We are using a windmill with photopolymer embossing plates. This is the first time we have tried cold embossing with this style of plate. It was very easy to setup and worked fine on the uncoated stocks but gave us issues with the 20pt Lettra. We got areas where the paper did not want to raise 100% up and appeared to tear or bunch up and did not give a clean finished look. It was like an air pocket in the paper and as such there was no paper to compress to the final image. It occured mostly on the lower shoulder of the inside loop of lower case a’s and o’s was very minor and you saw it best with a loop but not as much with naked eye. I did not know if the lack of heat or a issue of the built in clearance in the die was the problem. As the pressure was backed off it seamed to go away. We have also been using some of the Strathmore Impress Cotton which seamed to work fine and did not have quite the same problem but I did not have a large sample to test.
We wondered if the lack a calendering in Lettra is part of the issue. Sorry long post, but since I don’t really know what I am doing I must be missing something.

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i would think 20 pt anything would be a tall order for a poly die with no heat. i really think a metal die with heat would be better. lifting and relaying the counter die is always my first “go to” if embossing problems. Especially if you are changing pressure for different stocks.
I often have to “Make ready” under an emboss, just as with foil or ink.

Embossing - I’m finding this thread interesting, I have only embossed twice in my career, the first time nearly 50 years ago with a steel die and a counter made from plaster of Paris mixed with gutta percha covered in tissue. The second time printing my Christmas Cards in November using a magnesium die and polymer counter. The counter was approx. 0.045 thou thick which is just over packing thickness for a windmill, thus avoiding the gripper. So with a 200 gsm board gave a good result. I am a little surprised at the thickness of the material being mentioned, it doesn’t seem to meet the optimum printing requirements for a windmill. I look forward to seeing more comments from people who emboss regular basis.

Thanks for the feedback. I was wondering what is a good thickness range for embossing is. The reason we ask is we have done very little embossing in 40 years of business, just never got the call for it. In the last 5 years we began doing our own letterpress printing and keep experimenting. We did this partly as a test.

Hi ericm - we know heat would be better but did this as a test for cold embossing with a laser cut plate and counter from Crownflexo. They laser cut the both the male and female and it adds the pins for register. It took me 10 minutes to set up into position and I did not have the issues of a hot plate and bunter posts to fight. The cost is about 30% of what I would pay for a copper die and vendor made counter. For some types of projects that savings is the a large percent of a job total.

Where I get confused is how to pack this out. The total height of the counter ( including relief) is .063 inches (4.5 points) which we mounted to a 15 pt poly glass board which was 15.5 pt with tape. There is about .0241 inches(1.75 points) relief built into the counter. This gave us 20 pt base pack (amount included relief) mounted to the steel platten with a 20 pt Lettra sheet. Our pressure was close to 0 and we brought it up to taste. I am wondering how I should do the math and if I made a mistake somewhere. It seamed to work but we wonder. It was one of those things you crap here it goes, feed a sheet and say huh I think it worked.