I once worked with a client from India who ran a potato chips factory. His newly purchased VFFS (ختم التعبئة والتشكيل العمودي) machine kept having sealing problems, resulting in a high defect rate that frustrated his entire team. He sent me a photo: bags of chips with wrinkled seals that leaked air with the slightest squeeze.
Does this sound familiar? Poor sealing in vertical packaging machines is an extremely common issue that directly leads to product leakage, spoilage, massive waste, and production interruptions. Weak seals, wrinkles, air bubbles, or complete seal failure—these are all typical symptoms.
Don’t worry, today we’re going to break down this problem thoroughly. All sealing issues come down to three core elements: temperature, pressure, and time. A perfect seal is the art of achieving the optimal balance among these three factors.
- درجة حرارة: Heating the sealing layer of the packaging film (typically PE or PP) to its melting point.
- Pressure: Providing sufficient pressure for the molten film molecules to penetrate and bond with each other.
- Time: Ensuring the heat-seal material has enough time to melt and bond.
Now, let’s analyze the 5 main causes of poor sealing in آلات VFFS based on these three elements, and provide actionable solutions you can implement immediately.
Cause 1: Incorrect Temperature (Too High or Too Low)
This is the most common issue and should be the first thing you check. Temperature deviation directly causes sealing failure.
- Temperature Too Low: Insufficient heat to completely melt the sealing layer of the film.
- Symptoms: The seal tears open easily; the sealing surface looks smooth but has no strength.
- حل: Don’t completely trust the temperature controller display! Use a professional contact thermometer to measure the actual working surface temperature of the sealing jaw, ensuring the display matches reality. Then, gradually increase the temperature in 5-10°C increments from the current setting to find the optimal point.
- Temperature Too High: Burns through the packaging film or makes the seal brittle.
- Symptoms: The seal area shows excessive melting, brittleness, holes, or the seal area is pulled into “threads.”
- حل: Gradually reduce the temperature. If the problem persists, check your heating elements. A damaged heating rod can cause temperature loss of control even if the controller shows normal readings.
💡 Parts Recommendation: If your heating elements frequently malfunction or temperature control is inaccurate, it may be time for replacement. A high-quality [heating element](product link) is the foundation of stable production.
Cause 2: Uneven or Insufficient Pressure
Temperature alone isn’t enough—you need proper pressure to make the molten films “bond intimately.”
- Insufficient Pressure: Unable to adequately bond the two layers of molten film.
- Symptoms: The seal appears bonded, but close inspection reveals tiny gaps or air bubbles, and it peels apart easily.
- Uneven Pressure: Uneven sealing jaws or foreign objects cause some areas to seal firmly while others fail.
- Symptoms: Intermittent sealing, or the seal line is clear on one side but blurry on the other.
Solutions:
- Adjust Pressure: Refer to the equipment manual to correctly adjust the sealing cylinder pressure. Pressure should be sufficient but not excessive, as too much pressure can thin the seal edge, actually reducing strength.
- Check Parallelism: Power off, manually rotate the machine to bring the two sealing jaws together, place a piece of white paper between them, then gently pull it out. Observe whether the pressure marks on the paper are uniform. If uneven, the jaws are not parallel and need professional calibration.
- Clean! Clean! Clean!: Ensure the sealing jaw surfaces are free of any carbonized film residue, dust, or foreign objects. This is the most easily overlooked yet most critical point.
Cause 3: Critical Consumables Have “Reached End of Life” (PTFE Tape and Silicone Strip)
Sometimes the problem isn’t the machine itself, but those unsung consumable parts.
- PTFE Tape (Teflon Tape) Damage: PTFE tape provides non-stick, heat-resistant properties. If it’s worn, punctured, or aged and discolored, it causes:
- Sticking: Molten film sticks directly to the sealing jaw, damaging the seal when torn off.
- Uneven Heat Transfer: Damaged areas don’t transfer heat properly.
- Silicone Pressure Strip/Pad Aging: The silicone strip provides elastic back pressure to ensure uniform pressure. If it hardens, cracks, or wears out, pressure becomes uneven.
- Symptoms: Wrinkles appear on the seal, or the seal line width is inconsistent.
Solutions:
Both are consumable items—don’t try to “patch and mend for another three years.” Once you notice uneven surfaces, damage, or aging, replace immediately!
💡 Parts Recommendation:
•[High-Temperature PTFE Tape]- Choose products with uniform thickness and wear resistance.
•[High-Elasticity Silicone Strip] – Ensure your spare parts inventory always has stock.
Cause 4: Sealing Jaw Itself is Worn or Deformed
If you’ve ruled out all the above issues, consider the sealing jaw itself. After prolonged use, the jaw surface may become rough, uneven, or even corroded.
- Symptoms: The seal surface is not smooth, has strange patterns, and tends to crack along these patterns.
Solutions:
- Minor Wear: Use fine sandpaper or metal polishing compound for light polishing.
- Severe Deformation or Corrosion: Don’t hesitate—replace with a new sealing jaw. A problematic jaw will continuously produce defective products, which is not cost-effective.
💡 Parts Recommendation: We offer vertical packing machine sealing blades compatible with various mainstream machine models,https://fill-package.com/wp-admin/post.php made from wear-resistant alloy for longer service life.
https://youtu.be/4rwJtRFGj2g
Cause 5: The Packaging Film is the “Real Culprit”
Sometimes we disassemble the entire machine only to discover the problem is with the packaging film.
- Poor Heat-Seal Layer Performance: The film’s heat-seal layer (inner layer) has formulation issues, with an overly narrow heat-sealing temperature range, making it extremely sensitive to machine parameters.
- Uneven Film Thickness: Causes uneven heat and pressure transfer during sealing.
- Film Moisture or Contamination: Surface grease, dust, etc., directly affect sealing performance.
Solutions:
The fastest method is substitution testing. Switch to a roll of film you’ve confirmed is good and run a test. If the problem disappears, congratulations—you’ve found the root cause! Contact your film supplier immediately. Also, ensure your packaging film is stored in a dry, clean environment.
Ultimate Troubleshooting Flowchart
When poor sealing occurs, don’t panic. Follow these steps and you’re guaranteed to cure the problem:
Step 1: Cleaning and Visual Inspection
- Power off and disconnect!
- Thoroughly clean sealing jaws, PTFE tape, and silicone strips.
- Check PTFE tape and silicone strips for visible damage. (Found damage? Replace immediately!)
Step 2: Check “Temperature”
- Calibrate the actual sealing temperature with a thermometer.
- Based on film recommendations, fine-tune temperature settings (try increasing by 5-10°C first).
Step 3: Check “Pressure”
- Verify pressure settings are appropriate.
- Use the “white paper method” to check sealing jaw parallelism.
Step 4: Check “Time”
- If all the above steps fail, increase “Dwell Time” appropriately on the PLC or touchscreen.
Step 5: Substitution Testing
- Switch to a roll of confirmed good film for testing. If the problem disappears, it’s a film issue.
Through this systematic troubleshooting approach, 99% of poor sealing problems can be identified and resolved.
Need Help?
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