Press Brake

Press brake low pressure malfunctions typically manifest as the equipment failing to achieve its rated tonnage, producing inconsistent bends, or a slow-moving ram under load conditions. In practical workshop operations, this is a prevalent issue, yet it rarely calls for the replacement of major components when diagnosed accurately. This guide details a step-by-step approach to identifying the root causes of low pressure, conducting proper inspections of hydraulic and electrical systems, and implementing practical, safe, and efficient solutions to restore the press brake’s full pressure functionality.

Recognizing the Symptoms of Press Brake Low Pressure Issues

Prior to initiating any repair work, it is essential to accurately identify the specific symptoms of low pressure, as these can vary based on the machine’s configuration.

Inadequate Bending Force Under Load

A hydraulic system unable to build sufficient pressure will prevent the press brake from reaching its full tonnage during the bending process, which commonly leads to the following issues:

• Bending angles that deviate from the programmed specifications

• Incomplete forming of the workpiece material

• Unnecessary overcompensation attempts by the machine operator

Sluggish Ram Movement During Pressing

Excessive slowdown of the ram during the pressing stage is a telltale sign of either internal hydraulic leakage or insufficient pump output, a symptom that is particularly common in older hydraulic press brake systems.

Pressure Gauge Readings Below the Set Value

For CNC press brakes, a direct comparison between the actual pressure gauge reading and the preset value in the controller is a critical first check. A noticeable discrepancy between these two values is one of the primary indicators of a low pressure problem.

Step-by-Step Inspection of the Hydraulic System

The vast majority of low pressure issues stem from faults within the hydraulic system, and a structured, component-by-component inspection is recommended for accurate diagnosis.

Step 1: Check Hydraulic Oil Level and Quality

Low hydraulic oil level is the simplest and most frequently overlooked cause of low pressure. Key inspection points include:

• The oil level in the hydraulic tank

• Oil coloration (darkened or milky oil is a sign of contamination)

• The presence of air bubbles in the oil

A low oil level can cause the hydraulic pump to draw in air, resulting in unstable system pressure. If the level is insufficient, refill the tank with the grade of hydraulic oil specified by the equipment manufacturer.

Step 2: Evaluate Hydraulic Pump Performance

If the hydraulic oil level is normal, the next step is to test the hydraulic pump’s functionality. Common signs of a worn pump include:

• Unusual or abnormal operating noise

• Excessive heat generation during operation

• A drop in system pressure when under load

Worn internal components of the pump can reduce oil flow rate, directly causing low pressure issues. In some cases, a professional flow test is required to accurately assess the pump’s condition.

Step 3: Inspect Hydraulic Valves and Relief Valve Calibration

The relief valve is the primary component controlling the maximum pressure of the hydraulic system. An improperly adjusted or stuck-open relief valve will prevent the machine from building up full operating pressure.

Standard inspection and maintenance actions include:

• Verifying that the relief valve setting matches the machine’s rated pressure specifications

• Checking for valve blockages caused by hydraulic oil contamination

• Cleaning or recalibrating the valve as required

Incorrect relief valve adjustment is one of the most common triggers for hydraulic pressure malfunctions in press brakes.

Detecting Internal Leakage in Hydraulic Cylinders

Internal leakage within the main hydraulic cylinders can drastically reduce the pressure efficiency of the press brake system, and identifying seal wear is the core of diagnosing this issue.

Identifying Worn Cylinder Seals

Worn or damaged seals allow hydraulic oil to bypass internally, with typical symptoms including:

• Drifting of the ram when the system is holding pressure

• A sudden drop in pressure after the system reaches its peak value

If seal failure is suspected, a pressure-holding test should be conducted. Replacing worn seals is a straightforward solution that typically restores the system’s full pressure performance.

Electrical and Control System Factors in CNC Press Brakes

Low pressure issues in CNC press brakes are not exclusively caused by hydraulic faults; errors in the electrical control system can also restrict the system’s pressure output.

Malfunctions of Pressure Sensors or Transducers

Modern CNC press brake systems rely heavily on pressure sensors to provide real-time feedback. An inaccurate sensor signal can lead to the following problems:

• The CNC controller automatically limiting pressure output to protect the system

• The appearance of alarm errors on the control panel

• Fluctuations in the displayed pressure values

To diagnose this, verify the sensor’s calibration and inspect the wiring connections within the electrical control cabinet.

Power Issues with Servo Drives or Motors

In servo-hydraulic press brakes, insufficient output from the servo motor can directly cause a reduction in system pressure. Key inspection items include:

• The operating current of the servo motor

• The calibration parameters of the servo drive

• The stability of the electrical power supply to the system

In some instances, the root cause is not mechanical wear but rather fluctuations in the external electrical power supply.

Preventive Maintenance to Avoid Low Pressure Problems

Practical experience has shown that regular, scheduled preventive maintenance can significantly reduce the occurrence of low pressure issues in press brakes.

Routine Replacement of Hydraulic Filters

Clogged hydraulic filters restrict oil flow and reduce pump efficiency. Replacing filters according to the manufacturer’s recommended schedule prevents the buildup of contaminants in the hydraulic system.

Scheduled Hydraulic Oil Changes and System Cleaning

Contaminated hydraulic oil causes gradual damage to valves and seals over time. Maintaining clean oil ensures stable pressure output and extends the service life of all hydraulic components.

Regular Inspection of Seals and JUGAO

Small external leaks from seals or JUGAO are often early indicators of internal wear. Replacing damaged seals and JUGAO at the first sign of leakage prevents more severe hydraulic system failures.

Frequently Asked Questions

What is the most common cause of press brake low pressure issues?

In practical operation, the most frequent causes are low hydraulic oil level, contaminated hydraulic oil, or incorrect relief valve calibration settings.

Can I adjust the relief valve myself to fix low pressure?

Yes, manual adjustment is possible, but it must be performed carefully and in strict accordance with the machine’s rated pressure specifications. Improper adjustment can cause serious damage to the entire hydraulic system.

How can I tell if a hydraulic pump is worn out?

Key warning signs include unusual operating noise, excessive overheating, and the inability to maintain stable pressure under load. A professional flow test is the most accurate way to confirm the pump’s wear condition.

Do electrical problems cause low pressure in CNC press brakes?

Absolutely. Faulty pressure sensors, damaged wiring connections, and malfunctions in the servo drive system can all trigger pressure limitations in CNC press brakes.

Conclusion

Low pressure issues in press brakes can have a severe impact on bending accuracy, production efficiency, and even machine operational safety. However, by following a structured troubleshooting process—including checking hydraulic oil condition, inspecting pump performance, verifying valve settings, testing cylinder seals, and reviewing electrical control systems—the root cause of the problem can be quickly identified and resolved.

In daily press brake operation and maintenance, it has been proven that the vast majority of low pressure problems are preventable with proper routine maintenance and regular inspections. If you require technical support, calibration guidance, or professional consultation on hydraulic system maintenance, our team is always available to assist you in restoring your press brake’s full performance and ensuring its reliable, long-term operation.