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Do you know the working principle of an injection molding machine?

Do you know the working principle of an injection molding machine?

2021-01-19

The working principle of the injection molding machine; in the operation of the injection molding machine, when the screw rotates, the plastic will produce friction and mutual movement between the inner wall of the barrel, the bottom surface of the screw groove, the screw edge advancement surface and the plastic and the plastic. The advancement of plastic is the result of this combination of movements, and the heat generated by friction is also absorbed to increase the temperature of the plastic and melt the plastic.


The design and structure of the screw will directly affect the extent of these effects. At the same time, the rotation of the screw causes the melt film between the solid bed and the inner wall of the barrel to produce a shearing effect, thereby melting the solid at the interface between the melt film and the solid bed. As the spiral of the solid bed moves forward, the volume of the solid bed gradually decreases, while the volume of the molten pool gradually increases.


If the thickness of the solid bed decreases at a rate lower than the speed at which the depth of the screw groove becomes shallow, the solid bed may partially or completely block the screw groove, causing fluctuations in plasticization, or due to local pressure due to the melting speed of various plastics, the melt Viscosity, melting temperature range, sensitivity of viscosity to temperature and shear rate, corrosiveness of pyrolysis gas, and friction coefficient between plastic particles vary greatly.


The general molding process of a components of injection molding machine is as follows: First, granular or powdered plastic is added to the barrel, and the plastic is melted by the rotation of the screw and the heating of the outer wall of the barrel, and then the machine closes the mold and moves the injection seat forward. Then pass pressure oil to the injection cylinder.


The screw is pushed forward to inject the melt into a closed mold with a lower temperature at a high pressure and a faster speed. After a certain period of time and pressure maintenance (also known as pressure retention) and cooling, it is solidified and formed. The product can be taken out by mold opening


The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the prerequisite for realizing and ensuring the quality of molded products, and in order to meet the requirements of molding, injection must ensure sufficient pressure and speed. At the same time, due to the high injection pressure, a correspondingly high pressure is generated in the cavity, so there must be a sufficient clamping force.

The servo injection molding machine part controls the speed of the motor according to the required pressure and speed. The speed is very low when the pressure is maintained. When cooling, only the fan will rotate. Therefore, the longer the two action times, the more power is saved, but the electricity consumption is more Large, sometimes exceeding the power consumption of the fixed pump.


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