Troubleshooting guide for lay-Flat Tubing PE Blown Films Applications
Lay-Flat Tubing PE Blown Films Troubleshooting
Problem
Probable Cause
Suggested Remedy
Temperature Setting
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.
Blocking
- High extrusion temperature which produces high film temperature and cause or slip additives to volatalise at the extrusion die
- High wind-up tension causing pressure on film roll (the higher the film temperature at wind-up, the greater this effect)
- High pressure on the film at nip rolls causing internal blocking
- Excessive corona treatment of the film
- Unfavourable environmental conditions during extrusion or storage can also cause blocking, (high room temperature warms the film while stacking rolls create high pressure), very low temperature on the other hand may cause film shrinkage, both cause film blocking
- Thin gauge films are more susceptible to blocking because of higher build-up of static charge, also thinner films run at higher take-off speeds and higher tension which increases tendency to blocking
- Film characteristics which effect blocking are: film smoothness and density, higher density films have harder surface and has less tendency to block
- Lower the film temperature by reducing the temperature, reducing cooling ring temperature, increasing distance between guide rolls & nip rolls, supplying cooling water to one of the nip rolls
- Reduce wind-up tension
- Reduce the pressure at nip rolls & winding contact pressure
- Check the level of treatment and adjust accordingly
- Adjust treatment level according to substrate printability requirements or use segmented treatment
Wrinkles
- The frost line is too high causing poor gauge control around circumference of the tube and uneven gauge in film
- Die ring out of adjustment causing gauge variation at nip rolls and thumps on the roll
- Film too cold when it reaches the nip rolls and therefore its stiffness may cause crimping at the nip and wrinkling
- The pressure across the face of the rolls may not be uniform either because the rolls are not parallel or slightly eccentric
- Guide rolls not properly aligned with the nip rolls
- Wobbling of the bubble due to air currents
- Winder shaft may be pulling the film at an uneven tension or too high a tension
- Adjust the frost line by: Extruder output, take-off speed, blowing more cooling air against the bubble
- Adjust the die opening
- Increase the film temperature at nip roll by slightly lowering height of the nip rolls or raising the melt temperature by increasing the screw speed and the nip rolls speed or extrusion rate
- Restore parallelism by fitting rear nip roll with small hydraulic cylinder to provide uniform pressure, recondition the rubber rollers
- Adjust guide rolls accordingly
- Support the tube with horizontal guide bars at 2 or 3 locations
- Use a spreader or a expander roll for removing such wrinkles
Poor transparency
- Low blow-up ratio.
- Poor homogenisation of material
- Low melt temperature
- Low Frost line
- Try a blow-up ratio between 2 and 3
- Select a screw of proper design, use a dense screen pack
- Increase the melt temperature
- Raise the frost line
Non-uniform gauge
- Width of the die opening incorrect
- Non-centring of the die
- Non-uniform flow of cooling air from the air ring around blown tube
- Uneven film cooling
- Oscillation H off not working
- Adjust the position of mandrel within the die accordingly
- Adjust the die ring by adjusting the bolts so that it is centred
- Adjust air ring opening
- Prevent air from reaching to die, avoided by enclosing space between die & air ring with aluminium or copper sheet
- Oscillate H off gauge uniformity in higher output plant
Improving mechanical & physical film properties
he most important factors that affect the physical properties of the film are:
- Frost line height
- Blow-up ratio
- Take up speed
- Extruder output
All these variables have to be balanced to produce film with good physical properties and uniform gauge at an economical speed
