Pls help troubleshooting - Inline aqueous coating in sheetfed machine

DeltaE

Well-known member
Hello everyone,

I have a problem with inline aqueous coating in sheetfed machine:
- Heidelberg CD102
- Coating unit with tresu chambered blade
- Anilox 60 lpcm
- underlay thickness = 1.3 mm
- blanket thichness = 1.95 mm
- blanket tighten with torque wrench 45
- some area does not need to be coated therefore I have to remove the rubber layer of blanket in those areas.

There is a mark on the rear edge of each uncoated area. (Please see the pictures for more detail)
I had tried:
- to deal with underlay thickness (packing sheet) - increase or descrease
- to make kiss-pressure between anilox roller and blanket cylinder
- to deal with printing pressure between blanket cylinder and impression cylinder

But it still remains. Please help me or leave your idea about this! I am very appreciated!

Regards,
DeltaE
 

Attachments

  • photo7940.jpg
    photo7940.jpg
    190.1 KB · Views: 331
  • photo7941.jpg
    photo7941.jpg
    191.9 KB · Views: 331
The blanket cutting looks rough. The blanket surface may have lifted slightly away from the blanket backing creating a little bump which could cause application roller to lift causing a void. When you strip away the blanket surface delamination can occur for multiple reasons. Not cutting all the way through and you pull too hard. Not using a good blanket for cutting knock outs. Over packing. Over torquing.etc.
 
This is speculation.
It’s a form of starvation ghosting. Because of the cutout on the blanket the coating builds up in that area of the blanket. Then it gets dumped on the trailing edge making it thicker there. That in turn changes the thickness of the coating immediately after the cut out. That reduces the amount of coating there ceating a thinner patch of coating until the coating film thickness has a chance to recover.
Take off bars might help.
 
Last edited:
I'm going to go along with both suggestions. The blanket cut looks rough. Even at best it's a tough thing to pull off. And as Gord says, you're getting an excess buildup over the non print area. I think all you can try is very, very minimal pressure. I think the best thing would be to spot varnish off one of your print units.
 

PressWise

A 30-day Fix for Managed Chaos

As any print professional knows, printing can be managed chaos. Software that solves multiple problems and provides measurable and monetizable value has a direct impact on the bottom-line.

“We reduced order entry costs by about 40%.” Significant savings in a shop that turns about 500 jobs a month.


Learn how…….

   
Back
Top