Applications: Injection molding machines can form plastic products with complex shapes, precise dimensions or dense textures with metal inserts in one go. Therefore, they are widely used in defense, electromechanics, automobiles, transportation, building materials, packaging, agriculture, culture, education, health and people's daily lives.
Working Principle: Injection molding machine uses thrust of screw (or plunger) to quickly inject plasticized molten state (i.e. viscous flow state) plastic into closed mold cavity at high pressure, obtains product after solidification and shaping.

 

1. Locking mold: Mold plate quickly approaches fixed mold plate (including slow-fast-slow speed), and after confirming that there is no foreign matter, system switches to high pressure to lock mold plate (maintain pressure in cylinder).
2. Shooting platform moves forward to designated position (nozzle is close to mold)
3. Injection molding: Screw can be set to multiple speeds, pressures and strokes to inject molten material at the front end of barrel into mold cavity.
4. Cooling and holding pressure: According to setting of multiple pressures and time periods, pressure of barrel is maintained, mold cavity is cooled and molded at the same time.
5. Cooling and pre-plasticization: Product in mold cavity continues to cool, while hydraulic motor drives screw to rotate and push plastic particles forward. Screw retreats under set back pressure control. When screw retreats to predetermined position, screw stops rotating, injection cylinder retreats according to setting, and expected end is reached.
6. Shooting platform retreats: After pre-plasticization, shooting platform retreats to specified position
7. Mold opening: Mold plate retreats to original position (including slow-fast-slow speed)
8. Ejection: Ejector ejects product.

 

According to plasticizing method, it can be divided into: screw type and plunger type.
According to arrangement of injection device and clamping device, it can be divided into: vertical, horizontal and angle types.
Currently, the most widely used is horizontal screw type injection molding machine.

Pre-plastic structure is simplified, and there is no need for a diverter shuttle, so injection pressure is greatly reduced.
Rotation of screw causes material to tumble, and heat transfer conditions are good. Material is subjected to large shear stress inside, and plasticization efficiency is high.
No diverter shuttle, convenient for changing materials.
Fast injection speed.
It has a wide adaptability to raw materials and can process heat-sensitive resins.

 

There is a diverter shuttle, which makes it inconvenient to change materials and injection pressure drops significantly
Plasticizing effect is relatively poor and cannot process heat-sensitive resins.

 

Injection device and mold clamping device are arranged horizontally.
Machine body is low, easy to add materials, easy to operate and maintain, product can fall freely after being ejected, and it is easy to realize automation.
Disadvantages: large floor space, mold disassembly is more troublesome
Widely used

 

Injection device and clamping device are on same vertical center line, occupying a small area.
Easy to achieve insert molding. Because mold surface is facing upward, it is easy to position insert.
Weight of mold is supported by horizontal mold plate for up and down, opening and closing, phenomenon of falling forward due to gravity of mold, which makes mold plate unable to open and close, similar to horizontal machine, will not occur. It is conducive to maintaining accuracy of machine and mold for a long time.
Disadvantages: Hopper is high, and it is inconvenient to add materials. It is only suitable for production of products with an injection volume of less than 60cm³.

 

Injection device and clamping device are arranged vertically.
Application: between vertical and horizontal, suitable for products that do not allow for gates in the center.