When using an injection molding machine, there are many possible failures in the hydraulic system of the injection molding machine. It is the result of the comprehensive influence of many factors, and its discreteness is relatively large. Therefore, when performing fault diagnosis, it is necessary to analyze the factors causing the fault one by one, pay attention to their internal connections, and find out the main contradictions, so that they can be solved more easily.
Under normal circumstances, the failure of the hydraulic system of the injection molding machine is not accidental. Any failure will be accompanied by various abnormal signs before it evolves into a major failure. These signs can be summarized as follows:
(1) Abnormal sounds occur, such as abnormal sounds from pumps, motors, thermostatic valves, etc.
(2) The operating speed of the turning, traveling, hoisting hydraulic motors and the hydraulic cylinders of each working device decreased and became weak.
(3) The liquid level in the fuel tank drops and the oil deteriorates.
(4) Oil leakage occurs on the outer surface of the hydraulic component.
(5) The oil temperature is too high.
(6) Pipeline damage, looseness and vibration occur.
(7) There is a burnt core smell, etc.
The above phenomena can be discovered by naked eye observation, hand touch, and nose smell as long as you pay careful attention during use. In actual work, people use this on-site method as first-hand information to analyze faults, and then based on experience, synthesize these first-hand information to conduct detailed analysis of actual problems, find out the causes of faults, and solve them as soon as possible.
However, in actual work, it is often not possible to accurately diagnose the cause of the failure at one time. In this case, several iterations are required, that is, repeated analysis and inspection until the cause of the failure is found.
In actual work, engineering and technical personnel often follow the following steps to deal with faults in the hydraulic system.
(1)Understanding the system
When a hydraulic failure occurs in an injection molding machine, you should first understand the hydraulic system, which means you must be familiar with the relevant technical information and reports, understand the working principle of the liquefied pneumatic system, understand the basic structure of various components and their specific functions in the system, and be able to find out the liquid flow process under various working conditions. Before checking the equipment, you should first observe the working condition of the system and record the necessary technical data, such as working speed, pressure, flow rate, cycle time, etc.
(2) Ask the operator
Interview the operator of the malfunctioning injection molding machine. Ask about the characteristics and functions of the equipment; ask about the basic phenomena when the equipment fails, such as whether the hydraulic pump can be started, whether the system oil temperature is too high, whether the system noise is too loud, whether the hydraulic cylinder can drive the load, etc.
(3) Verify the phenomenon provided by the operator and double check
For the phenomenon raised by the operator, further verify the phenomenon by observing instrument readings, working speed, listening to sounds, checking the oil and actuators for malfunctions, etc.; then carefully search from the oil tank along the circuit according to the fluid flow process in the system, and record and observe the results on time.
During the inspection, carefully check the oil in the tank to determine whether dirt has entered the system and affects the normal operation of each component of the system; touch the oil inlet pipe and high-pressure oil pipe to see if they are cured, softened, leaked, or damaged; check the pipe joints of each control component and the mounting screws of the housing for looseness; finally, check the oil and the piston rod of the hydraulic cylinder. At each step of inspection, attention should be paid to whether there is any improper operation or maintenance to discover the cause of the failure.
(4) List the possible causes of the failure based on the information obtained from understanding, inquiry, verification, and inspection.
At this time, it should be kept in mind that one fault phenomenon may be caused by two or more reasons. For example, the speed of the actuator decreases, which may be due to wear of hydraulic pump parts, or increased internal leakage of the hydraulic cylinder. For example, if the oil temperature is too high, it may be due to insufficient oil in the tank, or oil contamination blocking the heat dissipation surface, or the pressure of the relief valve may be adjusted too high.
(5)Conclusion
According to the listed fault cause table, arrange the inspection sequence according to the principle of "easy first, then difficult". First select those equipment that can be restored to normal after simple inspection, verification or repair, so that the inspection work can be completed in the shortest time.
(6)Verification conclusion
Once you have gone through the above steps and found out the cause of the injection molding machine failure, start troubleshooting. Troubleshooting includes using appropriate test equipment to check pressure and flow, disassembling the housing cover, and inspecting pumps, motors and other components. These test inspections are the basis for determining replacement of parts and hydraulic components. In actual work, there are often no appropriate test devices for inspection. At this time, the replacement of pumps, motors, hydraulic valves and other component assemblies is an effective means of troubleshooting.
In the process of finding and troubleshooting faults, you should be serious, careful, cautious, and strive to be accurate, and avoid blindly disassembling parts or handling faults in improper ways to avoid causing new damage. Unless necessary, hydraulic components should not be easily disassembled, because unnecessary and premature disassembly will reduce the service life of these components.
(Source: Micro Injection Molding)