EN
1) First, Identify Which Seal Is Failing (Defect Mapping)
Before adjusting anything, define the failure mode. Different defects point to different root causes:
- Seal opens with light pull → insufficient heat / pressure / dwell time
- Seal looks “burnt” or brittle → overheating or excessive dwell
- Seal has channels / micro-leaks → contamination, poor pressure distribution, wrinkling
- Seal is uneven across width → heater zoning issue, misalignment, worn pressure pad
- Seal sticks and tears film → temperature too high, improper release layer, worn Teflon tape
- Bottom seal blows out during filling → seal strength low vs. film thickness, cooling too short
Tip for faster troubleshooting: keep 10–20 rejected samples labeled by time and machine speed. Patterns often correlate with temperature cycling or tension changes.
2) The 80/20 Root Cause: Temperature, Pressure, Dwell (But Verify with Data)
Most operators adjust temperature first. Maintenance teams should verify the whole sealing “triangle”:
A) Temperature: Not the Setpoint—The Real Surface Temperature
Common hidden issues:
- Heater cartridge aging (slow response)
- Thermocouple position drift
- PID tuning issues leading to overshoot/undershoot
- Loose wiring causing intermittent heating
- Heater zoning imbalance (hot left, cold right)
Maintenance checks
- Measure real seal bar surface temp with a calibrated probe/IR tool (use consistent method)
- Compare left/right temperature difference across the bar
- Inspect thermocouple mounting—tight, correct contact, no oxidation
- Check SSR/relay health (overheating, discoloration, intermittent output)
B) Pressure: Uniformity Matters More Than “Higher Pressure”
Too little pressure causes weak bonding; too much causes film thinning, edge squeeze-out, or distortion.
Maintenance checks
- Inspect pneumatic regulators and gauge accuracy
- Check for air leaks at fittings, cylinders, solenoids
- Verify pressure repeatability during high-speed cycles
- Inspect pressure pads/silicone rubbers: hardening, grooves, uneven wear
- Confirm parallelism between upper/lower sealing jaws
C) Dwell Time: High Speed Changes Everything
At higher line speeds, dwell time may become insufficient even if temperature/pressure are correct.
Maintenance checks
- Confirm timing settings vs. actual machine cycle (encoder verification if available)
- Look for mechanical play in linkages that shortens contact time
- Verify that sealing action is stable (no bounce)
3) Film Handling Problems That “Look Like” Seal Problems
On a trash bag making machine, sealing quality is often destroyed upstream by unstable web handling:
- Film wrinkling entering the seal area → creates channels and leaks
- Static electricity → film misfeeds, inconsistent contact
- Tension drift → seal position shifts, fold changes, uneven pressure
Maintenance checks
- Inspect dancer rollers / tension control components
- Check guide rollers for contamination or bearing wear
- Confirm edge guiding works consistently (if equipped)
- Clean rollers and sealing area frequently (dust + slip additives build up fast)
4) Contamination: The Silent Seal Killer (Especially for Recycled Film)
Trash bags often use recycled material or high-slip formulations. These increase:
- dust
- gels/contaminants
- surface additives that reduce sealing window
Maintenance actions
- Implement a strict seal-bar cleaning routine (scheduled, documented)
- Replace worn Teflon tape or release cloth before it fails
- Check if the sealing surface has scratches or carbonized spots
- Ensure compressed air is dry and filtered (oil mist contaminates seals)
If defects spike after raw material changes, don’t just blame the machine—confirm melt index consistency and additive package.
5) Common Seal Failure Scenarios and Fast Diagnosis
Scenario 1: Seal is weak only on one side
Likely causes:
- heater zone failure on one side
- uneven jaw parallelism
- pad wear on one side
Actions: - temperature mapping across bar
- check jaw alignment and pad thickness
Scenario 2: Seal is strong at low speed, fails at high speed
Likely causes:
- insufficient dwell time
- heater response too slow
- pressure drop during fast cycling
Actions: - verify timing/encoder; inspect pneumatics; check heater wattage and response
Scenario 3: Seal looks good but leaks during filling
Likely causes:
- micro-channels from wrinkles/contamination
- insufficient cooling/solidification time
Actions: - inspect web path; improve cooling; check flatness entering seal
6) Preventive Maintenance Checklist (Shift / Weekly / Monthly)
Shift Checklist (10–15 minutes)
- Clean sealing area; remove film debris
- Check Teflon tape condition and adhesion
- Confirm air pressure within spec during operation
- Record temperature setpoints + actual readings
- Collect and label sample bags for quick peel test
Weekly Checklist
- Inspect seal pads for hardening/grooves; replace if uneven
- Check thermocouple mounting and cable wear
- Inspect pneumatic cylinders for leaks and smooth movement
- Verify roller bearings and alignment at critical web points
Monthly Checklist
- Calibrate temperature sensors (or cross-check with reference tool)
- Check SSR/relays and electrical terminals for heat damage
- Inspect mechanical linkage wear and jaw parallelism
- Audit reject reasons and correlate to downtime logs
7) How This Impacts “Garbage Bag Machine Price” and Real Cost
When buyers compare garbage bag machine price or garbage bag manufacturing machine price, the hidden cost is usually not the initial purchase—it’s:
- scrap material
- lost output (downtime)
- labor for constant tuning
- customer claims and returns
A slightly higher-spec garbage bag on roll making machine with stable heat control, better jaw design, and easier maintenance access often wins on total cost within months.