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End effectors may consist of a gripper or a tool.
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=== Categories ===
When referring to robotic prehension there are four general categories of robot grippers:<ref name=":0">{{cite book |last1=Monkman |first1=G. J. |last2=Hesse |first2=S. |last3=Steinmann |first3=R. |last4=Schunk |first4=H. |title=Robot Grippers |publisher=Wiley-VCH |year=2007 |isbn=978-3-527-40619-7 |page=62}}</ref>
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The most known mechanical gripper can be of two, three or even five fingers.
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The end effectors that can be used as tools serve various purposes, including spot-welding in an assembly, spray-painting where uniformity of painting is necessary, and other purposes where the working conditions are dangerous for human beings. Surgical robots have end effectors that are specifically manufactured for the purpose.▼
A common form of robotic grasping is [[robotic force closure|force closure]].<ref name="fub20140320">
{{Cite book|last=Lynch|first=Kevin|url=https://www.worldcat.org/oclc/983881868|title=Modern robotics : mechanics, planning, and control|date=2017|others=Frank C. Park|isbn=1-107-15630-0|___location=Cambridge, United Kingdom|oclc=983881868}}</ref><!-- there appears to be no WP article on force closure so leaving a link to source the concept. -->
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The shape of the fingers' gripping surface can be chosen according to the shape of the objects to be manipulated. For example, if a robot is designed to lift a round object, the gripper surface shape can be a concave impression of it to make the grip efficient. For a square shape, the surface can be a plane.
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Though there are numerous forces acting over the body that has been lifted by a robotic arm, the main force is the frictional force. The gripping surface can be made of a soft material with high coefficient of friction so that the surface of the object is not damaged. The robotic gripper must withstand not only the weight of the object but also acceleration and the motion that is caused by frequent movement of the object. To find out the force required to grip the object, the following formula is used
<math display="block">F= \frac{ma}{\mu n}</math>
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For many physically interactive manipulation tasks, such as writing and handling a screwdriver, a task-related grasp criterion can be applied in order to choose grasps that are most appropriate to meeting specific task requirements. Several task-oriented grasp quality metrics<ref>{{cite journal |title=Grasp planning to maximize task coverage |journal=The International Journal of Robotics Research|volume=34|issue=9|pages=1195–1210|doi=10.1177/0278364915583880|year=2015 |last1=Lin |first1=Yun |last2=Sun|first2=Yu}}</ref> were proposed to guide the selection of a good grasp that would satisfy the task requirements.
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▲The end effectors that can be used as tools serve various purposes, including spot-welding in an assembly, spray-painting where uniformity of painting is necessary, and other purposes where the working conditions are dangerous for human beings. Surgical robots have end effectors that are specifically manufactured for the purpose.
The end effector of an assembly-line robot would typically be a [[Welding|welding head]], or a [[Spray painting|paint spray gun]]. A [[surgical robot]]'s end effector could be a [[scalpel]] or other tool used in surgery. Other possible end effectors might be machine tools such as a [[drill]] or [[milling cutter]]s. The end effector on the [[Canadarm|space shuttle's robotic arm]] uses a pattern of wires which close like the [[aperture]] of a camera around a handle or other grasping point.{{Citation needed|date=July 2013}}
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