I've been asked to try and find a resolution to a problem we've been experiencing on one of our presses. When we print an image, the image on the paper grows or expands about 1/64" operator side to gear side. In other words, it prints slightly wider than it is on the plate. I understand that because of the curving of the plate around the cylinder that there can be some growth in the length of the image in the direction of the web, but we're seeing it across the page, perpendicular to the cylinder. Could too much impression cause the image to squeeze out? Or should I be looking for something else? Anyone deal with this before? Thank you.
It must be either plate packing,blanket packing or uneven pressure when engaging impression. My first test would be to try another print unit if possible, if the problem still occurs it may caused by the type of paper you are printing on. To calibrate plate and blanket packing is easy enough but to adjust uneven impression or even bearer pressure is best done by your maintenance people.
Thanks John. We did several tests including checking our bearer pressure. The only thing we did find that seemed to help, and maybe it was just coincidence, but we didn't have a lot of plate to blanket squeeze... only .0025 so we think our operators were trying to compensate that lack of transfer by cranking their impression. We put a thicker blanket on (this press takes sticky back blankets, so we can't pack them) to give them 2 thousandths more squeeze, which gave them better transfer. Giving the operators better transfer between plate and blanket meant that visually they didn't think they needed to keep increasing the impression. Anyway, long story short... we're still seeing a slight growth, but not as much as we were before, and not enough to cause issues.
Many pressman are sure of pressure issues when they see it. I would double check the thickness of the blanket and have the plate and impression cylinders adjusted accordingly. It may be you have too much pressure in both your plate to blanket and from your blanket to impression cylinder.Check with the manufacture to verify what they need to be set at. Thicker blankets will add pressure to both plate and impression cylinders.