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Article | April 4, 2008
New servo platform brings costs down
A roll-fed, two-axis, continuous-motion card sheeter benefits from servo technology that eliminates the need for external motion-control hardware.
"For us it’s a new servo platform that helps us from a cost perspective because the motion controller is embedded in the servo drive," says Benchmark engineer, Jim Lindsey. "We don’t have any external motion control hardware as we did in the past. That was a primary driver in the design of this machine. It’s a cost issue."
Servo drives and motors are helping Benchmark Automation (www.benchmarkautomation.net) keep the cost of its packaging machinery in line.
The machine in this particular case is a card sheeter. It cuts cards from roll-fed paperboard and feeds the cards to another piece of packaging equipment. Take a flow wrapper, for example. The Benchmark unit would feed sheets of paperboard into the flighted infeed conveyor of a flow wrapper that might be used to wrap flexible film around pieces of candy that sit on the paperboard card.
A two-axis machine, Benchmark’s card sheeter is no stranger to servo controls. In fact, the firm has used practically nothing but servo motors since it was launched in 2001. But now the servo components used by Benchmark Automation represent newer technology from Bosch Rexroth (www.boschrexroth-us.com). Both the cutoff knife and the pulling mechanism that draws paperboard from the roll use Bosch Rexroth Indradrive servo drives.
In operation, the continuous-motion machine holds two rolls of paperboard, one active and one waiting in reserve. A rubberized pitch roller is programmed to pull just the right amount of paper from the infeed roll with each cycle. The other axis of servo motion is a rotary cutting knife that cuts individual sheets from the roll. Electronic camming—which wouldn’t be possible if the machine were mechanically, as opposed to servo, driven—keeps the two axes of motion tightly synchronized.
Also new on the card sheeter is that both servo drives have Bosch Rexroth multi-media cards.
"It allows all parameters in the servo drive to be backed up in storage," explains Lindsey. "These drives, in our experience, have been highly reliable, but should anything go wrong or a drive need to be replaced, we take one right off the shelf and plug it in. No parameterizing is needed. When the new drive is powered up, it reads all the parameters stored in the media card. So the drive is immediately ready to run."
Lindsey notes that the card feeder’s operator interface is a Bosch Rexroth HMI with Ethernet connectivity. "The IP-65 rating on the equipment also means it’s suitable for washdown environments," he adds.
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