UV Flexo Inks

CHECK, IN THIS ORDER

• Read the console and count the lamps that are actually lit, and compare line speed with the commissioned figure, before fetching an instrument.
• Pass a band-matched radiometer through the press at running speed and read dose and peak irradiance separately on the heaviest solid. At mercury stations use a four-band head and read UV-C as well as UV-A: a lamp that has lost short-wave shows as a falling UV-C to UV-A ratio against the commissioning trace while the UV-A figure still looks acceptable. At LED stations a UV-A head is the correct instrument.
• MEK double rubs following the practice of ASTM D5402, using the house method recorded with the result: cloth type, a 1 kg load, the solvent, and one forward-and-back stroke counted as one double rub. Look for at least 30 with no breakthrough on the solid at the delivery. Gloves, eye protection and a ventilated bench.
• With the press isolated and the lamps cooled, inspect quartz sleeves and reflectors for milkiness and film, and log lamp hours against the 1000 to 1500 h rating.
• Measure lamp to substrate distance and compare it to the commissioning figure.

THEN CHANGE

• Relight or reset the station to the job power, and return the line speed to the commissioned figure, before anything is changed on the ink.
• With the press isolated and the lamps cold, clean quartz sleeves and reflectors, then remeasure. A filmed reflector loses more output than a tired bulb.
• Restore peak irradiance next: close the lamp to substrate distance to commissioning, refocus or replace the reflector.
• Replace the lamp when measured dose at the commissioning setting has fallen 25 to 30 %.
• Correct the airflow pattern rather than the airflow volume: fit or repair the shrouding and air knives so the extraction draws from above the lamp housing and not across the web at the cure zone. Never reduce mercury lamp extraction to chase surface tack, because it is the ozone control and the lamp cooling.

CHECK, IN THIS ORDER

• Wetting tension test inks to ASTM D2578 on the reel you are about to run, read at two seconds, at both edges and the centre, and again after in-line treatment.
• Cross-cut to ISO 2409 with a tape pull, 24 h after cure at 23 C and 50 % RH. Use 2 mm cut spacing on flexible film, not 1 mm: ISO 2409 reserves 1 mm for thin coatings on hard substrates, and on film the finer lattice digs into the substrate and the classification stops meaning anything. Name the tape and its adhesion value on the report.
• MEK double rubs following ASTM D5402 on the same sample, to separate an adhesion fault from an under-cure fault.
• Check the reel certificate and the resin grade for recycled content in the printed face.
• Calculate corona watt density, treater watts divided by web width times line speed, and compare it with the setting sheet at the speed the job runs.

THEN CHANGE

• Raise in-line corona to hold 40 to 44 mN/m at the running speed, and re-measure at speed rather than on a stopped web.
• Bring the cure up to the grade minimum before changing anything else about the ink.
• Reject reels that will not treat, and specify virgin-grade film for printed faces.
• On difficult laminates and tube web, pre-test on the customer's own material before production and prove it on a full construction.
• Where the construction allows it, add the matched UniCure overprint varnish, which puts a continuous, more resistant layer over the print.

CHECK, IN THIS ORDER

• Look at the running band with a 100x hand microscope; compare a plugged area with the unused edge of the same roll.
• Read ink temperature at the chamber at running speed, not at standstill.
• Check the blade for a wire edge and the chamber seals for hardening, with the press isolated and gloves on.
• Compare density with a spectrodensitometer against the approved print at the same points, every reel, with the measurement conditions fixed and recorded: density status to ISO 5-3, status E for European work or status T where the customer specifies it, 45/0 geometry to ISO 5-4, polarising filter stated on or off, and the same white backing every time. Read tone value increase from the same strip to ISO 12647-6.
• Pull the anilox and have the volume audited if the roll has no recent certificate.

THEN CHANGE

• Deep-clean the anilox off press, ultrasonically or by an approved chemical or bicarbonate process, and re-audit the volume.
• Return blade load to the lightest clean wipe and reset impression to a kiss.
• Hold chamber temperature in the 18 to 28 C band, with cooling on the ink circulation if the press-room runs hot.
• Clean the anilox every time the ink comes off it: at every job change and every wash-up, not only when the roll is swapped out. Log each clean against the roll, and send the roll for deep clean and volume audit on a fixed interval rather than waiting for a density complaint.
• If audited volume has fallen, move the job to a roll with the specified volume rather than pressing harder.

