Friday, September 15, 2000
With the goal of increasing throughput by 20%, Zygot Automation
Inc. (Englewood, CO) developed a patented concept for its ZA series palletizers.
The units concurrently gather cartons, bags, or boxes into rows; form layers;
and strip the layers onto a pallet. However, the faster cycle times necessary
exceeded existing drive technology which consists of two-speed motors, pneumatic
brakes, and vector and servo drives.
By switching to gearmotors and brake motors from Mannesmann
Dematic (Cleveland, OH), engineers achieved better drive system response times,
yielded greater machine throughputs, and provided simpler controls and less
"We faced some tough challenges in trying to decrease cycle times
and reduce maintenance when designing the ZA-50 and its smaller sister units,
the ZA-30 and ZA-20 palletizers," explains Zygot President Youssef Hennes. "For
example, the response time of the two-speed motors we were using was so poor
that on smaller machines with a short travel requirement, we had to eliminate
the high-speed segment and traverse on slow speed only. Obviously, this slowed
down the operation. Servo controls turned out to be too expensive. The
sophisticated vector drives we tried required clean power, which was a real
headache because we had to isolate the palletizer from 'noise' with line
reactors and shielding to achieve reliable operation. Another nagging problem
was the high incidence of motor-brake housings working loose due to vibration."
Mannesmann Dematic Conical Rotor Brake Motors (type KB) and
Cylindrical Rotor Motors with and without brake (type Z, ZB) eliminated all
these headaches, according to Hennes. Simple PLC-controlled contactors operate
the new motors and brakes. Integral brake mechanisms eliminate components such
as a separate brake disk and lining, clamping device, coil, and rectifier.
Moreover, the gearmotors allowed Zygot engineers to upgrade from worm gears to
more efficient and reliable helical gearing.
"Since we have eliminated vector drives in our ZA-50, our
customers are happy that the drive systems are less expensive, more rugged,
require much less maintenance, and are simpler to troubleshoot. We are currently
investigating the elimination of servo drives in other equipment applications
with the Demag Cylindrical Rotor Motors."
For more information about Demag Gearmotors from Mannesmann
Dematic go to