Color contamination: AB Dick 9810 with a T-Head.

Discussion in '1-Color and 2-Color Offset Presses' started by lantz_xvx, May 12, 2011.

  1. lantz_xvx

    lantz_xvx Senior Member

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    I'm having the worst time of my life with this T-Head on an AB Dick 9810 in regards to color contamination. The sides of the rollers that have the lighter color pick up the darker color (usually black) and then everything looks crappy and inconsistent. Any ideas? I've searched the forum and seen brief mentions of this problem but not a whole lot.

    Thanks!

    - lantz.
     
  2. spike

    spike Senior Member

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    hey lantz try running lighter color on t-head with alittle reducer in the ink also make sure both plates are good and wet
    before you drop your rollers see if you can order ahigher tac black might help
     
  3. milo

    milo New Member

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    Yeah, I tried this info you've shared. It works for me. Good luck Lantz
     
  4. Mynte

    Mynte New Member

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    if the contamination starts at the sides of the rollers, try trimming the sides of your blanket. I run a worn out garbage press and the T-head will often run dry on one or both sides. A narrower blanket doesn't pick up the ink and also allows the edges of the plate to run a little wetter. Another trick is to shoot or burn your plates in different positions, IE: T-head plate lower and off to one side a little so that the edges of the plates don't line up when the images are in position.
     
  5. lantz_xvx

    lantz_xvx Senior Member

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    Thanks for all the advice, folks. I think the main problem I noticed is that the chrome water roller keeps picking up a ridiculous amount of ink, causing hardcore scumming. That is its own problem, of course, but when all that scumming is transferring to the blanket, serious color contamination will obviously occur. I've tried everything I can to desensitize the water roller, but nothing works. Any ideas? At this rate, with all the paper and money and time I'm wasting, I'd rather just treat it as a one-color press and trap the heck out of everything.
     
  6. spike

    spike Senior Member

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    try chrome roller cleaner with gum arabic
     
  7. lantz_xvx

    lantz_xvx Senior Member

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    I tried the chrome roller cleaner, and it cleaned it really well but didn't desensitize it. I think I do have a bottle of straight gum arabic lying around, never thought I'd really use it for anything. Should I just saturate the roller with it and then clean it off with fountain solution?
     
  8. spike

    spike Senior Member

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    hi lantz make amixture of gum and straight fountain soloution clean water roller wiith chrome cleaner then go over roller with gum and straight soloution for at least ten minutes. hope this helps
     
  9. printman73

    printman73 Member

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    Hi - just looking through the posts. I had this same problem on my 9840. I love using the T-Head. Saves a lot of time and other issues. The blanket has to be narrower than the plates. If not then you will always get contamination. I had to figure this out on my own.
     
  10. STW100

    STW100 Senior Member

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    comon blanket! doesn't the t-head color lay on the sheet first? I think it should be the heavier tac ink so less chance of picking.
     
  11. printman73

    printman73 Member

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    Yes it does. (I hope I can explain this properly.) However the plate cylinder is holding ink outside the plate on the t-head. With a blanket wider than the plate then this ink has a vehicle to travel back to the host. this then travels up the outside edges of the unit and travels backwards into the host ink fountain. It gets ugly pretty fast. If you cut your blanket 1/4 to 1/2 inch less than the size of your plate then your problems should be eliminated. I have to watch how much tack I use on my old t-head because the springs pop off the hard rollers and I have to stop and put back together so I don't worry about tack so much. Just try it and you'll be surprised how fast this problem will go away.
     
  12. lantz_xvx

    lantz_xvx Senior Member

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    Good to know. Does running a narrower blanket to accommodate the T-Head cause problems in other areas?

    I'll confess, I did print a few two-color jobs yesterday in two passes because I just couldn't bring myself to waste my entire day trying to desensitize the water roller. I haven't yet tried the mixture of fountain solution / gum arabic that spike recommended, and I will, but I wanted to be sure that I could get some things done before I leave on vacation for a couple of weeks. I'm convinced that the larger problem is that water fountain roller being sensitized to the ink, getting completely saturated and causing scumming issues. BUT, knowing that blanket trick does help, as well.
     
