Possible failures and diagnostic steps of the hydraulic system of injection molding machines

When using injection molding machines, the possible failures of the hydraulic system of injection molding machines are various. It is the result of a combination of many factors, and the discrete nature is relatively large. Therefore, in the fault diagnosis, it is necessary to analyze the factors causing the fault one by one, pay attention to its internal connection and find out the main contradiction, so that it can be solved more easily.

Generally speaking, it is not accidental that the hydraulic system of the injection molding machine generates faults. Any faults will be accompanied by various abnormal omens before they evolve into major faults, which can be summarized as follows.

(1) the appearance of abnormal sounds, such as pumps, motors, temperature flow valves, and other parts of the sound is not normal.

(2) the appearance of rotary, walking, winch hydraulic motor and the work device hydraulic cylinder operating speed decline and powerless phenomenon.

(3) appearing oil tank level decline, oil deterioration phenomenon.

(4) The phenomenon of oil leakage from the external surface of hydraulic components.

(5) The oil temperature is too high.

(6) The phenomenon of pipeline damage, looseness, and vibration.

(7) The appearance of coke nucleus smell and so on.



These phenomena, as long as the use of careful attention in the process, can be observed by the naked eye, hand touch, nose sniffing found. In practice, it is through this field means to analyze the failure of the first-hand information, and then based on experience, a combination of this first-hand information, the actual problem of specific analysis to find the causes of failure, early to solve. However, in practice, often can not be an accurate diagnosis of the cause of the failure, which requires several iterations, that is, repeated analysis repeated checks until the cause of the failure is found.

In practice, engineers and technicians often follow the following steps to deal with faults in the hydraulic system.

(1) Understand the system. When a hydraulic failure of an injection molding machine, the first step should be to understand the hydraulic system. It is to be familiar with the relevant technical information, reports, to understand the working principle of the liquefied gas pressure system, to know the basic structure of various components and specific functions in the system, to be able to find out the flow of liquid in various operating conditions. Before inspecting the equipment, observe the working of the system and record the necessary technical data, such as working speed, pressure, flow rate, cycle time, etc.

(2) Ask the operator. Question the operator who is manipulating the injection molding machine that is malfunctioning. Ask about the characteristics of the equipment and its functional signs; ask about the basic phenomena when the equipment fails, such as whether the hydraulic pump can start, whether the system oil temperature is too high, whether the noise of the system is too loud, whether the hydraulic cylinder can drive the load, etc.

(3) Verify the phenomenon provided by the operator and check carefully. The phenomenon proposed by the operator, by observing the meter readings, working speed, listening to the sound, checking the fluid and the executive components to further verify whether there is a false action; then according to the system flow process from the tank in turn along the circuit to carefully find, on time to record the observation of the knot. In the inspection to carefully check the oil in the tank, to determine whether dirt is into the system. Affect the normal work of the system components; touch by hand, check the oil feed pipe and high-pressure oil pipe has no prolapse, softening, leakage, broken; check the control components of the pipe joints and the housing mounting screws have days lose; finally check the oil and the piston rod of the hydraulic cylinder. In each step of the inspection should pay attention to the presence of improper operation or maintenance to find the resulting causes of failure.

(4) According to understand, ask, verify, check the information obtained by listing the possible causes of failure table. At this point should bear in mind that a failure phenomenon maybe two or more causes, such as the speed of the actuating element being reduced, maybe due to wear of hydraulic pump parts, may also be due to increased internal leakage of the hydraulic cylinder; then, for example, the oil temperature is too high, maybe insufficient oil in the tank, or oil pollution blocked the cooling surface, may also be the pressure of the relief valve is set too high.

(5) Conclude. According to the list of causes of failure, according to the principle of "easy first, then difficult", the order of inspection. First choose those who can make the equipment back to normal after a simple inspection and verification or repair, to complete the inspection work in the shortest possible time.

(6) Verify the conclusion. Once the above steps have been taken to identify the cause of the malfunction of the injection molding machine, proceed to troubleshoot. Troubleshooting includes checking the pressure and flow rate with appropriate test equipment, removing the housing cover, and inspecting the pump, motor, and other components. These tests are the basis for determining the replacement of parts and hydraulic components. In practice, there is often no appropriate test equipment to check, then have to change the pump, motor, hydraulic valve, and other components assembly to do as an effective means of troubleshooting.

In the process of searching and troubleshooting, should be serious, careful, careful, and strive to be accurate, to avoid blindly disassembling parts, or with the improper sound method to deal with the fault, so as not to cause new damage. Except when necessary, do not easily disassemble the hydraulic components, because unnecessary and premature disassembly will reduce the service life of these components.