Industrial & Specialty Printing - July/August 2012 - Insert2

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FUNCTIONAL PRINTING: New Opportunities for Roll-to-Roll Screen Printing
Interview with Christian Maas, Ph.D., Chief Technology Oﬃcer and Co-Managing Director at Kammann Maschinenbau GmbH

HOW WOULD YOU CHARACTERIZE FUNCTIONAL PRINTING? It is more process manufacturing oriented than traditional CMYK printing. Functional printing has a different set of demands with an emphasis on product consistency, repeatability, and ﬂexibility. The material deposition of electrical circuitry requires excellent printing registration and consistent layer thicknesses. WHAT ARE THE ADVANTAGES OF FLAT SCREEN PRINTING? Flat screen printing is possibly the most versatile method of printing available, enabling a wide variety of material substrates to be used along with the widest possible range of different inks or coatings. It can process almost every liquid or paste-like substance—conductive, semi-conductive, resistive, dielectric inks etc. Flat screen printing produces the high and consistent layer thicknesses required by almost all functional printing applications. And ﬁnally, screens are cost-effective to manufacture with a full range of applicable meshes. YOU REFER TO HIGH-END FLAT SCREEN PRINTING. WHAT DO YOU MEAN BY THAT? High-end screen printing overcomes the traditional limits associated with ﬂat screen printing. The combination of a modular, precise, roll-to-roll system with advanced drying technology results in a highly accurate, productive printing system. While a traditional ﬂat screen system can print at speeds of 65 ft/min and an accuracy of ± 100—200 µm, our K 61 roll-to-roll machine can print at speeds up to 131 ft/min with a print accuracy of up to ± 50 µm. WHAT ARE THE ADVANTAGES OF CONTINUOUS ROLL-TO-ROLL COMPARED TO SHEET-FED AND SEMI-ROTARY SYSTEMS? For sheet-fed systems, sheet handling and off-line drying consume a good portion of the overall cycle time. Continuous production can be achieved on a roll-to-roll system due to in-line hot air drying and sophisticated web-tension controls. Constant web tension controls allow for accurate registration and thin caliper substrates. The servo tension control can adjust for elastic changes in the substrate due to dryer heat. On semi-rotary systems, changing web-tension because of loop-boxes entails registration accuracy restrictions. HOW DOES KAMMANN ACHIEVE HIGH-END FLAT SCREEN PRODUCTIVITY? The productivity of our ﬂat screen printing module starts with precise servo-technology to facilitate ﬂexibility, modularity, and accuracy. The moving ink roller provides exact ink transfer while its 30° tilted ﬂat screen improves ink handling and printing results. It can not only handle a variety of substrates and ink ﬁlm thicknesses, but the screen stations as well as other modules can be conﬁgured in any order.

DOESN’T DRYING SPEED ULTIMATELY AFFECT HOW PRODUCTIVE THE SYSTEM CAN BE? Yes, the drying/curing process of the special inks dictates the production rate of machine. Drying is a balancing act where the thermal requirements of the printed piece meet the material limits of the substrate and inks. To maximize efﬁciencies, drying should be done in-line. Off-line drying ovens and slow conveyor dryers do not meet productivity standards. Rotary systems, however, can‘t take advantage of high-speed due to drying restrictions. The ﬂat screen roll-to-roll speed, however, is perfectly adapted to the solvent ink processes. The high-performance dryer module, which can be conﬁgured to hot air, UV, or IR, is engineered specially to print electronic devices. The compact and efﬁcient design handles over 26 ft of web in the dryer at one time—all in less than 6 ft of linear ﬂoor space. CAN YOU GIVE ME SOME EXAMPLES OF FUNCTIONAL PRINTING APPLICATIONS THAT KAMMANN HAS HANDLED? The range of functional printing that can be produced on our K 61 machine includes glucose test strips, electrodes for EKG machines and deﬁbrillators, solar, ﬂexible batteries, antennas, RFID tags, and even automotive sealing material. WHAT ARE SOME OF FACTORS THAT GO INTO THE LARGE SCALE PRODUCTION OF SOMETHING LIKE A GLUCOSE TEST STRIP? To produce the different layers of conductive ink and enzymes that make up simple electrical circuits entails accurately printing on 350 µm polyester material, using solvent-based ink and hot air drying. High registration accuracy is required to meet the circuit requirements. We’ve seen dramatic productivity improvements. For one customer, the previous sheetfed/conveyor dryer production speed of 2.25 ft/min was replaced by a roll-fed production speed of 32 ft/min which translates into more than 14 times more efﬁcient. FINAL THOUGHTS? Functional printing is exciting for us because of the technological challenges and its potential. We look forward to meeting those challenges every day in every application.

Flexible. Precise. Innovative.

www.kammann.com 630-513-8091 Sales@Kammann.com

Industrial & Specialty Printing - July/August 2012

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