Screen E-Book (.PDF) - MacDermid Autotype

At 100lpi we have exactly the same absolute dot gain (30µm) but because the spot is only203µm compared to 508µm there is 32% dot gain for a 50% dot.This is the key reason why printers have so much trouble when they go to higher lpi inresponse to demands from their customers. If they keep their same high Rz stencils, theirdot gain becomes enormous.Negative sawtoothing (Technical printing)Negative sawtoothing visibleonly on the leadingedge of horizontal linesThis is the opposite effect to positive sawtoothing. The printed line has chunks eaten outof it. And mysteriously (to the printer) the negative sawtoothing only takes place on theleading edge of the line.The cause is a high EOM stencil. The squeegee cannot get enough ink into the stencil atthis point, and if the ink doesn’t touch the substrate then it doesn’t get printed, so you getthe chunk eaten out of your printed line.Very often we ask “What’s the EOM of your stencil?” and the printer doesn’t know “ Becauseour screen supplier told us it would be fine”. We generally carry an EOM meter around withus, and on our laptop we have the Line Edge Demonstrator software that explains why thehigh EOM leads to the negative sawtoothing.85