Common Hydraulic Bending Machine Troubleshooting and Troubleshooting

A hydraulic press brake is a press machine that uses a hydraulic system to drive a slide to precisely bend metal sheets. It is widely used in sheet metal processing, automotive manufacturing, aerospace, and other fields. Its core features include high precision, large tonnage, and programmable control, making it a key piece of equipment in modern metal forming processes. Over extended use, hydraulic press brakes may experience mechanical, hydraulic, and electrical failures. The following is a classification of common failures, along with their cause analysis and solutions, to help quickly resume production and extend equipment life.

1. Mechanical Failure
Abnormal Slider Movement (Stuck, Asynchronous)
Possible Causes:
Guide Rail Wear: Excessive guide rail clearance (>0.1mm) due to long-term use
Slider Overload: Uneven pressure in the Y1/Y2 axis hydraulic cylinders (difference >5%)
Mechanical Deformation: Frame welding stress release or foundation settlement
Solution:
Adjust guide rail clearance: Use a feeler gauge, adjust the yoke, or replace the guide rails
Calibrate hydraulic synchronization: Use a pressure sensor to adjust the proportional valve (ensure the Y1/Y2 pressure difference is <2%)
Check frame level: Use a laser level (tolerance ≤0.1mm/m)

Inaccurate backgauge positioning
Possible Causes:
Servo Motor Step Loss: Encoder signal interference or driver failure
Drive Belt Looseness: Insufficient tension causing return stroke error
Loose mechanical limit stop: The stopper bolts are not tightened
Solution:
Check the servo system: Use an oscilloscope to monitor the encoder signal (A/B phase pulses) Check for complete flushing)
Adjust belt tension: The midpoint depression should be 10-15mm.
Recalibrate zero point: Perform the material stop reference point reset procedure.

2. Hydraulic system malfunction
No or insufficient pressure in the master cylinder
Possible causes:
Hydraulic oil contamination: Particles blocking the solenoid valve (ISO cleanliness > 18/16/13)
Oil pump wear: Plunger pump volumetric efficiency <85%
Relief valve failure: Broken spring or stuck valve core
Remedy:
Check oil cleanliness: Replace the filter element (β value ≥ 200) and send a sample for inspection.
Test pump output flow: Flow reduction > 15% at rated pressure requires replacement.
Disassemble and clean the relief valve: Clean the valve core with kerosene and check the free length of the spring.
Abnormally high oil temperature (> 60°C)
Possible causes:
Cooler blockage: Dust accumulation on the heat sink or scale in the waterway.
System leakage: Damaged cylinder seal causing continuous high-pressure overflow.
Improper viscosity selection: Use ISO 10000 in summer. VG46, use VG32 in winter.
Remedy:
Cooler cleaning: Use compressed air to purge the heat sink (pressure drop < 0.1 MPa).
Pressure hold test: If the pressure drops > 20% within 5 minutes after shutting down, check the seals.
Replace the hydraulic oil: The viscosity index (VI) should be > 150.

3. Electrical and control system failure
CNC system alarm (overtravel/drive failure)
Possible causes:
Limit switch failure: Contact oxidation or mechanical block displacement.
Servo overload: Acceleration/deceleration times set too short (should be > 0.3s).

Power supply interference: Frequency converter. The filter is not connected to the servo.
Solution:
Short-circuit limit test: Temporarily short the circuit to determine if there is malfunction.
Adjust servo parameters: Reduce the stiffness gain (reduce the Kp value by 20%).
Install a ferrite ring: Install a ferrite ring on the motor power cable.
The touch screen is unresponsive or distorted.
Possible causes:
Bulging of motherboard capacitors: Electrolyte drying out, resulting in unstable power supply.
Poor signal cable contact: Oxidation of D-Sub connector pins.
System crashes: Frequent abnormal shutdowns.
Solution:
Replace motherboard capacitors: Use 105°C temperature-resistant solid-state capacitors.
Reseat the signal cable. : Clean the interface with electronic cleaner.
Restore factory settings: Parameters (such as PLC programs) must be backed up in advance.

4. Die and forming issues
Workpiece angle inconsistency (excessive springback).
Possible causes:
Die wear: Lower die V-groove radius R > 2 times plate thickness.
Material variation: Yield strength fluctuation within the same batch of steel plates > 10%.
Insufficient compensation: DAK (Dynamic Angle Compensation) function not activated.
Resolution:
Measure die dimensions: V-groove bottom radius should be ≤ 1.5 times plate thickness.
Material hardness test: Spot check using a Leeb hardness tester (HRB tolerance ±3).
Enable intelligent compensation: Enter the measured springback value (the system automatically corrects the bottom dead center).

Bending cracks (aluminum/stainless steel)
Possible causes:
Bending radius too small: R < plate thickness, resulting in tensile cracking of the outer layer
Die surface roughness: Ra > 1.6μm, causing stress concentration
Insufficient lubrication: Failure to apply aluminum-specific lubricant (containing molybdenum disulfide)
Solution:
Increase the lower die opening: V-groove width = 6-8 × plate thickness (upper limit for stainless steel)
Polishing the die: Grind with diamond paste to Ra 0.8μm
Adding lubrication: Spray with PTFE-based dry film lubricant