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. |