The working principle of injection molding machine


The working principle of injection molding machine; In the work of injection molding machine, when the screw rotates, the plastic will produce friction and mutual motion for the inner wall of the barrel, the bottom surface of the screw groove, the pushing surface of the screw edge and between the plastic and the plastic. The plastic is pushed forward as a result of this combination of motion, and the heat generated by friction is absorbed to raise the plastic’s temperature and melt it.

The design structure of the screw will directly affect the degree of these effects. At the same time, the rotation of the screw makes the solid film between the solid bed and the inner wall of the cylinder produce shear action, so that the solid between the solid film and the solid bed interface melting. As the spiral shape of the solid bed goes forward, the volume of the solid bed gradually shrinks, while the volume of the molten pool gradually increases.

If the speed of the solid bed thickness decreases below the speed of the screw groove depth becomes shallow, the solid bed may be partially or completely blocked the spiral groove, the plasticizing fluctuations, or due to the partial pressure due to all kinds of plastic melting speed, melt viscosity, melting temperature range, the sensitive degree of viscosity to temperature and shear rate, pyrolysis gas corrosion, The friction coefficient between plastic particles varies greatly.

General screw injection molding machine molding process is: first of all, the granular or powdery plastic is added to the cylinder, and through the rotation of the screw and the cylinder wall heating to make the plastic into a molten state, and then the machine mold and injection seat forward, and then to the injection cylinder through the pressure oil.

The screw is pushed forward, so that the molten material is injected into the closed mold with low temperature at a high pressure and a fast speed. After a certain time and pressure maintenance (also known as pressure retention) and cooling, it is cured and formed, and the mold can be opened and the product can be taken out.

The basic requirements of injection molding are plasticization, injection and molding. Plasticizing is the prerequisite to achieve and ensure the quality of molding products, and in order to meet the requirements of molding, injection must ensure enough pressure and speed. At the same time, due to the high injection pressure, the corresponding high pressure in the mold cavity, so there must be a large enough clamping force.

The basic principle of injection molding: the plastic injection molding machine can melt into liquid after heating to a certain temperature, the molten liquid is injected into the closed mold cavity with high pressure, after cooling and shaping, the ejection of the mold to get the required plastic products. Two, the four elements of injection molding: 1. Plastic mold 2. Injection molding machine 3. Molding conditions three, plastic mold most of the use of two plate die, three plate die, there is also a part of the line with the slider die.


Principle of injection molding machine
Injection molding machine is a special plastic molding machine, it uses the thermoplastic plastic, after heating and melting, add high pressure to make it quickly into the mold cavity, after a period of pressure and cooling, into a variety of shapes of plastic products.

1.Working cycle of injection molding machine

1) Locking mold: When the mold lever is close to the fixed mold lever quickly (including slow-fast-slow speed), and no foreign matter exists, the system will turn to high pressure and lock the template (keep the pressure in the cylinder).

2) The launcher moves forward to the position: the launcher moves forward to the specified position (the nozzle is close to the mold).

3) Injection molding: the screw can be set with multi-section speed, pressure and stroke to inject the dissolved material in the front of the cylinder into the mold cavity.

4) Cooling and pressure holding: according to the setting of a variety of pressures and time periods, maintain the pressure of the cylinder, while the mold cavity cooling molding.

5) cooling and premolding: mold cavity products continue to cool, while the hydraulic motor drive screw rotation will push plastic particles forward, screw in the set back pressure control, when the screw back to the predetermined position, screw stop rotation, injection cylinder according to the set loose, expected to end.

6) Firing platform retreat: After the premolding is finished, the firing platform will retreat to the designated position.

7) Mold opening: pull the mold back to the original position (including slow-fast-slow speed)

8) Ejection: ejection of thimble products.

2.The power consumption of injection molding machine
The power consumption of injection molding machine is mainly shown in the following parts:
(1) pump hydraulic system power consumption.

(2) power consumption of the heater .

(3) power consumption of circulating cooling water pump (in the injection workshop, injection molding machine more commonly Shared a cooling water pump), the hydraulic oil pump motor power consumption accounts for more than 80% of the whole injection molding machine power consumption, so reduce the power consumption is the key to energy saving of injection molding machine.