A typical robotic arm is made up of several metal segments, joined by joints. The computer controls the robot by rotating individual step motors connected to each joint. Sometimes larger arms use hydraulics or pneumatics for joint control. Unlike ordinary motors, step motors move in exact increments. This allows the computer to move the arm very precisely, repeating exactly the same movement over and over again. The robot uses motion sensors to make sure it moves just the right amount.

In order to do different jobs, a robotic arm get a special 'hand' for each job. There are many types of special 'hands' called 'end effectors'. One common end effector can grasp and carry different objects. To give a robotic hand a sense of touch, it has built-in load cells that tell the computer how hard the robot is gripping a particular object. This keeps the robot from dropping or crushing whatever it's carrying. Other end effectors include blowtorches, drills and spray painters. A robot might twist the caps onto peanut butter jars coming down an assembly line or drill holes, or pick up a piece and put it on another piece. Robots can often do this repetitive work more efficiently than human beings because they are so precise. A robot always drills in the exactly the same place, and always tightens bolts with the same amount of force, no matter how many hours it's been working. Many industrial robots work in auto assembly lines, putting cars together. They are very strong, lifting large car pieces easily, and never get tired. Even though robots are capable of great strength, they are also capable of performing very delicate operations as well. This makes them very useful in the computer industry which requires an incredibly precise hand to put together a tiny microchip.