Screen E-Book (.PDF) - MacDermid Autotype

The reason the high-Rz gives such a large variation is subtle. There are two competingeffects. A high pressure can give more total ink printed and therefore a lower resistance.But much of that extra ink is along a sawtoothed edge which gives a higher resistancebecause there is no continuous path. If the total volume printed is the same (comparedto a perfect stencil) but more of it spreads out into the sawtoothed edges then the overallresistance is higher, which is what we measure.The extra widthgained by the Rzspreading providesvery poor conductivityso the effectiveconductive widthis likely to be thatshown between thered linesDot-gain (spreading) (Graphics printing)A high Rz stencil automatically causes the ink to spread. The amount of spread is underpoor control as it depends strongly on squeegee pressure and ink viscosity. To stop suchdot-gain you have no choice but to go to a low-Rz stencil.That blue ink is goingto spread alongthe Rz channelsand the amount ofspread is going todepend on viscosityand squeegee pressureso is going tobe out of control.83