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•When pallets are used, there is a fixture on top designed to hold the part in an accurate position so that robots and other equipment will be able to locate the part within some tolerance.

•Vision systems may be necessary if part orientation cannot be fixed.

39.4 END OF ARM TOOLING (EOAT)

•The best known universal gripper - the human hand

•Useful classifications are,

-Grippers

-multiple/single

-internal/external

-Tools

-compliant

-contact

-non-contact

•End of arm tooling is typically purchased separately, or custom built.

39.4.1 EOAT Design

• Typical factors to be considered are, Workpiece to be handled

part dimensions mass

preand postprocessing geometry geometrical tolerances

potential for part damage Actuators

mechanical vacuum magnet etc.

Power source of EOAT electrical pneumatic hydraulic mechanical

Range of gripping force object mass

friction or nested grip

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coefficient of friction between gripper and part maximum accelerations during motion

Positioning

gripper length

robot accuracy and repeatability part tolerances

Maintenance

number of cycles required

use of separate wear components design for maintainability

Environment temperature humidity

dirt, corrosives, etc. Temperature protection

heat shields longer fingers

separate cooling system heat resistant materials

Materials

strong, rigid, durable fatigue strength

cost and ease of fabrication coefficient of friction suitable for environment

Other points

interchangeable fingers design standards

use of mounting plate on robot

gripper flexible enough to accommodate product design change

•The typical design criteria are,

-low weight to allow larger payload, increase accelerations, decrease cycle time

-minimum dimensions set by size of workpiece, and work area clearances

-widest range of parts accommodated using inserts, and adjustable motions

-rigidity to maintain robot accuracy and reduce vibrations

-maximum force applied for safety, and to prevent damage to the work

-power source should be readily available from the robot, or nearby

-maintenance should be easy and fast

-safety dictates that the work shouldn’t drop when the power fails

•Other advanced design points,

-ensure that part centroid is centered close to the robot to reduce inertial effects. Worst case make sure that it is between the points of contact.

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robot arm	Part
	Gripper

Better - less chance of slippage

- holding pressures/forces/etc are hard to control, try to hold parts with features or shapes

robot arm

Part

Gripper

part will be more stable, and well located

-compliance can help guide work into out-of-alignment conditions.

-sensors in the EOAT can check for parts not in the gripper, etc.

-the gripper should tolerate variance in work position with part alignment features

-gripper changers can be used to make a robot multifunctional

-multiple EOAT heads allow one robot to perform many different tasks without an EOAT change.

-*** Don’t try to mimic human behavior.

-design for quick removal or interchange of tooling by requiring a small number of tools (wrenches, screwdrivers, etc).

-provide dowels, slots, and other features to lead to fast alignment when changing grippers.

-use the same fasteners when possible.

-eliminate sharp corners/edges to reduce wear on hoses, wires, etc.

-allow enough slack and flexibility in cables for full range of motion.

-use lightweight materials, and drill out frames when possible.

-use hard coatings, or hardened inserts to protect soft gripper materials.

-examine alternatives when designing EOAT.