Vertical packaging machines (especially VFFS vertical bag-making, filling and packaging machines) may malfunction during continuous operation due to issues such as material characteristics, equipment wear, and parameter settings. Here are 10 common faults and their corresponding troubleshooting and solutions, categorized by the process of "bag making - filling - sealing - finished product", to facilitate rapid problem identification in actual production:

1. Bag making stage failure: abnormal bag shape, film deviation

1. Film deviation (asymmetrical bag body, lateral sealing deviation)

Reasons: ① Uneven tension in the unwind of the film (due to a malfunction in the tension controller of the unwind frame); ② Wear or positional deviation of the guide rollers (causing the film's conveying trajectory to be skewed); ③ Improper installation of the former (resulting in asymmetric folded cylindrical films).

Solution:

Adjust the tension controller for the unwind roll to ensure the film is outputted smoothly and evenly (this can be determined by observing whether the edges of the film align with the scale marks on the guide roller);

Check whether the guide roller is worn, and replace it if there are scratches; loosen the guide roller fixing screws, and adjust the position slightly to align the film edge with the equipment reference line;

Recalibrate the former to ensure that its central axis coincides with the longitudinal centerline of the equipment, and confirm the levelness with a level meter.

2. The length of the bags is inconsistent (the length of the same batch of bags varies)

Reasons: ① The speed of the traction motor is unstable (or the pressure of the traction roller is insufficient, causing slippage); ② The set parameters for bag length do not match the actual traction speed; ③ The thickness of the film is uneven (local over-thickness causes sudden changes in traction resistance).

Solution:

Check whether the traction motor makes abnormal noise, replace worn traction roller bearings, and adjust the traction roller air pressure (or spring pressure) to ensure that the film is held smoothly without slipping;

Reset the bag length parameter in the control system, observe the actual length through "inching test", and gradually fine-tune it to be consistent;

Replace the film with one that meets the required uniformity standard (this can be verified by randomly measuring the thickness at different locations on the film using a caliper).

II. Faults in the filling stage: inaccurate metering, material blockage

1. Large deviation in material measurement (overweight or underweight)

Reasons: ① Wear and tear of metering devices (such as wear and tear of the screw of the screw metering device, deformation of the measuring cup); ② Changes in material fluidity (such as powder agglomeration due to moisture, particle adhesion); ③ Mismatch between filling speed and bag making speed (material not fully falling into the bag).

Solution:

Replace worn measuring components (such as screws, measuring cups), and regularly calibrate the measurement accuracy (spot check 10-20 bags with an electronic scale, with an error of ≤±1%);

Dry the damp materials (for example, a vibrating screen can be installed to disperse the powder agglomerates); increase the material mixing device to ensure uniform feeding;

Reduce the operating speed of the equipment, or adjust the filling delay parameters (to allow sufficient time for the material to fall into the bag before sealing).

2. The filling pipe is blocked (the material does not feed or feeds slowly)

Reasons: ① The material has high viscosity (such as sauce, high-moisture powder) and adheres to the pipe wall; ② The inner diameter of the filling pipe is too small (mismatch with the particle size of the material); ③ The remaining material in the hopper is insufficient (forming a "bridging" phenomenon, preventing the material from falling).

Solution:

Regularly clean the filling tube (an automatic cleaning device can be installed, or a food-grade stainless steel tube with a smooth inner wall can be selected to reduce adhesion);

Replace the filling pipe with one that matches the material (the diameter of the particle material pipe needs to be ≥ 3 times the diameter of the largest particle);

Install a stirring paddle or vibration device in the hopper to break the "bridging"; keep the amount of material in the hopper not less than 1/3 (automatically replenish material through the material level sensor).

III. Faults in the sealing stage: poor edge sealing, missing seals/burst seals

1. The edge bonding is not firm (easy to tear, leakage of liquid/powder)

Reasons: ① Insufficient heat sealing temperature (not reaching the melting point of the inner film); ② Insufficient heat sealing pressure (the sealing surface is not in close contact); ③ Too short heat sealing time (the film is not fully fused).

Solution:

Gradually increase the heat sealing temperature (by +5℃ each time, test until the sealed edge can be firmly torn off without burning). For different materials, refer to the following temperature ranges: PE film 120-160℃, CPP film 140-180℃;

Adjust the pressure of the heat sealing knife (or spring pressure) to ensure that the sealing surface is evenly compressed (a feeler gauge can be used to check whether the pressure on both sides is consistent);

Reduce the equipment operating speed (extend the heat sealing time), or increase the contact time parameter of the heat sealing knife.

