In the case of silicone rubber, there are basically two different systems: crosslinking by polycondensation and crosslinking by polyaddition. Physical properties, such as tear resistance or resistance to swelling in contact with solvents, are better in polyaddition crosslinking materials than in polycondensation systems. Obtaining the raw material is more expensive, however. The smoothness of the surface is a decisive factor in the quality of the print. The smallest impurities or air bubbles caused by defects in manufacturing result in unclear print. In the beginning, new pads tend not to pick the ink up from the cliche as well. This problem can be solved by making a few prints on paper or by a short cleaning operation using alcohol. If cleaned with aggressive agents, such as thinner, the pad immediately takes the ink from the cliche, but does not transfer it to the piece to be printed quite as well. Once a pad is “broken in”, it is recommendable to dab its surface with adhesive tape to remove any dust particles.
Regarding the pad itself, virtually all pads today are made of silicone rubber. At CAREPRINT we use only the best quality silicone rubber materials available. In the past, the first printing pads were made of gelatine and in these early days there was a limited range of pad shapes available due to the poor mechanical properties of gelatine, and these pads were designed much flatter than modern day silicone pads, because of gelatines lack of elasticity.
At CAREPRINT we provide both wood and aluminum bases – and ALL of our bases are mounted accurately and all wooden bases
We do not recommend having the operator use wood screws to mount the pad to his pad holder, as this old-school method makes it very difficult to get repeatable pad positioning and it results in lengthy set-up times. Furthermore if you use wood screws to mount your pads, after you have taken the screws in and out several times, the wood is quickly stripped out and will no longer firmly hold the pad to the mounting bracket. On many occasions, I have seen pads literally fall off the machine during production because of this problem.
Similarly, if a setup requires multiple pads (such as found on a keyboard matrix), aluminum bases are preferable because they will make pad positioning easier and more repeatable. Another advantage to using aluminum bases is that they can be recycled with CAREPRINT and we can remount these bases for you onto new silicone rubber.