Selecting Pad Printing Machine | Buy Guide
ORIGIN OF PAD PRINTING MACHINE
Who invented Pad Printing Machine?
Pad Printing is about 200 years old, where they used to transfer motifs on to Blue China Plates / Dinnerware with the help of Hand using a bag of soft gelatin material. Plates were made of copper which were engraved manually my hand.
Industrial Pad Printing Machine which was mechanical in nature was developed much later by Swiss Watch Industry to print their watch dials, Pads were still made of gelatine and they used Slow Drying Oil Based Inks.
In the late 1960s the process was further developed in Germany with the introduction of silicone rubber pads and mechanical machines; with the help of Wiederhold (now Coates Screen, part of Sun Chemicals) a range of pad printing inks were developed to allow the process to print onto a wide range of products and materials. Now Pad Printing Machine was ready for Mass Production
PROCESS OF PAD PRINTING
How Pad Printing is achieved?
Pad printing is an indirect photogravure process. An image is etched into a flat printing plate and ink is flooded and doctored across the surface leaving ink only in the etch. A silicone rubber pad then presses down onto the etched plate and picks up the ink, which due to solvent evaporation has become tacky.
The image is now on the surface of the silicone pad. Silicone rubber does not allow ink to penetrate its surface and therefore when the pad presses down onto the product to be printed it releases the ink as a clean film. The range of inks and solvents used enable the inks to adhere to the surface after releasing the ink the pad is then clean and free to repeat the process.
Because such a wide range of inks are available almost any material can be printed and due to the flexibility of the silicone rubber pads uneven, curved and awkward shaped surfaces can be printed. As the ink is quick drying, pad printing is capable of ‘wet on wet’ printing and high quality multicolour designs can easily be achieved including four colour process.
The more recent development of closed cup machines has made the process ‘cleaner’ and enabled the process to become more user friendly and automated.
INK TRANSFER IN THEORY
How Ink is transfered to the substrate?
Pad printing is an indirect offset (or a gravure) printing process, where an image is transferred via a soft silicone pad onto the surface to be printed. Today there are two primary doctoring methods used. One being the old traditional open inkwell system (illustrated below) and two being the newer more widely accepted sealed cup system. For the sake of starting with the basics, we have illustrated the old “standard” method below.
To do this, a clichÃ© plate is used that has the artwork chemically etched into the lapped smooth steel surface (photo polymer clichÃ©s can also be used). Typically the etch depth is around .001″ to .0012″ or 24 to 28 microns.
Using a “flood bar” the etched image is flooded (coated) with ink and then a doctor blade (steel ink blade) removes the ink from the flat printing plate, leaving a deposit of ink in the etched area only. The silicone pad or tampon then lifts the ink from the etched image and transfers the image directly onto the surface to be printed. By virtue of the shape of the silicone pad, the ink releases onto the product to be decorated and the silicone pad moves back to its “home” position, ready for another print cycle.
Today in pad printing, transfer pads made from silicone rubber are used almost exclusively since the silicone materials are the best known release agents for this printing process. Also there has been some pad printing done using Polyurethane pads, for specialized applications
APPLICATION OF PAD PRINTING
Still today, pad printing is not well known as a printing process, but we see and touch pad printed items every day. For example:
- Electronic micro components, such as cables, connectors, IC chips, relays, etc.
- Industrial Buttons and Keys as found on calculators, telephones and computer keyboards
- Electrical Household Appliances such as iron, VCR, TV, coffee pots, telephones, etc.
- Large Industrial Appliance panels such as on dishwashers, washing machines and dryers
- Toys such as figurines, dolls, cars, infant bottles, pacifiers, rattles and night lights.
- Advertising Specialty Items like pens, lighters, key chains, clocks, watch faces
- Sporting Goods such as golf balls, baseballs, tennis rackets, footballs