1. Power Supply/Circuit Board Failure (Most Easily Misdiagnosed) This is the most common electrical fault in toilet paper rewinding machines. A typical symptom is photoelectric protection failure: the cutter doesn't stop even when the photoelectric sensor is covered. Replacing the burnt-out power bridge rectifier results in the new rectifier quickly burning out again.
Core Cause: A burnt-out bridge rectifier leads to a short circuit, damaging the three-terminal voltage regulator (7805). Replacing only the bridge rectifier without replacing the voltage regulator will not solve the problem.
2. PLC System Interference Failure (Most Recurring) Typical Symptoms: PLC system fault indicator light illuminates, some drives stop irregularly, and the machine speed suddenly becomes unstable. The problem is resolved after a power outage and restart, but recurs after a period of operation.
Core Cause: Improper wiring (mixed high-voltage and low-voltage wiring, chaotic grounding), or electromagnetic interference from surrounding electrical equipment, can cause PLC data calculation errors and abnormal output control values.
3. Communication Bus Failure (Mostly Human-Induced)
Typical Symptoms: Some drive points do not respond to control, the system directly reports a communication error, and the production process cannot start.
Most Common Causes (Ranked by Number):
① Incorrect communication parameter settings (station number, baud rate, and system mismatch; human error accounts for the highest proportion);
② Burned-out or offset resistance resistor at the end of the bus, causing chaotic signal reflection;
③ Mixed laying of communication and power cables, resulting in signal interference and distortion.
4. DC Drive Failure
Typical Symptoms: The motor cannot start, the DC drive reports armature overvoltage/overcurrent/undervoltage fault codes, or the machine speed becomes unstable irregularly.
Common Problems:
Armature Overvoltage: Excessive inertia from the paper ejector roller causing overvoltage in the generator; adjusting parameters will resolve this.
Armature Overcurrent: Short circuit in the circuit or aging and breakdown of components in the DC drive.
Undervoltage: Loose or poor contact at the input terminals leading to insufficient power supply. Long-term exposure to high temperatures, dust, and humidity can cause the DC drive to age and directly lead to unstable machine speed.
5. Tension Control Failure (Most Affecting Product Quality)
Typical Symptoms: The equipment operates normally, but the finished paper rolls exhibit inconsistent tension, frequent paper breaks, wrinkles, or bursting.
Core Causes: Interference with the tension sensor signal, unreasonable tension parameter settings, or abnormal encoder speed feedback lead to excessive deviations between the actual tension and the set value, causing tension fluctuations.
