Insufficient pressure in hydraulic punch press? 7 main reasons

The working principle of hydraulic punch press is to use hydraulic pump to generate power, and transmit pressure to the oil cylinder through hydraulic oil, thereby driving the slider for stamping operation. The rated pressure of the system is the core to ensure the stamping tonnage. Insufficient pressure means that the punching machine is "not powerful" and cannot complete the set punching task. This not only affects product quality, but also exacerbates equipment wear and shortens the service life of hydraulic punch presses when operating in abnormal conditions for a long time.

The following are the seven common causes of insufficient pressure in hydraulic punch presses that we have summarized. It is recommended to investigate them in order from easy to difficult.

1. Insufficient hydraulic oil or oil contamination

This is a common and easily overlooked reason.
1. Cause analysis: Insufficient hydraulic oil in the oil tank can cause the hydraulic pump to empty and unable to establish sufficient pressure. Meanwhile, after long-term use, impurities and moisture may be mixed into the oil, causing oxidation and deterioration, resulting in the oil viscosity not meeting the standard, increased internal leakage, and possible blockage of the oil filter or wear of fine components.
2. Troubleshooting method:
Check the oil level: Observe the oil level gauge of the fuel tank in the shutdown state to ensure that the oil level is between the calibrated upper and lower limits.
Check oil quality: Take a small amount of oil sample and observe its color and odor. Clean hydraulic oil is usually light yellow or transparent and odorless. If the oil turns black, cloudy, or has a burnt smell, it needs to be replaced immediately.

Clean or replace the filter element: Regularly inspect and clean the oil suction filter screen, and replace the hydraulic oil return filter element.

2. Wear or damage to hydraulic pump

The hydraulic pump is the heart of the entire system and the source of power.
1. Cause analysis: After long-term use, the internal components (such as gears, blades, and plungers) of hydraulic pumps (such as gear pumps, vane pumps, and plunger pumps) will experience wear and tear, leading to severe internal leakage and a decrease in volumetric efficiency. The flow rate and pressure output by the pump cannot meet the design requirements.
2. Troubleshooting method:
Listen to the sound: Worn pumps usually produce significantly increased noise and vibration during operation, which may be accompanied by harsh whistling sounds.
Pressure measurement: Use a pressure gauge to measure the outlet pressure of the pump. If the pressure is still acceptable when unloaded, but drops sharply once loaded, it is likely that there is severe leakage inside the pump.

Professional maintenance: The maintenance of the pump is relatively professional, and it is recommended to have technicians disassemble, inspect or replace it.

3. Overflow valve malfunction or improper adjustment

The overflow valve is the "safety guard" of the hydraulic system, responsible for setting the high pressure of the system.
1. Cause analysis: Fatigue or breakage of the pressure regulating spring of the overflow valve, or blockage of the valve core in the open position by pollutants, can cause the system pressure to directly leak back to the oil tank without being loaded, resulting in the system pressure being unable to establish or being too low.
2. Troubleshooting method:
Attempt to adjust: Slowly rotate the adjustment handwheel of the relief valve clockwise while the hydraulic punch press is running and loaded, and observe if the pressure gauge reading increases accordingly. If there is no change, the valve is likely to have malfunctioned.

Cleaning and Inspection: After the machine is shut down and depressurized, disassemble and clean the overflow valve, check for wear on the valve core and body, and ensure that the spring is intact. Reinstall and test again.

4. Internal leakage of hydraulic cylinder

The oil cylinder is a component that executes pressure, and its internal sealing is crucial.
1. Cause analysis: The piston sealing rings (such as Y-shaped rings and Glay rings) inside the oil cylinder may age, wear out, or be damaged due to long-term use, which can cause the oil chambers on both sides of the cylinder piston to communicate, resulting in serious internal leakage. This causes some of the pressure oil to directly slide back to another chamber or tank, resulting in insufficient actual pressure acting on the workpiece.
2. Troubleshooting method:
Simple test: Run the slider to the bottom dead center and maintain pressure, observe whether the pressure gauge pointer continues to drop rapidly. Meanwhile, observe whether there is any oil leakage before and after the oil cylinder.

Professional diagnosis: Remove the oil pipe at one end of the cylinder and allow the other side to continue pressurizing. If a large amount of oil flows out from the removed oil port, it can be concluded that there is internal leakage in the cylinder.

5. The pressure gauge itself is malfunctioning

Sometimes, the problem may lie in the monitoring tools.
1. Cause analysis: The pressure gauge is damaged or inaccurate, giving you the false impression of "insufficient pressure".
2. Search method:

Replacement method: Replace the existing pressure gauge with a known and accurate one for testing to see if the reading returns to normal.

6. The electromagnetic directional valve is leaking or not in place

If the directional valve that controls the direction of the oil circuit leaks internally, it will also affect the pressure.
1. Cause analysis: The valve core of the electromagnetic directional valve is worn or stuck in the middle position due to oil contamination, which cannot completely close a certain oil circuit, resulting in partial pressure oil leakage and pressure loss.
2. Troubleshooting method:
Touch check: When the system is working, touch each valve body. If a valve body that should not be working has an abnormally high temperature, it may indicate that there is a leak inside.

Professional maintenance: Technical personnel are required to clean and inspect the relevant directional valves.

7. Motor or coupling issues

There is a problem with the source of power input.
1. Cause analysis: Insufficient motor speed (such as low voltage), decreased power, or slippage or damage of the coupling between the motor and the hydraulic pump can all lead to insufficient input power of the pump, resulting in the inability to output the rated pressure.
2. Troubleshooting method:
Check the motor: Check if the motor current and voltage are normal, and listen for any abnormal sound during operation.
Check the coupling: Stop the machine and check if the keys of the coupling are loose and if the rubber parts are worn.
Insufficient pressure in hydraulic punch press is a typical hydraulic system failure, and its troubleshooting process reflects the basic logic of hydraulic transmission: power source (pump) → control element (valve) → actuator element (cylinder). Following the principle of from outside to inside and from simple to complex, most problems can be quickly identified. Regular maintenance of your hydraulic punch press, such as replacing hydraulic oil and filter cartridges, is an effective and economical way to prevent such problems. If the problem is complex, please seek the support of professional technicians to ensure equipment safety and maintenance quality.