Troubleshooting Flexo Guide

 Defect Indicator Possible Cause Troubleshoot
Adhesion Poor tape test; Ink
flaking off; (poor crinkle);
Ink rubbing off
Insufficient treatment
level; Ink not drying
between traps; Substrate may be old or
contaminated; Wrong ink formulation for the job
Check and adjust
treatment level; Increase heat and air flow; Check surface substrate; Use correct ink formulation
Bleeding Discoloration of trapped
colors (White
particularly); Color
migrating in a dried ink film; Ink discoloring or wicking, not holding up to
the final application
(Chemical Resistance)
Ink not drying between traps; Poor pigment
selection; for the
application; Adhesives and/or Inks not fully dried or fully cured
Increase heat and
air flow; Use correct
ink formulation; Adjust lamps or reduce press speed to improve cure
Blocking Ink transferring
to the back side of web;
Not able to unroll
web-stuck together in the roll
Ink not drying
between traps; Dyne treatment level to high; Excessive web tension and/or
pH enhancer and/or re-wetting additives; Rewound at a high temperature
Increase heat and air flow; Check treated
surface, 38-40 dyne is sufficient; Reduce web
tension; Use fresh ink;
Use a chill roll if possible
Colors Too Strong / Dense Assuming a known color match: Color hits the stronger
Pantone color and/or appears generally darker
Anilox is in better shape than the one used in the
previous run? New Anilox? Ink to Anilox volume mismatch 
Change anilox to reduce BCM volume if possible and/or reduce pigment percentage in Ink by using
transparent white (aka Extending Varnish) On average, adding 10-20% extender will drop you 1 BCM anilox Volume (3BCM to 4 BCM) Meaning - You will require an addition 1 billion cubic micron of ink volume transferred to the substrate if you reduce the pigment load by 10-20% to achieve the desired color density. Assuming your ink is too dense for the Anilox you are using, reducing the pigment percentage should align your color to the proper volume. 
Colors Too Weak Assuming a known color match: Color hits the weaker
Pantone color and/or appears generally light
Dirty anilox. Old or worn aniloxes may not transfer the proper volume. lower anilox than previous run or wrong anilox for job. Weak ink Ensure a clean anilox. Change anilox to Increase BCM volume if possible and/or use fresh Ink. Increase Color strength by using High Strength Toners
Dot Gain Fill-in or
bridging/feathering
(Dirty Print)
Printed dot increasing in
size - bridging one letter
to another or letters filling
in basic dirty print
Excessive Ink Volume, Dot Dipping, Plate
Swelling; Low ink
viscosity v.s press speeds; Viscosity of the ink is heavy; Too much impression; Ink printing
dirty - not rewetting
properly
Maintain a 4 to 1
ratio anilox line count to screen count. 150 line screen - 600 line anilox; Adjust viscosity, use fresh ink; Reset
impression, Increase pH using pH enhancer 
Drying Too Fast Dirty Print - Fill in -
Bridging; Ink Drying on Plates; Poor transfer
Loss of pH Level; Air blowing on to the plates; Ink formulated for high speed printing Use a re-wetting pH enhancer to increase rewetting and retard drying; Readjust any unwanted air flow, ex: fan, blowers;
Use correct ink
formulation.
Drying Too Slow Picking; Blocking;
Offsetting; Ghosting
Over use of re-wetting pH enhancers.
Excessive ink film
thickness; Poor air
circulation - heat to low or clogged exhaust;
Ink formulation needs to be adjusted to higher speeds
Replace existing ink with fresh product; Reduce anilox volume if possible; Increase heat and air flow; Use correct ink formulation;
Reduce press speed
and maintain balanced air flow
Feathering Irregular string-like
edges around print
often on trailing
edges
Improper pressure
between ink transfer roll and plate; Ink drying on the plate or anilox;
Improper setting of ink roller nip; Improper ink rollers
Set proper pressure
between ink transfer
roll and plate
Foaming Excessive ink foam in fountain; Ghosting; Loss of image on the ends of channeled blade systems Ink viscosity too heavy; Old or reworked inks in fountain; High press speeds resulting in high shear; High agitation from ink pump  Adjust viscosity; Use a defoaming additive and/or
Reduce pump velocity or
agitation. Use Fresh Ink. 
Ghosting Excessive ink foam in fountain; Ghosting; Loss of image on the ends of channeled blade systems Ink viscosity too heavy; Old or reworked inks in fountain; High press speeds resulting in high shear; High agitation from ink pump  Adjust viscosity with ph enhacer and/or water. Use a defoaming additive Reduce pump velocity or
agitation
Ink Mottling Irregular appearance
in solid areas; Squiggly lines
Ink Viscosity to low; Poor treatment level of
substrate or
contaminated surface
Replace existing ink
with fresh product
and check film surface
Pin Holing Imperfections in the Print; Specs in Print -
Poor lay down
Ink viscosity to thin; Old or reworked inks in
fountain; Poor treatment of substrate or
contaminated surface
Adjust viscosity; Use a leveling additive; Check surface Dyne
level 38-40; Check for oil or contaminants on substrate (Foil). Use Fresh Inks. 
Poor Ink Transfer Insufficient ink
being applied
to stock
Ink reduced too much; Ink drying on plates;
Surface of stock not
receptive to ink
Rebuild tack with extender / transparent white; Leveling additive may help. Verify ink formulation with ink supplier.