A robot arm without a sensor is working blind. It follows a fixed program, moves to a pre-taught position, and picks or places whatever it expects to find there. If something shifts by a few millimeters, or a part arrives in a different orientation, the arm either misses entirely or grabs incorrectly. A 3D sensor changes that. It gives the robot a real-time map of its environment, not just a flat image, but a full spatial picture with depth. The arm knows where the object is,