CHECK, IN THIS ORDER

• Track the blade a few millimetres laterally with the press running, where the chamber allows it. If the line moves with the blade it is a blade fault; if it stays it is the roll. This settles the question in seconds and before anything is dismantled.
• With the press isolated and wearing cut-resistant gloves, remove the blade and inspect the edge against a light, drawing a cotton bud across the edge. Never run a finger or a fingernail along a used blade: the wire edge is effectively a razor. Used blades go into a sharps container.
• Strain the returning ink through a fine mesh and look at what the mesh catches.
• Check blade load against the chamber gauge or load scale, and the blade angle against the manufacturer's geometry.
• Inspect the end seals for hardening and compression set, and look at the anilox under 100x with the roll off press; a score will be visible as a bright line.

THEN CHANGE

• Fit a new blade, set it to the manufacturer's angle and the lightest load that wipes clean.
• Flush the chamber and filter the ink return; fit or renew an in-line filter if there is not one.
• Renew the end seals as a pair, not one side.
• If the anilox is scored, change the roll. A score does not polish out with load.
• Where the same line returns on every job, have the roll audited rather than changing blades repeatedly.

CHECK, IN THIS ORDER

• Take an impression print and back off to the first point where the solid is complete, then look at the shadows.
• Check the anilox ruling against the plate screen ruling: the roll should be at least 5 to 6 times the screen ruling, so a 150 lpi screen needs 800 lpi or finer and a 175 lpi screen needs 1000 lpi or finer. Below about 4 to 1 the dot picks up ink from several cells and prints larger than it is.
• Read the chamber ink temperature and the viscosity at 25 C on the same spindle and speed each time.
• Measure plate relief and check the plate for swelling against a new one from the same set. Dry a suspect plate off press and re-measure the relief before condemning it.
• Print and read a control strip, comparing tone value increase to the approved profile at the recorded measurement conditions.

THEN CHANGE

• Reset impression to a kiss on every deck, starting from zero contact.
• Move to a finer, lower-volume anilox for the halftone decks. UniCure IML is formulated to release from very fine cells, typically 1200 to 1500 lpi at 0.8 to 1.2 BCM, which is where fine work belongs.
• Bring chamber temperature back into the 18 to 28 C band.
• Replate with the correct relief and screen for the job, and change the plate wash to one approved for the plate material.
• Compensate the file to the measured press curve only after the mechanical causes are cleared.

CHECK, IN THIS ORDER

• Test inks to ASTM D2578 across the web, looking for a low band rather than a low average.
• Wipe a suspect area with isopropanol on a lint-free cloth, gloves on and away from ignition sources, and reprint that strip; a defect that disappears is contamination.
• Look into the chamber at running speed for foam on the ink surface.
• Check the treater against the film and speed by calculating watt density, treater watts divided by web width times line speed, and comparing it with the setting sheet. Confirm overtreatment by testing the unprinted back of the web with test inks, because backside treatment is the reliable marker. Do not use smell: if ozone can be smelled at the treater the extraction has failed, which is a stop-and-repair condition, not a measurement.
• Inspect idler rollers and the web path for silicone transfer from liner or lubricant.

THEN CHANGE

• Bring in-line treatment to 40 to 44 mN/m and no higher.
• Ban silicone sprays from the press-room and clean the web path and idlers with isopropanol.
• Reduce pump speed, keep the chamber return below the ink surface so it does not whip air in, and let the ink stand to de-aerate.
• Strain the ink and flush the chamber and lines after a wash-up, then prime with fresh ink.
• Reject a reel that shows contamination across its width rather than trying to print through it.

