Troubleshooting the pad-printing process requires the identification and control of associated variables. The tips presented here will help you avoid some of the persistent problems you encounter on press.
By Julian Joffe
Three major considerations when choosing a pad for a project include, but are not limited to, the geometry of the pad, the size of the pad, and the durometer or hardness of the pad. When choosing a pad, the operator must first consider the shape of the object he is printing on and the print position on that object. If the shape of the pad tends to trap air between the pad and the object being printed, then the ink will fail to transfer. Many operators opt for a flat pad, which causes this problem to occur.
One should not shy away from pointy pads (Figure 1). Ideally, an operator should choose a pad that will lead with a point or edge that will begin to compress onto the etched area of the cliche, slowly rolling out so as to prevent air bubbles from being trapped between the pad-and-ink interface, thus preventing the pad from picking up the molecules of ink and evenly pushing air out from underneath it in all directions, similarly onto the object being printed, therefore allowing the ink to release again without air separating the ink from the printed surface.
The shape of the object and the print on it will determine whether it is best to use a round or rectangular pad, an extremely pointy pad, a rooftop-shaped pad, or a gradually compounded curved pad. When setting up your print, always check for the location of the print on the pad. Try to avoid the print on the lead point of the pad where air can be trapped on the initial contact of the pad on the cliche. When there is no way of avoiding print at the point, opt for a pad with a more gradual curve in the center.
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