Screen printing has proven itself as an effective method of decorating three-dimensional items and unusually shaped products at high production speeds. This article introduces the printing systems used for such jobs and the innovations they feature to accommodate challenging products.
By Harald Gavin
Independent, servo-driven motors were originally seen as a means to overcome some of the limitations of mechanical drives. However, with growing expertise and experience, machine designers were able to optimize not only the movements during printing, but also the movements during the other stages of the decoration process. The complexity of modern servo control is not visible to screen printers; therefore, servo control gives new options for future enhancements to the screen-printing process without putting additional stress on press operators.
Current container-decorating machinery has overcome many of the limitations that screen printers faced with early version of decorating equipment. The advancements and features found in today’s screen-printing lines allow container decorators to print high-quality images onto a vast assortment of oddly shaped items, including those with difficult surfaces, more efficiently.
Printing a wrap-around onto an oval container
Synchronized movement of the screen and squeegee are required when printing onto a rotating plastic container. This diagram shows the requisite movement. The left side of the illustration depicts an oval container immediately after the start of the print sequence. The fixture has rotated the container slightly counter-clockwise, and the screen moves from left to right.
The center of the diagram shows the positions of squeegee, screen, and container once the container has rotated an eighth of a turn. The printhead with squeegee and screen has moved vertically upward to enable the fixture to turn the container. In addition, the squeegee has moved horizontally to the right to keep the squeegee edge in contact with the printing area. The screen has continued its horizontal movement from right to left. The speed of the screen moving from right to left is greater than that of the horizontal squeegee.
Finally, on the right side of the diagram we see that the container has almost rotated half a turn. The printhead with squeegee and screen has now moved downward. Superimposed onto this downward movement of screen and squeegee are horizontal movements of squeegee and screen to the left, whereby the screen simultaneously continues moving under the squeegee from left to right.
Harald Gavin earned a BSc in electronics and mathematics from the University of Hamburg, Germany and an MSc in control engineering from the Cranfield Institute of Technology, England. He has worked in web-offset printing, control-system design, contract engineering, and software. Gavin founded Path 2 Print Ltd. in 2000 as a marketing company for ISIMAT’s screen-printing machines in the UK and Ireland. He now serves as director of marketing and international sales for ISIMAT.
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