AB Dick 9870 - Image/Text Dropout?

[Duake]

Hello all.

I have a question about the AB Dick 9870 press. We used to have a regular Pressman who ran our presses and I was getting trained to use them as a backup to him. Well, he was let go before we got into situations like I have right now. It really baffles me that this happens.

I make a new plate (8 mil polymer) and it looks good. No issues seen on the plate at all. Clear text, etc. I start running the job (which in this case is just envelopes) and before I even get 2000 printed, the text seems to start to disappear in random areas. Almost like the plate isn't touching the blanket with enough ink. Looking at the blanket, which is brand new, the text looks just fine. Looking at the envelope, it seems the text on the right side of what I am printing is dissipating. Looks like the ink (or pressure?) is uneven and not touching correctly anymore.

Any thoughts on what I can do to fix this? Is it a fountain solution issue or a plate issue or a chemical for the plates issue? I just keep racking my head to figure it out since it will work fine and then it begins doing this. When our pressman was here, I could run this same press without it doing this, so maybe he was adjusting something and I just wasn't shown it. Any thoughts and ideas would help immensely! Thanks in advance!

 

[pdan]

Blanket low spot(s) comes to mind. Do you have blanket fix?
You blanket is a 3 ply? That's about .065 as I recall. They tend to smash pretty quickly compared to the 5 ply used with Itek & Ryobi.
Confirm that you plate chemistry is fresh (enough) and at proper temperature; probably 85 F. Don't chase your tail pondering fountain and plates. The plate image should be a nice strong silver. When the chemistry gets old it will appear more golden. (Years of looking at those plates helps.)

Smashes tend to be most pronounced where the seams of the envelopes overlap; an extra layer of thickness. Study the poor blanket area; look at the envelope(s) through a light table or just hold it up to the overhead light (like an experienced pressman). Do the problems areas seem to coincide with the envelope seam??? Smashed blanket. You'll need blanket fix if you will be printing envelopes. (And that is the bulk of this era's small press work.)

What is the plate maker? CTP, daylight camera or other? What is the development means?

 

[smalloffsetpressexperts]

The 9870 has a plate to blanket pressure knob. Also an impression cylinder pressure setting. Simple test is ink the plate up, image that to blanket, that should show any problems.

 

[Duake]

The envelopes have a straight flap for sealing. They are self seal. The return address lands within the flap area, so nothing is causing and issue there. The plate I was using was made about 3 days before I ran the job. I believe that shouldn't have anything to do with it, but I'm not sure, which is why I brought up chemicals. After the first case of 2500, I made a new plate and made this post about the issue while I finished the job. The new plate I made was fine all the way for another 2500 envelopes and barely had some drop out, but not noticeable if you aren't looking for it.

Our plates are CTP and I use the DPM2340 and MegaPro Plates.

Where are the knobs for the pressure settings? I swore I tried to find something just to see, but I could not have looked in the right place.

Thanks for the help!

 

[pdan]

The blanket (to) impression is set via the hole beneath the handwheel. You should have an allen wrench with an angle (45°). Best practice is just enough impression (pressure) for a good print. It "should" be adjusted every job, if the paper thickness changes. Tight for bond, way out for heavy cover, somewhere in between for everything else. Don't ask me which way to turn it.

I don't think that plate to blanket is changed by the operator on that press. If you always run the same plates you should not have to be concerned with it, assuming it is correct.

Smalloffsetpressexperts has a valid point (as always). Start the press. Ink up an old plate, completely, no fountain solution. Bring the plate to blanket perhaps two revolutions. Stop the press. The blanket should be evenly inked. Any low spots will be visible.

 

[SteveSuffRIT]

Adjustment for pressure between blanket and back cylinder (impression) is below handwheel. Use an allen wrench in hole to turn dial and see wheel with numbers on it move.

 

[keith1]

If the image is OK for a couple thousand and then begins to fade/break down, my guess is 99% old chemistry in the camera. Replace the chemistry and you should be good.
Increasing pressure on the blanket is only going to destroy the blanket. I would say that's a problem if your image was overlapping different thicknesses of the envelope, but from your description that doesn't seem to be a factor.

 

[Duake]

We always use the same plates and nothing has ever changed. Since I changed the blanket from the old one, which has been used for like over a year, could it be that? Seems odd, but just thought I'd mention it.
I'll mess with the pressure a little to see if loosening it will leave more ink on.

 

[Duake]

I messed with the pressure for one job yesterday and it seemed to hold ink better. I started another job after that, which has a screen, and in a certain section, the ink isn't holding all the way. I used blanket fix about 3 times to try and get it to fill it in, but nothing worked. The dropout is still happening.
I don't know why, but I think something isn't holding the ink correctly and it doesn't matter if I make a brand new plate or not.
I guess I will flip the image and the envelopes around and see if the middle of the blanket will make a difference.

 

[Duake]

So, it doesn't matter where the image is on the blanket. With a brand new plate, the text starts dropping out within a couple hundred impressions. This is the most aggravating aspect of this because I literally have no one here at my work to ask so I am left to my own devices to figure it out. The other issue is that I don't have enough chemicals to change out on the plate maker.
If there is a more clear cut aspect on my problem, let the suggestions come! I really appreciate all the help so far!

 

[rcreveli]

Have you run an exposure test on the DPM? If your chemistry is old the plates breakdown very quickly.

 

[keith1]

If your chemistry is old the plates breakdown very quickly.

Told him it was chemistry a couple days ago. Maybe he doesn't know how to change them.

 

[Duake]

The chemistry was my first thought when it wasn't holding. My problem is that I don't have the chemicals on hand right now to change them. We unfortunately have to be frugal in what we buy at my company and just getting it for when I need it is the mantra instead of having it here and not worrying.

 

[rcreveli]

The chemistry was my first thought when it wasn't holding. My problem is that I don't have the chemicals on hand right now to change them. We unfortunately have to be frugal in what we buy at my company and just getting it for when I need it is the mantra instead of having it here and not worrying.

Are your plates a clean white in the imaged areas or yellowish. If they are yellow the chemistry is old. You can up your exposure setting using the exposure test to get by. It's been 7 yrs since I ran that machine but I remember you could generate a visual exposure test. The images were circles inside of a square and you set the exposure to the one where you circle & square were the most blended.

 

[smalloffsetpressexperts]

Did you try the print quality test I suggested? Rule out the press by testing stripes to blanket, stripes to blanket and impression cylinder. Shows good? press is ok.
Is the DPM heater ok? A good tech that knows those machines could trouble shoot in 30 minutes. Run the exposure test, try a new roll of plates. Why beat your self up???? Pay a few 100.00 bucks to a pro.
Also those pressure settings are there for a reason, Blanket thickness and plate thickness change. Parts wear also. I know those machines. Good luck my friend.
Remember Stay Positive Test Negative

 

[turbotom1052]

try swinging your blanket around to see if its a blanket issue. If it prints better when you swing the blanket you needn't look any further.