UV Printing Troubleshooting: Questions and Answers

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1.Curing failure

No. Item Printing
System		 Phenomenon/
Situation		 Explanation Cause Counter-measure
101 Curing failure All Systems UV lamp does not light. If the lamp fails to turn on even after replacement or inspection, it is likely that there is an issue with the electrical system. Lamp failure If the issue persists, consult the lamp manufacturer for further assistance and troubleshooting.
102 Curing failure All Systems UV lamp turns on, but the UV products fail to cure. *Primarily due to lamp-related issues. A) Dirty Lamps and Lamp House
B) Expired Lamps
C) Inadequate Output Settings 		Lamp maintenance failure or insufficient lamp light intensity A) Clean Lamps and Lamp House thoroughly.
B) Replace the Expired or Degraded Lamps with new ones.
C) Inadequate Output Settings
・Increase the lamp output.
・Increase the number of lamps used.
・Reduce the printing speed to allow more curing time.
・Lower the feeding amount of the ink to facilitate better curing.
・Switch to the ink type that emphasizes curability.
103 Curing failure All Systems Insufficient curing after lamp replacement If the UV products cure properly after replacing the UV lamp with a different one, the original lamp may have been defective. Lamp initial failure If the issue persists, consult the lamp manufacturer for further assistance and troubleshooting.
104 Curing failure All Systems Not cure properly when using power-saving UV systems, including LED-UV lamps. A) The incorrect ink type is used for the specific power system. →Incorrect ink selection.
B) The correct ink is used for the power system. → Other factors may be causing the issue, such as excessive amounts of ink. 		Incorrect ink selection or excessive amounts of ink. A) Use the ink suitable for the specific power system.
B) Refer to section № 108 on “Curing failure” due to excessive amounts of ink.
105 Curing failure All Systems The addition of additives not intended for UV inks has resulted in poor curing. Additives not specifically designed for UV inks can inhibit the curing process. Incorrect additive selection Use additives designed for UV products
106 Curing failure All Systems Curing failure caused by excessive amounts of additives for UV inks. Additives for UV inks should be used in appropriate amounts, as excessive addition can deteriorate UV curability. Excessive amounts of additives Observe the amount of tack reducer, compound and other additives
107 Curing failure, Printing failure (Dirt) All Systems After cleaning the plate and blanket cylinders with the UV washing agent, the ink fails to cure, or scumming is observed when printing is restarted. If problems arise after cleaning, it is likely that some washing agents were left on the rollers. UV washing agents are often water-soluble solvents unrelated to UV ink components, and their residue can cause contamination, leading to inhibited curing. Cleaning failure After cleaning, ensure that no washing agents remain on the rollers before restarting printing.
108 Curing failure (Excessive amounts of ink) All Systems Ink does not dry sufficiently when the ink film thickness is too thick, such as in four-color overlays or two-pass printing of black ink. This can lead to issues such as poor adhesion and deterioration of scratch and rub resistance. This issue occurs because ultraviolet ray does not sufficiently penetrate the ink film, resulting in curing failure.

The difference from typical adhesion failure is noticeable: normal adhesion failure occurs even in thin or light-colored areas, whereas adhesion failure due to poor curing can be identified by the fact that adhesion is achieved in such cases.

Black ink is more prone to this issue, as it is more difficult for ultraviolet light to penetrate.
Paper type is also a factor. This problem is more likely to occur with papers that set and dry quickly, such as cast-coated paper. 		Excessive amounts of ink or Substrate characteristics A) Ensure the appropriate ink film thickness.
B) Print twice rather than once.
C) Use a high-density ink type.
D) Switch to an ink type that emphasizes curing or adhesion.
E) Change the paper used.
f) Pre-print transparent white as a primer, especially if paper absorption is an issue.
109 Curing failure Offset, Coating Insufficient curing on the gripper side (approximately 5cm) The gripper side is more susceptible to curing inhibition, as the grip claw and other parts of the press may cast shadows, preventing sufficient exposure to UV light. Machine setup A) Adjust the lamp mounting position.
B) Modify the shape of the grip claw.
C) Switch to ink and varnish that emphasize curing.
110 Curing failure Offset Curing failure caused by excessive emulsification of the ink. Dampening water in the ink can also inhibit curing, especially when printing light images or on non-absorbent paper.

→ Refer to the section on printing defects (emulsification). 		Excessive amounts of dampening water and ink Refer to section № 411 on printing defects (emulsification).
111 Curing failure Letterpress Flexo Marginal areas remain uncured and are prone to scuffing. Marginal areas are more prone to curing failures because the ink film thickness is often greater than in other areas. Excessive amounts of ink or Excessive printing pressure A) Refer to section № 108 on curing failure due to excessive amounts of ink.
B) Reduce marginal buildup by lowering the printing pressure.
112 Curing failure Letterpress Flexo When UV ink printing is followed by UV cationic varnish application, the cationic varnish fails to cure. If the underlying ink has not cured sufficiently, the radical-type amine sensitizer in the ink may act as an inhibitor, preventing the cationic varnish from curing properly. Curing failure or Incorrect ink selection A) Ensure the underlying ink is fully cured before applying the varnish.
B) Use amine-free base inks.
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