Thanks for all the replies. Agree in thinking it must be the heavy ink coverage/not completely dry although I just don't remember this being an issue until the last month or so. How long does a dye last in the grommet machine? Also it is definitely worse using the matte material than the gloss?? Not to get off subject but the matte ultraflex appears thinner than the gloss - or just my imagination? Again appreciate the input from everyone on this site! Have learned a lot from it.
Dies, it's 'die' not 'dye', in grommet presses measure their lives in geologic eras.
The matte version of a banner material may well be thinner or thicker that the gloss version. Banner material is categorized by weight not by thickness. The weight rating of any particular banner media means that's the weight on one square yard of the stuff. Weight only coincidentally maps into thickness if at all.
Back to your original problem. The cause of wrinkles around grommets has two fundamental causes which may or may not be exacerbated by more or less ink or whether Venus is in the third trine of Mars.
The first cause being setting the grommet too slowly. The faster you push down the handle of your grommet press the cleaner the grommet.
The second cause is draping the banner over the bottom die. I took a 4"x4" square of 3/4" MDO. I drilled a hole exactly the same size as the diameter of the bottom die of my press centered and about 1/4", depending you want the distance from the center of the hole to the edge to be 1", from one edge. Somewhere in the archives of this sand pile I posted a picture of it. Slip this mini table over the bottom die and now the banner media is supported and lays relatively flat as the grommet is set.
Not only that, the table serves as a gauge. It's exactly 2" from either edge to the center of the grommet and it's 1" from the back edge to the center of the grommet. If you scribe a line 1" on either side of the die hole you can line up banner corners with either scribed line and the back edge. If you scribe a line on the back edge centered on the die hole you can line up non-corner grommets on this line and the back edge and they'll be set at the right spot and the proper distance from the banner's edge. Since the edges are 2" from the center of the die you can line up coroplast with the edges and the grommet will be exactly 2" in.