Shear Cutting

Common failures in gate-type shearing machines primarily fall into five categories: hydraulic systems, electrical systems, mechanical components, nitrogen return systems, and shear quality. Below is a categorized breakdown of fault symptoms, root causes, and quick troubleshooting methods to facilitate on-site diagnostics.

I. Hydraulic system failure (most common)

-Inability to grip the blade properly / Weak movement / Failure to establish pressure

Causes: Insufficient/contaminated hydraulic oil, oil pump internal leakage, overflow valve blockage/failure, solenoid valve sticking, main cylinder seal internal leakage

Procedure: Oil replenishment/replacement; Inspection/oil pump replacement; Cleaning/calibration of relief valve; Disassembly and cleaning of solenoid valve; Replacement of cylinder seal

-Oil tank/pipeline oil leakage

Causes: Sealing aging, joint loosening, cylinder tube scoring

Procedure: Replace the sealing ring; tighten the joint; repair/replace the cylinder

Hydraulic oil overheating

Reason: The relief valve is often open, with significant internal leakage, cooler failure, and excessively high oil viscosity.

Action: Inspect the relief valve; identify internal leaks; clean the cooler; replace with hydraulic oil of appropriate viscosity

-Loud startup noise/screaming

Causes: oil pump cavitation, poor oil suction, bearing damage, valve component sticking

Procedure: Air venting; cleaning of oil suction filter element; inspection/replacement of oil pump; disassembly and cleaning of valve components

The blade holder fails to return to the top dead center during retraction.

Cause: Insufficient accumulator pressure

Procedure: Check the pressure gauge reading of the accumulator. If the pressure is low, press the liquid filling button until the required pressure is reached.

II. Nitrogen Return Cylinder Failure (Specific to Gate Type)

-Slow return stroke of the blade holder / Failure to return to top dead center / Automatic downward slippage

Causes: Insufficient nitrogen pressure, cylinder seal leakage, or one-way valve failure

Procedure: Charge nitrogen to the rated pressure; Replace the cylinder seal; Inspect the check valve.

-Weakness in foot pressure/Inability to press the board/Shearing of board material

Cause: Insufficient nitrogen supply in the pressing cylinder, wear of the pressing pad, and malfunction of the pressing sequence valve.

Treatment: Supplement nitrogen; Replace compression rubber pad; Inspect sequence valve

III. Electrical System Failure

No action upon switch activation / Tool holder remains stationary

Causes: Power supply phase loss, contactor/relay damage, PLC output failure, limit switch malfunction, loose wiring

Action: Check power supply; Replace contactor/relay; Inspect PLC; Replace limit switch; Tighten wiring connections

Abnormal movement

Cause: Poor contact of the switch, burnt-out solenoid coil of the solenoid valve, short circuit/grounding of the wiring, or program error.

Procedure: Clean/replace the switch; Replace the solenoid valve coil; Inspect the wiring; Re-calibrate the program

IV. Mechanical and Shear Quality Defects

-Large shear burrs/uneven cross-section/plate warping

Reasons: Improper blade clearance, blade chipping/wear, insufficient material pressing, and non-parallel blade holder.

Procedure: Re-adjust the clearance; sharpen or replace the blade; inspect the material pressing; adjust the blade holder parallelism

Knife holder tilt/shear deviation

Cause: Asynchronous operation of both hydraulic cylinders, balance cylinder failure, guide rail wear, and loose connecting rods

Procedure: Adjust the synchronizing valve; inspect the balance cylinder; repair the guide rail; tighten the connecting rod.

-Inaccurate rear material feeding / significant dimensional deviation

Cause: Malfunction of the material blocking motor/screw, failure of the positioning switch, and excessive transmission clearance

Treatment: Inspect the motor/screw rod; Replace the switch; Eliminate transmission clearance

V. Rapid Screening Mnemonic

-Check the electrical system before inspecting the hydraulic system if unable to proceed;

-Slow return trip for nitrogen inspection, replace seals in case of oil leakage;

-Adjust the backlash for burr adjustment and calibrate parallelism for runout correction;

Check for overflow in case of overheating, and inspect the oil pump for noise.