Scratch Foil Inconsistent
Hi All,
Looking for some tips for a foil dilemma. Were using a scratch-off foil that is suddenly giving very inconsistent results. After 23,000 impressions the foil isn’t sticking and it looks like it’s gassing. Not sure why it’s happening as the stock doesn’t have any AQ coating. I want to blame the foil but apparently, it is all new stock from the same master roll.
Faster, slower, hotter, cooler, (265-310) and trying different epoxy boards/phenolic boards aren’t cutting it. Adjusting make ready or foil tension doesn’t change it up either.
The foil is BG 501 stamped onto 100lb dull cover. Offset printed. The stamping press is a Kluge EHD. The die is .25” mag.
Thank You.
try stamping clear foil over the image, maybe even blind hitting with mylar. then the scratch. this kinda thing happens. something changed, the foil people won’t admit to it. the printer people won’t admit to it. the paper people won’t admit to it. it is your problem now, been there.
you can try block sanding the die. Mag dies get real soft when hot. if you happened to have have had a double or worse, a triple fed sheet, the die could be “cupped”. this could be causing your instantaneous problem. in the attached pic, you can see where the sanding block has worn around the perimeter. the block must be VERY flat. i use a large piece of letter.
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Hi Eric,
Thank you. Your input helped me understand the issue and I believe we were experiencing trapped air. We took an impression onto carbon paper that revealed the die to be cupped as you said. We block sanded the die a bit but also built layered paper “dome” under the makeready to focus pressure on the center outward. The area was a 2” circle so this was simple and it improved the results by a large amount.
Thanks again
wow, a 2in circle is a big area for scratch off. maybe try some latex under thin glassboard. definntly dome make ready
It’s 2x2 inch 3 up on a sheet.
I have some tough film I can try under the glassboard
I also have a softer black makeready board has been helping too. Thank you.
i think the black urethane is too firm. i like tough film under thin glass board for mag dies above 290 F indicated on set temp for the EHD
I switched to copper dies years ago, too many problems with magnesium dies. Cost is about the same.
30 years ago, Mag dies were a significant savings. But now, copper is about 15% more. Then there is the slight expense in weight in shipping, if, you are doing any volume. Okay, but, Copper is MUCH more valuable to recycle than mag. and Copper does not start on fire and burn through concrete. Go stop in to your local fire extinguisher store and ask for one one that puts out “Flammable Metals”.
Mag dies corrode quickly. dent easily when heated, scratch easily, cup under pressure of double feeds, and are just not worth the hassle. they no longer “Cute”….