  13. printman73

    printman73 Member

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    If you are talking about the (aluminum) water pickup roller on the t-head, the best solution for that is to clean it with blanket wash and get all of the ink off, take chrome cleaner (shake very well) and a cotton pad and really rub the roller well, then buff with dry rag until dry. A lot of black will come off. Take some straight fountain solution on another cotton pad and wipe clean and you are ready to go. You shouldn't have to do a lot of tricks just use the chrome cleaner every time you use the t-head and you will print clean. It is the only thing I have done for 20 years and the only thing that really works. AB Dick used to teach this when they had training courses years ago. To answer the blanket question, I figured this out years ago on my 360 when I added a t-head. The blankets they sold for the 360 were only 10 5/8 wide. I never had a problem with contamination until I got a 9840 and was using a 13" blanket all the time and a t-head. I have used 12" laser plates for 8 years and I battled contamination until I took the blanket off and cut it even on both sides to undercut my plates. If you need a wider blanket then use wider plates. I'm sorry I rambled on but those two things should eliminate your problems.
     
  14. lantz_xvx

    lantz_xvx Senior Member

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    Thanks, I'll give that a shot!
     
  15. Chris from Printshop

    Chris from Printshop Senior Member

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    Basics to start with ... is the press in good order and are the rollers and blankets good? Get the plates well-damped before you pull the lever to impression.

    Next ... the DARKER colour goes on the T-51. It hits the blanket AFTER the main press this way and most of the ink has gone by the time it gets back round there.

    ALSO ... once you've got the colours in register, use a deletion pen to delete as much as you can from one of the plates in terms of crop marks etc. ... ie: things that overprint each other. It sounds daft but crop marks and target marks will cause ink migration on common blanket presses.

    FINALLY ... make sure that there is nothing on either plate that goes beyond the edge of the paper during the run. Delete anything that does - colour bars, slug-lines etc. The ink builds-up on these areas and has nowhere to go, so it works its way back into the ink train and contaminates it.

    Oh, one more thing worth thinking about ... have a look at the platemaking side of things ... see if you can reduce the amount of trapping & overprinting on the artwork. You can normally get extremely tight register on common-blanket presses so you can get away with very little trapping where 2 colours meet.

    I hope this helps. I used to run a 9810 daily for about 5 years. Even if everything's perfect, you are still at risk of contamination. The only way I coped with it was to do everything I've listed about AND clean the blanket regularly. If I was doing ... say ... a 5k run in 2 spot colours, depending on the job I would expect to stop the press at 3 times to clean the blanket.
     
  16. ziggy33

    ziggy33 Senior Member

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    I run a t head all the time never in my life have i cut my blanket narrower and never have i had contamination but mine runs funny it likes the dark color on the t head and light on main. Just gotta find your presses niche and you won't have a problem.
     
  17. maverick1971

    maverick1971 Senior Member

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    Hi Guys,

    Not sure if any of you have a manual from Townsend Indusries (I do). The following recommendations in the T-51 manual might help together with the other suggestions.

    1. The lighter colour should always be run on the parent press!

    2. The chrome roller is desensitised using ordinary plate cleaner - once at the beginning of a run is sufficient.

    I have been running a Toko 4700N with a T-51 head for runs of 10K to 50K for over 6 years now and the above info from the manuals have helped.

    There is a lot of info in the respective manuals if you have a copy, unfortunately Townsend Industries closed down this year so you would have to source one privately.

    Hope this info helps.
     
  18. ziggy33

    ziggy33 Senior Member

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    I have the manual for the T-51 and would be more than happy to share it with someone who needs it.
     
  19. lantz_xvx

    lantz_xvx Senior Member

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    Thanks, folks. I do have the manual but the information contained in it is often not very helpful. It seems like ordinary plate cleaner no longer does the trick. I've been running the lighter press on the parent, cleaning the roller, buffing it, etc but nothing has seemed to work. I recently ran out of blue etch and haven't been able to go grab some more. It seems to help on the parent press water fountain roller, so I'm wondering if it will work on the T-head, as well.
     

  20. ziggy33

    ziggy33 Senior Member

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    yes it blue etch works good on the t head water roller also but some are so old you need a chrome cleaner on it first to get some of the old **** off
     
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