One of the most difficult questions to answer about the pad printing process is, “How do I determine what pad to use?” One answer won’t apply for every shop or application. Rather than lay down inflexible rules, this article will provide a methodology for determining the optimum pad characteristics and a framework you can work within to get the best performance from your pads time after time.
The key to good pad printing is to reduce and control the variables. Though the function of the pad seems simple – to transfer the image from the printing plate onto the substrate – it is subject to print quality fluctuations if the correct pad type is not chosen or used properly.
Five key pad characteristics can affect the quality of the printed image. These include shape, size, hardness, surface finish, and material. Vary any one of these and the print quality will shift. These factors must be taken into account when planning the job and ordering pads from suppliers.
Shape and Size
Shape is the most important variable in selecting a pad. In order to achieve a satisfactory print, the pad surface must roll onto the plate and the image area of the substrate. The shape of the pad largely determines how well the pad will achieve this rolling action. This makes shape the most important variable in selecting a pad. Most pad suppliers have hundreds of pad shapes in their standard inventory, but the majority are based on three basic shapes: round, rectangular, and bar Each of these shapes could have either curved or flat printing surfaces, depending on the nature of the part to be printed. Regardless of what shape the pad has, it must roll onto both the plate and substrate for good printing results. Try to avoid flat-bottomed pads, as they have a tendency to trap air when they come into contact with the plate, hampering ink pick-up.
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