print defects in heatset
TRANSCRIPT
Print defects in heatset
Paper related
• print through• optical mottling
Paper surface related
• backtrap mottling, water mottling• scuffing (rub-off)• picking, hickeys
Drying related
• smearing, blistering• fluting, cockling• fibre roughening, cracking
Accumulation related
• carry-over piling, dusting• ghosting, vanishing dots
Scuffing with matt/silk grades
Printed signature goes through many operations that involve pressure and movement at the same time
Too low drying
• Inadequate drying
Too high drying
• Blistering• Fibre roughening• Cracking• Fluting
Drying problems
Runnability
Good runnability is usually connected to accumulations on blanket vs. washing interval
There is always something accumulating on blankets
• washing interval can be from 20 000 copies up to hundreds of thousands copies
Accumulation can be said to affect runnability if
• washing interval is reduced significantly• print quality detoriates• risk of blanket damage
Accumulation problems
Coating picking (Hickeys)
• usually not surface strength problem but connected to papermaking process
Carry-over piling
• printing ink printed in previous unit gets tackier in following units and starts to pick coating surface
Dusting / Linting
• accumulation of pigment / fibre particles on non-image area of the blanket
Ghosting / Vanishing dots
• the most current problem in heatset printing!• main mechanism still unsolved• a lot of studies in recent years
Coating picking
Carry-overpiling
Dusting
Hickeys
Vanishing dots and ghosting
ghosting vanishing dots