The latest generation of roll-to-roll screen-printing systems marks a significant evolutionary step in the press technology that has dominated since the early 1900’s. Now, the incorporation of more sophisticated electronic controls reduces the need for time-consuming manual adjustments that typify earlier and less sophisticated equipment. In this discussion, we will consider how state-of-the-art electronic controls and software integration are changing the capabilities of roll-to-roll screen-printing systems, including both flatbed models and cylinder-based equipment.
The underlying electronics and software engineering that now have bearing on screen-printing technology are cut from the same cloth as the electronic controls we now see in a wide swatch of industrial equipment. At the core are programmable logic controllers (PLCs)— computers geared to provide stability in real-world manufacturing conditions and able to handle multiple inputs and outputs. PLCs, originally developed for the automotive industry, are now programmed with more sophisticated instructions than when they were originally introduced, enabling expert programmers to fine tune industrial controls to an unprecedented extent. This includes today’s PLCs that can fully automate the steps in roll-to-roll screen printing.
Adjustments to the screen clamps, as well as squeegee and floodbar pressures, can now be achieved with touch screens operating pneumatic controls via the system’s PLC. This eliminates a good deal of time that had previously been spent by operators making mechanical adjustments to balance these components for each job. On today’s roll-to-roll presses, no tools are required to make these adjustments—they are all done electronically and with greater precision and repeatability than what human operators can typically muster. If and when fault conditions arise, they can also be corrected with a few keystrokes.
Going from a manually sheet-fed printing process to an automated web process can speed throughput by 50% or more. The actual speed improvement varies, and is dependent on the size of the job, among other factors.
Once a skilled operator has set up all the required job parameters for a particular application—web speed, web transport settings, squeegee angle, screen height, dryer settings, etc.—the PLC will automatically store all these parameters. For repeat runs of the same job, a far less skilled operator is able to quickly initiate and set up the system by recalling those parameters.
The greater precision electronic controls also are key to enabling many specialty graphics companies to expand into electronics applications that have requirements for exact ink thicknesses and minimal screen stretch that non-automated presses cannot consistently achieve. Since membrane switches and other printed electronic products are a growing segment of the specialty graphics industry, we can expect that the capacity and sophistication of PLC-enabled control systems will become more and more a determining factor of where the industry can go.
More precisely, it is the software engineering that makes the real difference between one screen printing system and another. The best-in-class roll-to-roll systems use standard industrial components that one can source worldwide, and customize the software for the precise application requirements of a particular specialty graphics company. These systems typically use higher capacity PLCs that are able to finely control all the inputs and outputs of a web printing line, including unwinding, web tension, material positioning, printing head position, web transport, drying systems, and rewinder
