Category Archives: Gravure

Foaming

Agitation is excessive

Reduce pump agitation

Circulation of aqueous ink is inadequate

Slightly increase sump circulation

Antifoam level is too low in aqueous ink

Add defoamer and/or adjust ink formulation

Solvent ink or coating contains an additive that is prone to foaming

Remake ink or coating

Drying In

Ink viscosity too high

Reduce ink viscosity

Ink is drying too fast

Add slower drying solvents

Air drafts are blowing on the cylinder

Eliminate air drafts

Ink is short bodied

Add clear extending varnish

Doctor blade wipe is improper

Check and reset doctor blade setting

Print impression is excessive

Reset for lighter impression

Press speed is too fast

Decrease press speed or increase ink fiow to applicator

Ink resolubility is poor

Use active solvent or reformulate the ink

Drag Out

Ink is too thin

Increase ink viscosity

Doctor blade is wavy

Align doctor blade properly

Blade angle is too flat

Sharpen blade angle for a better wipe

Blade position is incorrect

Move back up blade closer to the doctor blade edge

Tension control is poor

Check and adjust tension

Ink is drying too slowly

Add faster drying solvents. For aqueous inks check and adjust pH

Foreign matter such as paper, substrate dust or pigment particles are present in the ink

Filter and/or replace ink. Eliminate source of foreign matter

Cylinder worn – wide walls

Scope cylinder – check chrome for wear, copper showing

Donuts

Ink is drying too fast

Add small amounts of slower drying solvents

Ink viscosity is too high

Reduce ink viscosity and adjust for better flow out

Foaming is occurring in the ink

Minimize ink freefall and avoid over agitation

Solvent balance is poor

Consult your local Sun representative

Film treatment is marginal

Check film for proper treatment

Porosity in substrate is too high

Use lower porosity substrate or try adding wetting agent to the ink

Cell volume is excessive for high hold out substrates

Reduce cell volume on high hold out substrates

Cell geometry is inappropriate

Adjust cell geometry

Ink may be too tacky

Make the ink harder using an alternate resin

Solvent (blend) is too Polar, picking up moisture

Add Ester or Aromatic Aliphatic Hydrocarbon

Comets

Pattern changes with oscillation

Check for foreign substance under the blade. Clean blade and filter the ink

Cylinder surface is nicked

Lightly polish or replace cylinder

Ink is too dry

Slightly slow down ink drying for “wetter” printing

Chrome is poor or has worn surface

Inspect cylinder against engravers proof and check for loose or flakey chrome areas

Bulleyes / Hickeys

Dust or dirt particles are on the substrate

Clean or change substrate

Particles are in the ink

Filter the ink

Voids are on the substrate

Check the substrate and replace if needed

Pits, corrosion or dirt are on the impression cylinder

Check and clean impression cylinder

Brittleness

Web heat is excessive

Decrease web temperature

Moisture is lost from the substrate

Introduce moisture by adding steam or add a small amount of plasticizer

The level of plasticizer in the ink is incorrect or plasticizer is lost through migration

Add plasticizer or change ink

Excessive non stick is occurring

Reduce non stick or add a small amount of plasticizer

Blocking / Offset

Ink is not drying properly

Add faster drying solvents & increase air flow

Solvents are trapped

Add faster drying solvents & increase air flow

Web is rewound too tight

Reduce chill roll temperature

Rewind pressure is excessive on web

Reduce web tension

Ink or varnish is over plasticized

Remake ink or varnish. Add anti block agent

Ink or top lacquer is soft or has a low melting point

Remake ink or lacquer

Web temperature is low

Increase web temperature

Moisture condensation appears on the chill roll

Reset chill rolls to above dew point eliminate moisture

Check to see if the film is treated on both sides

Try one-sided film

Blistering / Offset

Web temperature is excessive

Decrease web temperature

Solvent selection is poor

Change solvent blend

Cylinder is too deep

Re-etch or replace cylinder

Ink/lacquer is drying too slowly

Add faster drying solvent. For aqueous inks check and adjust pH

Oven balance is incorrect

Reset balance, adjust dampers

Ink Bleed

Drying is insufficient

Increase web temperature and check air velocity. Make sure that first down ink is dried properly

Ink is drying too slowly

Reduce first down ink viscosity and/or thin with a faster drying solvent. Increase the viscosity of the second down color and use a lean solvent blend that won’t attack the first down color

Ink is incorrect

Reformulate or replace the ink