Created on:2021-06-28 11:48

Principle of hydraulic system of AZ560 injection molding machine

Principle of hydraulic system of AZ560 injection molding machine

(1) A2560 injection molding machine

Injection molding machine is a multi-stage pressure and flow control system. In order to ensure that the injection molding machine works accurately and effectively according to the process requirements (certain pressure, speed, time, temperature) and action sequence, the electro-hydraulic proportional control system is widely used in modern injection molding machines. The common small injection molding machine is a constant displacement pump with electro-hydraulic proportional valve control system, which is suitable for the occasion of low power; The injection molding machine with higher power is proportional volume control. The hydraulic system of AZ560 injection molding machine is a typical variable displacement pump control system with compound regulation of flow and pressure.

AZ560 injection molding machine is composed of two independent injection molding machines and a rotary table with 16 sets of molds. One injection molding machine injects the upper and the other injects the sole. Each rotation of the rotary table produces 16 pairs of imitation leather boots. The hydraulic pump of injection molding machine adopts Rexroth V4 variable double vane pump, one of which is F-type control mode, the other is C-type control mode. F-type control mode can control flow and pressure, C-type control mode is constant pressure control with manual pressure regulation.

Figure f is the schematic diagram of hydraulic system of a2560 injection molding machine. Hydraulic pump P1 is F-type control mode of V4 variable pump, and P2 is C-type control mode of V4 variable pump (constant pressure control mode with manual pressure regulation). Its displacement is 80 ml / R and motor speed is 1440 R / min. Comparing figure B with figure F, relief valves 3, 4 and 5 in Figure f form a multi-stage pressure valve group together with solenoid valve ev30, replacing proportional pressure valve 4 in Figure B; Shuttle valve 7, logic valve 6, throttle valve 8 with check valve and solenoid valves ev21 and ev22 replace proportional throttle valve 5 in Figure B. The control valve 2 (see Figure b) on the pump body is used to control the pressure difference between the inlet and outlet of logic valve 6 and throttle valve 8 in Figure F. as long as the openings of logic valve 6 and throttle valve 8 remain unchanged, the flow through them will not change and the feeding speed and injection speed will remain unchanged; By adjusting the opening of logic valve 6 and throttle valve 8, the feeding speed and injection speed can be easily controlled.

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Relief valves 9 and 10 act as safety valves, and their adjustment pressure is 17Mpa; The pressure of relief valve 3 is the working pressure, which is adjusted to 14MPa; The pressure of relief valve 4 is high pressure injection pressure, which is adjusted to l2mpa; The pressure of relief valve 5 is low pressure injection pressure, adjusted to 8 MPa. The working pressure of hydraulic pump P2 is adjusted to 10MPa through the control valve of pump body. There is also a temperature sensor on the hydraulic oil tank. When the oil temperature is higher than 60 ℃, it will be forced to shut down for heat dissipation.

(2) Working cycle process of a2560 injection molding machine

When the hydraulic pump starts, the solenoid valves ev92 and ev94 are powered on, and the relief valves 9 and 10 start to act as safety valves. The hydraulic pumps P1 and P2 enter the internal unloading state. At this time, if the pressure is measured by pressure gauge 11, the pressure P3 and P4 are about 1MPa. In fact, the pressure of hydraulic pump P1 and P2 has reached 14MPa and 10MPa respectively, but because their output flow is very small, they can only maintain internal leakage, and the external pipeline pressure gauge can not detect correctly. At this time, the whole system has less energy loss, less heating and high efficiency than the quantitative pump system. When the mold of the rotary table was delivered in place, the injection molding machine began to feed from the funnel, the solenoid valves ev23 and ev24 were not powered, and the injection port was blocked. Solenoid valve ev22 is powered on first, then solenoid valve ev21 is powered on, logic valve 6 is opened slowly, and the opening height is adjustable. At this time, if pressure P3 is measured from pressure gauge 11, a sudden pressure rise will be observed, which is due to the increase of pump flow. The motor 12 starts to rotate, drives the screw to rotate backward, and the PVC particles enter the chamber. When the screw rotates backward, the hydraulic oil in the left chamber of the screw returns to the oil tank through the throttle valve 8 with one-way valve, the solenoid valve ev22 and the relief valve 17. The rotation speed of the motor 12 is controlled by the opening size of the control valve 2 (see Figure 2-2) on the hydraulic pump P1 body and the logic valve 6. After feeding, the solenoid valves ev21 and ev22 are powered off and delayed for a period of time until the PVC particles are plasticized in the container. This period of time is controlled by ps24 PLC produced by German Golden Bell Moller company on the console, and the length of time is set by the operator. When the delay time is up, the solenoid valve ev24 is powered on, and the pressure oil P4 enters the 15b end of the hydraulic cylinder through the pressure reducing valve 13 and the solenoid valve ev24, so as to drive the whole injection head forward, close to the injection hole on the rotary table mold. When it is in place, the solenoid valve ev23 is powered on, and the pressure oil P4 enters the l6b end of the hydraulic cylinder through the pressure reducing valve 14 and the solenoid valve ev23 at the same time, opening the injection door in the injection head. When the solenoid valves ev30b and ev22a are powered on, the pressure P3 drops to 12MPa, and the pressure oil enters the left end chamber B of the screw through the solenoid valve ev22 and throttle valve 8 to push the screw forward and start high-pressure injection; After a period of delay, the solenoid valve ev30b is powered off, ev30a is powered on, the pressure P3 is reduced to 8Mpa, and low pressure injection is started. After the screw is pushed to the bottom, the solenoid valve ev24 loses power; The pressure oil P4 enters the 15A end of the hydraulic cylinder through the pressure reducing valve 13 and the solenoid valve ev24a, and the injection head retreats completely. The rotary table rotates to enter the next cycle. The whole injection molding machine system circulates, continuously produces various specifications and forms of products with high quality and high efficiency.

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