Printing pads can dramatically differ in size. The smallest of printing pads can weigh a few ounces, why the largest pads can weigh as much as 50 pounds. Choosing the correct pad size can be determined by many factors, including image area, product shape, surface of product to be printed on and machine dimensions.
Choosing the correct printing pad size for a specific application requires a sufficient amount of silicone to be present to avoid image distortion. When the pad compresses onto the printing plate and part, the print surface of the pad is absorbed into the pad body. The body of the pad acts as a support mechanism for the pads print surface. If the print surface is not
adequately supported (tooling, holding fixture), it will deform, resulting in image distortion. It may seem that the simple solution is to oversize all the printing pads, but before making this decision there are important factors that need to be considered:
1. The printing pad must fit into the machine. Specifically, it must clear all obstacles that a
2. When compressed, the printing pad must not stretch into the ink buildup that could be present on the ink cup path perimeter.
3. The machine must be capable of compressing the mass of silicone present. Silicone durometer is part of this variable. If these criteria points cannot be satisfied, the pad is too large.
Pad Tip Placement
The tip, or peak of the printing pad should not be used to pick up or transfer ink. The pad tip should be placed in non-
printing areas, offset tip from the image on the printing plate. There are many reasons to not print with the tip of a printing pad:
1. The printing pad tip has very little or no angle of descent.
2. The printing pad tip area tends to slide, leaving an imperfection on the printing surface.
3. The printing pad tip is a high wear area, because it is part of the pad surface that comes in contact first with the printing plate and the parts to be printed. This is a problem that may not show up until some cycles later and effects the print quality.
Repositioning the printing pad to the image on the printing plate can be accomplished with an adjustable pad coupler or sometimes called an adjustable pad stem holder, repositioning the artwork location on the printing plate, or make other adjustments on the machine itself.
Pad Care and Maintenance
Receiving of Printing Pads
Once you have received your printing pads, it is recommended to check the pads for blemishes or defects that could hinder print quality.
Storing Printing Pads
Were and how you store printing pads is important, it is recommended that pads be stored in a cabinet with doors, away from dust and dirt. An important note is to not store printing pads in plastic bags which causes the silicone to sweat. All printing pads should be stored with the bases down and nothing touching the silicone. If anything touches or lays on the
silicone for any extended period of time it can cause an imperfection that could be permanent. If an imperfection is in the printing area, the pad cannot be used successfully. Used pads should be cleaned with isopropyl alcohol (IPA) and a soft towel before storage to ensure that the surface is clean and ready for the next use.
Getting the Longest Pad Life
Printing pad life has a range from 10,000 cycles to 70,000 cycles depending on the application and how aggressive the ink system may be. When hardener is used in the ink system pad life will be reduced. The surface of the product to be printed will also have an impact on pad life. Surfaces that are flat and free of ridges or protrusions will promote longer life than surfaces that have these factors. A few recommendations to help extend pad life:
1. Use a good quality silicone type for the ink you are using.
2. Try not to use the same printing pad every day. Alternate pads at least every other day.
3. Only use clear cellophane tape or Isopropyl Alcohol (IPA) to clean pads if possible. (Aggressive solvent that do not contain any oils can be used but will shorten the pad life.)