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Need Help UV Ink not adhering to Coroplast signs. (Peeling Ink, Sun Exposure)

Discussion in 'General Signmaking Topics' started by AllStarNow, Nov 4, 2020.

  1. AllStarNow

    AllStarNow New Member

    Mar 20, 2017
    Lafayette, La
    We have had some issues with our UV Ink not adhering to Coro signs. Mainly 10mm but sometimes 4mm. The sun facing side receives the most damage with these signs being only 6 months to a year old (some even less). The printer is a HP Scitex FB550 with HP FB794 series UV ink. The signs are allowed to cure but are unlaminated. We've been told before by our substrate supplier that this was due to a bad batch of Coro, but it has happened on more than one batch. Just wondering if someone with more experience could tell us why this might be happening and the best way to prevent it. I've attached a picture of an example.

    Attached Files:

  2. Christian @ 2CT Media

    Christian @ 2CT Media Major Contributor

    Jun 15, 2009
    Mesa, Arizona
    This is common on coro with HP inks. The ink is incredibly sensitive to changes in dyne levels of aging corona treatments. You need to make sure your coro is fresh. Possibly switch from coro for 1 year plus signs

    WYLDGFI Merchant Member

    Oct 27, 2006
    Linden, NJ
    Check your max ink in your rip software. If you have the ability to limit to CMYK only...avoid using Lc Lm if you can. Even on So/so coroplast we have had good luck from day one of our UV printer experience.
    • Agree Agree x 1
  4. FireSprint.com

    FireSprint.com Trade Only Screen & Digital Sign Printing

    Try Kolorcure Metal and Glass Primer, and try a different supplier.

    Print some tests and soak them [submerged] in water overnight for another test that might show poor adhesion.

    We can help with this as well:
    4mm Wholesale Yard Signs
    10mm Wholesale Yard Signs
  5. we have had this issue on and off for years with our HP45500 and now with our HP FB750. We have noticed that it is a combination of bad (old) UV lamps that do not get hot enough after supposed 500 hours of use and bad coroplast. I don't completely undersdtand how the UV lamp can affect this in such a huge way. A light bulb is a light bulb, in my opinion.

    WYLDGFI Merchant Member

    Oct 27, 2006
    Linden, NJ
    We used to have Vutek printers with Mercury Vapor UV Lamps...they wore out over time similar to the HP's mentioned above. The lamps dont go bad, they wear out over time. The wavelength generated to Cure the inks degrade and dont cure as well. Its not a heat process but a hardening process initiated by the light wavelengths. Heat is more associated with Solvent, Eco Solvent and Latex inks. Heat is Bad with UV printers as most know...it warps substrates like Styrene and Coroplast. The other issue could be Quartz filters over the lamps that aren't clean as well. They prevent heat from getting to the material (some but not all) and allow the proper wavelength thru to cure the inks. We always changed our lamps around 400-500 hours maximum. The Led lamps today last 10k hours or more before replacement.
    • Like Like x 3
    • Informative Informative x 1
  7. bigben

    bigben Very Active Member

    Sep 3, 2007
    sorry for the :thread but is there a process or a printer that would ''garantee'' the print would look good on coro for around 10 years? We are working on an architectural product that is printed on coro or have to be on something lightweight like that and need to last around 10 years outdoor.
  8. zspace

    zspace Merchant Member

    Jul 9, 2013
    Houston, TX
    Corona treatment on 10mm Coro is always questionable since it doesn't move through distribution as fast as 4mm. The comments about UV lamp degradation are on target. Eventually you will have to replace lamps. In the interim, increasing passes may help some, you could also check profiles to make sure you aren't over saturating some colors.

    Good luck,

  9. Gino

    Gino Premium Subscriber

    Jun 7, 2006
    Never happen. There are no inks gonna last much more than 4 to 6 years regardless of what machine puts it down or what manufacturer produced the inks. The 10mm Cor-X seems to not take ink as well for us, either. Never has. It seems to have a slightly different surface.

