Automation Supplement
Battling Robots
By Mark Stephen, associate editor
Ask any boxing fan and they’ll tell you: the key to a good contest lies
in the matchup. When it comes to robotic automation, the champions have
long been beam, or linear, robots, which are the first choice in North America
owing to their speed, affordability and easy programming. The contenders
in recent years have been the six-axis articulated-arm robots, which provide
the same flexibility as the human arm, and are highly adaptable for performing
secondary processing on injection molded parts. For the injection molder
looking to make the right purchase, understanding the strengths and weakness
of each is crucial.
ROUND ONE: COST, MAINTENANCE & RELIABILITY
In comparing the two technologies, some manufacturers begin by suggesting
that beam robots are inherently better suited for injection molding operations,
period. “Beam robots developed along with the injection molding machine,
while the articulated-arm robots are really general-purpose systems,” said
Jim Healy, vice president, sales and marketing, for Sepro America. “For
suppliers of general-purpose articulated arm units, plastics are just another
market.” Manufacturers and suppliers of articulated-arm robots argue that
that actually works in their machines’ advantage, beginning -- in some instances
-- with price. Although beam robots are often less expensive, the increasing
use of articulated-arm robots in the automotive and other manufacturing
industries has driven production volumes up, allowing for lower, often competitive
prices for plastics production. “The return on investment (ROI) on a six-axis
unit is still not as attractive as on a top-entry servo beam robot for smaller
tonnage presses, but as you move to 500 tons and larger, costs equal out
and the ROI on articulated-arm robots is similar,” said Doc Breger, automation
sales manager for ACS Group, a channel partner integrator for ABB Inc. A
related benefit, some suggest, is reliability. “Leading manufacturers of
six-axis robots make between 12,000 and 15,000 units world-wide every year,”
said Doug Niebrugge, plastics segment manager, North America, for ABB. “The
sheer volume allows for greater reliability in six-axis robots.” Less need
for maintenance is a third advantage, they continue. “In general, six-axis
models require less maintenance than beam models,” said Larry Pascucchi,
general manager for Negri Bossi Inc., a supplier for Kuka Robotics Corporation.
“During the first 20,000 hours of operation of a Kuka six-axis robot, for
example, there is virtually no maintenance required beyond periodic checks
of fuel levels; this is not true for beam units.”
ROUND TWO: SPEED
Manufacturers of articulated-arm units concede, however, that beam robots
are still faster. “Even the fastest articulated–arm robots can’t match the
speed of a servo beam robot for getting into a mold and picking out a part,”
said Martin Pemberton, president of Sierra Automation Inc. But this gap
is narrowing, they suggest, as articulated-arm models get faster, particularly
for larger tonnage machines. “Above 500 tons, and especially into the 1,000
ton or more range, the speed advantage of the beam robot is decreasing,”
said ABB’s Niebruegge.
ROUND THREE: PROGRAMMING, TRAINING & INTEGRATION
Another longstanding advantage of beam robots is easy programming, and
this has not been seriously challenged by articulating-arm units, according
to some. “The six-axis robots often need a dedicated person trained to operate
them,” said Troy Smale, automation manager for En-Plas Inc., which represents
Yushin Precision Equipment. “They are not user friendly because they are
designed to be a general-purpose robot rather than for injection molding.”
The opposite is true for beam robots, according to Sepro’s Jim Healy. “The
control systems of today’s beam robots were developed specifically for injection
molding and they include a lot of built-in programming that facilitate their
use in injection molding,” he said. “Programming can often be performed
by a relatively low-skill operator with little or no formal training.” Others
counter that the articulated-arm units of today are much simpler to set
up and operate than just a few years ago, thanks to software that does the
programming and simplified graphic interfaces that guide a technician through
set-up. “ABB’s RobotWare Plastics programming environment offers an icon-driven
touch-screen set-up that makes it easy for someone who is a top-entry robot
user to transition to the controls of an ABB six-axis robot because it presents
in the same fashion,” ACS Group’s Breger said. Nonetheless, the perception
of more complicated programs on a six-axis robot remains a barrier to wider
acceptance, ABB’s Niebrugge said. “There is a big fear in the marketplace
that articulated-arm robots are very complex,” he noted. “And although the
industry is addressing this with easy to use operator interface, it’s true
that the programming is still more complicated.” This more difficult learning
curve has, potentially, other disadvantages that purchasers should consider,
some suggest. “Many employers don’t want to risk paying to send their employees
on a three-week training course for an articulating arm robot only to have
them leave and possibly join competitors a short time later,” said Michael
Wittmann, general manager of Vienna, Austria-based Wittmann GmbH “There
can also be problems integrating the articulating arm robots into a production
line,” said Christian Weiss, technical sales, robots and automation, for
Wittmann Canada. “There are many companies that know how to integrate a
beam robot, whereas with articulated arm there are a very limited number
of integrators, other than the actual supplier of the robot.” In response,
manufacturers of the articulated-arm units point out that they are developing
new relationships with systems integrators to ease a customer’s transition
into the new technology.
