Parts of a Robotic Arm – Six-Axis Robot Arm Labeled

All 13 parts on the diagram

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The arm 7

Base It is fastened to the floor or a table. The rest of the arm turns on it.
Waist It turns the whole arm round on the base, left or right. Makers number it axis 1.
Shoulder It raises and lowers the upper arm. Makers number it axis 2.
Upper arm The link from the shoulder to the elbow. Some makers call this one the lower arm.
Elbow It raises and lowers the forearm. Makers number it axis 3.
Forearm The link from the elbow to the wrist. The end effector is carried on its far end.
Motors An electric motor at each joint turns it through gears or belts. The controller tells each one how far to turn.

The end of the arm, and the controller 6

Wrist It tilts and turns the end effector. Pitch is up and down, roll is turning about the arm's own line. On a six-axis arm the wrist has three axes.
Mounting flange The flat face at the very end of the arm. The end effector is bolted to it.
End effector (gripper) Whatever is fitted to the arm's end to do the work. A gripper picks things up. Other end effectors weld, spray or hold a tool.
Controller It holds the electronics that control the arm and drive its motors.
Teach pendant A hand-held unit joined to the controller. With it a person moves the arm from point to point and records the moves for the robot to repeat.
Cable It runs from the controller to the base of the arm. It carries the power for the motors and the signals back.

How this list was compiled: Every name checked on 2026-09-30 and kept only where at least two independent sources use it. (1) A maker's user manual for a small training robot arm, full text at https://archive.org/details/manualzilla-id-5830973 : base, shoulder, elbow, upper arm, forearm, wrist pitch and wrist roll, gripper as end effector, motors, encoders, controller, teach pendant, the cable from robot base to controller, and what each joint moves. (2) A second maker's robot manual, https://archive.org/details/manualzilla-id-5677880 : waist, shoulder, elbow, wrist, upper arm, forearm, flange, end effector and gripper, controller, teach box, cables to the robot base. (3) A third maker's product manual for a large industrial robot, https://archive.org/details/manualzilla-id-5634044 : manipulator and controller, base, lower arm, upper arm, wrist, mounting flange, end effector, motor and gearbox units for axes 1 to 6, teach pendant, cabling. (4) A US teacher's curriculum guide, Introduction to Robotics for Industrial Technology Education, https://archive.org/details/ERIC_ED353484 : base with the waist axis, shoulder, upper arm, forearm, wrist, end-effector, controller, teach pendant. (5) Wikipedia, Industrial robot and Robotic arm, https://en.wikipedia.org/wiki/Industrial_robot : links, joints driven by motors, base, wrist and its three axes, end effector, controller, teach pendant. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's machine, nothing traced. Licence: own work

How it works

The parts of a robot arm are named after a human arm. This one is a six-axis industrial arm, drawn from the side, then with its wrist enlarged beside the controller and teach pendant.

Read the full guide

Six joints, from the floor up

The waist turns the arm round on its base. The shoulder raises and lowers the upper arm, and the elbow does the same for the forearm. Those three joints carry the wrist to any point in reach. The wrist's three axes then turn and tilt the end effector to face the work.

The arm is half the robot

A motor drives each joint, and a cable joins them to the controller. People teach the arm its moves with the teach pendant.

One large maker calls the two links the lower arm and the upper arm, and numbers the joints as axes 1 to 6.
The end effector is not always a gripper. It is whatever tool the job needs.

Questions and answers

What are the parts of a robotic arm?

A base, a waist, a shoulder, an upper arm, an elbow, a forearm and a wrist, with a mounting flange on the end for the end effector. A motor drives each joint, and a controller with a teach pendant runs them.

What is the end effector of a robot arm?

It is the device fitted to the wrist to do the work, often called the business end of the robot. A gripper, for picking things up and placing them, is one kind; others weld, paint or hold a tool.

Why does a robot arm have six axes?

Three axes are needed to reach any point of space. Three more, at the wrist, are needed to turn the end of the arm to any angle once it is there.

What is a teach pendant?

A hand-held control and programming unit joined to the robot's controller. The operator uses it to move the arm to each position and record it, and it usually has a large emergency stop button.