COVER STORY:
Tooling Gets Flexible
May 2008
Reprinted with permission from
Assembly
Magazine.
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Frame-based
EOAT has long been used for machine
tending. Photo courtesy ABB
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 Amid
all the talk of robots and controllers, it can be
easy to forget about end-of-arm tooling (EOAT).
Nonetheless, while it’s true the cost of a gripper
will pale in comparison to the robot wielding it, an
effective gripper is crucial to the success of any
material handling system.
In the beginning, end-of-arm tooling was the
exclusive purview of robot manufacturers themselves.
However, the industry has since evolved to where a
number of companies now specialize in robotic
tooling, in the process providing engineers with
increased functionality, greater ease of use and
lower prices.
Among other products, EOAT equipment manufacturers
offer a host of different modular systems and
components, including brackets, clamps and
connectors used to hold together a framework of
slotted or tubular aluminum sections. Carbon-fiber
sections are also available for especially
weight-sensitive applications. This framework is
then used to secure the suction cups, magnets,
pumps, grippers, slides, guides and even sensors
that serve to grasp, manipulate and ultimately
release the actual workpiece.
Specific examples of
this kind of tooling include the BodyBuilder, CPI
and SpiderGrip lines from workholding and automation
company DE-STA-CO (Auburn Hills, MI); the Vacuum
Spider line from Schmalz Inc. (Raleigh, NC); a
comprehensive line of modular tooling, including
profiles, grippers and clamps from SAS Automation
LLD (Xenia, OH); the press automation equipment line
from robot-maker ABB (Auburn Hills, MI); and the
Modular Automation Tooling line from vacuum
equipment manufacturer PIAB USA (Hingham, MA).
In spite of their
occasionally ungainly appearance, frame-based end
effectors offer an appealing combination of light
weight, rigidity and adaptability. On the one hand,
end users can often fine-tune their own EOAT
equipment in-house, using tools as basic as a simple
hex wrench. On the other, by mixing and matching
standardized components, assemblers, systems
integrators and robotics companies can easily create
an infinite number of different EOAT, using
expensive customized components only as a last
resort.
“Most all industries
have used some sort of modular EOAT for quite some
time now, but just within the last 10 years have the
aluminum tools become a major competitor due to
price and weight,” says Tom Herndon, regional sales
manager for Schmalz Inc.
“Modular and flexible
end-of-armtools, grippers and end effectors help the
robot to do more,” agrees Trent Fisher, PE,
president of SAS Automation. “Modular systems give
the integrator the flexibility to…meet their
ultimate goal of reducing production costs while
increasing speed to market.”
In particular,
modular, framed based tooling enables manufacturers
to set up their own EOAT that much more quickly and
then perform on-the-fly changes once the tooling is
in production. “Both help reduce downtime,” says
PIAB applications engineer Andy Lovell.
Jesse Hayes,
automation production manager for gripper
manufacturer Schunk Inc. (Morrisville, NC), notes
that his company has even built EOAT that self
adjusts depending on the part being manipulated. “We
installed a vacuum gripper on the end of a slide to
automatically configure to another part,” he says of
the system.
Molding and Manipulation
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Today’s
modular systems make it easy to both build
and adjust a robot’s EOAT. Photo
courtesy Schmalz Inc.
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Given the planar
nature of an extruded aluminum framework, it should
come as no surprise that frame-based EOAT systems
have long been used for packaging and machine
tending in the stamping and injection molding
industries. Whether it’s feeding galvanized sheets
to a press, or removing and manipulating molded cell
phone housings, multiple suction cups or mechanical
grippers are a natural. The same thing goes for
packaging, whether the product being handled is the
bumper for a pickup truck or a couple of dozen boxes
of breakfast cereal.
What is not so obvious is the fact that these
seemingly routine tasks are often surprisingly
difficult to execute. In many cases, it’s important
the robot not mar the finish of the product being
processed. In others, actually removing the part, or
parts, from the mold can be problematic, especially
if the mold wasn’t built with automation in mind. In
fact, reach and extraction issues are one of the
reasons human operators continue to tend machines in
countless factories across the world.
Then there are those
applications in which a single robot is required to
perform more than one task: for example,
transferring a molded or stamped part to another
automated workstation for some kind of processing;
or manipulating a component so that it can be
effectively and safely packaged.
As an example of this
kind of application, SAS engineering manager John
Westbeld cites the case of a manufacturer that was
using a robot to transfer molded electrical panels
directly from the mold to a divided container. In
addition to the challenge of having to accommodate
the parts’ porosity, SAS engineers had to overcome
the fact that the distance between the mold cavities
was greater than that of the packaging.
