Stork Prints Finds Solution for High Paste Dot Application

BOXMEER, the Netherlands—Stork Prints, the inventor of rotary screen printing technology, may have found a solution to a problem that the coating and printing industry has been coping with for a long time—how to apply high dots of paste on a substrate without the problem of smearing. Wim Claassen, application specialist at Stork’s Technology Centre, found the answer while working in a situation where the required dot height was causing the pre-flow problem of paste pouring through the screen before the substrate reached the application point.

“I found that we could solve this problem by using special screens, and extra rollers to guide the substrate around the screen. This way, the substrate itself stops the paste from dripping through, at the exact spot where it should be applied anyway,” he explains. “Once we discovered this worked, I just couldn’t imagine why nobody had thought of it before. Just think of glue dots, anti-skid patterns, relief printing and lots of other applications, both for functional and aesthetic reasons. Combined with the advantages of rotary screen technology, this is a great way to add value to products.”

At Stork’s Technology Centre, specialists have already succeeded in applying dots and patterns from 50 to 1,000 µm, instead of the 50 to 200 µm that has always been considered the maximum possible dot height.

“It is very likely that we will succeed in applying even higher dots,” says Claassen, “but we are still testing this. Our invention also provides more design freedom because it enables the use of larger screen holes and lower viscosity pastes.”

After succeeding in guiding the substrate around the screen, Claassen also tested if it could solve another persistent screen printing problem: screen blocking caused by dried out paste. His solution turned out to do so, by preventing the evaporation of solvents in pastes, which often occurs in processes requiring a slow printing speed, such as coating cling film.

“For both these solutions there’s one important condition,” concludes Claassen. “The use of good, stable screens that can resist the increased fabric tension. But, for the kind of applications concerned, you’d need thick screens anyway.”