CASE SUMMARY:
Electronic line shafting boosts speed and flexibility of die-cutting machines.
OEM:
Zerand Div. of the North American Cerruti Corp., New Berlin, Wis.
ENGINEERING ACTIVITY:
Designs and builds packaging equipment for the folded carton industry. Its platen die-cutting machines generate a variety of containers from cereal boxes to soda and beer can cartons.
DESIGN CHALLENGE:
The torsional wind-up of mechanical line shafts often limits modularity in web-fed paper converting equipment — a challenge in machines with sections that must simultaneously start and stop. Other problems with mechanical drive components and gears include web scuffing (caused by rolls running at speeds slightly different from web speed) and gears that must be manually changed to prepare for different cut lengths.
GOAL:
To build a truly modular platen die-cutter that eliminates the mechanical drive shaft.
ENABLING TECHNOLOGY:
Electronic line shafting (ELS) using ac servo systems from the Electric Drives and Controls unit of Bosch Rexroth Corp., Hoffman Estates, Ill. The design includes Rexroth 2AD servomotors, PPC controller, and DKC and DKR servo drives.
DESIGN IN ACTION:
The Zerand Series 800 platen die-cutter produces cut carton forms from a continuous web of printed boxboard moving at 800 ft/min. With ELS, servomotors can provide a high constant torque throughout the entire operating range, while intelligent drives, high-speed microprocessors, and built-in high-resolution encoders communicate and duplicate the exact position of each axis in the system.
Unlike mechanical drive shafts, which require a single large drive motor because of the build-up of friction from all the mechanical drive components, ELS eliminates most of the mechanical friction and sectionalized drives permit smaller motors, resulting in lower maintenance and energy consumption.
ADDITIONAL BENEFITS:
The system provides high resolution and feedback, allowing drive-based camming or the ability to synchronize a cam profile among all axes with high accuracy. Each drive's SERCOS interface lets parameters be input via the controller, reducing downtime and commissioning time.
In addition to transmitting the standard position, velocity, and torque demands, the SERCOS interface communicates errors, drive and motor status, and related diagnostic information back to the controller, where corrective action can then be relayed to the drive.
For more information:
Bosch Rexroth Corp., Electric Drives and Controls
(847) 645-3600
www.boschrexroth-us.com