Mylar film is not tight around the buttons or buttons come loose?
*What?* If the film is not tight around the edge of the buttons it is often due to one of the following reasons. Mylar film and paper must be able to move very smoothly in the moulds. Otherwise they will rub against each other too much causing air bubbles on the edge of the buttons . In extreme cases, the foil may even hang loose or the button may come apart.
1: rough button dies* For perfect operation, the 3 dies (2 bottom, 1 top) must be very clean and completely free from bumps or sticky layers of dust. You can clean the dies by vigorously rubbing them with household roll or a cotton cloth. Do this until they really shine again!
The slanting inner edge of mould 2 is particularly important! You should also lubricate these surfaces a little with a super smooth pure silicone grease. Use it sparingly and rub the moulds lightly afterwards so that no residue remains on the paper and foil. Your dies are now supple and smooth again. Repeat per ca. 500 buttons.
2: Heavy/dark printing* With some paper types with printing (usually laser prints with a dark or full colour) up to the edge of the cut paper, you get too much friction between paper and foil. This is microscopic and cannot be felt. Your prints, however, should appear very smooth. If you test blank papers without any printing, you will notice that the foil closes tightly. (If point 1* above is correct)
The friction is mainly on the outer edge, where the paper disappears into the button backing. The solution is to limit the printing to the visible zone of a finished button (to the edge where the paper disappears between the cans). So at the back of the finished button you will see a white border as small as possible. But not visible in use.
The picture above makes this clear. The outer circle is your thin printed cutting circle. Then there is a white unprinted border to avoid rubbing. The central circle with cross is the front (button size) of your buttons. What lies beyond is the visible side of the buttons that continues until the white zone where the side disappears into the back.
For all formats, this white border is slightly different (and the small formats are not affected):
38mm > total diameter from visible zone to white border: approx. 40.50mm
44mm > total diameter from visible zone to white border: approx. 46.50mm
56mm > total diameter from visible zone to white border: approx. 59.00mm
75mm > total diameter from visible zone to white border: approx. 79.90mm
Finally, limiting the printing to this edge is always recommended in order to achieve extra smooth edges (and save ink).