2. Edge banding is burnt and wrinkled, affecting both the sealability and appearance

Reasons: ① The heat sealing temperature is too high (the film is excessively melted); ② The surface of the heat sealing knife is uneven (local pressure is too high); ③ The film slips during sealing (the tension is unstable, causing wrinkles).

Solution:

Reduce the heat sealing temperature or shorten the heat sealing time (to avoid local overheating);

Polish the surface of the heat sealing knife (remove scratches and foreign objects) and replace the worn heat sealing knife;

Increase the traction tension to ensure that the film is flat and wrinkle-free during sealing, and add a flattening guide roller if necessary.

3. Bottom sealing deviation (the bottom of the self-supporting bag is uneven and cannot stand upright)

Reasons: ① The position of the bottom folding mechanism is offset (asymmetrical folding); ② The horizontal heat sealing knife is not aligned with the bottom crease; ③ The traction speed is unstable (film movement during bottom shaping).

Solution:

Re-calibrate the bottom hemming mechanism to ensure that the hemming width is symmetrical on both sides (measure the hemming dimensions on both sides with a ruler);

Adjust the position of the horizontal heat sealing knife slightly to align its centerline with the bottom crease;

Check the traction motor and encoder to ensure stable speed (by monitoring the fluctuation of traction pulse values through PLC).

IV. Faults in the finished product stage: abnormal cutting, damaged bag body

1. Deviation of cutting position (cutting outside the edge banding or not cutting)

Reasons: ① Poor synchronization between the cutting knife and the horizontal heat sealing knife (position misalignment); ② Wear and tear of the cutting knife (blunt blade, unable to cut the film); ③ Bag length setting error (cutting position not between the two bag seals).

Solution:

Adjust the timing belt or chain to ensure the cutting blade and heat sealing blade move in sync (observe their positional relationship through "single-step operation");

Grind or replace the cutting blade (ensure the blade remains sharp, and pay attention to the installation direction of the upper and lower blades);

Reset the bag length parameter to ensure that the cutting position is in the middle of the sealed edge (usually the sealed edge width is 5-10mm, and the cutting needs to be centered).

2. Damage to the finished bag (holes or tears on the side or bottom)

Reasons: ① Foreign objects in the heat sealing knife (such as metal debris, which pierces the film during sealing); ② Excessive tension in the film (overstretching causes weak spots to rupture); ③ Hard impurities in the material (such as stones, metal pieces, which pierce the bag during filling).

Solution:

Stop the machine to clean the surface of the heat sealing knife, check for scratches or protrusions, and replace the knife pad if necessary;

Reduce the tension during unwinding and traction (especially for thin films) to avoid excessive stretching;

Install a screening device (such as a metal detector or vibrating screen) in front of the hopper to remove hard impurities.

V. Common faults of equipment: abnormal operation noise, alarm shutdown

1. Abnormal noise during equipment operation (metal friction sound, impact sound)

Reasons: ① Lack of oil in transmission components (such as insufficient lubrication of gears and bearings); ② Loose components (such as loose screws and belt pulleys); ③ Foreign objects entering the interior of the equipment (such as film fragments and material particles).

Solution:

Regularly add lubricating oil to transmission components according to the equipment manual (gear oil for gears, butter for bearings);

Conduct a comprehensive inspection of all connection parts of the equipment, tighten loose screws and pulleys;

Stop the machine to clean the foreign objects inside the equipment and check whether the protective cover is closed in place.

2. The equipment suddenly stops due to alarms (such as "tension abnormality" and "temperature overrun")

Reasons: ① Sensor malfunction (such as false alarms from tension sensors, temperature sensors); ② Parameter settings exceed the device range (such as setting the heat sealing temperature to 200℃, but the device's maximum is only 180℃); ③ Unstable power supply voltage (causing abnormalities in the motor or control system).

Solution:

Calibrate or replace the faulty sensor (use a multimeter to check whether the sensor output signal is normal);

Reset the parameters to match the device specifications (refer to the parameter range specified in the device manual);

Install a voltage regulator to ensure that the power supply voltage is stable at 220V±10% (three-phase power 380V±10%).

Core principles of fault prevention

Regular maintenance: Clean the heat sealing knife and cutting knife daily; check the lubrication and tightness of transmission components weekly; calibrate the measuring device and sensor monthly.

Material adaptation: Ensure that the film material and thickness are compatible with the equipment (e.g., thicker films require higher heat sealing temperatures), and perform material pre-treatment (removal of impurities, control of humidity).

Parameter recording: Create files for different product packaging parameters (temperature, speed, tension), which can be directly called when changing products, reducing debugging errors.

More than 80% of common faults can be quickly resolved through the above methods. If complex issues such as circuits and PLC programs are involved, it is recommended to contact the equipment manufacturer for professional maintenance.