Discoloration on side of press sheet.

[lantz_xvx]

Hi folks,

I'm running an Itek 3985 with Crestlines, and right now I'm doing a save the date postcard for a client, just one color on Mohawk 100# Eggshell cover stock. I'm having this issue where the sides of the printed image are a lot different in color, thus creating what seems to be a hard line. In the below image, I'm running a 6x9 postcard landscape, so the gripper/ink keys are along edge. What's confusing is that it seems like the keys are open enough because the edges of the sheets are pretty even all the way across. The below image is a little weird because there *is* a gradation in their file, so even though it looks like the middle just doesn't have enough ink, it does look that way in their file.

Anyway, anyone know what do about it? I've had the issue before with other, more straightforward solids where the edges always seem to be either darker or lighter than the rest of the solid and that creates a line. There's no line in the plate (which I print off our Xerox C75 digital press) and there's an appropriate amount of plate-to-blanket pressure. I tried changing blankets but still had the same issue on both. What am I missing?

Thanks,
- Lantz

 

[lantz_xvx]

Alibryan, the gripper is the 9" side. So, like I said... it's running landscape. I'm running it one-up landscape on a 9.5" x 13" sheet because we're using the other half of the sheet to duplex afterwards. Do you think that the mechanical ghosting is still a possibility? Another variable is that I typically use plate cleaner to prep plates - kind of a holdover from when I used to image plates on an HP5000, but I'm wondering if the plate cleaner is breaking down some of the information in the solid and giving me issues. I'll try a fresh plate tomorrow, but I'm interested in this mechanical ghosting. What is it about the configuration of the rollers that it "can't handle" laying down enough ink to print a solid? And how would I fix that?

Thanks,
- Lantz

 

[lantz_xvx]

Sorry for any confusion. The press sheet is portrait but the image is horizontal. The gripper is at the short edge of the sheet but the long edge of the image on the plate.

The Itek 3985/Ryobi 3302 is perfectly capable of running big solids. I frequently run 11x17 posters on it with large solids that bleed with no issue. I've seen incredible work come off of it. I don't think the issue has anything to do with its capability. It's no Heidelberg, but three form rollers have a lot of capacity. I'll try moving the image on the sheet to see if that helps, though I can't understand right now why that would matter.

Any other thoughts on this would be appreciated.

Thanks all.

- Lantz

 

[bill kahny]

move the sheet out of center to the plate either direction does the heavy area shrink or enlarge or stay consistent to the rest of the image? If it stays consistent look at a new plate. if it moves look at pressure or your ink is contaminated.

 

[lantz_xvx]

Hey Bill, I'm not sure I understand. The issue goes across the sheet laterally, so moving the sheet position won't do anything. Do you mean I should move the image on the blanket, either up or down, to see if the problem area changes or stays consistent? And when you say look at pressure, which pressure are you referring to? Form to plate? Form to oscillator? etc.

Thanks,
- Lantz

 

[bill kahny]

Sorry miss understood feed direction too, yes move the image on the blanket, what was that effect? you checked blanket pressure so yes roller pressures, weird things happen. I would also try running the stock the other direction grain for some stocks cause strange effects.

 

[lantz_xvx]

After moving the image down on the blanket, the issue moves with the image. I really am thinking that it could be roller pressures but I'm still not clear on which pressures to check. Anyone have any suggestions? Is it the pressure of the forms as they ink the place or something else?

- Lantz

 

[Alois Senefelder]

Hello lantz,


What you are seeing - IS Mottle, not discoloration .

1) DO not change anything, Print a a Gloss paper, same gsm and Uncoated paper and see the printed result .

2) IF possible use a Metal Imaged Plate.

A quick of the Cylinder Pressures - 1) Roll up the Plate - SOLID with Ink - NO Damp
2) Put press on Impression - while stationary, and then check the INK STRIPE on Blanket Cylinder, next Ink up the Blanket Solid and check Impression Cylinder Stripe
3) The INK stripes should be about 2mm EVEN WIDTH across the wiidth of the cylinders.

Regards, Alois

 

[lantz_xvx]

Hi Alois. Thanks for your comments. I ran some glossy stock and had the same issue. Form to plate stripes are a little off, so I made a couple of adjustments and will get back to it after lunch. I'm hoping to not have to go to the form to oscillator stripes, which involves taking out all the rollers. How would I go about adjusting the impression cylinder stripe? Is that just with the impression knob, to adjust the blanket to impression pressure? If I back off the impression too much, the image gets a little spotty. I don't generally set it very heavy but I'm not sure how much less I can run.

