The Real Reason For Success Or Failure in Pad Printing:
Keeping Track of What's Going On in Your Operation

KEEPING track of what is really going on in your pad printing department is the tool that will make it possible to attain and maintain your production goals. If you have talked to our support team, attended printing training or have been involved in pad printing for a while, you are aware that there is not always a ‘black and white’ procedure when establishing your printer setup and ink mixture. There are many reasons for the lack of certainty surrounding the process, but they do not need to remain a mystery.

Identify the Variables
Identifying the variables and determining the solutions are accomplished through the use of some inexpensive ‘tools’ and a monitoring schedule. The tools required are a thermometer, a humidistat and a pencil and paper. I have included a short (two hours) sample monitoring chart. Although it probably won't fit your needs exactly, it can be used as a guideline. You need to monitor the process closely to gather enough data to make a reliable determination. You might wonder if the results will be worth the effort. The answer is a resounding "yes"!

What are we looking for?
What does the data tell us? To make use of the data, we need to review the printing process. The steps in the printing process are: (1) the ink must be cleaned off the cliché while leaving ink in the etched area; (2) the exposed ink on the cliche needs to tack up enough to be picked up by the pad; (3) the pad picks up the ink by compressing the pad onto the cliché; (4) the exposed ink on the pad tacks up enough to be transferred to the part; (6) the image is transferred to the part by compressing the pad onto the part.

Let’s suppose the data we collect shows that the temperature stays consistent through the day (within five degrees) but the humidity drops from 65% in the morning to 35% by mid-afternoon (with the air conditioning running) or humidity stays consistent, but the temperature goes from 75 degrees in the morning to 95 degrees in the afternoon (with no air conditioning). Our reject and stoppage data shows that around lunch time, we start to see voids in the image on the part and the operator struggles the rest of the afternoon trying to correct the problem. Production suffers and the operator loses a little more hair.

What has happened here?
When the problem occurs the following day, we interrupt the print cycle immediately after picking up the ink and find that only part of the image is on the pad. This tells us that the ink is drying too quickly in the cliché. The drop in humidity or increase in temperature is making the solvents evaporate quicker. We compensate for the change in humidity by switching to a slower evaporating thinner at lunch time– before the problem starts. An alternate solution would be to adjust the speed of the machine: run slower to lengthen the time the ink is exposed in the morning and run faster to shorten the time the ink is exposed in the afternoon.

On multicolor pad printing machines, you may find that different colors or different image sizes require different thinner types and/or mix ratios to perform properly (even though they are running on the same machine). Some inks will require more thinner to promote good doctoring (cleaning of the plate) than what would be ideal for the printing process alone. A large, open image will require more drying time during printing than a small or fine-lined image. You might be able to speed up the drying with a pad blower (blowing compressed air on the image or pad) or pad delay (the printer pauses after picking up the image).

As you can see, the causes and solutions are many and can be hard to find without some detective work. The good thing is that the detective work can be done in a very orderly and logical way and a cause can be determined. As always, our support staff is always ready to assist you with solutions.