Robots used to be thought of strictly as stationary machines. They were bolted to a floor, table, ceiling or wall and that’s where they stayed. Now, thanks to collaborative robots, that’s changing.
Since they are simple to program and don’t require guarding, cobots can easily be redeployed wherever they are required. Need to load and unload a machining center? You could have a highly paid skilled worker do the job—or you could wheel a cobot into place and have it tend the machine for the day. If, the next day, you need to tend a dispensing cell or a test instrument, you can simply move the cobot where it’s needed most.
This sort of flexibility is the idea behind Bosch Rexroth’s new APAS line of products.
The APAS Assistant is a six-axis robot equipped with a soft, highly sensitive skin that can sense when the operator approaches. If the distance is too small, the arm stops immediately—before there is any contact between operator and machine.
The robot is mounted to a compact mobile cart that can easily be positioned in front of a machining center or alongside a pallet-transfer conveyor on an assembly line. As a complete mobile system, the APAS Assistant includes a 3D image processing system with integrated lighting, which enables the identification of objects and spatial referencing.
The robot has a maximum reach of 911 millimeters and a maximum payload of 7 kilograms. If can perform a standard pick-and-place cycle in 4 to 8 seconds, or 3 to 5 seconds with distance monitoring. Repeatability is ±0.03 millimeter, depending on the image processing method.
Thanks to its sensitive three-finger gripper, the robot can flexibly and reliably grasp and hold components and products. It is particularly well-suited to gripping round or cylindrical objects. In the event of collision, the gripper fingers automatically retract, helping to avoid pinching and jamming. Gripping force is adjustable from 40 to 120 newtons, and the gripper has a maximum opening radius of 130 millimeters. The APAS Assistant can also be equipped with application-specific third-party grippers while adhering to all relevant safety standards.
Using a mobile touchpad, engineers can intuitively operate the APAS Assistant without special expertise or programming skills.
With optional distance monitoring, the APAS Assistant can adjust its working speed in response to the presence or absence of employees. As long as no one is nearby, the kinematics system works at maximum speed; as soon as it senses someone enter its application-specific far range, it automatically reduces speed. If an employee advances further, the robot stops completely. When the person has left its close vicinity, it will start working again at reduced speed. Only when the application-specific far range has also been cleared will the robot accelerate to its maximum speed again.
Standardized interfaces enable APAS Assistants to communicate with one another, as well as with external machines and systems.
One factory that is already using APAS Assistants is the Bosch auto parts plant in Homburg, Germany. The plant makes fuel injection systems for commercial vehicles. Previously, these components were manufactured with a semiautomatic system. Workers manually aligned magnetic cores and sleeves for the component at a cramped workstation, assembled them, and then placed the assembly into a laser welding station. After welding, the assembly is tested and inspected for quality control.
Rising demand for the product meant the factory needed to increase output. The welding process would have to be automated.
After six months of development, the line was retrofitted with a pair of APAS Assistants, which work side-by-side with people. The cobots were installed over a weekend, so there was virtually no production downtime. One cobot performs the complex process of aligning, assembling and inserting the parts into the laser welder. The second cobot tends the test and measurement instrument. An operator reloads the machine every 30 minutes.
“The APAS Assistants are doing an excellent job at our plant,” says Stefan Betz, group design manager at the plant. “We are also going to use APAS systems for the next generation of products.”