Working principle and maintenance points of injection molding machine part A

Molding process of injection molding machine

Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding - melting and plasticization - pressure injection - mold filling and cooling - mold opening and taking out the parts. After taking out the plastic parts, the mold is closed again for the next cycle. The operation items of the injection molding machine include three aspects: control keyboard operation, electrical control system operation and hydraulic system operation. The injection process action, feeding action, injection pressure, injection speed, selection of ejection type, monitoring of the temperature of each section of the barrel, adjustment of injection pressure and back pressure, etc. are performed respectively.

The working principle of the injection molding machine: Similar to the syringe used for injection, it uses the thrust of the screw (or plunger) to inject the plasticized molten state (i.e. viscous flow state) plastic into the closed mold cavity, and obtains the product after solidification and shaping.

The molding process of a general screw injection molding machine is: first, add granular or powdered plastic into the barrel, and make the plastic molten by rotating the screw and heating the outer wall of the barrel, then the machine closes the mold and moves the injection seat forward, and then passes pressure oil into the injection cylinder to push the screw forward, so that the molten material is injected into the closed mold with a lower temperature at a very high pressure and a faster speed. After a certain period of time and pressure maintenance (also known as pressure holding), cooling, it solidifies and forms, and then the mold can be opened to take out the product.

The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the premise for achieving 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 high pressure is generated in the mold cavity accordingly, so there must be a sufficiently large clamping force. It can be seen that the injection device and the clamping device are key components of the injection molding machine.