    Also, with the lamps...... with your first pass, if the lamps are weak, they are not adhering to WHATEVER surface you're printing to, therefore each and every pass after that just adheres to the inks already there. So, your initial ink which has no adhesion will peel back, taking all the other ink with it. Kinda simple equation. If you painted a board with tempera paints for a primer and then painted it with 6 top coats of whatever paint you desire..... think it's gonna stay, just because you put 8 passes down ?? It's the old weakest link theory.
  10. balstestrat

    balstestrat Active Member

    Aug 25, 2020
    Between the bits
    Latex ink sticks to Coro really well. Doesn't chip and not easy to scratch off.
    But even if you laminate that I don't think the Coro would last that long as "looking good".
  11. StratoJet

    StratoJet Merchant Member

    Aug 31, 2020
    It’s kind of the perfect storm with Coro and things not going as planned. Coro doesn’t like heat exposure but older UV ink systems require more UV curing exposure to it = more heat. UV inks do not like to stick to heated surfaces, they adhere great to each other but not to some Coro without extra steps. You can try to wiping them down with alcohol (some Coro has a film/coating left over by the manufacturing process) and/or try to apply a promoter. Coro over the years has also changed and the surface is generally less porous, making it difficult to print on and low ink durability. UV printers from years ago and even now, do not provide enough velocity that inks are propelled through the print heads for the newer media with less porous and harder surfaces to penetrate the substrates’ surface deeper (microscopically) to begin with.
    Low UV lamp efficiency is a killer (UV lamps produce less and less UV wavelength every time you use them, at some point, they need to be replaced). On top of that, HP had stoped developing their UV inks to keep up with changing media years ago
    • Agree Agree x 1
  12. TammieH

    TammieH Very Active Member

    Nov 28, 2011
    Pacific NW
    Find a wholesale silk screen company that use Coro-Gloss ink...I know. Blasphemy!
  13. Superior_Adam

    Superior_Adam Member

    Dec 13, 2017
    Wichita, Kansas
    When it comes to curing ink a light bulb just isn't a light bulb. Over time they lose the power which in turn does not cure ink. That is why they have a life and most printers now are LED.
  14. signage

    signage Major Contributor

    Oct 5, 2005
    LED's also degrade with time.
  15. Superior_Adam

    Superior_Adam Member

    Dec 13, 2017
    Wichita, Kansas
    Yes all lights will degrade over time. We are talking
    about LEDs at 10,000 hours vs mercury bulbs at 500 hours. LEDs also produce less heat so they can put out a stronger wavelength to cure inks better without having the concern of heat warping the material.
    • Like Like x 1
    • Agree Agree x 1
  16. petepaz

    petepaz Major Contributor

    Feb 14, 2007
    we have a fuji, acuity UV and a roland LEJ uv. for whatever reason the fuji inks don't stick as good as the roland inks with coro.
    we have big uv dryers we use for silk screening and with the acuity prints we sometimes have to run them through the uv dryers to give them better curing.

    WYLDGFI Merchant Member

    Oct 27, 2006
    Linden, NJ
    Agfa inks stick very well to Coroplast and 99% of substrates for us. We have issues with Polycarbonate and some other other low dyne factor substrates.
  18. MarkH42

    MarkH42 Member

    Aug 11, 2010
    Birmingham, AL
    We had this exact issue. We resolved it (after a LOT of trial and error) by coating every coroplast sign we print with an adhesion promotor we bought from Grimco made by Supply55. The product is "AP3155". A little goes a long way. At the same time we bought that product, we changed the coroplast profile in our FB550 to a newer one that uses less ink. I can't say for sure which of these resolved the issue, but between these two adjustments, we have not had a problem since. Good luck!

    WYLDGFI Merchant Member

    Oct 27, 2006
    Linden, NJ
    Wow...thats a lot fo added labor just to print to coroplast. I would say the Lower ink levels would have worked on the 550. Also changing to CMYK and removing LC & LM if you have those would also help.
  20. Troy Lesher

    Troy Lesher Merchant Member

    May 23, 2018
    a lot of valid info above, Dyne levels, UV lamps settings, and deterioration mostly on the old style Merc vapor Lamps, and too much ink., but the biggest real issue is just inks that don't stick. The good News is we have an inkset that sticks absolutely, the bad thing (maybe/maybe not) is its formulated for our Printers.

    https://www.dropbox.com/s/2h499tlqmz76yer/Scratch test.wmv?dl=0

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