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The end effectors that can be used as tools serves various purposes. Such as, Spot welding in an assembly, spray painting where uniformity of painting is necessary and for other purposes where the working conditions are dangerous for human beings.
==Mechanism of Gripping==
Generally, the gripping mechanism is done by the grippers or mechanical fingers. The number of fingers can be two, three or even as high as five. Though in the industrial robotics due to less complications, two finger grippers are used. The fingers are also replaceable. Due to gradual wearing, the fingers can be replaced without actually replacing the grippers.
There are two mechanisms of gripping the object in between the fingers (due to simplicity in the two finger grippers, in the following explanations, two finger grippers are considered).
=====Shape of the gripping surface=====
The shape of the gripping surface on the fingers can be chosen according to the shape of the objects that are lifted by the grippers. For example, if the robot is designated a task to lift a round object, the gripper surface shape can be a negative impression of the object to make the grip efficient, or for a square shape the surface can be plane.
=====Force required to grip the object=====
Though there are numerous forces acting over the body that has been lifted by the robotic arm, the main force acting there 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 due to frequent movement of the object. To find out the force required to grip the object, the following formula is used
:<math>F= \mu W n </math>
where:
<dl><dd>
{|cellspacing="0" cellpadding="0"
|-
| <math>\,F</math>
| is
| the force required to grip the object,
|-
| <math>\,\mu</math>
| is
| the coeffecient of friction,
|-
| <math>\,n</math>
| is
| the number of fingers in the gripper and
|-
| <math>\,W</math>
| is
| the weight of the object.
|}
</dd></dl>
But the above equation is incomplete. The direction of the movement also plays an important role over the gripping of the object. For example, when the body is moved upwards, against the gravitational force, the force required will be more than towards the gravitational force. Hence, another term is introduced and the formula becomes:
:<math>F= \mu W n g </math>
Here, the value of <math>\,g</math> should not be taken as the acceleration due to gravity. In fact, here <math>\,g</math> stands for multiplication factor. The value of <math>\,g</math> ranges from 1 to 3. When the body is moved in the horizontal direction then the value is taken to be 2, when moved against the gravitational force then 3 and along the gravitational force, i.e., downwards, 3.
==Examples==
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 others tools used in surgery. Other possible end effectors are machine tools, like 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.
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