CTP background scatter

[onwsk8r]

Alright experts, blow me out of the water. Prove to me that, at age 27, I'm a noob.

It's a Ricoh 900. It can print plates up to like 300 line screen or something with the Fiery Pro Printer package. Yeah, nobody believes that. When we get metal plates, everything on our Multi 1650 works like a dream.. When we print plates on the Ricoh, we get background scatter. Screens (halftones for you old folks) break up, edges get dirty, and life does not go on. Why does this happen? I'm mostly concerned with the black outlines on the blanket.

 

[prepressdork]

This may not help any but you mentioned background scatter. Are you using Absolute Colorimetric for your rendering intent in your RIP? It's been my experience that using this particular rendering intent will create a background scatter dot.

As for the other issues you mentioned, do you actively maintain the 900? Is the environment around the 900 clean? Do you see these issues when printing other things to the 900 (meaning not plates)?

Best regards,
pd

 

[onwsk8r]

We don't use Absolute Colorimetric.

The environment is fine and we have a maintenance agreement. There is no visible background scatter on the plate when it's printed, or on other things we print. We generally scrub the plates (for runs longer than, say, 1M) with digital plate cleaner, which rubs off toner with no issue. After a thousand or so impressions, the blanket is black (or whatever color) in the areas outside the sheet. This doesn't happen with metal plates. It has the benefit of making it extremely simple to tell if a sheet or an envelope went through at an angle

 

[samB]

I won't call you a noob, perhaps just a touch arrogant in the first post

I'm the newb, since I didn't know you could make plates on a digital press. "Oh, what will they think of next". Actually, I might have heard and dismissed it.

Anyway, it doesn't sound like background scatter on the pate. Sounds like you're getting toning on the press. More of a chemistry and/or press condition issue with the plates. Traditional metal plates are still the best and most forgiving medium out there.

I'd start there, diagnosing for press toning. Don't spend a fortune on experts and equipment for short run work on a little diddy. Make sure the rollers are in good condition. Check the pressures, plate to blanket, blanket to back cylinder, roller, etc. Are the plates getting sensitive? Why? Check the PH, talk to Ricoh about the PH required for their plates. Get free samples of different inks and fountain solutions until you get get dialed into a combination that works better. Tell the companies what you're running.

If your halftones are also breaking up, I'm guessing something mechanical. Rollers, or pressures, or perhaps paper lint. Something scuffing up the plate. Sensitizing the non-print areas while picking off the halftone dots. Adding a little pressure to wearing rollers works fine on metal, but wax and polyester (or whatever those plates are made from) just can't take the abuse.

In the meantime makes things easier on yourself. Run on oversized stock so you can trim off the bad instead of flipping through it. If you have to clean the press every 1000 sheets, so be it. I doubt you're running 50,000 runs on that setup. Make sure you're taking extra good care cleaning the back cylinder and bearers in those conditions!

 

[tomcatinc]

SamB has good point. Simple logic says that if it is not plate, it can not be printed. So if you don't have problems at start of printing, than it is press issue.

According to your description, plate picks up color in image and non-image areas; significantly less in non-image areas but it makes buildup. My experience says that there is no universal press chemistry for metal plate and poly plates. Also, the pigment (press color, dye) used for metal plates can be incompatible with poly plates. Or both. So as SamB says, troubleshoot the press issues.