Is the glue line intermittent and disjointed? Two hour troubleshooting record for an automatic sealing line

Direct answer: The real reason for the intermittent sealing line on this sealing line is the bridging of the feeding port of the melt glue pot, which causes the liquid level to intermittently decrease, and the carbonization residue inside the nozzle is partially blocked. After cleaning the pot and changing the material+adjusting the feeding method, the glue line resumed continuity, and the sealing and opening rate decreased from 4.8% to 0.2%.

On site situation

The automatic sealing line of a daily chemical packaging factory in Dongguan produces about 900 boxes per hour. Starting from last week, the operator noticed that the glue line on the cardboard box was sometimes missing – normally it should be two consecutive 180mm glue lines, but in reality it often turned into a “dotted line” with three or four sections broken in the middle. Downstream inspections have found that the sealing rate has increased to 4.8%, leading to customer complaints.

First hour: Investigate in order

• Check the temperatureThe melt glue pot is set at 175 ℃, and the measured panel shows 174 ℃, which seems normal. But when a thermometer was used to hit the surface of the adhesive, the reading was only 161 ℃ – there was a deviation of 13 ℃ between the panel and the actual temperature, and the temperature probe position was too high.
• Look at the pressureThe pointer of the output pressure gauge of the glue pump swings back and forth during production, which is not a stable value, indicating discontinuous glue feeding.
• Check the liquid levelOpen the lid of the pot and observe that the liquid level is indeed replenished after a periodic decrease, approaching the suction port at its lowest point.
• Look at the nozzleRemove the nozzle, there is a black hard residue around the edge of the orifice, and the actual aperture is reduced by about one-third.

Second hour: Identify the root cause

When the three phenomena are linked together, it becomes clear. The rubber particles in the automatic feeding tube have slight adhesion due to high humidity in the workshop, forming a “bridge” at the feeding port. The rubber particles cannot continuously fall down, resulting in periodic low liquid levels; When the liquid level is low, air is introduced into the suction port, causing fluctuations in the output pressure of the glue pump and natural interruption of the glue line. However, the actual low temperature of the glue (161 ℃) also increases the viscosity of the glue, exacerbating the problem of poor glue dispensing; Residual glue that has been repeatedly heated at low temperatures for a long time will gradually carbonize and coke at the nozzle.

Measures

• Stop the machine to clean the pot, disassemble and wash the nozzle and filter screen, and remove carbonization residue.
• Replace with sealing special rubber particles with more uniform particle size and better anti caking properties to reduce the probability of bridging.
• Install a vibration device on the feeding pipe and change the temporary storage area for adhesive particles in the workshop to an off ground pallet and sealed bag.
• Re calibrate the temperature probe, and the actual temperature of the adhesive solution remains stable at 172-176 ℃.
• Establish a weekly boiler cleaning and bi weekly nozzle cleaning inspection system.

Results and Review

After processing, continuous tracking for three days: the glue line has no broken strands, the sealing and opening rate has dropped to 0.2%, and the single box glue consumption has slightly decreased compared to before. The most memorable point during the review is——The panel temperature is not equal to the adhesive temperatureMany judgments of ‘glue not working’ are actually based on distorted readings.

Frequently Asked Questions

Q: Do I have to change the glue if the glue line is intermittent?
Answer: Not necessarily. First, investigate in the order of “temperature measurement – pressure observation – liquid level inspection – nozzle disassembly inspection”. In most cases, it is a problem with the equipment and material status.

Q: How to prevent rubber particles from getting damp and clumping?
Answer: Store off the ground, use up on duty after opening the bag, and avoid directly facing water vapor and air conditioning vents in the temporary storage area.

Q: How often is it appropriate to clean the pot?
Answer: It is recommended to have two consecutive production shifts once a week; For intermittent production with multiple daily on-off cycles, it is recommended to shorten it to 3-4 days.

Guangzhou Sunlife Trading provides customers with advice on selecting adhesive particles, troubleshooting, and inspection systems for automatic sealing lines. Sunlife’s hot melt adhesive sealing series has been optimized for anti caking and thermal stability.