Explaining Pad Printing
Closed Inkwell System
Through these diagrams we will explain how pad printing works with an closed inkwell system. A complete cycle is explained here step-by-step to provide better insight into the pad printing techniques. The main advantage of the closed inkcup system is that it reduces constant monitoring of an open inkwell, reduces potential contamination, reduces ink fumes, and increases print time.
The starting point. In this position, the cliché is covered with ink from the inkcup. The image in the cliché is filled with ink after the inkcup moves forward depositing ink inside the inkcup dimensions. Typically these are circular but other inkcup shapes can be sold to increase the print size. The depth of the cliché image is carefully engraved to approximately 25 microns.
The pad and the inkcup move back. The ceramic or steel ring on the inkcup scrapes all the excess ink backwards. From the moment ink is left in the recessed image area of the cliché, the outside air begins to evaporate making the top layer of the ink tacky. This tacky ink is important and is what is relied upon by the pad to pull the ink from the recessed image.
The pad and the inkcup move back. The inkcup ring scrapes all the excess ink backwards. From the moment ink is left in the recessed image area of the cliché, the outside air begins to evaporate making the top layer of the ink tacky. This tacky ink is important and is what is relied upon by the pad to pull the ink from the recessed image. Using the controls on the machine the pad must be adjusted with the lowest amount of pressure possible to pickup the image entirely without deforming the image.
The pad moves up and pulls the ink off the cliché. From that moment on, the bottom of the ink layer is now exposed to the air becoming tacky. Now, as in step 2, the thinner begins to evaporate from that side of the image.
At the same time the pad is moving forward to get into the position to deposit the image onto the part, the inkcup moves forward, once again filling the cliche and the recessed image with the ink to print on the part. The pad is now above the product to be printed.
The pad moves downwards and presses onto the product. The ink is transferred from the pad to the product. The force with which the printing is done is not important for the transfer of the ink. The mere touch of the pad ensures transfer. At this step, the lowest possible pressure is necessary to prevent deformation.
The pad moves back up to the starting position. The pad printing machine is now ready for the next cycle. This entire process from steps 1-7, is measured in mere seconds.