Troubleshooting the pad-printing process requires the identification and control of associated variables. The tips presented here will help you avoid some of the persistent problems you encounter on press.
By Julian Joffe
The most common mistake made in pad printing is to change several variables in the process at once. To know what to avoid, we should first understand what variables commonly cause problems. For example, if you have a problem and think that it may be directly related to a particular setting or variable, make only one change to that single variable and review the result. If the change is made to multiple variables at once, the results get confusing and you run the risk of never solving the essential problem. If the problem goes away after several changes, you still may never know what the real problem was or its related solution.
Case in point
After printing an image onto a smooth plastic substrate, the image only partially transfers with small, irregular missing parts. I look at the pad and see what missing pieces are not there. Logically, those parts were not picked up by the pad; therefore, they could not be transferred. I decide to replace the pad and to re-etch the cliche. I choose a harder pad, thinking that it would do a better job. Next, I re-etch the cliche a little deeper because I think that the etched area is not deep enough, and that is why the image has not been picked up. I remix the ink. I do not record the viscosity, but I remember to document the viscosity and the amount of thinner used. After all this, the image comes out perfect.
I have no idea what fixed the problem, but everyone is happy. The next day, while working on the same job, my operator mixes the ink and uses a different formula—mixing the ink with retarder as well. She uses the same pad and cliche that I had changed to the day before. This time the image looks terrible. The ink that is missing on the image is left behind on the pad. The operator then grabs the old pad and cliche and replaces her ink cup with her ink mix-ture in it. The image comes out perfect. What happened?
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