Mechanical Gripper

Mechanical Gripper

A mechanical gripper is used as an end effector in a robot for grasping the objects with its mechanically operated fingers. In industries, two fingers are enough for holding purposes. More than three fingers can also be used based on the application. As most of the fingers are of replaceabletype, it can be easily removed and replaced.

A robot requires either hydraulic, electric, or pneumatic drive system to create the input power. The power produced is sent to the gripper for making the fingers react. It also allows the fingers to perform open and close actions. Most importantly, a sufficient force must be given to hold the object.

In a mechanical gripper, the holding of an object can be done by two different methods such as:

·        Using the finger pads as like the shape of the work part.

·        Using soft material finger pads.

In the first method, the contact surfaces of the fingers are designed according to the work part for achieving the estimated shape. It will help the fingers to hold the work part for some extent.

In the second method, the fingers must be capable of supplying sufficient force to hold the work part. To avoid scratches on the work part, soft type pads are fabricated on the fingers. As a result, the contact surface of the finger and co –efficient of friction are improved. This method is very simple and as well as less expensive. It may cause slippage if the force applied against the work part is in the parallel direction. The slippage can be avoided by designing the gripper based on the force exerted.

µ n_f F_g = w ………………… 1 µ => co –efficient of friction between the work part and fingers

n_f => no. of fingers contacting F_g => Force of the gripper

w => weight of the grasped object

The equation 1 must be changed if the weight of a work part is more than the

force applied to cause the slippage.

µ n_f F_g = w g                                 …..…………….2

g => g factor

During rapid grasping operation, the work part will get twice the weight. To get rid out of it, the modified equation 1 is put forward by Engelberger. The g factor in the equation 2 is used to calculate the acceleration and gravity.

The values of g factor for several operations are given below:

^§    g = 1 –acceleration supplied in the opposite direction.

^§    g = 2 –acceleration supplied in the horizontal direction.

^§    g = 3 –acceleration and gravity supplied in the same direction.

A pneumatic gripper is a specific type of  pneumatic actuator that typically involves either parallel or angular motion of surfaces, A.K.

When combined with other  pneumatic, electric, or  hydraulic components, the gripper can be used as part of a "pick and place" system that will allow a component to be picked up and placed somewhere else as part of a manufacturing system.

Some grippers act directly on the object they are gripping based on the force of the air pressure supplied to the gripper, while others will use a mechanism such as a gear or toggle to leverage the amount of force applied to the object being gripped. Grippers can also vary in terms of the opening size, the amount of force that can be applied, and the shape of the gripping surfaces— frequently called "tooling jaws or fingers". They can be used to pick up everything from very small items (a  transistor or chip for a  circuit board, for example) to very large items, such as an  engine block for a car. Grippers are frequently added to industrial robots in order to allow the robot to interact with other objects.

Common industrial pneumatic components include:

· pneumatic direct operated  solenoid valve

·        pneumatic pilot operated solenoid valve

·        pneumatic external piloted solenoid valve

·        pneumatic manual  valve

·         pneumatic valve with air pilot actuator

·         pneumatic filter

·        pneumatic  pressure regulator

·         pneumatic lubricator