How Pad Printing Works
Pad Printing is probably the most versatile of all printing processes due to its unique ability to print on three-dimensional objects, compound angles and textured surfaces.
 
The theory behind the pad-printing process was derived from the screen, rubber stamp and photogravure processes. 

Pad printing gives us the ability to print on the following substrates and many others not listed:


ABS Plastic     Acrylic     Aluminum     Brass     Ceramic     Coated Paper     Copper     Felt     Galvanized Steel     Glass     Kraft Paper     Latex     Leather     Mylar     Natural Fabrics     Neoprene     Painted Surfaces     Plexiglass     Polyethelene     Polypropylene     Polyvinyl Chloride     Porcelain     Rubber     Silicon     Stainless Steel     Styrene     Synthetic Fabrics     Textiles     Urethane     Vinyl     Wood

Pad Printing Machine
The Process

Step 1: Flooding
The image to be transferred is etched into a printing plate commonly referred to as a cliché. Once mounted in the machine, the cliché is flooded with ink. The surface of the cliché is then doctored clean, leaving ink only in the image area. As solvents evaporate from the image area, the ink's ability to adhere to the silicone transfer pad increases.


Step 2: Pick Up
The pad is positioned directly over the cliché, pressed onto it to pick up the ink, and then lifted away. The physical changes that take place in the ink during flooding (and wiping) account for its ability to leave the recessed engraving in favor of the pad.


Step 3: Print Stroke

After the pad has lifted away from the cliché to its complete vertical height, there is a delay before the ink is deposited on the substrate. During this stage, the ink has just enough adhesion to stick to the pad (it can be easily wiped off, yet does not drip). The ink on the pad surface once again undergoes physical changes: solvents evaporate from the outer ink layer that is exposed to the atmosphere, making it tacky and more viscous.


Step 4: Ink Deposit
The pad is pressed down onto the substrate, conforming to it's shape and depositing the ink in the desired location. Even though it compresses considerably during this step, the contoured pad is designed to roll away from the substrate surface rather than press against it flatly. A properly designed pad, in fact will never form a 0-degree contact angle with the substrate; such a situation would trap air between the pad and the part, resulting in an incomplete transfer.


Step 5: Pad Release

The pad lifts away from the substrate and assumes its original shape again, leaving all of the ink on the substrate. The ink undergoes physical changes during the head stroke and loses its affinity for the pad. When the pad is pressed onto the substrate, the adhesion between the ink and the substrate is greater than the adhesion between the ink and pad, resulting in a virtually complete deposit of the ink. This leaves the pad clean and ready for the next print cycle.
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