ROUND FOUR: FLEXIBILITY & PAYLOAD CAPACITY
These manufacturers also stress that even the addition of wrist motions
on beam robots cannot alter the articulated-arm system’s advantage of a
more flexible work envelope. “A six-axis robot has a spherical work envelope;
it can reach above, below and all around itself, which adds versatility
for performing actions outside the press,” said David Arceneaux, business
development, marketing, for Staubli Corporation. In addition, they note,
articulated-arm robots can be mounted in wider variety of positions than
most customers realize, such as on top of the fixed platen, on the machine
frame, or even upside down on the ceiling of the machine. “The average processor
thinks articulated-arm robots are still mounted on the floor,” said John
Nelson, plastics sales manager for Kuka. “The message that we’re trying
to put out is that these units actually can do much more.” Others deny that
six-axis robots have an advantage in this regard. “There are many configurations
available for beam robots,” En-Plas’ Troy Smale said. “For example, Yushin’s
three-axis robots have single arm or double arm for stack and three-plate
molds, as well as a T-style traverse frame so you can discharge products
on both operator and non-operator sides.” Manufacturers also point to developments
with optional servo-wrist motions that have brought five- or six-axis capability
to the beam models. Payload and required reach are other factors to keep
in mind when shopping for a robot, manufacturers say; but here, too, opinion
is divided. “A beam robot has the same payload across virtually the entire
length of its stroke, whereas the articulating-arm unit may have lower payload
capability at its maximum extension,” Michael Wittmann said. Manufacturers
or articulating-arm robots counter that recent refinements have virtually
eliminated this deficiency. According to ABB’s Niebrugge, for example, the
company’s new IRB 6650s six-axis unit, which has a 3.9-m reach and a 90-kg
payload, can manipulate parts as large as bumper fascias.
AND THE WINNER IS…
Manufacturers and suppliers of articulated-arm robots claim an increasing
interest in the machines. “There’s definitely a growing demand for them
in North America,” said Harold Luttmann, general manager, robotics, for
Engel Canada. But despite a concerted push from manufacturers, and the growing
buzz surrounding them, articulated-arm robots actually account for only
a small portion of overall robot sales. “World-wide, articulated-arm models
have only a four to five per cent share of the robot market,” said Michael
Wittmann. “Linear robots remain the workhorses of the industry, and with
recent developments in flexibility there’s very little they can’t do.” Wittmann
also noted that, contrary to popular perception, linear beam robots are
actually gaining market share in some segments of the plastics industry.
“The cell phone industry was dominated in the past by suppliers who used
articulated-arm robots exclusively,” he said. “Recently, however, more of
them have been moving towards beam robots because of the quick part removal.”
The debate among manufactures and suppliers over strengths and weaknesses
of beam and articulated-arm robots will likely continue, but everyone agrees
that both have a proper place, and that a customer’s selection should be
based on this understanding. ”If the cycle time on an injection molding
machine is short, and a pick-and-place movement is all that’s needed, then
beam robots are the right choice,” said Negri Bossi’s Pascucchi. “However,
if a molder wants to add value to a part or perform multiple tasks such
as inspection, deburring and assembly during longer cycle times, articulated-arm
units are an option they should consider.”
Resource List
ABB Inc. -- Business Unit: Robot Automation (Brampton, Ont.)
www.abb.com/robotics;
800-293-4503
ACS Group (Schaumburg, Ill.)
www.acscustomerservice.com;
847-273-7700
Engel Canada Inc. (Guelph, Ont.)
www.engelglobal.com/na;
519-836-0220
En-Plas Inc. (Toronto)
www.en-plasinc.com;
416-286-3030
Kuka Robotics Corporation (Clinton Township, Mich.)
www.kuka.com; 866 873
5852
Negri Bossi Inc. (Mississauga, Ont.)
www.negribossi.com;
905-625-7257
Sepro America (Pittsburgh, Pa.)
www.seproamerica.com;
412-459-0450
Sierra Automation Inc. (Cambridge, Ont.)
www.sierraautomation.com;
519-653-2919
Staubli Corporation, Robotics Division (Duncan, S.C.)
www.staublirobotics.com;
864-433-1980
Wittmann Canada Inc. (Richmond Hill, Ont.)
www.wittmann-canada.com;
888-466-8266
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