Cobots: What you need to know

Follow @TheManufacturer

Types of cobot operation:

Speed and separation monitoring: sensors detect human presence and reduce the cobot’s operating speed as the human gets closer.

Power and force limiting: this defines today’s typical cobot. By limiting speed, payload and force, the cobot stops almost instantly when it encounters an obstacle and the energy of any collision is kept below ISO-defined maximum levels.

Safety-rated monitored stop: proximity and other sensors stop the robot when a human enters its workspace. Either the robot or the human operator moves, but not both at the same time.

The robot can swiftly resume its tasks when the human leaves but this operating model loses most collaborative advantages and still requires traditional safety guards.

Hand guiding: the human operator uses a hand-operated device to directly control the robot.

(Source: ISO/TS 15066 guidelines)

Will cobots wear out?

Where industrial robots are big heavy pieces of machinery with sealed drives that might work for decades, cobots are lightweight with aluminium arms and joints powered by less robust harmonic drives.

In Universal Robots machines, those drives are designed for a minimum lifespan of 35,000 hours. That’s about four and a half years of continuous operation which equates to many more years of use in real world applications like machine tending.

The company has robots that have been in service for more than 10 years. For high load applications, it quotes five to six years before a joint might need to be replaced. That task involves removing 12 bolts and takes around 45 minutes.

Connecting cobots to the Industrial Internet

To cope with short-run customised production and reach Industry 4.0 goals, all robots also need standardised protocols to connect to the Industrial Internet.

Projects like the EU’s PERFoRM are now creating the middleware needed to interface data from systems like ERP and SCADA to cobots, CNC mills and PLCs.

One PERFoRM use case involved a UR10 that tests Whirlpool microwave ovens for electromagnetic compliance.

Automatically generating the cobot’s path from markers in the oven’s CAD design file meant that, when the CAD file changes, so does the arm’s movements.

“When a different model is being produced, the robot will automatically follow the new path,” says Evangelia Dimanidou, research engineer at the Manufacturing Technology Centre.