 

[Alois Senefelder]

Hello lantz.

Set ALL the rollers ___ Correct !!!!!!!!!!!!!!!!!!

Just try my suggestions with your present Press Settings and see what the result is first.

Also these areas of "Cloudy Print" could be areas of emulsified ink and could be mistaken for "Mottle"


Regards, Alois

 

[lantz_xvx]

I know it looks weird, but that really is how their file is and is what they want. I'm just trying to figure out why there's that hard line on the left side of the card (i.e. the tail edge of the image as it appears on the plate). I guess I'll go into the form-to-osc and start there... thanks.

 

[dabob]

It might be how the plate is imaged . . . I'd take a close look at the plate and see how the gradation goes from the middle to the edge . . . could you post a press ready pdf for us to look at?

 

[lantz_xvx]

It won't let me post a PDF here, only an image file. I took a pretty close look at the plate and, I mean sure, it's being made on a laser printer, so it's not smooth like it would be if it were made on an imagesetter for a metal plate. But I don't see any obvious hard line or any sharp turn in the gradation. (Incidentally, I originally thought the line came from having the edges be darker than in the middle, but it's only on that one side and it's quite a difference, so I ruled it out.)

I went through and made some fine-tune adjustments to my form-to-osc pressures and saw no change...

- Lantz

 

[Alois Senefelder]

Hello lantz,


Lost in Translation !!!!!!


Hard Line ?? ---- do you mean the area of "Back Ground Scum " on the Lefthand side in the " non image areas" ?????

You need to learn the Nomenclature of Lithographic Printing Terms.

Also, as suggested look at you Plate Imaging Process - USE proper Litho Plates !!

 

[lantz_xvx]

Hey Alois, I'm not sure what you mean. I know the nomenclature, and I'm using the same poly plates that I always use and that others always use. Did you see the photo in my original post? The job is a 6x9 vertical postcard on 100# uncoated cover stock. The sheet is being fed portrait, but the card is rotated counterclockwise so that it's horizontal. The issue I'm having isn't scumming, it's that the left edge of the card (when viewed vertically) is significantly darker to the point of creating a literal hard line, that is different from the rest of the image area. It's about 3/4" thick. Because the image is horizontal, that means that the problem area is closer to the tail edge of the sheet. Hopefully I'm making sense, but if you haven't looked at the photo in the original post, please do, as it may provide a bit more context.

At this point I've switched to a brand new blanket, imaged a new plate, adjusted form-to-oscillator pressures, adjusted form-to-plate pressures (they always get a little off when it gets cold, so no surprise there), tried different amounts of impression pressure - nothing works. The one last thing I have to try is to run the job on the other head, to eliminate the possibility of ghosting from the second unit blanket. But if that doesn't work, I'm at a loss. I have no idea what else it could be..

Thanks,
- Lantz

 

[bill kahny]

I think its a file issue. Incorrect layering on a digital device will produce prints like this. If they created the bleed by drawing a box and filling it with the background color it would be hard to see on the plate. Do you have the full pro version of acrobat where you can click on the image and see if a box coincides with the darker area. An update to acrobat could cause this to be different than a previous version handled it. I've seen rotating the image before processing take care of this.

 

[lantz_xvx]

Thanks for your input, Bill. I wondered originally if it was a file issue, but I've seen the same issue pop up fairly recently with some cards we designed in-house to promote a book we're publishing, and I know for sure that we set it all up properly. Although now that I'm looking at some samples of those cards, it doesn't seem to be nearly as drastic. In any case, the file they sent us was a .TIFF with just one layer. Do you think there's some sort of weird transparency thing happening that I would only see with a file that has its layers?

 

[Alois Senefelder]

Hello Lantz,

I'm getting lost now !! all I can see is a Diagonal View of a printed sheet - just " indicate the area" of concern ?

Regards, Alois

 

[lantz_xvx]

Alois, look at the words "Save the Date" and then let your eye follow left to where the top left crop marks are. Do you see how that side of the sheet is significantly darker than the rest of the sheet? It goes all the way down the image. But it doesn't have anything to do with the ink keys because the image is horizontal, so running on the long edge. But the edge opposite the problem area doesn't look like that. Does that clarify things?

 

[dabob]

Its such a sharp line I still think that its an imaging problem especially now that you say it was done on a laser printer . . what line screen are you using, what resolution is the laser printer set on, what kind of laser is it . . . we use a laser printer for our quick print type of work but not for screens or halftones . . .