Introduction
As the core power source of press brake, the operating state of hydraulic system directly affects the working accuracy and production efficiency of the equipment. Hydraulic failure usually has multiple causes, including failure of single hydraulic component, comprehensive effect of multiple elements of the system, improper selection of hydraulic oil, oil contamination, as well as mechanical, electrical and external factors. Some failures gradually appear after long-term accumulation, while others appear suddenly.
Many equipment users ignore preventive maintenance and only passively repair the equipment after failure. What’s more, in order to meet deadlines or pursue short-term benefits, the equipment is allowed to work with “diseases”, which seriously shortens the service life of the equipment. The time to eliminate hydraulic failures varies, ranging from a few hours to several days, causing different degrees of impact on production.
This article takes the hydraulic system of a multifunctional press brake as an example to explore the rapid fault diagnosis and troubleshooting methods without special instruments, helping maintenance personnel to conduct effective fault analysis even with limited knowledge of hydraulic technology.
Basic composition of hydraulic system of bending machine
Typical multifunctional bending machine is used for bending processing of Φ4.5~Φ12mm metal materials, mainly composed of the following parts:
- Host (actuator)
- Hydraulic station (power source)
- Electrical control cabinet (control system)
Hydraulic system usually includes:
- Hydraulic pump (provides power)
- Electro-hydraulic reversing valve (controls direction)
- Speed regulating valve (controls speed)
- Hydraulic cylinder (actuator)
- Filter, oil tank and other auxiliary components
System fault analysis and troubleshooting methods
1. Pump drive system fault diagnosis
Diagnostic steps:
Subsystem isolation inspection method
- Turn off the main engine and plug the electro-hydraulic reversing valve 12 with a plug to ensure that there is no oil leakage
- Start pump 3 and check whether the system pressure reaches the rated value
- If the pressure exceeds the rated value, check the hydraulic reversing valve 7
- If the pressure does not reach the rated value, proceed to the next step
Extended isolation inspection
- Turn off the system and plug the electro-hydraulic reversing valve 14 at the same time, keeping the plug of the electro-hydraulic reversing valve 12 unchanged
- Start pump 3 and check the system pressure
- If the pressure exceeds the rated value, check the hydraulic reversing valve 7
- If the pressure does not reach the rated value, proceed to the next step
Pump performance confirmation
- Turn off the system and plug the electro-hydraulic reversing valve 4
- Start pump 3 and check the system pressure
- If it reaches the rated value, it indicates that the electro-hydraulic reversing valve 4 is damaged and needs to be replaced
- If it still does not reach the rated value, the hydraulic pump 3 is worn and needs to be replaced
2. Noise increase and pressure drop fault
Diagnostic steps:
Bubble observation method
- Check whether there are bubbles in the hydraulic oil in the oil tank
- Distinguish the types of bubbles:
- Large bubbles are concentrated on the surface: system air intake, possible reasons include oil inlet hose leakage, joint seal damage or pump shaft skeleton seal damage
- Small bubbles are distributed in the oil: usually caused by filter blockage or oil return line problems
Solution:
- Large bubble problem: replace the oil inlet hose, joint seal or pump shaft skeleton seal
- Small bubble problem: clean or replace the filter, replace the oil return hose (use oil-resistant hose)
- When the oil is seriously contaminated, it must be replaced with a new one of the same model and specification. Hydraulic oil
Pump body temperature detection method
- Adjust speed regulating valves 6 and 5, and apply the rated load of the system
- Touch hydraulic pumps 2 and 3 by hand to observe temperature changes and vibrations
- If the temperature rises rapidly and the vibration is abnormal, it indicates that the internal parts of the pump are damaged
Solution:
- Replace the pump or perform professional repairs
No noise and no pressure failure
- Observe whether the oil return from the system return port is normal
- If normal, listen for oil flow sounds at speed regulating valves 5 and 6 to determine the abnormal valve
- If the oil return is abnormal, it indicates that the pump is damaged
Solution:
- Clean or replace the abnormal speed regulating valve
- Repair or replace the pump when it is damaged
