Robotics

ISO 8373 defines an industrial robot as an automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes. The key word is programmable: the robot performs a movement it has been taught beforehand – quickly, repeatably and without tiring.

The payload of a robot includes the gripper and applies at a given distance of the load’s centre of gravity from the flange. A heavy gripper or a part that projects a long way reduces what can actually be moved.

A robot moves mass at high speed and does not see who is standing in its workspace. The safety requirements for robots and robot systems are set out in the ISO 10218 series. The usual approach is separation by a guard fence with interlocked doors, or monitoring of the space by sensors.

Collaborative robots – cobots – may share the workspace with people. The technical specification ISO/TS 15066 describes, among other things, limits for force and pressure on contact. In practice this results in limited speed and payload. And it is never the robot alone that is collaborative but the whole application, including gripper and workpiece – a sharp-edged sheet remains dangerous.

The robot wins when the same movement repeats in large numbers, the parts are presented in order and the process runs stably. It then delivers a constant cycle over three shifts.

As soon as variants, short runs, rework or the operator’s judgement come into play, the calculation shifts. A hand-guided manipulator carries the weight and leaves path and decision to the person. It needs no program, no machine vision and no guard fence, and it takes heavy loads at which a cobot reaches its limit.

The typical mistake is to treat the decision as a question of being modern. It is a question of volume, variety and process stability.