermosets and engineering plastics. This gives the injection molding process a great deal of flexibility in terms of product performance requirements.

Production of complex shapes

The can produce plastic products with complex shapes and precise dimensions, such as products with inserts, threads, convex and concave surfaces, and other structures. This is difficult to achieve with other molding processes.

Saving of raw materials

Recycling of raw materials. For engineering plastics with high raw material prices, there are significant economic benefits.

As a result, it has become the preferred method of plastics processing because of its obvious advantages in terms of efficiency, precision, material suitability, product shape complexity and raw material savings.

What are the challenges that injection molding typically faces during production?

High Mold Costs

Manufacturing injection molds is often expensive, which can be a challenge for some small businesses.

High Technical Requirements

requires precise control of process parameters and operating techniques, which can place high demands on technicians.

High energy consumption

requires large amounts of electricity to heat and plasticize the plastic, which can lead to high power consumption.

Waste disposal problems

The production process generates a large amount of scrap and waste, and how to effectively dispose of these wastes is a problem that needs to be solved.

Low equipment utilization and productivity

It is difficult to automatically obtain the operating status of the equipment and to track and manage the production progress, material usage and work in progress in real time, resulting in low production efficiency.

Difficulty in product quality control

There are more defects in the production, such as air bubbles, fusion seams, dimensional differences, etc., which need to be strictly controlled and detected during the production process.

Problems in production environment

needs to be carried out under specific temperature and humidity conditions, and the stability of the production environment directly affects product quality and production efficiency.

Complexity of material selection and formulation

Material properties and formulations are critical, and different materials and formulations will have different impacts on the performance and quality of the product.

Injection molding process

Design mold

Mold design and creation is a fundamental part of the molding process. Machinists use CAD design and CNC machining processes to determine the mold’s specifications.

filling stage

Filling is the first step in the entire injection molding cycle, starting from the time when the mold is closed and injection molding begins, until the mold cavity is filled to approximately 95%.

Holding stage

The material expands when heated and contracts when cooled, so the contraction is compensated by applying pressure and further feeding.

cooling phase

The molten plastic injected into the mold cools and gradually solidifies in the cavity, forming the preliminary shape of the product.

Mold opening and demoulding

Once the plastic has solidified, separate the mold and remove the product. It is necessary to ensure that the product is intact and free from defects such as burrs.


Products may require post-processing, such as deburring, grinding, assembly, spraying, etc., to meet final usage requirements and aesthetic standards.

application field

Automotive industry

manufacturing internal and external accessories, lamps, etc.

Electronics and electrical

production socket, switch, shell, etc.

Medical equipment

producing medical equipment, containers, etc.

Packaging industry

production bottle cap, packaging box, etc.

Consumer products

Make tableware, toys, tools, handles, etc.


Make lightweight, high -intensity parts