What is injection molding

Injection molding, also known as injection molding process, is a plastic processing method primarily used to manufacture plastic products of various shapes using plastic molds.

The molding process can be broadly divided into the following stages:

Mold Closing: The moving and fixed halves of the injection molding machine close to form a cavity.

Injection Unit Advancement: The injection unit, carrying the injection mechanism, moves forward so that the nozzle is securely pressed against the entrance of the main runner of the mold.

Injection: The thermoplastic or thermoset plastic, having been heated and plasticized within the barrel of the injection molding machine, is injected through the nozzle, main runner, sub-runners, and gates into the mold cavity.

Packing: After the injection phase, the screw of the injection molding machine continues to apply pressure to the plastic to compensate for any shrinkage due to cooling.

Cooling: Concurrently with packing, the plastic within the mold gradually cools and solidifies.

Mold Opening: Once the plastic has fully cooled and solidified, the moving and fixed halves of the mold open.

Ejection: Ejection devices are used to push the molded plastic product out of the mold cavity.

Injection molding is capable of producing complex shapes with precision or incorporating metal inserts in a single operation and boasts high production efficiency, making it easy to automate. Therefore, injection molding has found widespread application in the plastic industry, particularly in the automotive, electronics, appliances, instrumentation, telecommunications, and daily consumer goods sectors.

Furthermore, advancements in injection molding technology, such as gas-assisted injection molding, water-assisted injection molding, and multi-layer co-injection molding, have further expanded its application scope and enhanced the quality and performance of molded products.

Advantages of injection molding

High production efficiency: Injection molding is a highly automated process with a short production cycle and high output.

Stable product quality: By accurately controlling the process parameters, products with high dimensional accuracy and good surface finish can be obtained.

Wide range of applications: Injection molding can produce a variety of plastic products with complex shapes and precise dimensions, and are widely used in electronics, automobiles, home appliances and other industries.

Material diversity: Injection molding can use a variety of plastic materials, such as polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS, etc.

Specialized terms related to injection molding

Thermoplastic Injection Molding: The process of molding thermoplastics by heating them to a molten state and then injecting them into a mold to form the desired product.

Injection Molding Machine: The equipment used to perform the injection molding process.

Mold/Die: The tool used to create plastic products of specific shapes and sizes.

Mold Cavity: The hollow space within the mold where the molten plastic is injected to form the product.

Mold Core: The cylindrical structure within the mold that forms the internal shape of the plastic product.

Molten Plastic: The plastic material heated to a flowable state.

Resin/Plastic Material: The granular or powdered plastic used in injection molding.

Injection Rate/Speed: The speed at which molten plastic is injected into the mold cavity under a certain pressure.

Holding Pressure: The pressure maintained in the mold after filling to compensate for material shrinkage near the gate.

Cycle Time: The total time required to complete one injection molding cycle, from filling to ejecting the product.

Ejector Pin: A metal pin used to eject the molded product from the mold.

Heater Bands/Heating Elements: Components that surround the barrel or mold to heat the plastic or maintain mold temperature.

Screw: The core component of the injection molding machine used for plasticizing and injecting plastic.

Barrel: The cylinder that houses the screw and is used for plasticizing the plastic material.

Nozzle: The component that connects the barrel of the injection molding machine to the gate bushing of the mold.

Clamp Force: The force applied by the clamping system to keep the mold closed against the forces that tend to open it during injection and packing phases.

Mold Temperature Controller (MTC): The equipment used to control and maintain the mold temperature within a set range.

Flash: Excess plastic material that forms around the mold parting line or on the product.

Weld Line: A visible line formed where two molten plastic flows meet and fuse together.

Shrinkage: The dimensional reduction of a plastic product during cooling.

What products can be injection moulded

Injection molding is a versatile manufacturing process used to create a wide array of plastic products.

Everyday Items:

Bottles and Containers: Water bottles, food containers, shampoo bottles, etc.

Toys: Building blocks, action figures, dolls, etc.

Kitchenware: Utensils, cutting boards, food processors, etc.

Electronics: Phone cases, computer housings, appliance parts, etc.

Automotive:

Bumpers

Dashboards

Interior trim

Headlights

Engine components

Medical:

Syringes

Medical trays

Prosthetic limbs

Surgical instruments

Industrial:

Automotive parts

Aerospace components

Packaging

Machinery parts