A collaborative robot can share a workspace with humans: physical separation is not required. This is a break from past practice where robots had to be caged to avoid harming anyone who got in their way. Now, with the change of sensor and robot controller technology, a robot can reliably detect and adapt to intrusion into its work envelope, meaning physical barriers are no longer essential for safe operation. Updated robot safety standards account for these advances but require the robot to possess at least one of the following characteristics to work collaboratively:
- Safety-rated monitored stop
- Cell-hand guiding
- Speed and separation monitoring
- Power and force limiting
Robots employing the power and force limiting approach have compliance in case of impacts, but also lack speed, accuracy and payload capabilities. More industrial robots employ speed and separation monitoring, and safety-rated monitored stop strategies through controller and sensor features, such as FANUC’s Dual Check Safety (DCS) system.
The most obvious benefit from deploying a collaborative robot (besides automating a task previously done manually) is elimination of the safety cage. This frees floorspace and can lower the cost of implementing robotics. For example, a non-collaborative robot used in an automated cell must be guarded to keep operators outside. The guarding itself can be expensive, especially when gates, interlocks and interfacing to the cell controller are included. However, the cost of moving material in and out of the cell is often overlooked. While simple roller conveyors might be inexpensive, belt and pallet systems can add significantly to the cell's cost; but with a collaborative robot, an operator can work alongside the automation, positioning the material or workpiece and removing finished pieces from the cell as needed.
Less obviously, collaborative robots also permit more flexible manufacturing practices. Even when equipped with vision systems, there are limits to a robot's ability to handle unexpected conditions. Take a palletizing application: if one sack or bag shifted, it could destabilize the whole pallet. A collaborative robot, alerted by vision or other sensors, would summon human assistance, pausing until the problem has been fixed and then resume. Without collaborative capabilities the robot would be shut down for the operator to enter the cage. When restarting, depending on the programming, it may need to begin the cycle again with an empty pallet. Similarly, consider a material removal cell where a robot is trimming plastic moldings. Excess material builds around the tool and workpiece and pushes the plastic away from the tool. In a collaborative setup a human operator can step in to the cell and the robot will pause while the buildup is removed. Then, with the operator safely out of the way, production will resume.
Collaborative robots can save space and money and increase flexibility. Still, it is essential to conduct a formal risk assessment before ditching the cage: The tool the robot carries or the process it works on may mean guarding is still needed.