CHECK, IN THIS ORDER

• Confirm the anilox ruling and its own volume as a pair: UniCure NX FD Opaque White at 120 l/cm and 10 to 12 cm3/m2, or at 180 l/cm and 7 to 9 cm3/m2. A fine ruling quoted against a coarse roll's volume cannot be engraved, so a roll ordered that way arrives as a compromise and the white is blamed for it.
• Weigh the applied white by differential weighing of printed against unprinted web.
• Radiometer pass at running speed, UV-A band, read on the white itself rather than on a process solid.
• Cross-cut and MEK rub the white alone before any colour goes over it.
• Measure opacity on a light box against the approved sample, or with a contrast-ratio reading over black and white backing.

THEN CHANGE

• Move to the specified white ruling and its matching volume before changing anything in the ink.
• Raise the dose on the white deck towards 150 to 250 mJ/cm2 UV-A and check peak irradiance as well as dose.
• Change to a gallium-doped mercury lamp, or run the white station at 395 or 405 nm, to get light past the titanium dioxide absorption edge.
• Print two hits of white with a cure between them rather than one heavy hit. This is also the answer where the opacity target would otherwise need a fine ruling and a coarse roll's volume at the same time.
• Confirm the grade is the first-down opaque white, NXW-1000, and not a transparent or tint white.

CHECK, IN THIS ORDER

• Walk the ink path with the press stopped and room lights on, looking for gaps in guards and reflected light.
• Feel and measure the pump body, hoses and chamber temperature at the end of a run.
• Check whether any part of the circulation is sealed or run full with no air contact, and whether any container has been decanted and sealed to the brim or blanketed with nitrogen.
• Check the batch number and date against the 6-month shelf life on the 5 kg pack, and check whether the pump, hose or chamber has been used for another chemistry.
• Check the store: 15 to 25 C, closed original containers, out of direct light.

THEN CHANGE

• Shield the ink line completely; guard lamps and fit opaque hose and covers.
• Empty and clean the chamber, pump and lines at the end of the shift; do not leave ink standing in a warm press or in a dead leg of the circulation.
• Leave an air headspace in stored and part-used containers, and do not blanket UV ink with nitrogen or run it in a sealed airless loop. Keep the chamber return below the ink surface so it does not whip air in: the ink needs air contact, not agitation, and a chamber that foams gives pinholes, blade skip and lost density.
• Dedicate pumps and hoses to UV, and never share with a two-pack or peroxide-cured product.
• Scrap gelled ink. It is irreversible, and thinning or straining it will not recover it. Treat a warm or gelling container as an exothermic reaction in progress: do not seal it, move it to a designated safe area away from heat and combustibles, keep it under observation until it is cold, and dispose of it as hazardous waste to the safety data sheet. Never return suspect ink to a bulk drum.

CHECK, IN THIS ORDER

• Cross-cut to ISO 2409 with a tape pull on the coated sample after 24 h at 23 C and 50 % RH, at the cut spacing the standard gives for the substrate, and with the tape named on the report.
• Measure interstation dose on the deck below; over-cure here is as real a fault as under-cure.
• Confirm the OPV grade against the end use from the matched coating list, and confirm the code on the drum label.
• Check the elapsed time and storage between the print pass and the coating pass.
• Test wetting of the OPV on the printed solid with test inks or by a simple draw-down.

THEN CHANGE

• Reduce the interstation dose on the deck below to pin rather than cure out, typically 20 to 50 mJ/cm2 UV-A, which sets the film but leaves residual surface unsaturation, and give the full dose after the varnish.
• Do not apply that pinning fix on UniCure FP low-migration work. On low-migration constructions every layer is cured to the grade minimum, because residual monomer and photoinitiator fragments are the migration and odour route, and keying is solved instead with the matched low-migration coating, in-line coating and inter-deck corona.
• Move to the correct matched UniCure OPV for the end use rather than the general-purpose gloss.
• Coat in line where the press allows it, and within the same shift where it does not.
• Where slip is being carried by the ink, move the slip into the OPV, for example HSC 81RC where labels must slide through downstream handling.

CHECK, IN THIS ORDER

• Thumb twist and MEK double rubs following ASTM D5402 at the delivery on the last colour down.
• Measure web temperature at the rewind with an infra-red thermometer, and again after the last lamp.
• Check rewind tension and taper against the setting sheet.
• Check chill roller water temperature and flow.
• Measure static and dynamic coefficient of friction to ASTM D1894 on the finished face against the reel backing.

