At 100lpi we have exactly the same absolute dot gain (30µm) but because the spot is only 203µm 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 in response to demands from their customers. If they keep their same high Rz stencils, their dot gain becomes enormous.
Negative sawtoothing (Technical printing)
Negative sawtoothing visible only on the leading edge of horizontal lines
This is the opposite effect to positive sawtoothing. The printed line has chunks eaten out of it. And mysteriously (to the printer) the negative sawtoothing only takes place on the leading edge of the line. The cause is a high EOM stencil. The squeegee cannot get enough ink into the stencil at this point, and if the ink doesn’t touch the substrate then it doesn’t get printed, so you get the chunk eaten out of your printed line. Very often we ask “What’s the EOM of your stencil?” and the printer doesn’t know “ Because our screen supplier told us it would be fine”. We generally carry an EOM meter around with us, and on our laptop we have the Line Edge Demonstrator software that explains why the high EOM leads to the negative sawtoothing.
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