What's My Line?
August 1999
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Experts debate the role of electronic line shafts in register control.
By Susan Friedman
Earth-shattering advances, break-through innovations? Well, not exactly. Developments on the register control front are a little more low-key at the moment.
"Not a lot has happened [recently in register controls], other than improvements in human-machine interface to make life easier," notes Jack Woolley, president of PC Industries. "Refinements will be subtle, small, and ongoing."
However—if the focus is expanded to include progressions in press motion control systems, specifically the electronic line shaft and its ultimate implications for register control, the discussion becomes a little more animated.
Some suppliers believe electronic line shafts can eliminate, or at least minimize, the need for separate register control systems; others say opting for such state-of-the-art press designs won't improve or change register control requirements, and in fact may just confuse the issue by adding an overload of electronic complexity.
State-of-the-art realities
In an exploration of the true advantages of electronic line shaft designs, several suppliers emphasize flexibility and efficiency gains.
"The replacement of mechanical line shafts with individual servo motors allows the decoupling of individual printing units, thus reducing the time necessary to initially phase multiple cylinders of a variable repeat press," explains Bud Lewis, president of CC1. "Another advantage is the capability of running true variable repeat on a flexographic press with the elimination of finite pitch gears." Lewis cautions these advantages must be weighed against the higher cost, complexity, and increased maintenance of sophisticated power electronics.
Electronic line shafts do provide a little more versatility in that stations can be run at different speeds, agrees Chris Popp, sales manager for Diequa Corp. He estimates, however, that 90 percent of the time printers stick with running stations at the same speed.
Moreover, Popp believes mechanical line shafts are still preferable in many cases, particularly to narrow-web package printers, because they are more predictable in terms of performance and maintenance.
Suppliers who support the possibility of an electronic line shaft functioning as a stand-alone register control device do so on a case-specific basis.
Dan Jahn, director of sales/marketing at Hurletron, states the electronic line shaft can play the role of register control, "if the information gathering and control functions include accurate feedback from the web."
"Position-matching two rotating cylinders will not, in itself, provide accurate register-control due to the dynamics of the substrate," Jahn elaborates. "Web stretch, web thickness variations and tension upsets are the dynamic variables encountered during the printing process and each of these can cause misregister. If the electronic line shaft is not capable of analyzing substrate and tension variables, and responding to the changes, a separate automatic register control will be required to maintain registration."
By Susan Friedman
Earth-shattering advances, break-through innovations? Well, not exactly. Developments on the register control front are a little more low-key at the moment.
"Not a lot has happened [recently in register controls], other than improvements in human-machine interface to make life easier," notes Jack Woolley, president of PC Industries. "Refinements will be subtle, small, and ongoing."
However—if the focus is expanded to include progressions in press motion control systems, specifically the electronic line shaft and its ultimate implications for register control, the discussion becomes a little more animated.
Some suppliers believe electronic line shafts can eliminate, or at least minimize, the need for separate register control systems; others say opting for such state-of-the-art press designs won't improve or change register control requirements, and in fact may just confuse the issue by adding an overload of electronic complexity.
State-of-the-art realities
In an exploration of the true advantages of electronic line shaft designs, several suppliers emphasize flexibility and efficiency gains.
"The replacement of mechanical line shafts with individual servo motors allows the decoupling of individual printing units, thus reducing the time necessary to initially phase multiple cylinders of a variable repeat press," explains Bud Lewis, president of CC1. "Another advantage is the capability of running true variable repeat on a flexographic press with the elimination of finite pitch gears." Lewis cautions these advantages must be weighed against the higher cost, complexity, and increased maintenance of sophisticated power electronics.
Electronic line shafts do provide a little more versatility in that stations can be run at different speeds, agrees Chris Popp, sales manager for Diequa Corp. He estimates, however, that 90 percent of the time printers stick with running stations at the same speed.
Moreover, Popp believes mechanical line shafts are still preferable in many cases, particularly to narrow-web package printers, because they are more predictable in terms of performance and maintenance.
Suppliers who support the possibility of an electronic line shaft functioning as a stand-alone register control device do so on a case-specific basis.
Dan Jahn, director of sales/marketing at Hurletron, states the electronic line shaft can play the role of register control, "if the information gathering and control functions include accurate feedback from the web."
"Position-matching two rotating cylinders will not, in itself, provide accurate register-control due to the dynamics of the substrate," Jahn elaborates. "Web stretch, web thickness variations and tension upsets are the dynamic variables encountered during the printing process and each of these can cause misregister. If the electronic line shaft is not capable of analyzing substrate and tension variables, and responding to the changes, a separate automatic register control will be required to maintain registration."
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