By allowing for the application of a 2D image to a 3D object, pad printing has revolutionized the business of marketing. No longer has confined to flat sheets of paper or a workforce of artisans that paint logos on oddly shaped items. Companies were able to industrialize the production and distribution of their images.
A Brief History
More than 200 years ago, it was discovered that by using a bag of gelatin, ink could be transferred from a hand-engraved metal printing plate to any item imaginable. This first became popular for plate makers to decorate dinnerware with the famous blue designs but soon was industrialized by the Swiss for watches. Though time consuming with the gelatin now have images carved into it then filled with ink, it proved that it was potentially beneficial for mass production. However, it wasn?t until the 1960s that it really took off in popularity following the introduction of silicon as a replacement for gelatin. This simple switch allowed for the use of different inks that then allowed for even more surfaces that could be printed on.
Two Methods
Currently, two methods of pad printing are in use today.
The first and more popular method is the closed cup process. All this really means is that the ink is kept in a closed container. When ready to print, this cup is positioned over the etching and then fills it with ink. As soon as the cup moves off of the now filled etching, its surface becomes tacky due to the air starting its process of drying out the ink. The silicon pad presses down on this and the ink sticks to the silicon. After being lifted up, the bottom of the ink is now exposed to the air, creating a second tacky surface, while the original top layer rehydrates, making it less adhesive. The pad is now pressed onto the object being printed on and the transferal is complete.
The second method is the older method and is known as open inkwell. Next to the etched image sits an open inkwell. When ready, a doctor blade transfers ink from the inkwell into the etching by pushing it forward. It then scrapes away excess ink as it is pulled back to the well. The rest of the transference process is the same as the closed cup.
General Information
Pad printing is an extremely favorable method of printing as the items used to make it happen have a high longevity. Steel plates alone can produce over 1,000,000 imprints. That being said, steel is rather expensive, leading many to use nylon plates. The tradeoff, though, is that these can only produce around 40,000.
As for the silicone pads, these are offered in a vast array of shapes, densities and sizes.