VARIOPRINT Pad printing
Technology, application and different models according to your needs
The printing plate holds the deeper printing image to be printed in its surface. The scraper presses the paint into the deeper printing image and cleanly scrapes off the excess paint. At the same time as the scraping process, a pad made of silicon rubber moves from the printed goods to the plate. The pad is lower over the printing block and thereby takes on the printing image. Pad printing is therefore an indirect printing method. Then, the pad lifts and moves to the printing material. There, the pad lowers and fits itself to the plate.
The advantage of this print transfer is the malleability of the pad, through which printing of curved surfaces (convex, concave or irregular) is enabled. Due to its elasticity, the pad takes on the shape of the item to be printed on and can therefore ideally transfer the motif to the printing material. The printing image is transferred to the print item. The transfer of paint onto the printing material is nearly 100%, due to the silicon oil base in the pad.
Due to its adaptability when printing, pad printing can be used on any conceivable items. Examples of fields of application are the printing of syringes, toys, CDs, crockery, screw caps, lighters and tool handles. Particularly also in the automotive sector, many parts are decorated using pad printing. Each of us has already touched an indicator or windscreen wiper lever.
In the advertising media industry and with model trains, this printing technique is used particularly frequently, as a great deal of advertising merchandise and railway models do not have even surfaces.
The mechanical structure of the painting system is differentiated into three basic types:
Open painting system
From approx. 1971, the paint is in an open paint reservoir, is painted over the printing block by the paint spatula and the excess paint is scraped off by the scraper. An advantage of this system is given with large printing surfaces. With small printing surfaces, this painting system is regarded as being obsolete.
Closed painting system
From approx. 1983, paint is in a hermetically sealed paint pot, which simultaneously contains the scraping element and scrapes off the excess paint, through a surrounding scraper ring made of hard metal or ceramic. The scraper ring is simultaneously the sealing element. In order that paint does not leak, the pot is press against the printing block, with some machines, this takes place with magnets, with others, using an adjustable spring preload or a pneumatic press.
Rotation pad printing
From approx. 1981, for printing on round parts or for continuous printing. The pad and the printing blocks are shaped as rolls and therefore allow a continuous movement process. The paint is in an open paint reservoir. Application, e.g. in systems for printing bottle caps or plastic profiles.
With some pad printing machines, the movements take place pneumatically, while with others, primarily fast machines, they take place electromechanically using curved disks. The latest generation of pad printing machines is driven by electromechanical linear axle, which ensures a programmable process flow. Through automatic parts recognition, diverse print images can be specified, without the printing block needing to the changed.
High-quality machines usually have automatic equipment for cleaning the pad (pad cleaning, residual paint collection). Machines to be integrated in automation are purposefully equipped with SPS controls and matching interfaces.
1-color pad printing machines
2 color pad printing machine