Key Factors for Building a Robotic End-of-Arm-Tool
Richard Petz,
PE, General Manager for >SAS< Automation
 "We need our robot
to do more - handle multiple tasks, precision
placement or awkward parts, but don't know where to
begin." How many times have you heard that
concern? It is a reality that efficient automation is
the key to cost effective manufacturing in today's
global economy. While robots certainly can reduce
costs and speed production, the key that is often
overlooked, is the value that the robotic end-of-arm
tooling brings to your production line.
Simply, the End-of-Arm
Tool must compliment the robot. When designing or
building an EOAT, the overall results will depend
on:
- How well the EOAT
secures, manipulates, holds, and handles the part
throughout the robot motion
- How consistent the
operation performs.
- The reliability of
each individual component on the EOAT.
When it comes to being
cost effective, the proper combination of capital
investment, labor content and the speed of operation
will provide the best result. Although most times the
EOAT is a relatively small investment compared to the
other components of a work cell, the proper design and
construction can make a big difference. Thus, it is
the ease, consistency and flexibility, versus people,
that provides the motivation behind the EOAT to move
and assemble parts.
End-of-Arm Tooling
specialists have the ability to match your EOAT to
your robot cost effectively. This assistance can come
from helping you to select the proper components for a
less complicated EOAT to build in-house, or by
purchasing a custom EOAT for more complex jobs.
Specialists will have proven concepts for manipulating
parts for many operations. Robot companies can be
limited to tools just for their robot and distributors
typically offer only a partial segment of EOAT parts
or usually are lacking in technical support.
To be successful in
your EOAT building and application, keep the following
factors in the forefront:
Basic EOAT
Configuration Requirements
The proper use of
components and design will have a major impact on the
total project's cost savings, as a well designed EOAT
will perform many functions. When choosing the
End-of-Arm Tool, the following four concepts are
imperative to success:
Modular components
- Allow for standard, off-the-shelf components and
spare parts; no need to build your own custom parts
when approximately 2500 different stock components
already exist.
Weight - Don't
overload the robot. Lightweight tooling will reduce
robot wear and maintenance costs, as well as allow
maximum traverse speeds on robots.
Flexible -
Allows for multiple fine adjustments along slotted
frames, slotted and rotational clamps
Rigid/durable
- Extruded aluminum profiles provide long life, low
maintenance and repeatable accuracy along with
lightweight.
Interfacing with the
Robot
Building a modular EOAT
component system begins with the interface with the
robot. The use of quick change chucks, which can be
mounted directly to the robot arm with mounting hole
patterns to match the robotic arm, are used for short
runs and fast changeover time. A mating dovetail plate
on the EOAT quickly slides into the chuck and locks
and locates into place. This method will have quick
disconnect fittings that plug into the chuck for air
and vacuum lines. A "smart" junction box may
also be used for the electrical interface with LED's
to assist troubleshooting. Long run tools can be
bolted directly to the robot arm with the proper
plate.
Constructing the
EOAT
Whether long run or
short run, the next step is to mount the rigid
extruded, aluminum profile to the dove tail plate
based on the dimensions and weight required for the
EOAT. Keep in mind that the payload includes both the
EOAT and the part being manipulated. Gripping
components can then be added to the frame with a
variety of standard adjustable clamps. The combination
of the frame, clamps and grippers should allow for
adjustment in three axis. Secure locking nuts in the
framework will ensure long term repeatability
Gripping
Solutions
Gripping components,
such as pneumatic gripper fingers vacuum cups and air
grippers are the components that will be mounted on
the frame to securely hold the part to be
manipulated.
The use of vacuum cups
will provide the simplest and least expensive solution
where the application presents a suitable part surface
for a vacuum grip. The cups also come in various
sizes, shapes, materials. Polyurethane, for example,
is the choice for high abrasion and wear resistance,
silicone or viton for higher heat applications and
nitrile for good overall performance in a wide variety
of conditions. Oval cups are useful when the part is
long and narrow or if the work piece has raised ribs
or edges. Flat vacuum cups are used for flat part with
smooth to slightly textured surfaces. In general, they
have a wide range of diameters for different-sized
part. They also hold up best to shear when a
perpendicular load is applied and have faster response
time than the bellows-style cups. Bellows vacuum cups
provide a flexible sealing lip for parts with
irregular, smooth or contoured surfaces. They also
work well with slightly flexible surfaces.
Special cups are also
available for more porous surfaces (such as corrugated
or deeply grained) or non-marking applications (such
as plastic Class A surfaces on auto parts).
Pneumatic grippers are
normally used for applications requiring more grip
force or hard to reach areas on a part. Applications
of both grippers and vacuum cups used together would
be to pull large plastic parts from an injection mold
or a high speed palletizing application.
Custom End-of-Arm
Tooling
Many times parts need
to be manipulated during material handling or
packaging operations. In order to accomplish this, the
modular component system must integrate various types
of (1) pneumatic cylinders to perform desired motions
such as rotary cylinders, slide table cylinders, and
parallel cylinders, (2) special contoured nests or (3)
cutting tools.
When reviewing your
overall robotic project, custom design and / or build
should be considered under these conditions: (a) the
complexity is beyond the in house ability, (b) overall
labor hours are not available, (c) timing is
short.
A Robot is only as
good as its EOAT!
As the robot and EOAT
are required to multi-task, they must compliment each
other. The EOAT requires the robot to be repeatable,
while the robot must have the EOAT grip, hold or
position consistently as needed in the automation
cell. The more you can do with an EOAT, the less that
will be required of auxiliary operations and robotic
movements. The ability of a robotic cell to function
efficiently depends as much on the EOAT as it does on
the robot.
SAS Automation LLC
>SAS< is a
leading supplier of modular EOAT components &
robotic gripper systems - capable of servicing any
part and any robot. >SAS< manufactures in the
USA "get a grip!", and
distributes "nip it!" Nile sprue
nipper line, and "GRIP IT!" Asian
chucking/gripper line. >SAS< is ISO 9001:2000
Quality Certified. Specialists in robotic end-of-arm
tooling & gripper systems, custom tools,
automation cells, sprue nippers, CNC degating &
Insert Mold tooling for manufacturing, packaging &
plastics industries. Sales, service and support to:
USA, Canada, Mexico, Europe.
Email: getagrip@sasgripper.com
Web: www.sasgripper.com
Toll Free: 888-727-EOAT (3628)
Author: Richard Petz, PE is the General Manager
for SAS Automation. R. Petz oversees all of the
engineering, new product development, manufacturing
and sales of robotic end-of-arm tooling. Petz is a
professional engineer with a mechanical engineering
degree from Clarkson University and MBA from the
University of Dayton.
Published by Manufacturing
Technology
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