Injection Molding Technology Overview
Injection molding is a widely adopted plastic processing technique in modern manufacturing. This process involves heating thermoplastic or thermosetting materials to a molten state and injecting them into a pre-designed mold cavity under high pressure. Once cooled and solidified, the material takes the desired shape. With its exceptional repeatability, high production efficiency, and excellent product consistency, injection molding has become an indispensable manufacturing method in industries such as automotive, electronics, medical devices, and consumer goods.
Complete Injection Molding Process
The injection molding process consists of the following key steps:
Plastic Melting and High-Pressure Injection
Plastic raw materials are dried and fed into the injection molding machine hopper.
In the heating barrel, the material is melted through heating elements and the shearing action of the screw.
The molten plastic is injected into the mold cavity at high pressure (typically 70-150 MPa) by the injection cylinder.
Filling and Holding Pressure Stage
Once the molten plastic fully fills the mold cavity, the process transitions to the holding pressure stage.
The holding pressure is maintained at 30-60% of the injection pressure.
The holding time is determined by the product thickness and material characteristics (typically 3-10 seconds).
Cooling and Solidification Phase
The mold is equipped with cooling channels for efficient heat exchange.
Cooling time accounts for more than 60% of the entire molding cycle.
The part is fully solidified to achieve dimensional stability.
Part Ejection and Demolding
The mold opens, and the ejection mechanism pushes out the molded part.
A complete molding cycle typically lasts 15-60 seconds.
Major Application Areas
Injection molding technology is widely applied across various industries:
Automotive Industry (Approx. 35%)
Exterior Components: Bumpers, headlamp covers
Interior Components: Dashboards, door handles
Functional Parts: Fuel tanks, air ducts
Electronics and Electrical (Approx. 30%)
Casings: Mobile phone housings, TV frames
Structural Components: Connectors, cooling fans
Insulating Parts: Switches, sockets
Medical Devices (Approx. 15%)
Disposable Products: Syringes, IV sets
Surgical Instruments: Handles, casings
Implantable Devices: Temporary fixation equipment
Consumer Goods (Approx. 20%)
Home Appliances: Washing machine drums, refrigerator drawers
Daily Necessities: Storage boxes, toys
Packaging Containers: Bottle caps, food boxes
Classification and Applications of Injection Molding Materials
| Material Category | Typical Materials | Key Properties | Typical Applications |
|---|---|---|---|
| General Plastics | PP / PE / PS | Low cost, easy processing | Packaging containers, daily-use items |
| Engineering Plastics | ABS / PC / PA66 | High mechanical strength, good heat resistance | Electronic housings, automotive parts |
| High-Performance Plastics | PEEK / PPS | High temperature resistance, excellent chemical stability | Aerospace, medical implants |
| Elastomer Materials | TPU / TPE | High flexibility, excellent rebound resilience | Seals, cushioning components |
Key Process Parameter Control
Temperature Control: Barrel temperature (180-320°C), mold temperature (40-120°C)
Pressure Control: Injection pressure (70-200 MPa), holding pressure (20-100 MPa)
Time Control: Injection time (1-5s), cooling time (10-60s)
Speed Control: Injection speed (50-300 mm/s)
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