“If at first you don’t succeed, keep on sucking till you do succeed” – Curly Howard. Thankfully, we don’t have to be a Stooge by not meeting customer expectations. We can clearly see that the failure to understand common flexographic print issues is costly. The good news: productivity, down press time and excessive waste can be minimized or avoided altogether with a bit of observation and corrective action.

I would like to take the next few pages to lay out many recognized defects and outline their possible causes, as well as point you in the direction of a proper response. While this is not an exhaustive list, I’ve tried to include as many routine issues as I can in a short amount of time. Just think of the following as a troubleshooting guide for common possible solutions spanning a wide range of printing and packaging problems. Let’s get right to it:

ProblemProblem CausesCorrective Action
Poor Ink Adhesion to substrateImproper ink formula / chemistryCheck with your ink supplier to make sure the correct ink is being used for each substrate
Ink thinned out too much, poor binding agentStabilize viscosity, add fresh ink or binding resin
(Ink fails tape test)Dyring issues, low temperature or air flowIncrease drying temp or air velocity
(Ink fails crinkle test)Low surface treatment on substrateCheck substrate surface and varnish being used
Ink fails scuff testSubstrate could be contaminatedCheck correct material being used with supplier, may need wash coat before print
Substrate may require treatmentPrimer may be needed
Binding, Gear Marks, ChatterWeb tensionAdjust web tension and check web control system, clean and lubricate rollers
(Dark lines across web and density variation)Gears bottoming outMake sure plate and mounting undercut matches gear, too much squeeze
Plate slurUse barrier bars outside print area
Ink viscosity too highCheck and maintain viscosity frequently
Stickyback and plate durometerMatch tape cushion and plate durometer with print application
Anilox and plate cylinder/sleeve TIRCheck concentricity of anilox and print carriers
Bleed
(Undercolor / trapping of color)
Colors drying too slow or too fastCheck viscosity and ink film thickness, use faster or slower solvents
BlockingTrapped solventAdjust drying condition, check solvent balance
Improper pH and viscosity levelsCheck and maintain viscosity/pH balance periodically
HaloToo much plate pressureCorrect pressure setting, Kiss impression
(Line around printed area, double-edged print)Cupped edges on plateMake new plates
Plate cylinder out of round, poor TIRInspect cylinder and possible wear of gears and bearings
Plate or tape durometer too highUse softer plates and tapes
Too much ink appliedCheck or lower anilox volume
Print cylinder and substrate at different speedsCheck and maintain proper web to cylinder speed
Out of RegisterPlate not mounted in registerCheck mounting and sleeve defects
Uneven pressure between CI and plate cylinderAdjust correct pressure
Drive gear damagedReplace gear
Idle rolls drag or rotate differentlyReplace or lubricate idle roll bearings
PickingFirst color too slow, second color too fastCheck drying conditions
(Ink transfers to subsquent plates)High viscosity of second colorIncrease press speed, lower viscosity of second color
Too much pressure of plate to substrateUse Kiss impression
PinholingAnilox wearConduct audit from anilox supplier, replace or re-engrave anilox
(Small holes in solids)Ink drying too fastAdjust solvents, add retarder
Wrong anilox selectionUse 60º anilox angle
Dirty central impression cylinderClean CI drum
Ink does not form homogenous uniform filmIncrease film thickness, check dilution rate of ink, check anilox pressure
Rough surface of substrateConsult substrate supplier
BridgingAnilox volume too high or line count too lowAdjust volume and anilox lpi
(Dots connecting to each other)Too much pressureAdjust pressure between print cylinder to anilox
(Adhesion between two surfaces)Excessive pressure in rewindReduce rewind tension
Web too warm during rewindLower drying tunnel or lower chill roll, check room temperatures
Web wound with moistureAvoid over chilling, room humidity
Dot GainPrint pressure too highLower print cylinder pressure, kiss impression
Improper stickybackCheck cushion density to match print application
Poor ink meteringUse chamber doctor blades and proper installation
Printing plate not correct size or swollenCheck plate thickness
Incorrect viscosity or anilox volumeMaintain proper viscosity settings, lower anilox volume
Dirty impression and/or plate cylinderTrapped air under plate, clean impression and plate cylinders
Ink Drying Too FastImproper use of solventsRefer to you ink supplier for proper balance
(Ink dries on plate or anilox, fails to transfer to substrate)Air movement near plate and aniloxEliminate air movement fans, windows/doors, dryers
Low pH (water based ink)Check pH level, optimum balance between 8.8 – 9.2
Dried ink on platesWash plates after setup, too much air movement
Pressroom temps too high or low humidityControl pressroom environment
Ink Drying Too SlowlyUse of slower drying solventsUse faster drying solvents
(Improper trapping, Ink is picking, tacky print surface, ink penetrating into paper)Excessive ink film thicknessCheck anilox volume
Viscosity too highMaintain proper viscosity balance
Excessive press speed not allowing for proper dryingAdjust press speed
FeatherImproper anilox and plate pressureDecrease pressure
(Irregular edges around print area)Dried ink on plate or anilox, ink buildup around dotsClean plates, apply proper anilox and plate pressure, cover ink pans/buckets
StaticUse anti-static devices
Surface tension not transferring ink correctlyCheck substrate dyne levels
Poor dotsCheck shoulder supporting the dot
Viscosity too high for screen printingMaintain proper viscosity levels
WringlingNon-uniform substrate thicknessReplace roll
(Wrinkles in substrate)Equipment not aligned properlyAdjust all rollers to proper set up and alignment

Of course, there are many variables in flexo printing and I can’t get into every possible issue here, but in my experience these are the most common problems and they often have very simple solutions. Just remember that when you invite trouble by overlooking maintenance and observation, it is usually quick to adapt, costing you time and money. Don’t wait when it’s so easy to get ahead of the ball before things fall apart!

One last note to leave you with: it’s worthwhile to bring technology and automation into the conversation here because they can assist in monitoring and sustaining your optimal press conditions in hugely impactful ways. For instance, GAMA systems are capable of controlling and automatically maintaining pH, viscosity and temperatures. Grafikontrol can assist in color monitoring, web viewing / print defection, registration and waste management. As a rule of thumb: when in question, it is always best to consult with your suppliers. After all, that’s what we’re here for.

Dan Dietrich
Bingham Flexo Services
Technical Sales
dan.dietrich@binghamflexoservices.com

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