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.