The injection pressure and position are the key parameters that affect the injection speed and injection volume. In general:
1. In a certain injection stroke, the greater the injection pressure, the faster the injection speed in this stroke.
2. The injection position is mainly used to control the injection volume of each injection stage. For example, from the beginning of injection A to the flow to the gate position B, it is generally fast filling, and the gate is used to prevent injection marks and stress at a low speed. There needs to be a switching position B. The injection pressure is high during the stroke from A to B, and the injection pressure is small after passing B.
The role of the injection system: the injection system is one of the most important components of the injection molding machine, generally there are three main types of plunger, screw, screw pre-plastic plunger injection. The most widely used is the screw type.
Its function is that in a cycle of the plastic injection machine, a certain amount of plastic can be heated and plasticized within a specified time, and the molten plastic can be injected into the mold cavity through a screw under a certain pressure and speed. After the injection, the molten material injected into the cavity is kept in shape.
The working principle of the injection molding machine is similar to the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous fluid state) into the closed mold cavity. The process of obtaining products after curing and shaping.
Injection molding is a cyclic process, each cycle mainly includes: quantitative feeding-melting plasticization-pressure injection-mold filling and cooling-mold opening and taking parts. After taking out the plastic part, the mold is closed again for the next cycle.
The molding process of a general screw injection molding machine is as follows: first add granular or powdered plastic into the barrel, and make the plastic into a molten state through the rotation of the screw and heating of the outer wall of the barrel, and then the machine closes the mold and moves the injection seat forward. Make the nozzle close to the gate of the mold, and then pass pressure oil into 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 mold can be opened and the product can be taken out (the purpose of pressure holding is to prevent the backflow of the melt in the mold cavity, add materials to the mold cavity, and ensure that the product has a certain density and dimensional tolerance).
The basic requirements of injection molding are plasticization, injection and molding. Plasticization is a 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 (the average pressure in the cavity is generally between 20 and 45 MPa), so there must be sufficient clamping force. It can be seen that the injection device and the clamping device are the key components of the injection molding machine.More about:Injection Machine