In the use of injection molding machine, injection molding machine hydraulic system may occur a variety of faults. It is the result of the comprehensive influence of many factors, and the discreteness is relatively large. Therefore, in the fault diagnosis, we must analyze the factors causing the fault one by one, pay attention to their internal relations, and find out the main contradiction, so as to be easier to solve.

In general, the failure of hydraulic system of injection molding machine is not accidental. Any failure will be accompanied by various abnormal omens before it evolves into a major failure. These omens can be summarized as follows:
(1) Abnormal sound occurs, such as the sound of the pump, motor, temperature flow valve and other parts is abnormal.

(2) The operation speed of rotary, walking and winching hydraulic motors and hydraulic cylinders of each working device decreases and becomes weak.

(3) The liquid level of the tank drops and the oil deteriorates.

(4) There is oil leakage on the outer surface of the hydraulic component.

(5) Oil temperature is too high.

(6) Pipeline damage, loosening and vibration.

(7) The smell of coke nuclei and so on.

These phenomena, as long as in the use of careful attention, can be observed by the naked eye, hand touch, nose smell found. In the actual work, it is through this on-site means to analyze the first-hand information of the fault, and then according to the experience, the comprehensive of these first-hand information, the actual problems are analyzed in detail, find out the cause of the fault, as soon as possible to solve.

However, in the actual work, often can not be a fault can be accurately diagnosed at a time, then several repeated, that is, repeated analysis, repeated checks, until the cause of the fault is found.

In the actual work, engineers and technicians often according to the following steps to deal with the failure of the hydraulic system.

(1) Understand the system

When a certain injection molding machine hydraulic failure, the first should understand the hydraulic system. It is necessary to be familiar with relevant technical data and reports, understand the working principle of the liquefied pressure system, understand the basic structure of various components and specific functions in the system, and be able to find the liquid flow process under various working conditions. Before checking the device, observe the system and record necessary technical data, such as working speed, pressure, flow rate, and cycle time.
(2) Ask the operator

The operator of the malfunctioning injection molding machine was questioned. Inquire about the characteristics and functional characteristics of the equipment; Ask the basic phenomenon when the equipment fails, such as whether the hydraulic pump can start, whether the system oil temperature is too high, whether the system noise is too big, whether the hydraulic cylinder can drive the load and so on.

(3) Verify the phenomena provided by the operator and check them carefully

The phenomena put forward by the operator shall be further verified by observing the instrument reading, working speed, monitoring the sound, checking whether the oil and the executing element have wrong action, etc. Then according to the liquid flow process in the system from the tank along the loop carefully search, timely record observation knot.

During the inspection, the oil in the tank should be carefully checked to determine whether dirt has entered the system. Affect the normal work of each component of the system; Touch by hand to check whether the inlet oil pipe and high pressure oil pipe is preserved, softened, leaked, damaged; Check that the pipe joints of each control element and the mounting screws of the shell are loose; Finally check the piston rod of the oil and hydraulic cylinder. In each step of the inspection should pay attention to the presence of improper operation or maintenance phenomenon, in order to find the cause of the resulting failure.

(4) List possible failure causes according to the information obtained through understanding, inquiry, verification and inspection
At this time, it should be kept in mind that a fault phenomenon may be caused by two or more reasons, such as the speed of the actuator is reduced, may be due to the wear of the hydraulic pump parts, may also be due to the increase of the internal leakage of the hydraulic cylinder; Again, if the oil temperature is too high, it may be that the oil in the tank is not enough, or the oil pollution blocked the cooling surface, or the pressure of the relief valve may be too high.

(5) Draw a conclusion

According to the fault cause list, the inspection sequence is sorted out according to the principle of “easy first, then difficult”. Select those that can be restored to normal after a brief inspection or repair, so that the inspection can be completed in the shortest time.

(6) Verification conclusion

Once through the above steps, find out the cause of the injection molding machine fault, start to troubleshoot. Troubleshooting includes checking the pressure and flow rate with appropriate test equipment, removing the casing cover plate, and checking the pump, motor and other components. These tests are the basis for determining the replacement of parts and hydraulic components. In the actual work there is often no appropriate test device to check, then had to change the pump, motor, hydraulic valve and other components assembly as an effective means to troubleshoot.

In the process of finding and troubleshooting, we should be careful, careful, prudent, and strive for accuracy, avoid blindly disassembling parts, or using improper sound method to deal with the fault, so as not to cause new damage. Hydraulic components shall not be disassembled unless necessary, as unnecessary and premature disassembly will reduce the service life of these components.