THEN CHANGE

• Fix the cure first: raise peak irradiance and clean the optics, and confirm 30 or more MEK double rubs.
• Fit or repair chill rollers, and fit dichroic cold-mirror reflectors where the substrate is heat-sensitive.
• Reduce rewind tension and set a taper so the core is not the tightest part of the reel.
• Apply the matched UniCure OPV, for example SRC 89RC where the highest scratch and scuff resistance is needed or HSC 81RC where a very low coefficient of friction is wanted.
• Let reels cool to ambient before stacking or shipping, and do not stack a warm reel on its side.

CHECK, IN THIS ORDER

• Confirm the ink grade is an LED-cure grade before anything else.
• Radiometer pass with a UV-A band head at the LED station, at running speed, on the heaviest solid.
• Measure the working distance from emitting window to web and compare it with the array manufacturer's figure.
• With the press isolated and locked off and the array switched off, cooled and confirmed dark, clean the emitting window with the cloth and solvent the array manufacturer specifies, because many quartz and coated windows are damaged by ketones. Remeasure and record before and after. Never clean or inspect a window on a live array, and never judge from the absence of visible light whether an array is emitting.
• MEK double rubs following ASTM D5402 on the heaviest solid at the delivery.

THEN CHANGE

• Change to UniCure LED 395 for LED decks. It is formulated for 395 nm LED cure and also cures under mercury, so it suits a hybrid press-room, and a 365 nm version is available on request. Speeds of up to approximately 150 m/min have been reached on process colours at 1.2 to 2.0 g/m2 under a single 16 W/cm2 395 nm array at the specified working distance; opaque white, dense black and heavier lays need more. That is a formulation capability, not a guaranteed line speed, and the achievable speed is established on the customer's press and substrate.
• Fit the correct UV-A band head and recalibrate the radiometer to that band.
• Set the working distance to the array specification and hold it with the guard fitted.
• Clean the emitting window on a shift schedule, with the station isolated and cold.
• Move opaque white to the 395 or 405 nm emitters rather than to a shorter wavelength.

CHECK, IN THIS ORDER

• Radiometer pass on the heaviest solid and compare with the 150 to 250 mJ/cm2 UV-A band that low-migration sets normally need.
• MEK double rubs following ASTM D5402 on every colour, not just the one that looks worst.
• Check the interstation settings deck by deck and confirm every layer is cured out, not pinned.
• Audit the full construction: every ink, primer, varnish and adhesive, by grade code.
• Run a sensory check to DIN 10955, the closed-jar Robinson test, on printed and converted material against unprinted substrate as the reference, with a trained panel, the storage time and temperature stated, and the result reported on the 0 to 4 scale. Where the brand owner has their own sensory method, run theirs and report against their acceptance. Check wash-up practice and what solvent was last through the chamber.

THEN CHANGE

• Bring the dose up to the grade minimum and raise peak irradiance; confirm with a radiometer pass, not a console figure.
• Reduce film weight to the minimum that gives the required density, and split heavy lays into two cured hits.
• Cure every deck out on low-migration work and solve keying with the matched low-migration coating, in-line coating and inter-deck corona instead of pinning.
• Use the matched low-migration coatings, LMC 83RC gloss or LMM 72RC matt, over UniCure FP, not a general-purpose varnish.
• Keep the food-contact face free of print and keep set-off out of the reel with correct tension and a cool rewind, and change wash-up solvent and drying practice so nothing is left in the chamber or on the rollers.

CHECK, IN THIS ORDER

• Compare a seam-area sample with a sample 50 mm away from the seam. A defect that stops a few millimetres from the seam is the seaming solvent, not the cure and not the film weight.
• Radiometer pass and MEK rubs; look for over-cure as carefully as for under-cure on this class.
• Weigh the film in the high-draw area and compare with the low-draw area.
• Confirm the ink grade and the film type against the specification, and check whether PP is in the construction.
• Map the tunnel with a travelling thermocouple or a profiling logger through a full pass, and test inks to ASTM D2578 on the in-line-treated printed face.

