FLEXOGRAPHIC INKS - Flex Pre-Press

1 TROUBLESHOOTING GUIDEFLEXOGRAPHIC INKSSC6-0204 12/9/02 5:31 PM Page 1 Even under the best circumstances, there will be timeswhen things go wrong on a FLEXOGRAPHIC press. Andwhen you encounter such problems in your printingprocess, we encourage you to refer to the material pre-sented in this troubleshooting guide. You will be able tofind an easy solution to most any problem right here inthese pages. But if there is an unusual situation that wehaven t covered in this guide, then we are still here tohelp. Take advantage of our experience and the largestcommitment to research and development in the printingink and coating industry. We are your source for compre-hensive ink 12/9/02 5:31 PM Page 2 TABLE OF CONTENTSF lexographic Troubleshooting printing /dot bridging ..5 Dirty printing /feathering ..6 Dirty printing /halos.

2 7 Donuts in tone screens ..8 Fill-in ..9 Ink smearing/bleed ..10 Mottle .. ink trap ..13 Weak color OF CONTENTSSC6-0204 12/9/02 5:31 PM Page 3 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSADHESION Ink and/or top lacquer do not bind to each other or to substrate. Ink lifts off with 3M brand#610 Scotch 12/9/02 5:31 PM Page 433 PROBLEM1. Surface is not ink or lacquer Ink is not drying Ink is brittle due to insufficient amount of Ink choice is improper for Ink viscosity is too Web temperature is toolow for substrate and Treat substrate if treatable, but do not over-treat; changeto recommended ink type;and/or use coating primer if Add faster drying solventsand/or increase air and heatdelivery. Thin inks if Add small amount of Reformulate ink for Reduce ink viscosity to proper Increase web temperature toadequate level for substrateand 12/9/02 5:31 PM Page 5 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSBLOCKING/OFFSET Undesired adhesion between surfaces.

3 Ink is sticking to reverse side of print when rewound or 12/9/02 5:31 PM Page 644 PROBLEM1. Ink is not drying Solvents are Web is rewound too Rewind pressure on webis Ink or varnish are Ink or top lacquer is soft or has a low melting Web temperature is too Moisture condensationappears on chill Add faster drying solventsand/or increase air Add faster drying solventsand/or increase air check for ink Reduce chill roll Reduce web Remake ink or varnish. Add anti-block Remake ink or Increase web Check and reset chill roll temperature above dew 12/9/02 5:31 PM Page 7 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSDIRTY printing /DOT BRIDGING Appearance of adirty, grainy effect as a result of two or more process dotslinking together. The gaps between dots are bridged byink. Fly-specks also appear in the process 12/9/02 5:31 PM Page 855 PROBLEM1.

4 Anilox volume is too deep for dot size and anexcessive amount of ink is metering to the Ink is flooding plate dotsdue to loose ink meteringor worn doctor Stray air is blowing onplate or Plate impression or platerelief is Ink is drying too Reduce anilox volume orincrease plate dot Check and adjust ink metering; check and replacedoctor blade if Block stray air; balance dryersto eliminate blow-down Reset plate high spots if bridging is Add slower drying 12/9/02 5:31 PM Page 9 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSDIRTY printing /FEATHERING Ink is drying onplates and/or anilox rolls, is printing screen patterns,and/or is drying along plate edges and type edges resulting in a ragged, feathery 12/9/02 5:31 PM Page 1066 PROBLEM1. Impression between plateand substrate is Water-based ink pH is too Ink is flooding due to highanilox Ink is drying too Air hitting plates or aniloxroll is Ink viscosity is too Dust or lint is picked upfrom Reset plate pressure to kiss Increase water-based ink Reduce anilox Check ink formulation; addslower drying Block stray air; balance dryersto eliminate blow-down on Reduce ink Check to be sure ink filters are working; filter ink; change substrates or use web 12/9/02 5:31 PM Page 11 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSDIRTY printing /HALOS An undesirable outlineappears around the printed image or 12/9/02 5:31 PM Page 1277 PROBLEM1.

5 Pressure between plateand substrate is Plate or stickyback tape is too Edges are cupped on Plate cylinder is out ofround causing Reset plate pressure to kiss Use plate with softer durometer; switch to a cushion stickyback Check plate and replace Check run-out of plate cylinder and anilox roll;replace plate and/or anilox 12/9/02 5:31 PM Page 13 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSDONUTS IN TONE SCREENS Appearance of dots that only print on the circumference of the cells with a void in the center. Due to slur, dots may also appearelongated or oval-shaped with center 12/9/02 5:31 PM Page 1488 SOLUTION1. Reset plate pressure to kiss Avoid hard tapes; switch to acushion stickyback Add slower drying solvents to reduce tack. Tacky inks will usually show stringingfrom Check viscosity and inkmetering; adjust for optimum amount of ink on Use plate with softer Print impression is Stickyback tape is Ink is drying too fast and is too Ink film is too thin and isnot hitting dots Plates are hard and 12/9/02 5:31 PM Page 15 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSFILL-IN Printed type and designs are very such as A s , O s , and P s are filled-in andpoorly defined.

