What must the first motion in a robot program be?

The first motion in a robot program must be a PTP (Point-to-Point) motion. This is primarily because PTP motion is designed to move the robot's end effector from its current position to a target position in a direct path, typically at a maximum speed without consideration of the trajectory or path being followed.

Starting a robot program with a PTP motion allows for quick initialization of the robot's position before engaging in more complex movements or operations. It provides a clear and controlled transition, helping to ensure the robot is positioned correctly before proceeding with additional motions that may require more precision or coordination, such as linear or circular movements. This initial PTP motion is crucial in settings where the robot needs to quickly reach a safe and defined start position, thereby minimizing the risk of collisions or errors in program execution.

Other options like CIRC or linear motions serve specific purposes and might not be suitable as initial movements due to their complexity or the need for defined paths and points. Additionally, external triggers, while important in some robotic applications, cannot define the robot's starting state effectively compared to a PTP motion. Thus, utilizing PTP as the first motion ensures a reliable and efficient start to the robot's program.