The work envelope is the range of motion over which a robot arm can move.In practice, it is the set of points in space that the end effector can reach.

The size and shape of the work envelope depends on the coordinate geometry of the robot arm, and also on the number of degrees of freedom.Some work envelopes are flat, confined almost entirely to one horizontal plane. Others are cylindrical; still others are spherical. Some work envelopes have complicated shapes. The illustration shows a simple example of a work envelope for a robot arm using cylindrical coordinate geometry. The set of points that the end effector can reach lies within two concentric cylinders, labeled “inner limit” and “outer limit.” The work envelope for this robot arm is shaped like a new roll of wrapping tape.

When choosing a robot arm for a certain industrial purpose, it is important that the work envelope be large enough to encompass all the points that the robot arm will be required to reach. But it is wasteful to use a robot arm with a work envelope much bigger than necessary.