Why are thermal direct plates etching on press

[BEL]

Using a thermal direct plate on a ryobi 750 series offset press. After running for awhile, usually on the magenta unit first a series of small dots appear: .................... evenly spaced up and down and not across the sheet. Then inspection of the plates show small gouged holes in various positions in straight lines. Causes could be the water conductivity, blankets or bad rollers? Anyone with ideas to help would be appreciated.

 

[Al Ferrari]

The fact that it is only happening on one unit certainly supports the idea that it is roller related. Is it always in the same position from the edge of the plate? Inspecting the form rollers (both ink and water) for a stuck bit of hard debris may locate the problem.

Let us know what you find.

Al

 

[BEL]

plate etching

plate etching

No the position of the dot trail varies and on occasion does show up in different units. The press just had a overall maintenance done...so other than age the rollers should be clean.

 

[Al Ferrari]

The varying position and it showing up on the other units rules out the press (i think). But the varying position does suggest the plate processor or gumming unit. Have you looked for a cause there?

Al

 

[BEL]

We use processor free plates. They are imaged on a Magnus 400. There are no marks coming out of prepress.

 

[PantherMac]

Physical scrapes in the emulsion, or a blind spot? Trying to rule out Chemical/Physical sources of the problem.
It sounds like the problems occurring on-press somewhere's. You can hand-develop the plates w/ a clean cloth and Windex. Shot a plate or two and develop by hand on a table. See if the spots appear. If not, you're ruling out Prepress.

- Mac

 

[Awaltd@kodak]

BEL,

Your description suggests that there is some type of debris in the form rollers which is gouging the plate and creating the defect. This would first appear as a single dot, and progress to a series of dots and eventually a solid line due to the difference in size of the form roller compared to the plate. Being that maintenance was recently done, a small piece of metal may have become stuck in a form roller.

Check the form rollers for debris in the location of the dots/lines on the plate.

- Awaltd@kodak

 

[BEL]

Yes these are physical gouges in the plate...A plate specialist said it might be from ink build up (Bad roller) and pressure digging little ink balls into the plate, conductivity of the water could be an issue also...Prepress has been totally ruled out as an issue. They vary in position on the paper, sometimes there are multiple rows of dots.

 

[John@advantage]

We are having the same issue on our ryobi 780. We use Anthem Pro and Presstek says that their plates will not run on our press. They want to switch us to an agfa plate, until they get a plate that runs with delta damperns.

 

[billy gold coast]

gday if there is nothing on your rollers its a plate problem for sure id be trying different brand of plate if it still happens then you know its the press if metal has been coming off your rollers could be full of it pitted rollers are good for nothing

 

[Syed]

We faced the same issue of dots with a Komori Lithrone when using Presstek Anthem Pro plates. There is no solution for it except to change the plates to a different manufacturer.