There are countless applications for pad printing – really any object or part that isn’t flat but requires some form of graphics. Common uses though include sporting items, the letters on keyboards and calculators, computers, TVs, monitors, children’s toys, items with serial numbers, branded items, medical devices, glasses, bottles and more.
How Does it Work?
First the image will be etched onto a plate called a ‘cliché’ or a ‘stereotype’ (an interesting bit of etymology there). This will effectively be the stamp that you are going to use to transfer the image over and over and what will ensure that the image is identical each time. Typically this plate will be made from steel or ‘photopolymer’ (which is easier to use), with thicker plates being more suitable for long runs – a hardened steel plate can last for well over a million impressions. This plate will then be covered with an ink cup (a cup containing ink). This ink cup will be sealed to avoid the ink drying and to help keep the ink in place.
Once the ink (a solvent based ink that requires mixing with additves prior to use) is placed onto the design, it will begin filling up the etched image. Once this is full, the ink cup will move away taking away the excess ink not in the lines. Exposed to the air for the first time, the ink will then become sticky.
Next a ‘transfer pad’ (which gives pad printing its name) will be pressed up against the printing plate. This transfer pad as you can imagine will then pick up the ink from the printing plate, retaining the desired design (though it will be reversed of course). This transfer pad will be made from a flexible, silicone material meaning it will be able to easily flex and wrap around the shape of the part you want to print onto. In this scenario your part will be known as a ‘substrate’, and of course it’s important that it be clean and free from contamination.
The pad will be pressed against the substrate making sure that it touches each surface firmly to transfer the ink, before it is carefully removed and the ink on the substrate is allowed to dry. Often this entire process will be carried out automatically via assembly line systems.
Advantages and Disadvantages
The advantages of pad printing are obvious, allowing you to easily transfer images to any products you can think of. On top of this, pad printing is also relatively cost effective and highly versatile whether you have convex, concave, curved, discontinuous or recessed surfaces. The finished article also tends to look pretty good with pad printing, creating images with high resolutions and edge definition suitable for ‘premium’ products. Printing fine details is no problem, and tooling-up is quick and easy.
There are also downsides to pad printing though, as with any manufacturing technique. If you have a large flat surface for instance, then there are much quicker and more efficient methods that can be used for printing. There are also limitations in the size of the motif, based on the size of the plate and the efficiency of the pad printing machine. Usually this upper limit is around 30cm in diameter.
You need to think carefully as well about how you are going to design your graphics, and about how they will look once they have been wrapped around the 3D object and transferred. This means thinking about where bends and creases will be once the image has been applied to the three dimensional surfaces, and designing it in such a way that everything lines up. This can be visualized using 3D modelling software and applying your graphics as skins to the models.
