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Pad printing - 27 Sep, 2012

Pad printing


Pad printing, also known as “tampon” printing, is a centuries-old technology that is now the most common method used in the toy industry to print fine color images on the surfaces of models and toys. The reason is simple: the printing quality surpasses other types of decorating methods, such as silk-screen printing and wet-transfer decals.



5-head multi-color pad printing machine that can print 5 different colors at the same time.


The origin of pad printing can be traced back more than 200 years, when the first offset type of hand-transfer printing was done using a bag of soft gelatin material to transfer the image. This type of hand-transfer was originally used to transfer images onto blue-china plates and dinnerware. The first true industrial application using a mechanical pad printer was accomplished much later in Switzerland to imprint watch faces. Later, a German firm was known to have developed a pad printer, and the first application was reported to be for the imprinting of multi-colored eyes on china dolls.  This industrial process was implemented to help speed production along, and to eliminate the need for intensive painting skills.


The main advantage of pad printing over other similar printing methods is that it is able to print onto many types of irregularly shaped surfaces, while other printing methods are typically limited to flat, two-dimensional surfaces only.



The silicon pad of pad printing


Tampon printing, as developed by the German firm Tampoprint AG, is an automated indirect offset printing process, or one in which an image is robotically transferred from a negative plate to the model surface via a soft silicone pad. The starting point is a steel plate that has the artwork chemically photo-etched into its surface, which is then lapped to a smooth finish.  Using an inking tool called a “flood bar,” the etched image is flooded, or coated with ink, and then a scraper resembling a doctor’s scalpel removes the excess ink from the plate, leaving a deposit of ink only in the etched area. A mechanical arm presses the silicon pad, or “tampon,” against the steel plate and the pad imprints with the ink from the etched image. The pad then lifts off, slides over to the model, which has been set in a fixture by the operator, and lightly presses down, transferring the image directly onto the surface to be printed. By virtue of the shape of the silicon pad, the ink releases onto the surface to be decorated. Then the silicone pad moves back to its home position, ready for another print cycle.



Tampon printing has the limitation of width. Printing of long striping in a single hit usually  not longer than 6” (15 cm)


Tampon-type pad printing can be so fine that it is often used to print very delicate lines and images on watch dial faces. In the case of car-model manufacturing, most of the dashboard gauges, knobs, and color trim are done with tampon printing. The process can even simulate a wood-grain or carbon fiber texture.



Wood grain texture console by pad printing


Colorful racing livery also appears best when applied using pad printing. The colors stay shiny for years, but there are also limitations to pad printing, including:


  -  The printed area is limited to the size of the silicon pad.
  -  Each printing cycle only transfers one color, and only in a small area.
  -  Long lines require multiple prints and must be aligned correctly.



Single or multiple tampon hits in one small print area and in one color are fairly inexpensive and straightforward. However, when it comes to printing long striping with multiple colors (i.e.: BMW’s M-Motorsport three-colored stripes), it is a complicated, challenging, and costly process. A race car such as the BMW 3.0 CSL has long, multi-color striping all over the body. To accurately replicate this look on the model, it requires 155 precise tampon print transfers because of the width limitation in tampon printing. To achieve 155 hits—and in multiple colors—with precise accuracy is extremely difficult. There is a high margin of error and a significant rejection rate.


When a multi-color striped racing livery stretches across the car, the tampon striping process will involve multiple stampings to connect the stripes and make it seamless and perfectly aligned. Even a slight misalignment, particularly on a curved body panel, will be obvious to the naked eye and the model will be flawed, calling for the removal of the ink. This, in itself, is a painstaking process that adds to the cost.  In the worst-case-scenario, the body has to be scrapped. When the stripe is comprised of three colors, as is the case with the BMW, the chance of misalignment is multiplied by three.



However, AUTOart insists on using long, multi-color tampon printing on a racing car because the end result is shiny and vibrant and true to the look of the real race car. There are similar scale models in the marketplace offered by competitors at marginally lower prices, on which the long striping is applied only with wet-transfer decals.  These are made with all the colors pre-printed on a flat piece of clear membrane that is glued to a piece of backing paper.  When dipped into water, the glue softens and the pre-printed membrane separates from the backing paper and can be transferred onto the model.  The water decal process is more simple and less-costly when the graphic consists of multi colors as compared to tampon printing.


However, there are disadvantages using water decal. When the graphic consists of irregular shape, lines or multi letters, there must be a layer of transparent membrane connecting them in between or else, it would be almost impossible for the worker to apply the decal on the surface nicely and accurately when the water decal consists of many individual lines or letters.  The clear membrane portion of decal reflects the body color duller and over time, it turns yellowish. The membrane itself is also susceptible to scratching and age-related cracking.



In between the letters, there must be a transparent layer to connect them together to become one sheet of water decal enabling the worker to apply it easily onto the surface.  Over time, the clear portion of the decal turns yellowish and susceptible to scratching.


Tampon printing allows the color to sit securely on the surface of the paint without being scratched off easily, and it remains shiny and vibrant for years. For premium collectible products, AUTOart believes this is the ideal method.



When the printed surface angle is too steep or the color striping extends into an area where the space is too confined for the silicon pad to work its way onto the surface area, then a water decal must be used in combination with tampon printing—but only in those areas where tampon printing alone is no longer able to perform the job.  Moreover, when the graphic consists of colours with gradient effect between darker and lighter shades, it would be very difficult to achieve by tampon printing; in this case, water decal is the ideal way to achieve such effect.



The multi-colored long striping is curved in different angles; it is very challenging to apply it nicely by pad printing.


To the naked eye, pad printing can be so fine that it may appear to be a scratch on the model car’s surface. But a closer inspection with a magnifying glass reveals that it is in fact a brand name that has been printed to the accurate scale.

A Youtube short video clip shows how tampon printing works.