The solution
consisted of a frame-based gripper equipped with a
slide assembly that brings the panels closer
together after they are removed from the mold. The
EOAT was also equipped with a photoelectric sensor
to confirm part presence and ensure quality.
In response to
applications like these, EOAT equipment
manufacturers have created a dazzling array of
interchangeable components, including larger and
smaller extrusion sections, adjustable clamps,
junction boxes and relay boards. In addition, EOAT
builders are increasingly creating “hybrid” systems
employing a combination of magnetic, vacuum and
finger grippers to meet the needs of especially
demanding applications. The resulting systems can
perform tasks that might otherwise only be possible
for a human being. They may also be able to perform
multiple tasks using a single gripper.
“An example of this
in packaging is a multifunction gripper with one
area of the robotic gripper [using] vacuum cups to
secure products such as totes or boxes and another
area of the gripper utilized for the moving of
pallets with gripper fingers,” Fisher says. “This
type of a multifunctional gripper pushes the
efficiency envelop while reducing costs as only one
robot and one gripper handles both loading the
product and the placing of a new pallet to begin the
next palletizing cycle.”
Along these same
lines, Schunk’s Hayes cites the EOAT his company
helped build in which mechanical grippers were used
to do the actual lifting while vacuum cups kept the
part stable. In another application, Hayes says a
single tooling system employed vacuum to pick up one
kind of component and a finger gripper to pick up
another. The two parts were then simultaneously
placed in a workstation for processing.
EOAT Considerations
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This EOAT
incorporates both aluminum and carbon
fiber components to make it as light as
possible. Photo courtesy DE-STA-CO
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No matter what the
specific application, when designing and fabricating
frame-based EOAT, assemblers need to keep in mind
many of those same concerns that apply when
integrating any other type of robotic tooling.
For example, as is the case in any robotic
application, it is important to anticipate the loads
that will be generated by the workpiece and
the tooling when the robot is doing its job. When
working with larger frame-based EOAT, in particular,
it is critical that builders figure out torque and
moment values in advance to avoid problems with
quality and repeatability down the road.
“The gripper mounting location [relative] to the
robot must be selected to minimize excessive torque
or moments for the least amount of stress and
strain. It is best to use components that allow
flexibility [so that] the designer can easily select
the best mounting location, typically either center
or end-boom,” Fisher says.
Along these same
lines, it pays to go with the lightest gripper and
framing components possible and not “overkill” the
application with heavy, fixture-type tooling. In
addition to reducing robot wear and tear, lighter
components will also enable faster cycle times.
“Keep it simple. Talk
to the people who will be using this tooling every
day for practical feedback,” says DE-STA-CO vice
president of engineering Robert Pitera. “Always be
aware of the weight expectation of the robot.
Whether an in-house
design team is capable of making these kinds of
decisions depends on the complexity of the
application, says Schmalz Inc.’s Herndon. However,
he notes it is often worth the effort, if for no
other reason than that it provides the manufacturer
with an added degree of control. “Some [EOAT
systems] are built on-site by end users who have a
good inventory of the modular parts,” Herndon says.
“This enables them to change tooling on the fly as
major part changes are made.”
Of course,
manufacturers also need to be careful not to
overreach themselves, especially when working with
trickier parts or assemblies. According to PIAB’s
Lovell, these include packaging applications in
which there is no standard case size, or automotive
applications in which there is substantial
variability in the parts being handled.
“It is important to
have experience in designing tools with an
understanding of the robot payload and part
manipulation needed,” agrees Fisher. “Anyone
designing tools needs to understand the automation
required, in order to design the tool appropriately
and cost effectively.”
“Many of our products
are off the shelf and easy to use,” agrees DE-STA-CO’s
Pitera. “However, we have shown tremendous payback
by building the tools ourselves and then shipping
them to integrators for install.”
No matter what the
specific tooling and application, engineers need to
remember that even the most flexible system in the
world will have its limitations. Not only that,
asking too much of a specific piece of tooling can
quickly backfire due to breakdowns or compromised
product quality.
Nonetheless, Herndon
says in the future, framed-based EOAT, like so much
in modern manufacturing, is only going to get better
and easier to work with. “I think the future will
hold lighter and more adjustable tools at an
extremely reasonable price,” he says. “There will
also be tools that can be adjusted automatically to
handle any product, no matter if it’s a box, a
bumper or a cell phone face plate.”
Adam Cort
corta@bnpmedia.com
Technical Editor
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