THEN CHANGE

• Reduce dose to the grade minimum rather than the press maximum, and verify by MEK rubs, not by appearance.
• Cut the seaming solvent volume and the application width, and check the dwell on the seaming machine, where the defect is seam-located.
• Reduce film weight in the high-draw zone by moving to a lower-volume anilox on those decks.
• Confirm UniCure Shrink is on all decks including the white; opaque white is available in standard and LD high-slip versions for reverse-printed sleeves.
• Soften the entry of the tunnel profile so the film starts to relax before the print is fully heated, and bring in-line corona on the printed face to 40 to 44 mN/m.

CHECK, IN THIS ORDER

• Check the moulding line first: magazine setting and spring load, vacuum cup condition and vacuum level, die-cut edge quality and burr.
• Measure static with a field meter at the die-cut, at the stacker and in the magazine, and record press-room humidity.
• Measure static and dynamic coefficient of friction to ASTM D1894 on both faces of the finished label.
• Check the anilox against the specification and lay ten labels on a flat surface to measure the lift at the corners as a curl check; then check the film grade, the store conditions and how the cut labels were stacked.
• MEK double rubs following ASTM D5402 and a short injection trial on the customer's tool.

THEN CHANGE

• Correct the moulding line causes first: magazine, vacuum, die-cut edge, static bars at the die-cut and stacker, and press-room humidity.
• Apply ASC 88RC anti-static, benzophenone-free overprint varnish where static at the magazine is the limiting factor on pick.
• Reduce ink film weight to the specification as good practice, but look first at the film grade, the press-room and store humidity and the stacking and conditioning of the cut labels for curl.
• Bring the cure to the grade minimum so the film has the cohesive strength to resist injection washout.
• Condition cut labels flat, under light weight, before they go to the magazine.

CHECK, IN THIS ORDER

• Confirm anilox rulings against their own volumes: process 800 to 1200 lpi at 1.1 to 2.2 BCM, spot 360 to 800 lpi, white 280 to 600 lpi.
• MEK rubs following ASTM D5402 and a mandrel or fold test on the printed flat web.
• Check which overprint varnish is on the job, by code on the drum label, and against what specification.
• Form and seam a short trial length on the customer's own laminate and head setting.
• Fill a small number of tubes with the actual product and hold them at 40 C for four weeks, then squeeze and inspect.

THEN CHANGE

• Confirm UniCure Tube grades throughout, which are pumpable at 800 to 2000 mPa.s and above on peristaltic pumps.
• Apply UniCure 5500PE OPV or the TLC lamitube grade as the matched coating; the coating is not optional on this work.
• Reduce film weight in the seam area by moving to a lower-volume anilox on the decks that print there.
• Bring the cure to the grade minimum and no higher, and verify by rubs rather than by hardness.
• Pre-test every laminate with the customer before production.

CHECK, IN THIS ORDER

• Measure the band spacing on the print and compare it with plate and anilox circumference to identify which cylinder is responsible.
• Back the impression off to a kiss on that deck alone and rerun the section.
• Check the tape specification against the job; record what is fitted.
• With the press isolated, rock the cylinder by hand and feel for backlash.
• Run the same plate at three speeds and record whether the banding moves or disappears.

THEN CHANGE

• Reset impression to a kiss on every deck, starting from zero contact.
• Change to a harder mounting tape under heavy solids and a softer one under fine halftone.
• Separate solids and fine halftones onto different plates or different decks where the job allows it.
• Raise web tension into the nip to the press setting sheet.
• Report backlash for mechanical attention rather than trying to print around it.

CHECK, IN THIS ORDER

• Read register off the printed register marks with a linen tester or the press camera at three reel diameters, and record web tension and web temperature at the same three points.
• Run the press at two speeds and record whether the drift follows speed, which points at impression and tension, or follows time, which points at temperature.
• Check every plate and sleeve for lift, bubbles and seating with the press isolated, and check the tape specification against the job.
• Spin every idler and chill roller by hand with the press isolated and feel for drag or a flat spot.
• Back each suspect deck to a kiss impression on its own and rerun the section.

