Pad Printing: The Process, its Advantages, and Applications
What is Pad Printing?
Pad printing is the process of printing a two-dimensional image on a three-dimensional object.
It is also called tampography and is basically an indirect photogravure process. This means that the process involves the heat transfers of an image to the medium or substrate using a silicone pad (or an indirect offset/ gravure, as it is called) in a printing machine or print equipment.
The image is etched on to a flat printing plate, which is then filled with ink.
A smooth surfaced silicone pad with chemical resistances is then used to carry the ink from the plate and transfer it onto the object. The silicone pad used in the pad printer is what gives the process its name.
Silicone is used as the transfer medium as it does not absorb the ink into itself.
The History of Pad Printing
Pad printing has undergone a lot of development from the time it was used first. These days we have automated pad print which is highly efficient.
One of the main reasons pad printing has found itself in today’s printing industry is due to the discovery of silicone as the perfect medium in the printing press.
Although it is unclear who invented pad printing or when, printing items using this method finds its roots in the watch industry.
In early years, a gelatine pad was used instead of silicone to transfer images onto the surfaces of watches by using flame treatment.
The Advantages of Pad Printing
The main advantage of pad printing lies in the silicone pad.
Since silicone can easily adapt to irregularly shaped surfaces, pad printing can be done on almost any kind of object.
From printing on plastic three-dimensional parts to embossed or etched surfaces or even golf balls, pad printing can be used for a wide variety of applications.
The process makes use of height compensators for ink cups to print at different levels in one printing run.
Is Pad Printing Better Than Other Methods of Printing?
Each type of printing method has its own advantages and disadvantages.
It is not a question of whether pad printing is the best printing method among the others like the inkjet printer, but if pad printing is ideal for the task at hand.
The Process of Pad Printing
Pad printing makes it possible to easily print simple images such as a printed logo as well as high-resolution photo prints on irregular three-dimensional objects.
Once the production runs of the printing cycle start, the ink is applied over the image (inside the etching) and excess ink is cleared off by a ring blade.
Thus the ink seeps into the depression of the plate containing the image. The pad is then made to come in contact with the printing plate, and the image is transferred onto it.
This ink is then transferred on to the surface to be printed on. The sticky ink film detaches from the surface of the silicone pad and sticks onto the medium. The silicone pad is then returned to home position.
In pad printing, the ink layer is about 4 to 20 microns thin. Thus it is possible to apply a second layer of ink without even drying the first layer.
This saves precious time during multicolour printing.
Devices such as pad sliding devices, rotary or shutter tables, etc. are used for such heavy duty purposes.
How To Select The Pad For Printing?
The printing pad is the most important component of the hot stamp or pad printing process. It is essential that you choose hard, pointed, and large transfer pads in color pad printers for the following reasons:
- The harder the printing pad, the sharper the contours and finer the lines in your plate etching. This is because you are printing on hard, irregular, three dimensional surfaces, and it is hard otherwise to get a perfect etched image or print.
- A steep color pad allows air trapped in the ink to escape easily during the pickup and transfer of a specified amount of ink from inkwell systems in sealed ink cup.
- Larger pads are less likely to deform, thus greatly reducing any distortions that may be caused by the pad during printing.
Activation, Maintenance, and Storage of Printing Pads
Activating a New Printing Pad
Before you use the printing pad for the first time, it is important to de-oil them carefully.
To do this, soak some thin paper towels in ink thinner and gently wipe down the surface of the custom pad. Rough or dry scrubbing of the automated pad will easily damage the printing pad surface.
Dry the cleaned pad and it is ready for its first use.
Cleaning and Storage of Printing Pads
In case dust or ink residue collects on the surface of the printing pad, it should be cleaned with a mild adhesive tape. The stickiness of the tape will ensure that the residue is gently removed from its surface.
Once cleaned after use, the printing pads can be stored in a dimly lit area.
Be careful to avoid the surface of the pad coming in contact with objects or even other printing pads or cup systems, as this can damage it.
Plates Used in Pad Printing
The plate holds the image that is to be transferred by the printing pad to the surface to be printed on.
The print is directly affected by the quality of this laser plate. Some of the most commonly used plates for pad printing are:
- Plastic Plates
- Steel Plates
- Ceramic Plates
Preparation of The Plate:
Depending on the application, there are many different kinds of plates that can be used in tampography.
The images are etched onto the plates, which have a photosensitive layer on them. However, ceramic plates are not easily etched by conventional marking systems, so they are lasered.
A thin film that contains the image is placed on the plate and UV light (ultraviolet radiation) is applied to it in exposure units. The parts covered by the image are then either washed out or etched.
1. Plastic Plates:
Plastic plates are used for many different applications. They are cheaper than other types of plates, are flexible, and are easy to work with.
They can be used for small and medium-sized productions in heat press.
They consist of a thin metal sheet that is covered with a photosensitive plastic layer. The plates are exposed to UV light and then washed off with water or a solvent.
2. Steel Plates:
These plates are made of high-quality steel. They are tough and durable and can be used for larger productions.
Based on their application, some steel plates are polished or coated with chrome.
Steel plates are etched using a laser engraver.
Inks Used in Pad Printing:
Depending on their application, various types of printing inks are used in pad printing machines.
The pad printing ink contains binding agents such as epoxy, resins, or polyester, and color pigments are added to it.
Apart from these main components, the inks contain solvents, additives, fillers, and other materials.
Depending on their contents, pad printing inks are of 4 types – one component inks, two component inks, mixed inks, and LED inks (which can be cured/ dried faster using LED light).
Pad Printing Applications:
Pad printing is a very popular printing process and is used in a variety of printing applications.
Industries such as medical equipment, automotive, promotional product or promotional items, business cards, garments, electronic goods, toys, sports equipment and apparel, etc. prefer the pad printing process over digital printing to print product logos and other images onto objects.
This method of printing by using pad printing equipment is used in many other industries as well, such as the electronics industry, computer industry, telecommunications industry, in automobiles, household appliances, jewellery making, plastic industry, etc.
For more information on pad printing, contact Unipipes Malaysia!