How to Troubleshoot Common E21 Hydraulic Press Brake Problems？

The Estun E21 controller is one of the most widely used NC control systems in hydraulic press brakes. Its simple operation, reliable performance, and cost-effectiveness make it a popular choice for small and medium-sized sheet metal fabrication workshops.

However, like any industrial equipment, an E21 hydraulic press brake may occasionally experience operational issues. Understanding the most common faults and their solutions can help operators minimize downtime and maintain stable production.

1. Press Brake Ram Does Not Move Down

Possible Causes

• X-axis and Y-axis actual values do not match the preset target values

• Emergency stop circuit activated

• Foot switch malfunction

• Hydraulic pump not running

• Electrical wiring failure

Solutions

• Check the E21 controller display and verify that X and Y values correspond to XP and YP settings.

• Reset the machine and perform a reference return procedure.

• Inspect the foot pedal and emergency stop button.

• Verify hydraulic pump operation.

• Check electrical connections inside the control cabinet.

In many cases, correcting the X and Y axis values on the E21 controller restores normal ram movement.

2. E21 Displays “OUT OF UDP” Alarm

Possible Causes

• Ram has not reached Top Dead Center (TDC)

• Limit switch malfunctionTravel stop position incorrect

• Sensor failure

Solutions

• Raise the ram to its highest position.

• Check whether the limit switch is properly activated.

• Adjust the travel stop.

• Verify sensor wiring and connections.

The OUT OF UDP alarm is commonly caused by incorrect ram position feedback and can often be resolved through limit switch adjustment.

3. Insufficient Bending Pressure

Possible Causes

• Low hydraulic oil level

• Blocked hydraulic filter

• Relief valve malfunction

• Hydraulic pump wear

• Prefill valve leakage

Solutions

• Check and replenish hydraulic oil.

• Replace contaminated filters.

• Inspect pressure control valves.

• Test hydraulic pump performance.

• Check prefill valve sealing condition.

Insufficient pressure can prevent the machine from achieving the required bending force, especially when processing thicker materials.

4. Inaccurate Bending Angle

Possible Causes

• Incorrect material parameters

• Tooling wear

• Improper pressure settings

• Machine calibration error

Solutions

• Verify material thickness and tensile strength.

• Inspect punch and die condition.

• Recalibrate machine parameters.

• Check backgauge positioning accuracy.

Regular calibration helps maintain consistent bending accuracy and repeatability.

5. Main Motor Stops Unexpectedly

Possible Causes

• Overloaded hydraulic system

• Clogged oil filter

• Poor hydraulic oil quality

• Thermal relay protection triggered

Solutions

• Clean or replace hydraulic filters.

• Replace hydraulic oil according to maintenance schedules.

• Check pressure valve operation.

• Inspect circuit breakers and thermal relays.

Poor oil quality and blocked filters are among the most common reasons for motor overload.

6. Backgauge Does Not Move Correctly

Possible Causes

• Servo drive alarm

• Encoder failure

• Damaged signal cable

• Mechanical obstruction

Solutions

• Check servo driver error codes.

• Inspect encoder wiring.

• Clean guide rails and ball screws.

• Verify motor coupling condition.

Accurate backgauge movement is essential for maintaining bending precision.

Preventive Maintenance Tips

To reduce E21 press brake failures, operators should perform routine maintenance:

Daily

• Check hydraulic oil level

• Inspect tooling condition

• Clean machine surfaces

Weekly

• Inspect electrical connections

• Lubricate moving parts

• Check hydraulic hoses

Monthly

• Replace filters if necessary

• Verify machine calibration

• Test safety devices

Regular preventive maintenance can significantly extend machine service life and reduce unexpected downtime.

Why Choose BAIZHUO Hydraulic Press Brakes?

BAIZHUO CNC provides reliable hydraulic press brakes equipped with E21, Delem DA53T, ESA, and other CNC control systems.

Our machines feature:

• High-strength welded steel frames

• Precision hydraulic systems

• Stable backgauge positioning

• Professional technical support

• Global after-sales service

Whether you require an economical E21 hydraulic press brake or a high-precision CNC press brake, BAIZHUO offers customized solutions for your sheet metal fabrication needs.

Conclusion

Most E21 hydraulic press brake faults can be resolved through systematic troubleshooting and routine maintenance. By understanding common issues such as ram movement failures, pressure loss, alarm messages, and backgauge errors, operators can maintain efficient production and maximize equipment reliability.