Troubleshooting guide for Blown Film Applications
Blown Film Troubleshooting
Problem
Suggested Remedy
Temperature setting are crucial parameter for proper plastic processing ,hence one should check temperature controller, thermocouple and solid state relay(SSR)
- when you cold start the machine ,wait for 2hours.
Melt Fracture
• Widen die gap
• Increase melt temperature
• Increase temperature of last two extrusion zones
• Increase temperature of die lips
(do not go above 500 °F (260 °C) in systems with process aid)
• Insulate air ring from die & surroundings
• Add / increase process aid (be aware of regulatory limits)
• Use a higher melt index (MI) resin
• Use a higher melt flow ratio (MFR) resin
• Reduce output rate
• Add 5-10% LDPE
Bubble Instability
• Reduce melt temperature
• Use chilled air
• Use a lower MI resin (A higher MI resin may at times reduce melt
temperature sufficiently to improve bubble stability)
• Add 5-10% LDPE to linear PEs (preferably frac melt or autoclave)
• Lower output rate
• Narrow die gap
• Install / use stabilizing frame
• Check for even air flow to / through air ring
• Upgrade air ring (dual lip, collars)
• Check for outside air drafts (AC, doors, etc)
• Adjust blow-up ratio (BUR)
• Reduce die diameter
• Use properly designed extrusion screw
Excessive Amps or Melt Pressure
• Increase extruder temperature settings; check zone heater operation
• Widen die gap
• Use coarser screen pack
• Use larger diameter die
• Use a higher MI resin
• Lower output rate
• Regear motor for higher power at lower screw RPM
Excessively High Melt Temperature
• Use a higher MI resin
• Check extruder cooling systems
• Lower RPM
• Widen die gap
• Check extruder output vs. screw RPM
• Use properly designed extrusion screw
Surging or Variable Output
• Check for uneven feeding due to hopper bridging or blockage
• Check for uneven feeding of reclaim
• Check for pellet cut uniformity
• Check for mix uniformity of resin(s) and masterbatch(es)
• Check extrusion temperature profile
• Adjust temperature of 1st zone; add cooling water
to 1st zone or extruder throat
Thickness Variation
• Clean air ring
• Check air ring alignment
• Clean die / die gap
• Check die gap alignment
• Check for even air flow to / through air ring
• Check alignment of tower, nip rolls (vis-à-vis die)
• Lower frost line and keep it level
• Use IR gauge to check melt temperature uniformity around bubble
• Use oscillation to minimize appearance of problem
(although this doesn’t solve the problem)
Inadequate Drawdown
• Increase melt temperature
• Increase frost line height
• Narrow die gap
• Check for gels, contamination in film
• Use a higher MI resin
• Add 10-20% LLDPE to LDPE film
Poor Optical Properties
• Use refrigerated (or cooler) air
• Increase melt temperature
• Reduce antiblock usage or change type to silica
• Add 5-10% LDPE to linear PEs
Gels – Unmelts
• Adjust extrusion temperatures
• Check for resin contamination by different polymer
• Check for extruder cold spots
• Replace screen pack
• Change to a finer screen pack
Gels – Resin Degradation
• Check for hot melt temperature or extruder hot spots
• Remove / reduce reclaim
• Increase AO in resin
• Clean die and/or screw of buildup
• Change production rate (may need to go faster
or slower based on exact conditions)
