Heidelberg GTO 52 CRISIS

[DavyDee]

Hi I work in a small printing company in Ireland. We operate a GTO 52 and we have recently encountered a serious problem with the press. For some reason bar marks are appearing on the printed page (see pics attached). I was wondering if anyone here has encountered this problem before, this is occuring when running poly or metal plates, we have tried everything, blankets, rollers etc, etc etc . We have had engineers and 'experts' who are all baffled! Any advice or suggestions would be greatly appreciated!

 

[mrheidelberg]

Have your inks or fount solution changed ?

 

[Di Nut]

We had the exact same problem many years ago on our 46. After pulling our hair out we found it to be a roller pressure problem. We double checked our water rollers and ink train rollers and found several to have too much pressure or not enough. Also make sure your rollers have been deglazed etc.. Hope this helps.

 

[Mechanic]

Well, if u say that u checked rollers and blankets, then I believe u. U have 2 check roller bearings, journals (its where the rollers sit on) and the drive belt. Also check oscillating mechanism. From the fotos it doesnt look like a dampening problem. I ve heard that the delivery chains might cause stripes, might wanna check those too.

 

[exheidmech]

This could even be a more serious problem. I would take the drive side side cover off and check the condition of the gears. It could also be a cylinder bearing issue. Does adding or subtracting packing change the intensity of the streaks? Does adding or subtracting back cylinder pressure change streaks. If you play with packing and pressure this will reveal if you have a problem with bearer pressure. If you do you may be able to simply readust bearer pressure or you may have to replace blanket cylinder bearings and housings. Hopefully nobody has played with your bearing bolts or blanket cylinder spring load, this for sure will create this problem.

 

[elektorus]

I ve seen theese. Possibilities:
1. Too much IPA in your dampening solution
2. Thoroughly check and adjust pressure between oscilators and form rollers (most likely this is the problem) look like u have too much pressure.
3. Check your ink, if it is too "liquid" these kind of thigs do occur

 

[DavyDee]

Sorry Ive been away. Didnt think id get so much help, thanks! Ill give afew of these suggestions a go!

 

[Grant B]

I agree with exheidmech, looks to be a pressure problem between blanket and impression cylinders.

 

[exheidmech]

Just to be clear, I was not refering to back cylinder pressure (blanket to Impression), I was refering to bearer pressure (plate to blanket). You can tell is this is an issue by adding or subtracting packing or back cylinder pressure and see if the streaks get better or worse. I think your bearer pressure is the issue.

 

[Grant B]

I thought that perhaps the pressure adjustments were not adjusting properly and could be stuck at a low value. It has not been mentioned if this is occurring on a single unit or on all units. I've seen that pattern when board weight stock has been run through at text weight settings.

 

[exheidmech]

Typically if you run board weight paper at a text weight setting you will get smashed blankets and this will be noticed rather quickly. While it is possible that the settings are off they usually wont result in streaks. If its too low it will result in low printing pressure which can be corrected by increaseing pressure. If its high it will result in smashed blankets. Usually streaks will be because the bearer pressure is too low and you can get chatter from the gears or gap streaks from contact from plate to blanket coming on and off with each revolution.

I thought that perhaps the pressure adjustments were not adjusting properly and could be stuck at a low value. It has not been mentioned if this is occurring on a single unit or on all units. I've seen that pattern when board weight stock has been run through at text weight settings.

 

[western411]

We had the same problem for 2 months when we switched to a new CTP system. After trying every adjustment and fix we switched to soy ink from the oil base and a new fountain and the problem was gone. I don't know where you are located but here in So California we must use low voc solvents and cleaners. We also found these were contaminating our DDS rollers and contributing to the head marks just like in your pics. We finally found a combination that works fine and never had it return.

 

[Reihl Printing]

I have seen this many times with that type of plate, usually it's not a problem on the printed piece and we just forget it. If you get toning on live copy, then work on it with:

1) blanket packing.
2) pressure of water forms.
3) fountain solution mixture.

 

[4 color GTO]

My GTO's don't like loose bodied inks. The thicker the better. I also get streaks if my alcohol% is too low. Also can come from running too slow. HTH

 

[jtdoonz]

I agree with your other posts. Does look like pressure streaks, check your packing and bearer pressures. Check your rollers and their durometer. I would also take some deletion fluid and wipe the non image area and see if it doesn't streak in this area. Wipe in the area where the streaks are showing up. Just trying to think outside the box. Maybe the processor isn't cleaning the back-round out properly. Make sure your roller nips are a little heavier to the vibrator than to the plate. Most times when we have plate issues it appears to be a press issue but ended up a processor issue or lazer issue on the trend setter. We had problems like this on Akiyama presses and went over everything like your saying pressure, rollers, checking gears. Had mechanics checking everything. Nothing in the pressroom seemed to solve the issue. Now we don't have the issue and we really didn't do anything in the pressroom to solve it. That's why I always go after the prep dept. If you haven't changed anything in the pressroom. The season is changing do you keep the place heated and how about your tap water, maybe something has changed - hard or soft water --etc.

Good Luck,
Hope I get a chance to visit Ireland some day. Still have a relative in County Roscommon.

jtdoonz

 

[Chris from Printshop]

It almost looks like the damper form roller are bent or something. Stick a kompac unit on there instead.

 

[FSA]

DavyDee
what type of damps do you have, from what i see in the pics is that you have a dampener issue, gear marks are usually across the whole blanket not with a heavy area in the middle. So I would say you should look at setting the damps to get more water through the nip at the chrome, and then you can turn down your swipe,then if it is a continues dampener you should be able to put a couple more clicks of squeeze on the meter.

 

[Variprint]

I had similar problems years ago with small presses...a stripe of light ink tone printing across the sheet. I finally realized that a water miscible press wash was at fault. The remaining chemistry from the wash was enough to break the ink pigment down to extremely small particles, floating around the ink train and depositing in mechanically vunerable areas, even though there was no mechanical problem per se. I switched to a petroleum wash without water miscible properties. I am a very small user of press wash now, and use "Oderless Mineral Spirits" from the hardware store.