In-depth analysis of common problems of bag making machines: cause analysis and practical solutions

In the daily production of the packaging industry, bag-making machines are a core piece of equipment, and their operational stability directly impacts production efficiency and product quality. Whether operating a small workshop or a large-scale production enterprise, operators may encounter common technical issues. If these issues are not promptly addressed, they can not only lead to downtime and delays, but also increase unnecessary repair costs. This article discusses common bag-making machine issues and, drawing on practical experience, provides detailed analysis and solutions to help you better maintain your equipment and optimize your production processes.

1. Heat sealing problem: unstable temperature or loose seal

Heat sealing is a key step in the bag-making process, but many users report problems such as loose seals, temperature fluctuations, or edge warping. The causes of these problems are diverse, including:

• Aging or damage to the heating element : After prolonged use, the heating rod or heat seal knife may oxidize or wear out, resulting in uneven heat conduction. It is recommended to regularly check the resistance of the heating element and replace it promptly if any abnormality is found.
• Temperature control system errors : Failure to calibrate the PID temperature control module or fouling of the sensor probe can cause the actual temperature to deviate from the set point. This can be alleviated by cleaning the sensor and recalibrating the controller.
• Material compatibility : Packaging materials of varying thicknesses (such as PE, OPP, or composite films) require different heat-sealing temperatures. Before operation, parameters must be adjusted based on the material's characteristics and small-batch testing must be conducted.

Solution: First, ensure that the heat-sealed areas are clean and free of residue. Second, regularly maintain the temperature control system and record the temperature curve to monitor stability. Finally, establish a material database and standardize operating procedures.

2. Inaccurate cutting or knife jamming

The bag making machine's cutting system is responsible for cutting to length, but problems such as inconsistent cutting lengths, blade jamming, or rough cutting edges often occur. This may be due to:

• Wear of mechanical transmission components : Loose timing belt or insufficient lubrication of guide rails will cause cutter stroke deviation. The tension and lubrication of transmission components should be checked monthly.
• Drive motor or encoder failure : Abnormal servo motor encoder signal can cause positioning errors. This can be resolved by resetting the software or replacing the encoder.
• Improper or blunt blade installation : Loose blade holder screws or curled blade edges can affect cutting accuracy. Regularly tighten the screws and sharpen or replace the blade.

Solution: Optimize the maintenance schedule for the cutter mechanism, use blades made of highly durable materials, and incorporate a soft start function into the program to reduce impact losses.

3. Feeding system deviation and tension loss of control

Uneven feeding or tension fluctuations can lead to uneven bag lengths, pattern misalignment, and even material breakage. Common causes include:

• Insufficient or worn roller pressure : Uneven pressure on the feed roller can cause the material to slip. Check the air line for tightness and adjust the air pressure to within the standard range.
• Tension sensor malfunction : Electrical interference or mechanical vibration may affect the sensor signal. Shielding the cable and reinforcing the mounting base can improve stability.
• The material roll is installed off-center : The roll is not centered or has excessive inertia, causing a sudden change in tension. When loading the material, ensure that the roll core is parallel to the guide rail and enable the tension taper control function.

Solution: Introducing a closed-loop tension control system, regularly calibrating sensors, and training operators on a standardized loading process.

4. Photoelectric tracking error

For printed bag making, inaccurate photoelectric eye tracking can lead to offset cutting position and misaligned pattern. Such problems are often caused by the following factors:

• Photoelectric head contamination or decreased sensitivity : Dust or oil can obscure the lens, affecting signal acquisition. Daily cleaning of the photoelectric head and adjustment of the sensitivity threshold are key.
• Reflector position deviation : Mechanical vibration or human collision may change the reflector angle. The mounting bracket should be fixed and high-contrast color tape should be used.
• Ambient light interference : Direct strong light sources may interfere with photoelectric sensors. Installing a protective cover or switching to an anti-interference fiber optic sensor can improve this problem.

Solution: Perform photoelectric calibration tests regularly to avoid sudden environmental changes and set up automatic compensation algorithms in the program.

5. Abnormal noise and vibration of mechanical transmission

Abnormal noise or vibration during equipment operation is often a precursor to failure, which may involve:

• Bearings or gearboxes lack oil : Long-term high-speed operation causes the grease to dry out. Add high-temperature grease according to the manual and replace worn bearings.
• Loose structural parts : Loose baseplate screws or frame deformation can amplify vibration. After shutting down the machine, tighten all connections and perform leveling adjustments if necessary.
• The motor and reducer are not properly matched : power mismatch or coupling misalignment can cause resonance. Recalibrate the power parameters and perform dynamic balancing.

Solution: Create a preventive maintenance checklist, conduct quarterly full-line inspections, and use vibration analyzers to monitor critical components.

The stable operation of bag-making machines requires meticulous daily maintenance and standardized operation. The common problems listed here are only typical examples; in actual production, flexible solutions must be implemented based on the equipment model and process characteristics. It is recommended that companies maintain fault records, regularly train their technical teams, and maintain close communication with equipment suppliers for the latest technical support. Through systematic management, failure rates can be significantly reduced, improving production efficiency.

Finally, remember the old saying in the industry: "30% depends on the equipment, 70% depends on maintenance." Only by implementing preventive measures can the bag making machine truly become a reliable partner in production.