THEN CHANGE

• Set tension and taper to the setting sheet for the substrate and hold it, rather than correcting register against a tension that is still moving.
• Bring web temperature down with the chill rollers and cold-mirror reflectors before chasing register on thin PE and shrink film; register and web temperature are the same fault on these substrates.
• Remount plates that show lift or bubbles, and seat sleeves fully before blaming the press.
• Free or replace dragging rollers, and report bearing drag for mechanical attention.
• Reset impression to a kiss on every deck, starting from zero contact.

CHECK, IN THIS ORDER

• Fix and record the measurement conditions before arguing about colour: density status to ISO 5-3, 45/0 geometry to ISO 5-4, polarising filter stated, same white backing, and tone value increase from the same strip to ISO 12647-6. Report colour difference in CIEDE2000 and state the illuminant and observer.
• Read the same patch on the approved print and on the reel with the same instrument at the same conditions, rather than comparing two instruments.
• Check anilox cell condition at 100x and audited volume, and weigh the applied film against the approved run.
• Measure the substrate: white point, opacity and gloss against the reel that was used for the approval, and check whether the white under a clear film has changed.
• View the print and the proof under the customer's specified illuminant as well as under press-room light, and record whether the pair separates.

THEN CHANGE

• Bring the measurement conditions into line first, and re-judge before touching anything on the press.
• Restore anilox volume and film weight to the approved run by cleaning or changing the roll, not by impression or by temperature.
• Match on the customer's own substrate and construction, including the white and the overprint varnish, rather than on a press-room stock.
• Where a pair is metameric, take it back to the colour build rather than to the press, and agree the illuminant with the customer in writing.
• Question the ink batch last, and when you do, send the batch number, the retained sample and the drawdown conditions with the complaint.

CHECK, IN THIS ORDER

• Print the same plate and ink on a filmic stock. If it runs clean, the fault is the paper surface, not the ink or the deck.
• Look at the plate and the chamber after 500 m for fibre and dust build, and strain the returning ink through a fine mesh.
• Back the impression to a kiss on the affected deck alone and rerun the section.
• Ask the stock supplier for the surface strength of the face stock and for a pick resistance figure from a printability tester, and compare the reel with the reel that ran clean.
• Read ink temperature at the chamber at start-up and at running speed, and check web cleaning and extraction at the unwind and after the die station.

THEN CHANGE

• Reset impression to a kiss on every deck before anything else; picking is an impression fault far more often than an ink fault.
• Move to a stock with the surface strength for the job, or to a coated face stock, and take the matter up with the stock supplier with the printability data.
• Fit or repair web cleaning at the unwind and after the die station, and extract dust at the slitters.
• Raise anilox volume on rough and uncoated stocks rather than raising impression to close the solid.
• Bring the chamber up to the 18 to 28 C band before running, so the first reel is not the tackiest one.

CHECK, IN THIS ORDER

• MEK double rubs following ASTM D5402 with the house method recorded, including the 1 kg load and the cloth, looking for at least 30 with no breakthrough. Read a press-side figure at the delivery as a cure check, and read the acceptance figure 24 h after cure at 23 C and 50 % RH once cross-linking has completed. State which of the two a reported number is.
• Rub test on a Sutherland-type tester at the load and cycle count the customer specifies, dry and wet, on the cured-out sample.
• Gloss to ISO 2813 at 60 degrees, and at 20 degrees where a high gloss is specified, to confirm the coating is there and at weight.
• Coefficient of friction to ASTM D1894, static and dynamic, against the actual contact surface.
• Weigh the coating: 1.5 to 3.0 g/m2 is typical for a UV overprint coating.

THEN CHANGE

• Bring cure to the grade minimum first; no coating will rescue an under-cured ink underneath.
• Test at the right time before rejecting a reel: a press-side figure is a cure check, not the acceptance figure.
• Specify the matched coating for the duty: SRC 89RC for maximum scratch and scuff, HSC 81RC where a very low coefficient of friction is needed, HMR 70RC for a high-rub matt specified below 20 GU at 60 degrees.
• Bring coating weight up to specification by anilox change rather than by pressure, and reduce ink film weight to the minimum that holds density so the dose available cures it fully.
• Review the handling line for guides and brushes that are doing the damage.