This discussion expains how you can make the most of your machine by considering all aspects of production, from climate and press location to substrate readiness and ink preparation.
Much has been written about pad-printing machines. Closed-cup, open-ink-well, single-color, and multicolor systems are regularly explored in industry trade journals. When you get right down to it, the goal with all these machines is simply to lay down a controlled thickness of ink and replicate the original artwork consistently. Although the pad press is at the heart of this process, what can really make the difference between an accurate and efficient printing system and a complete disaster is the way ancillary equipment and consumables are involved.
The trap that most people fall into when they buy their first pad-printing press is that they don't prepare for its arrival. They fail to think through the entire process and all the other components and procedures that must be in place for it to work properly. For many, this lack of preparation can lead to months, or years, of suffering with an unpredictable and uncontrollable system. The printers blame their difficulties on inherent faults in the equipment that they feel they have to live with. What they don't realize is that they must understand and control the variables that affect the process for pad printing to become an effective decorating method.
On the following pages, we'll explore a range of concerns that newcomers to pad printing frequently overlook. We'll also explain how these issues can be overcome with certain tools and techniques that should be familiar to every pad-printing operation.
The image-transfer mechanism of pad printing is based on the evaporation of solvents in the ink (Figure 1). As solvents evaporate from the ink, they increase the surface tack of the ink film, which enables the ink to transfer from the cliche to the pad and from the pad to the final substrate. The speed at which evaporation occurs depends on the solvent mix used in the ink, as well as the temperature, humidity, and air movement around the machine. Altering any of these conditions will affect the solvent-evaporation rate and, consequently, the effectiveness of ink transfer. You want the solvents to evaporate fast enough to increase surface tack while keeping the ink fluid below the surface so that it lifts from etched cliche and transfers from the pad.
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