UV CRACK !! Any Idea how to stop ....

[saifu7]

Some one said after UV, guillotining is difficult, as it cracks. Also some one said after UV on Magazine covers or creased jobs, it cracks. is that true? how to stop this issue.......

 

[GJOHN]

Make sure that the UV coating is not over cured.

 

[apolloUVGOD]

You crack me up !

You crack me up !

Here is a common problem in digital printing

Most printing engines use heat in printing. This removes moisture from the paper. The paper does not perform in folding cutting ect. as a litho sheet that adds moisture.

A dry surface structure fails more often. The paper surface fails EVERYTHING CRACKS ! On the cutter it chips.

Solution:
Process: Reduce the UV power setting to 200 watts and increase belt speed to reduce heat in the UV curing process.
Some machines have larger UV units that trap a lot of heat.
Clean your air filters , check reflectors and lamp to help run at 200watt.
"Blower Rotation" Some UV dryers are able to put air out in reverse rotation. At all installs we check this. The Rookies ? Click blower on and use a flashlight to see the fan rotation. Air flow keeps the unit cool.
Some units run real hot and there is little you can do. Did someone say China. Retrofit is a possibility.
Try different papers also.
Overcure ? Years ago this was an issue.
Adhesion of coatings and helpful characteristics of our coating may solve this also.

GOOD LUCK

 

[jonprintz]

Some one said after UV, guillotining is difficult, as it cracks. Also some one said after UV on Magazine covers or creased jobs, it cracks. is that true? how to stop this issue.......

This is not true in my experience. Digital toners from certain machines will crack when folded or cut whether scored or coated but the UV coating added does not increase the risk of the cracking.

When choosing a UV coating for your particular application you will be best served by sending multiple examples of your print to your coating supplier and let their lab determine the best coating for your printed surface. The combination is the key and not just one component.

 

[MacDaddy]

Look at the Morgan Digifold pro it creases and folds in one pass and has cured the cracking issue off or KM 6501.

 

[apolloUVGOD]

O say can you see ?

O say can you see ?

UV coating is clear and cracking of it alone can only be seen under magnification. What everyone sees is the WHITE CRACK. Scratch off most or the time revels a colored flake , a bond of the ink or toner to the UV.
The UV God says
1) Take a sheet of paper from the packet and fold and cut it. Looks Good ?
2) Take another sheet after print then run it through the UV lamps without UV .
3) Compare the unprinted white area under a 10X loop ( old school litho) See if there is surface fracture.
4) If the surface fractures UV will not hold it together.
5) This process of substrate qualification should be done to qualify your paper.
Some papers print better than others and some finish better than others.
For the real smart guys. Is your paper a mill brand (i mean the same sheet meeting mill specs.)
or a distributors brand. Is it a converted job lot sheet. Duh Duh Duh
Curtis the UV God

 

[GRAPHIC COATINGS]

Lots of good info here, We also run into these problems, we use a "softer" UV
coating that we have made for our use when we run into these problems.
We did lots of R&D with our UV Supplier, your Supplier should help in these
situations.

Graphic Coatings, Inc.
Santa Fe Springs, Ca