What is Pad Printing?
Any way you look at it, Pad Printing is an unlikely imaging process. It borrows a unique amalgamation of features from gravure, screenprinting and rubber stamp printing, yet its most frequent industrial decorating competitor is none of these processes. Instead, Pad Printing most often encroaches on jobs once dominated by Hot Stamping. Even the process itself is somewhat befuddling. If the ink is so attracted by the silicone pad that it leaves the recessed areas of the printing plate, why does it abandon the pad so completely upon touching the substrate? Unlikely as it may be however, this process is finding increasing favour in a host of commercial and industrial applications. Why?
It is adaptable to a variety of shapes and contours on parts with a variation in the surface, yet fine detail and precise copy can be achieved. Four color process is obtained with exact registration. Pad printing is ideal for decorating toys, plastic housewares, and injection molded components. This technology also lends itself to marking electronic components such as resistors, canisters, and connectors. Any part, plastic, ceramic, or metal can be production marked by this process. The equipment can be semi or fully automated, yet remains a low capital expenditure technology.
Features of Pad Printing:
Following are the unique features of the Pad Printing process.
Can print on convex, concave, curved, recessed and discontinuous surfaces allowing product designers a substantially broader range of shapes and designs.
Pad printing is able to print shapes and surface structures well outside the capabilities of Screen Printing and Hot Stamping opening up a way to decorate a whole new range of products.
Allows wet-on-wet multicolour printing (without intermediate drying) on non-absorbent surfaces - therefore much reduced down time.
Is capable of 90 degree wraparound on three-dimensional objects.
Offers better edge definition and higher resolution than most other printing systems therefore offering a method of decorating high quality high priced items.
Is a relatively inexpensive printing system particularly for multi-colour and process colour printing which means reduced capital outlay.
The many advantages of Pad Printing:
Variety of substrates - Almost any material including glass, ceramic, metal can be printed with suitable inks.
Ability to print fine details - Resolution is far better than that of screen printing in fact up to 120 lines / Cm (300 lines per inch)
High resistance of printing inks - Depending on ink type used extremely high resistance against mechanical abrasion or chemicals can be achieved.
Easy handling and little maintenance - Compared to other printing processes pad printing is easy to learn
Multi-colour printing: wet on wet - Possibility to apply multiple prints without intermediate drying
Short tooling-up times - Plates and inks can be exchanged within a few minutes
Low set up cost - Plates can be produced in-house
Relatively low space requirement - Compared to other printing machines pad printing equipment is space efficient
Low drying cost - In the most simple case air drying at room temperature is sufficient.
Integration into complex systems, inline production and assembly lines - For years now there has been a successful combination of pad printing systems with injection moulding equipment or assembly lines.
Limitations of Pad Printing:
Size of motive - Motive sizes are limited by plate, pad and efficiency of the pad printing machine. The diameters of the largest efficiently printed motives are currently approx. 30 cm.
Layer thickness of ink film - The pad process uses plates up to a depth of approx. 20-25µm (at the most 35µm). Thus conventional inks will result in printed ink films of approx. 7µm. This layer thickness can be increased correspondingly by multi-layer printing. Rough particles (e.g. glitter pigments) are difficult to print in an efficient manner
Printing speed - Even substrates can be printed a lot faster with other printing processes.
What does the process require?
Artwork i.e. the image that is to be printed. Because Pad Printing is often used for its ability to print very fine detail Artwork can be quite specialised.
A film positive, which is produced from the artwork.
A printing plate, which is either a "plastic" or steel printing plate, referred to as a cliché. Onto this cliché we have etched an image (from the film positive) into the surface. So the image is said to be in relief rather than in profile as in letterpress printing.
A Pad Printing machine to facilitate the inking and doctoring of the image, the pick up of the image from the cliché and the put down of the image onto the item being printed.
A Tampon or Pad, which is moulded from silicone rubber.
Specialist Pad printing ink.