Basic Knowledge of Injection Molding Machine

Basic Knowledge of Injection Molding Machine

Plastic injection machine is the main equipment of injection moulding. It can heat, mix and plasticize thermoplastic or thermosetting plastic in the plastic barrel to reach the melting state, exert pressure on the plasticized material, inject and inject into the mould cavity, and obtain the moulded product by cooling and solidifying.
Injection moulding machine is mainly composed of injection system, clamping system, hydraulic system and electrical system. It also includes heating and cooling system, lubrication system, safety and monitoring system.

1.Closing system

The clamping system mainly includes clamping device, adjusting device and ejecting device of products.
The main functions of the clamping system are as follows:
(1) Ensure that the die can be closed, opened and ejected quickly, flexibly, accurately and safely;
(2) The die closure is. It can provide enough clamping force to resist the pressure of injection melt cavity and prevent the mould from expanding.

1.Closing system

Injection system mainly includes pre-plasticizing device and injection device, so it is also called pre-plasticizing and injection system. Its main functions are:
(1) Heating uniformly and plasticizing a certain amount of molten plastics within a specified time;
(2) Under a certain pressure and speed, the quantitative melt is injected into the die cavity.
(3) After the injection, the melt in the cavity is kept under pressure.

3.Hydraulic control system

The hydraulic control system of injection moulding machine is mainly composed of various hydraulic components, circuits and hydraulic auxiliary components. Its main functions are to ensure that the injection moulding machine can work accurately and effectively according to the predetermined process conditions and action procedures.

4.Electrical Control System

Electrical control system is mainly composed of various electrical and electronic components, instruments, heaters, sensors and so on. Its main functions include: cooperating with the hydraulic control system, accurately realizing the predetermined technological requirements, and providing power for the realization of the action program.

5.Heating and cooling system

It is mainly used for heating the barrel and nozzle, and the cooling system is mainly used for cooling the feeding section of the mould, hydraulic oil and barrel.

6.Lubrication system

Lubrication system is a circuit which provides lubrication condition for the relative moving parts of injection machine, such as adjusting template, adjusting device, connecting rod winch, etc.

7.Safety and Detection System

Safety protection device of injection machine mainly consists of safety door, travel valve, mechanical protection rod, etc. The main function is to protect the personal safety of operators and the operation safety of equipment.

Basic Knowledge of Injection Molding

The so-called injection moulding is the plastic material in the cylinder of the injection moulding machine through the external heating and screw rotation generated by the shear heat to plastic resin material into the melt, through the application of certain pressure, the melt into a certain shape of the cavity after cooling and shaping of the product is injection moulding.
Injection moulding is a cyclic process. To complete injection moulding, there are four major processes: pre-moulding measurement, injection filling, pressure holding and feeding, cooling and shaping.
(1) Pre-moulding stage
The screw begins to rotate, and then the plastic conveyed from the hopper is conveyed to the front end of the screw. Under the action of high temperature and shearing force, the plastics are plasticized evenly and gradually gathered at the front end of the barrel. With the agglomeration of molten plastics, the pressure is increasing. Finally, the screw is pushed back step by step to overcome the back pressure of the screw. When the plastic in the front of the barrel reaches the required injection volume, the screw stops retreating. Rotation, the pre-plastic stage is over.

(2) Injection stage
The screw moves forward under the action of injection cylinder. The plastic stored in the front of the cylinder is pushed forward with multi-stage velocity and pressure, and injected into the closed die cavity through the runner and gate.

(3) Pressure-holding and feeding process
The injection pressure in the holding stage is called the holding pressure. Under this pressure, the melt in the cavity is compensated by cooling, and the products are compressed and densified. In this process, the holding pressure plays a leading role.

The characteristics of the holding stage are that the melt flows slowly under high pressure, the screw has a small feeding displacement, and the material gradually forms with the increase of cooling and density. In the holding stage, the velocity of melt flow is very small and does not play a leading role, while the pressure is the main factor affecting the process. In the holding stage, the pressure and specific volume in the die are constantly changing.

(4) Cooling finalization stage
Plastics in the mold cavity by holding pressure, prevent plastic backflow until the plastic solidification, cavity pressure disappeared. Cooling time accounts for the largest proportion in a production cycle.

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