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Troubleshooting in UV offset printing
Incidents
 
  1. Misting (ink splatter)

  2. Picking substrate

  3. Insufficient drying

  4. Poor ink transfer

  5. Poor adhesion to the substrate

  6. Polymerisation of the inks in their container
     
Probable causes and remedies
 

 1. Misting (ink splatter) (back to incidents)

 
Cause
Too much ink on the rollers.
Remedie
Reduce the inking.
Cause
Rollers incorrectly adjusted.
Remedie
Check the pressures (reduce if necessary).
Cause
Incorrect pH or imbalance in the fount solution.
Remedie
Check the fount solution and correct if necessary.
Cause
Temperature of inking rollers too high.
Remedie
Lower the temperature of the printing units or renew the ink
regularly.
Cause
Too much water in the ink.
Remedie
Reduce the amount of dampening if possible.
Cause
Unsuitable ink.
Remedie
Consult the supplier.
 
2. Picking substrate (back to incidents)
 
Cause
Ink too “sticky” or “tacky” for the substrate used.
Remedie
réduReduce the stickiness or tack of the ink (add UV Tack Reducing Paste or UV Thinner > See « UV Additives ».
Cause
Paper coating too fragile.
Remedie
Change the paper.
Cause
Unsuitable blanket lining.
Remedie
Adapt the linings as per the manufacturer’s recommendations.
Cause
Substrate temperature too low.
Remedie
Store the substrate at the same temperature as the print shop and follow the recommendations of the substrate manufacturer.
Cause
Unsuitable colour sequence.
Remedie
If possible, do not apply the densest colours on the first printing
units
 
3. Insufficient drying (back to incidents)
 
Cause
Too much water in the water / ink balance.
Remedie
Adjust the amount of fount solution.
Cause
Unsuitable ink.
Remedie
Consult the supplier.
Cause
Printing speed not adapted to the number and power rating of the UV lamps.
Remedie
Reduce the printing speed while maintaining the same output
from the lamps, or modify the drying installation in order to
increase the overall power output.
Cause
Unsuitable dryers sequence.
Remedie
Adapt the sequence to suit the print run.
Cause
High inking levels.
Remedie
Reduce the inking levels or adapt the colour.
Cause
The dryer requires maintenance.
Remedie
Check the condition and efficiency of the lamps, the number of
hours used and the reflector cleanliness.
Cause
Too much water in the ink.
Remedie
Reduce the dampening if possible.
Cause
Unsuitable ink.
Remedie
Add Photoinitiator to the ink in the recommended proportions.
> See « UV additives ».
 
Specific cases: Drying of black.
Remedie
Use iron doped lamps.
Use 2 printing units to prints blacks with OD above 2.00.
 
Specific cases: Drying of white.
Remedie
Use gallium doped lamps.
 
4. Poor ink transfer (back to incidents)
 
Cause
Dirty or badly cleaned rollers.
Remedie
Clean or deglaze the rollers.
Cause
Rollers incompatible with the ink.
Remedie
Check the rollers are compatible with UV inks.
Cause
Temperature of the ink too low.
Remedie
Store the ink at the temperature of the print shop (or use a mixer).
Cause
Viscosity of the ink unsuited to the press
Remedie
Add UV Thinner > See « UV additives » or consult the supplier.
 
5. Poor adhesion to the substrate (back to incidents)
 
Cause
Too much water in the water / ink balance.
Remedie
Adjust the amount of fount solution.
Cause
Incorrect surface treatment or surface treatment that is out of date.
Remedie
Check the surface tension of the substrate or consult the supplier to find out if the treatment is still valid.
Cause
Unsuitable ink.
Remedie
Consult the supplier.
 
6. Polymerisation of the inks in their containers (back to incidents)
 
Cause
Inks stored at a too high temperature or in sunlight with
the containers open.

Inks kept for longer than one year.
Remedie
Check the storage conditions of the UV inks and how stocks are
rotated.
 
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