Diagnosis and solution of common faults of slitter and rewinder: a must-have guide for engineers

Slitting and rewinding machine is a key equipment in packaging, printing, film and other industries, and its operation stability directly affects production efficiency and product quality. The following is a systematic summary of common fault diagnosis and solutions for engineers' reference:

First, material-related failures

1. Wrinkles/creases on the surface of the coil

◦ Causes: uneven tension, deviation of the parallelism of the guide rollers, insufficient air pressure (air shaft), uneven thickness of the material itself.

◦ Solution:

▪ Check and adjust the unwinding/rewinding tension gradient (increasing or decreasing step by step).

▪ Calibrate the parallelism of the guide rollers with a spirit level (error ≤ 0.05mm/m).

▪ Clean or replace the air expansion shaft airbag to ensure that the air pressure ≥ 0.6MPa.

2. Fracture of the edge of the material

◦ Causes: passivation of the slitting knife, deviation of the angle of the tool holder, brittleness of the material (such as BOPP film).

◦ Solution:

▪ Replace the round blade (it is recommended to check the sharpness of the knife edge every shift).

▪ Adjust the blade tilt angle (usually between 15°-25°).

Second, mechanical transmission failure

1. Uneven winding (chrysanthemum pattern)

◦ Causes: core eccentricity, uneven pressure of the pressure roller, EPC deviation correction failure.

◦ Solution:

▪ Use a dial gauge to detect core radial runout (standard ≤ 0.02mm).

▪ Calibrate the linear pressure of the roller (tested by a pressure distribution meter).

▪ Clean the EPC photoelectric sensor and check the cylinder response speed (normal ≤0.1s).

2. Abnormal vibration of the device

◦ Causes: Bearing wear (especially slitting shaft bearings), balance failure, loose foundation.

◦ Solution:

▪ Use the listening stick to determine the position of the abnormal noise, and replace high-precision bearings such as SKF/NSK.

▪ Dynamic balance correction for high-speed rollers (>800m/min) (G2.5 standard).

Third, electrical control system failure

1. The tension fluctuates greatly

◦ Causes: Encoder signal interference, PLC PID parameter drift, brake slippage.

◦ Solution:

▪ A magnetic ring filter is installed, and the encoder wire is changed to a twisted-pair shielded wire.

▪ Retune the PID parameters (proportional band recommended initial value of 40%-60%).

▪ Check the magnetic particle brake clearance (standard 0.3-0.5mm) and replace the expired magnetic particle.

2. The human-machine interface (HMI) is unresponsive

◦ Cause: communication module failure, power supply voltage fluctuation, program jamming.

◦ Solution:

▪ Restart the PLC (pay attention to the backup parameters) and check the stability of the 24V power supply (fluctuation ± less than 5%).

Fourth, the tool system failure

1. Slitting burrs/dust

◦ Causes: Mismatch of blade material (e.g., tungsten steel knife is required for cutting PET), improper overlap of upper and lower knives.

◦ Solution:

▪ Choose the tool according to the hardness of the material (refer to the Mohs scale).

▪ Adjust the amount of overlap (typically 10%-20% of the thickness of the material).

2. Automatic sharpening fails

◦ Causes: Worn grinding wheels, overloaded feed servos.

◦ Solution:

▪ Replace the CBN grinding wheel (120-180 grit size recommended).

▪ Check the servo motor current (within ±15% of the rated value).

Fifth, hydraulic/pneumatic failure

1. The pressure roller is stuck in the lifting and stagnation

◦ Causes: aging of cylinder seals, blockage of solenoid valves, and insufficient lubrication of guide rails.

◦ Solution:

▪ Use a high-temperature sealing ring (e.g. fluoroelastomer).

▪ Clean the SMC/FESTO solenoid valve and confirm the oil supply to the lubricator (3-5 drops/min).

Sixth, preventive maintenance recommendations

1. Daily spot check: check the barometer, tension display value, and tool status.

2. Monthly maintenance: lubricate the linear guide (using ISO VG68 lubricating oil) and calibrate the sensor.

3. Annual overhaul: change of gear gear oil (Mobilgear 600XP recommended), full calibration of the control system.

Typical case: The winding serpentine misalignment problem of a PE film production line was finally found to be due to the stain on the EPC correction mirror, which caused the photoelectric signal to attenuate (the misalignment was reduced from ±5mm to ±1mm after cleaning).

Through systematic diagnosis and precise maintenance, the failure rate of the slitter rewinder can be significantly reduced (empirical data: downtime is reduced by more than 60%). It is recommended to establish a device health file and record the historical curves of key parameters for trend analysis.