Toning on tail edge of sheet/blanket

[wiscowi]

Hello, just got bumped up to the 4 color hamada b452a, and had almost no training on it. We switched from a thicker poly plate (.008) to a thinner metal plate (.006). Had to play around with a few different fountain solutions, stuck with the one produced by the plate manufacturer, but I've been having a toning issue with the tail edge of sheet/blanket not staying clean and building up ink over time. It only seems to happen on the C/Y units, and after adjusting stripes countless times I'm a little dumbfounded as to what it could be. It seems if I open the metering roller to the chrome pan roller it helps, but then it's a fine line of almost too much water.

Any suggestions?

 

[FourFingerRing]

Could be lots of things. Something that comes to mind right away is how old are your blankets. If blankets lose the ability to release ink and/or start to glaze over they will carry excess ink and can cause sensitivity to your plate. This will make you want to increase water to get a cleaner image (natural reaction) Look at your blankets do they look excessively inked or have a certain part of the blanket that looks "plugged in" usually from my experience its pretty noticable horizontally. Eliminate certain problems as you go. I assume you are running the same series of inks for your four color. you are running the same plates all units,fountain solution is the same, paper is the same, you checked settings. If cost is a major issue you could change sequence and see if you get the same results on other colors.

 

[turbotom1052]

Considering you just switched over to a different plate, and assuming that things were fine with the poly plates, Id be looking at a plate issue first. Are you imaging exposure strips on the gripper of the plates? If not i would suggest that you do. Exposure strips will allow you to monitor every plate that gets spit out of your CTP for not only proper exposure but also for correct development. If you know that your exposures are correct and that the plates are being developed correctly then you can move on to troubleshooting possible press issues.

 

[wiscowi]

Thanks Tom, that's a good idea, I'll have them add that to the plate. It shouldn't be a blanket issue because I have swapped out the blankets for new ones and nothing changed. I also just replaced one of the metering rollers and swapped 2 between units to see if that makes any difference, but I haven't really had anything to run.

 

[alibryan]

1) What’s the max size sheet for that press?
2) Is the tone line it in the same place, regardless of sheet size?

.....

 

[wiscowi]

1.) Max sheet size is 14" x 20".
2.) Our typical sheet size we run is 12.5 x 19, but it does it on different sizes too.
3.) Yes the tone is faintly there on every sheet, depending on how high the water is spinning.
4.) The tone line is about 9 inches back from the lead edge.
5.) It's like a stripe all the way across, it doesn't show up on the sheets but it shows up on the blanket, anything from the line and back is covered with ink and before it is clean.

 

[wiscowi]

This isn't the best picture but this is the tail edge of the blanket, the cyan tones from the tail side and works its way up til it gets where it is.

Edit: nevermind, the picture didn't upload into the comment.

 

[Color Printing Forum Admin]

To include your photo with a post, click the "Upload a File" button below the reply area. Then choose the jpg from your computer to attach to the forum post.

 

[FourFingerRing]

3.) Yes the tone is faintly there on every sheet, depending on how high the water is spinning.
5.) It's like a stripe all the way across, it doesn't show up on the sheets but it shows up on the blanket, anything from the line and back is covered with ink and before it is clean.

OK so it does show up or it doesnt ? on the sheet.

If your blanket is fine and you changed chrome rollers to different units. Then start narrowing things down. I assume you have run different colors in that unit and it still does it. It could be roller pressure to your plate. Or your impression pressure. Im not familar with the ink train on your press. If you have oscillation on those form rollers, if engaged it can cause friction and heat, causing drying, hence you give it a lot of water and it goes away. The journal could be worn on that roller causing movement side to side. Just checking a roller stripe is not going to tell you that. Its a fine line with a lot of settings on a press , slight variations cause problems........Thats why this forum is here.

 

[wiscowi]

Here is the picture, yes it will show up on my sheet and I have to keep an eye out for it and keep my water higher than all the other units, which washes it out on start ups. When my water is good it still tones on the very edge of the tail, which can be bad if one slightly crooked sheet goes through since it'll pull it out.

 

[turbotom1052]

Judging by how dirty your blanket cylinder bearer is ,its not a big stretch to assume that housekeeping and maintenance are not a big priority in your shop. I fear that your toning issue just might fall under the category of "not giving a sh_t", until we can no longer print. Good luck, I think you will need it!!!

 

[FourFingerRing]

Here is the picture, yes it will show up on my sheet and I have to keep an eye out for it and keep my water higher than all the other units, which washes it out on start ups. When my water is good it still tones on the very edge of the tail, which can be bad if one slightly crooked sheet goes through since it'll pull it out.

OK so we have established that you are toning.....You have not replied stating you have tried any suggestions that you have gotton from anyone in this thread.

Giving more water or "my water is good" only lets you slide by ...day to day. If you are unfamiliar with the ink train and how the rollers work then im sure the folks here can walk you through it. Like I said Im not familiar with that ink train......but assume its somewhat common. Check your journals and or roller brackets depending on how its set up........something is out of whack. Have seen the toning a million times its not always the same solution every go round.

 

[alibryan]

Judging by how dirty your blanket cylinder bearer is ,its not a big stretch to assume that housekeeping and maintenance are not a big priority in your shop. I fear that your toning issue just might fall under the category of "not giving a sh_t", until we can no longer print. Good luck, I think you will need it!!!

That press doesn’t run on bearers, as evidenced by the amount of buildup on the cylinder. And seeing now that it doesn’t run on bearers, it’s possible that there could be too much plate to blanket pressure. And if there’s too much plate to blanket pressure, that could be a cause for excessive toning.

 

[turbotom1052]

That press doesn’t run on bearers, as evidenced by the amount of buildup on the cylinder. And seeing now that it doesn’t run on bearers, it’s possible that there could be too much plate to blanket pressure. And if there’s too much plate to blanket pressure, that could be a cause for excessive toning.

I agree but to let any part of the press to get that bad speaks volumes about a shops policies on maintenance and housekeeping. When I see that level of neglect, Im right away thinking things like how old are your rollers, or how often do you change your fountain solution, or how much calcium has been allowed to build up on your rollers???

 

[wiscowi]

Sorry I've been on vacation for the past few days... Yes the cylinder is bad along the blanket and it was worse, I've been wiping it down and it has gotten better but now that we are slow from covid I'll have time to pull the blankets off and scrap it all away. I'll check the journals this week to see if there is slop somewhere, and you are right I do not 100% have knowledge of the rollers. I have them set to the books specifications but maybe they need to be tweeked somewhere, and I just changed my fountain solution and run a de-cal every Friday when I was up. I'm talking with someone from prepress today to set up that exposure strip too. Also the blanket/plate pressure is hard for me to 100% nail because I kept the same permapack on there from the poly plates and we went down .002" from a .008" to a .006" metal plate.

 

[Travis Young]

I feel for ya man!
I got chucked on our 4 colour MO after the last guy walked out.
No training. Neglected press.
Not every shop is perfect. That's life.
Probably going to take quite some time to get that thing into shape.
Incorrect plate to blanket pressures will definitely cause a problem like that though normally you would associate it with excessive pressure (I bet that statement gets a few bites) and you've reduced yours.
Maybe you could slip a bit of packing behind the plate and see if that fixes it?

 

[turbotom1052]

have you tried doing the deletion pen test?