Blog post by Ian Mogab, Controls Engineer
Often times you may hear of manufacturers opting to replace their human workforce with robots in order to increase productivity. However, there are some drawbacks to doing this; robots are not good at doing everything. What if you could add robots to your operation, while keeping everything that you love about your human workforce? The answer is here: collaborative robots.
What is a collaborative robot?
Collaborative robots are designed to work alongside their human counterparts in a variety of configurations, often teaming up to accomplish tasks that neither could do on their own. Collaborative robots are defined by ISO 10218, which defines four main collaborative robot features: Safety monitored stop, speed and separation monitoring, power and force limiting, and hand guiding.
Safety Monitored Stop
This is perhaps the simplest method of collaborative robots and is used in applications when human interference with the robot is infrequent. This type of collaboration utilizes a traditional industrial robot in conjunction with safety devices such as a laser scanner that detects employee entrance into the designated robot zone. If an employee is detected entering the robot zone, the robot stops and the employee can perform any necessary work operations, and then resume the robot at the push of a button. For example, this type of collaboration is often used when a large industrial robot is needed due to loads, but a secondary operation has to be performed by an operator.
Speed and Separation Monitoring
This type of collaborative robot installation also uses traditional industrial robots, but it is more suited for environments where employees will be frequently interacting with the robot. In this type of installation, the area around the robot is constantly monitored by a vision system, which can detect employee proximity to the robot. If the employee enters the “warning” zone, the robot slows to a safe speed and if the employee enters the “stop” zone, the robot pauses until the employee has left the zone. Once the employee leaves the zone, the robot automatically resumes operation. This robot is better than safety monitored stop in instances with frequent employee interaction because the robot will automatically determine the safe running speed based on the location of the employee.
Power and Force Limiting
Power and force limiting robots are the most collaborative of the types mentioned in this article and are the only ones that can truly work alongside humans without any additional safety devices and process interruption. These robots are designed with collaboration in mind meaning they don’t have any sharp corners, exposed motors, or pinch points. They have sensitive force monitoring devices, and often have a padded “skin” to dissipate force in the event of a collision. These robots work alongside humans and stop instantly if any collision is detected. This means that no vision system, laser scanners, or fencing is required when the robot is properly configured. Oftentimes the extra cost of the force limited robots is offset by the cost savings of not having to purchase and program a network of safety scanners. Currently, these force limiting robots are limited to smaller applications 35kg or less.
Hand Guiding is a collaborative feature that some robots have. It allows a programmer to “teach” robot paths and positions simply by moving the robot with their hand to the desired position. This is especially useful in instances when the robot needs to be reprogrammed on the fly. The new positions can be taught quickly which limits downtime. It should be noted that if the robot is not a force limited robot, the proper safety guarding and logic should still be in place for regular operations.
With all collaborative robots, a risk assessment of the application should be done to determine all possible risks and proper devices and procedures to mitigate the risk should be implemented. All collaborative robot applications should follow ISO 10218. However, not all processes are applicable to collaborative robots, which is why a risk assessment needs to be done by a qualified person for each application.