6 Overall appearance is 12/9/02 5:31 PM Page 1699 SOLUTION1. Reset plate pressure to kiss Increase water-based ink Add slower drying solvents toreduce tack. Tacky inks willusually show stringing fromtype Check plates and replace Reduce ink Adjust plate relief to correctheight Filter or replace ink; eliminatesource of Print impression is Water-based ink pH is too Ink is drying too Plates are worn, uneven,cupped or poorly Ink viscosity is too Plate relief height is Foreign matter appears in 12/9/02 5:31 PM Page 17 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSINK SMEARING/BLEED Appearance of ink transfer orbleed of one color into another. Single color smears 12/9/02 5:31 PM Page 181010 PROBLEM1. First down ink is not fully Second down ink, top lacquer or adhesive is toorich causing first down ink to Foreign object is draggingon wet Increase drying speed of ink by:a) Reducing ink ) Reducing ink thickness by changing metering ) Adding faster drying ) Adjusting air balance and Check second downmaterial and reformulate fornon-aggressive your Sun Chemicalrepresentative for a moreresistant first down Trace web and remove dragging 12/9/02 5:31 PM Page 19 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSMOTTLE An uneven appearance usually in areas ofheavy ink coverage characterized by small light and darkinconsistencies in the ink film.

7 Print is not smooth 12/9/02 5:31 PM Page 201111 PROBLEM1. Substrate is poor or marginally Surface of substrate Surface tension of ink is not low enough to properlyflow out on substrate. (Seenmostly in aqueous inks .)4. Impression between plateand substrate is too Stickyback tape is too Ink viscosity is too Check and adjust treatmentlevel or change Check substrate and reduceink viscosity for better wetting. Consult your substrate Reduce surface tension of inksby adding wetting Increase plate impression andcheck print Use hard tape for solid printareas when Increase ink 12/9/02 5:31 PM Page 21 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSFLEXOGRAPHIC INKSFLEXOGRAPHIC INKSPINHOLING Appearance of small holes or voids in theprint area; usually more visible in solid print areas. Inkfails to form a smooth, continuous 12/9/02 5:31 PM Page 221212 PROBLEM1.

8 Substrate is poor ormarginally Surface of substrate Surface tension of ink is not low enough to properlyflow out on substrate. (Seenmostly in aqueous inks .)4. Impression between plateand substrate is too Stickyback tape is too Ink is drying too Dried ink, dirt or rust is onimpression Use of defoamer in waterinks is Check and adjust treatmentlevel or change Check substrate and reduceink viscosity for better wetting. Consult your substrate Reduce surface tension of inksby adding wetting Increase plate impression andcheck print Use hard tape for solid printareas when Add slower drying Check and Add fresh ink or check formula and reformulate 12/9/02 5:31 PM Page 23 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSPOOR INK TRAP Print appearance of second downcolor over first down color is poor. Print mottles over firstdown ink.

9 Ink coverage is not smooth in trap 12/9/02 5:31 PM Page 241313 PROBLEM1. First down color is notfully Second down ink is dryingtoo fast and not Wax or slip-aid in firstdown ink is Second down ink is notcompatible with first down Increase drying speed of firstdown ink by:a) Reducing ink ) Reducing ink film thickness by using shallower anilox ) Adding faster drying ) Increasing dryer temperature and air velocity in Check and eliminate air blowing on plates; add slower drying Check formula and remake ink if Consult your Sun Chemical representative for proper ink 12/9/02 5:31 PM Page 25 FLEXOGRAPHIC INKSFLEXOGRAPHIC INKSWEAK COLOR PRINT Print fails to meet desired colorstrength or 12/9/02 5:31 PM Page 261414 SOLUTION1. Increase ink Increase anilox to proper Use harder tape for line work to achieve good ink Check formula and add fresh Check raw ink formula for proper strength; check to see if ink is re-work and has proper Check substrate surface; checkfor proper film Eliminate any excess air blowing on plates and anilox;add slower drying Make sure ink is properlymixed, with no settling onbottom or signs of ink Ink viscosity is too Anilox volume is too Stickyback tape is too Ink is Ink formulation is Substrate is not receptiveto Ink is drying on plates Ink is kicking-out or 12/9/02 5:31 PM Page 27 The information contained in this document is general in nature only, and is pro-vided without representation or warranty of any kind.

10 Sun Chemical s products areprovided subject to standard terms and conditions. Sun Chemical recommendsconsultation with its technical experts and trials before general use of any this troubleshooting guide on-line at 12/9/02 5:31 PM Page 28