QMDI PRO Unit #4 Toning

[Richard_Hardin]

Hello all!

So we are running a QMDI classic and Pro. On our pro, I have been getting toning/banding issues for a few months now on the #4 unit. It only takes less than 50 sheets for the toning to start. Sometimes it can be on the first sheets coming off. I have pulled all of the rollers, adjusted them, shimmed them to get rid of any play and chatter in them, changed blankets, adjusted blanket pressure and roller pressure. The toning happens with process or pantone inks. I actually just put a pantone on it this morning (172 orange from Toyo) and it was horrific toning on the first few sheets. The ink also had bodying compound in it to help clear up the toning. It usually helps with the process colors, but didn't help with the pantone. I switched units this morning and put the pantone in unit #2 and there was no toning at all. I'm wondering if this is a mechanical issue now? If anyone has suggestions, I would really appreciate it. Thanks!

 

[Paul Cavanaugh]

There are a few things that can cause this:
1. You are printing on uncoated paper. (Tough to fix, try increasing the tack of the ink.)
2. Blanket overpacked in that unit. The bearers are undercut .090" if the blanket is over this by .002" or more it will prematurely wear the plate causing it to tone.
3. You have an IR dryer in that unit and the heat is not being evacuated well enough.
4. The ink itself. Yellow is typically the lowest tack ink of the process colors, you need a higher tack. PMS colors, especially ones that have high amounts of mixing varnish are very difficult to run due to the low tack.
5. The temperature of the room is over 74 degrees. This usually causes all of the units to start toning.
6. Rollers stripes are too heavy. They should be set at 3mm, 3mm and 2mm. (The third form roller sometimes may have to go as low as 1.5mm.)

Hopefully this will help fix your problem.

 

[Richard_Hardin]

Hello and thanks for your response on this issue.
1. This was printed uncoated stock(70# husky uncoated) but I will get this issue whether is on 50# uncoated or 100# gloss cover. I have tried a higher tack yellow at one point. It didn't clear up the issue, but it did help it. I can usually come to a decent balance with a higher tack yellow and bodying compound, but then of course its a battle to keep the color up.
2. I will check the blanket and make sure it has the correct torque on it. We are using the same packing today as we did 10 years ago, but it is possible that the blanket may not be torqued down enough. I believe we set them to 185 inch pounds. This is the only unit I really have an issue with.
3. Our IR dryer isn't working on this press. Although if anyone reading this knows where to get some IR bulbs that dont cost $1500 bucks each let me know!
4. I have had the worst issues with pantone colors for toning. Reflex and 172 have been the latest culprits but usually base inks like pantone green do okay, but I always have to use bodying compound in them.
5. The temperature is usually under 72 degrees. We know longer have the presses in a climate controlled room so during the summer months it has reached 78-80 which is most definitely too high but hasn't caused too many issues.
6. I pulled all of the rollers and reset the stripes. As of now, form rollers to plate are set at 3mm, 3mm, 2mm. Oscillator rollers to form rollers are set at 3.5mm, 3.5mm, 2.5mm. I also pulled the bearings from the rollers and re-shimmed them to remove any play and chatter.
The blanket pressure and ink tack to me seems to be the most logical explanation for it. If this doesn't help and there are any other suggestions, let me know. I'm game to start pulling anything apart to get this resolved!

Thanks a ton for taking the time to help.

 

[Richard_Hardin]

Hello.

I went ahead and reset the rollers again yesterday and checked the packing and the blanket pressure. Everything seems to checkout fine. I tried backing off the 3rd form roller pressure and adjusted the pressure from the oscillator rollers to the form rollers. I had no success with clearing up the toning. However, when I opened up the side panel on the OS side, I wanted to check the cam wheel that the oscillators ride in and feel for any jerking movement. There was some vibrating on one of the brass joints and a little skip/jerkiness in the other one. Can this cause toning issues? Part of the toning looks like roller chatter as well.

 

[Paul Cavanaugh]

Not unusual...