Pad Printers - Principle of Operation



Step One Pad Printing: Flooding

This is commonly referred to as being the machine's "home" position. The hermetically sealed ink cup is over the image area of the cliché, thus flooding the image area with ink.

Step Two Pad Printing: Doctoring

Doctoring occurs when the either the cliché actuates under the ink cup as in this example, or the ink cup actuates over the surface of the cliche. In either case the end result is that the surface of the cliche is left clean, with ink only in the etched image area. As solvents evaporate from the surface of the ink, the ink's ability to adhere to the silicone transfer pad increases.

Step Three Pad Printing: Image Pick-up

The pad is pressed onto the surface, then lifted away. The physical changes that take place in the ink during flooding and doctoring allow it to leave the etched image area in favor of the transfer pad.

Steps Four and Five Pad Printing: Print Stroke

Once the pad is lifted away from the cliché, the ink on the pad's surface undergoes physical changes as solvents evaporate from the outside of the ink layer, making it tackier (increasing surface tension).

Step Six Pad Printing : Image Transfer

The pad is compressed onto the substrate to transfer the image. Even though the pad compresses considerably during this step, the contour of the pad is designed to roll out onto the substrate's surface, rather then press flat against it. A properly selected pad, in fact, will never form a zero degree angle of contact with the substrate. Such a situation would trap air between the pad and the substrate, resulting in the incomplete transfer of the image.

Upon completion of the print stroke the machine returns to “home” and is ready for the next printing cycle.