Friday, November 10, 2000
Chicago, IL--Given the need for high accuracy, speed
regulation, and the ability to change profiles on the fly, servo motors may seem
like an obvious choice for engineers who design packaging machines. In fact,
many motion control vendors consider packaging the next killer application after
machine tools and semiconductor equipment.
So to what degree are packaging equipment makers actually
embracing servo technology today? It varies, from all the time to not at all to
everything in-between, as a quick survey this week of some of the exhibitors at
Pack Expo--one of the world's largest packaging shows--revealed.
"We developed our first servo-based equipment in the late 1970s,
and haven't looked back since," says William J. Heilhecker, President of DOBOY,
a division of SIG Pack, Inc. (www.doboy.com).
"In fact, we do not have a mechanical wrapper today. All of our machines are now
servo-based." DOBOY manufactures high-speed horizontal wrappers, bag closing,
and tray and carton formers.
Heilhecker cites the ability to obtain higher speeds, better
control, and greater flexibility as the main reasons why his company has gone
the servo route entirely. And as for cost--the higher price tag on servo has
been one obstacle to wider acceptance of the technology--Heilhecker says that
his company is able to produce economical, servo-based machines. "We try and use
standard, off-the-shelf technology wherever possible, which helps to keep costs
in check," he says.
Higher cost, however, is precisely the reason that engineers at
Lantech, Inc. (www.lantech.com) have ruled
out servos for the moment. The company manufactures stretch wrappers and
palletizing systems.
"We've explored servos, but the technology is still fairly
expensive and more difficult to justify," says Marketing Product Manager David
Luking. By using ac variable frequency drives, says Luking, engineers at Lantech
have been able to improve the performance of their machines, including the new
Q-Pal combination stretchwrapper/palletizer. They are also considering using the
drives in a new line of conveyors.
"We like the technology because we're getting good speed control
at a lower price," says Luking. "But we'll continue to monitor servo technology,
particularly as the price comes down."
For Alvey Systems (www.alvey.com), a manufacturer of high-speed
palletizing and conveying systems, the choice to use servo technology is not
black or white. "We use both, depending on the specific requirements of the
machine," says Frank Pellegrino, Vice President, Machine Products.
"For example, we are very dependent on servo for our gantry
palletizing robot, which requires extremely accurate positioning and has a
fairly complex, pick-and-place motion profile," says Pellegrino. On display at
Alvey's booth, the 4-axis robot achieves accuracies up to ±0.02 inch.
"On the other hand, we don't need servos on our high speed case
palletizer, because we can obtain the required motions using sensors and
variable frequency or vector drives."
Like Lukins, Pellegrino says that servo should become even more
attractive if the price comes down, although he does not foresee a time when
engineers would convert their designs to all-servo. "Our customers would panic
if we had all servo," he says.
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