Pin holes in cold foil

Ask or answer questions related to the flexo pressroom environment

Moderator: Frank Burgos

Pin holes in cold foil

Postby amitahuja » Wed Jul 06, 2011 11:39 am

Hi,

We are doing cold foil on our press with the following:

Aniloxes tried: 250 LPI, 360 LPI, 400 LPI, Apex GTT L, Apex GTT M, Apex GTT XL
Foil: OP foil from Kurz
Adhesive: Foilbond from Flint
Plate thickness: 1.14mm (Cyrel Fast)
Tape: Tesa 52015 Medium Hard 0.381mm
Substrates tried: Mirror Coat 80 GSM, Self adhesive stock with face of mirror coat, Self adhesive stock with face of chromo paper

We have changed aniloxes, plates, different lots of foil, different lots of adhesive but still the problem of pin-holing in the foil does not end. The shore hardness of the nipping roller for foil is currently 70 -75 shore. Kurz suggests 80-85. Some other opinions are that we should try 30-35 or 40-45 shore nip rollers. Will this help?

Changed the foil unwind and rewind tension to high and low. Changed the nip pressures (since it is pneumatically operated nip roll for foil). Changed the UV power levels (GEW), changed foil unwind and rewind path. Made sure that there are absolutely no wrinkles at the point of nipping and no air trapped until it goes through the UV. Once it passes through the UV and goes to the roller beneath that, the foil is separated and we see some air trap at this roller where the paper and foil separate. Could this cause problems?

Examined the foil against sun and can see some pinholes in the foil itself (but far lesser than what we see when it is transferred to paper) and hence come to the conclusion that maybe the foil is ok. Ordered some more foil to see if we can get better foil and can reduce this problem.

Really tried everything we could but something is missing.

Worst part is that when we tried the foil at previous occasions with same variables, no pinhole problems were seen. Only change is that now the design is more solid (like a band of 12mm going around the label - it is a liquor label)

H E L P !!!!!

I am at my wit's end!
amitahuja
 
Posts: 5
Joined: Wed Jun 09, 2010 12:19 pm

Re: Pin holes in cold foil

Postby Fuzz » Wed Jul 06, 2011 2:26 pm

I have found a harder nip roll to work better than soft. What are the condition of your UV bulbs and reflectors? Press speed may need to be adjusted. Make sure all rollers clean and free of any debris. Try this foil on a different substrate and see if you still have the problem, you may need to prime the stock?
Also, I think Flint makes a foilbond for paper and for foils. Besure to use the correct one.
Fuzz
 
Posts: 206
Joined: Mon Jan 19, 2009 3:37 pm

Re: Pin holes in cold foil

Postby dutchflexo » Fri Jul 08, 2011 1:10 pm

hi amitahuja,

mine experince is that a harder tape works better for solids,when i run coldfoil i always use hard tape such as purple ore the baby bleu from 3m (i don`t now the codes for the tapes out of mine head) and it works very well for us,what fuzz says about the press speed is worth trying it couldt help with a better lay down of the gleu when you slow it down

Grtz dutchflexo
dutchflexo
 
Posts: 42
Joined: Tue Jul 07, 2009 1:06 pm

Re: Pin holes in cold foil

Postby flexo.uk » Sat Jul 09, 2011 12:07 pm

For cold foil I would recomend a 90 shore nip-roll. A hard tape is best, the blue 3M one is very good (1815 I think). Once you have tried different web paths, foils and adhesives all thats left is the material. Check the surface tension and prime if needed. We tend to put down a blockable varnish floodcoat just before the cold foil as this gives great results .
flexo.uk
 
Posts: 134
Joined: Tue Sep 25, 2007 11:29 am

Re: Pin holes in cold foil

Postby amitahuja » Wed Aug 24, 2011 12:36 pm

thanks all for your suggestions. a 90 shore roll with a hard tape did the trick for silver foil, but for gold foil, it has improved by 90%. 10% of the times it still has some problems in the gold foil. Adjusted the UV power but no result.

Thanks anyways for all the suggestions and getting us upto the 90% mark
amitahuja
 
Posts: 5
Joined: Wed Jun 09, 2010 12:19 pm

Re: Pin holes in cold foil

Postby univacco » Fri Aug 26, 2011 3:07 pm

I would suggest trying Univacco's cold foils. They run very well and are an excellent value. You can contact them at mweidman@univaccofoils.com.
univacco
 
Posts: 2
Joined: Fri Aug 26, 2011 2:03 pm

Re: Pin holes in cold foil

Postby gavinb » Wed Sep 21, 2011 7:21 am

univacco wrote:I would suggest trying Univacco's cold foils. They run very well and are an excellent value. You can contact them at mweidman@univaccofoils.com.


I agree with the above comment we running Univaco foils with excellent results.
gavinb
 
Posts: 12
Joined: Fri Nov 19, 2010 9:16 am

Re: Pin holes in cold foil

Postby flexolover » Tue Oct 25, 2011 1:47 am

Hi amit,
To get 90-95% you need to run the speed at 20-25 mts per minute with UV primer on the subsrtate on top and you need to use foil bond with differnt angle of nip roller and its diameter.
More over you need to avoid the bubble trap by having smaller dia of the seperater idle roller.
Which machine you use/
Better change the foil to some other roll and retry if the problem still persist !!!
good luck.
Regards,
Flexo lover.
flexolover
 
Posts: 65
Joined: Wed Nov 14, 2007 12:29 pm
Location: India


Return to Pressroom

Who is online

Users browsing this forum: Bing [Bot] and 1 guest

cron