Feeding screws in order to screw two components together is one of the typical applications in the automation industry.
Followed by the subsequent assembly process of the screw connection itself. We would like to show you a few applications how this can also be implemented with cobots.
The focus is on the cobots from UR, the world market leader in cobots. But since it is always about the application and not the robot / cobot alone, we would also like to show an example with the FANUC CR7ia.
The collaboration between humans and robots is more than just hype. In the following video we show how a worker works side by side with a Cobot from Universal Robot (UR). A real human-robot collaboration (HRC). The speeds and constructional designs were strictly based on the specifications from DIN ISO / TS 15066: 2017-04 for collaborative robots.
Since, according to the specifications, no collision may occur in the head area, a plexiglass pane was attached over the UR Cobot as an additional protective device for this application. Sharp corners and edges have also been avoided with the screwdriver. A lot of work was done with large radii in order to reduce injuries to an absolute minimum.
After the screws have been fed into the component, the next step often comes – the screw connection. Today this is often still a manual activity by a worker.
With our following example we would like to show that screw connections can also be implemented using cobots
Due to the variety of products, full automation can no longer be implemented everywhere. These are the typical applications in which cobots are used.
In the application shown here, 4 cobots – by Universal Robots – were mounted on a mobile platform. This “screwing platform” is guided under the conveyor belt by an employee. The simultaneous work of the 4 UR cobots enables 14 screw connections to be realized in the specified cycle time. Driverless transport systems were deliberately avoided here, as the focus was on making the screw connections more flexible.
Those familiar with HRC applications will notice the Sick scanner attached to the side. The background to this safety element is that people in the vicinity of the screwing platform do not reach over the Plexiglas pane and are thus injured by the sharp-edged screwdriver. The employee also guides the platform using the consent button, so he can stop the robot at any time and return it to the safe starting position.
This application shows that HRC always exist in different forms. It is not a question of whether the application is collaborative, cooperative or coexistent, but rather that the cobot application matches the customer’s requirements for cycle times and flexibility.
More often than 4 cobots working in parallel on a screw application, the challenge will be to hit the screw with the screw head. A camera support can be helpful for this.
The system solution is based on a robot that has a screwing unit with a camera system, an electric screwdriver, a holding system and a screwdriver bit. The highlight is the small screwing unit that is plugged into the screwdriver. It is designed in such a way that the screw blade cannot injure the employee. A spring-loaded sleeve protects the sharp-edged blade and detects a collision. Thus, the whole thing is also designed in such a way that collaborative operation with people is made possible. The standards are for such a collaborative operation between man and machine DIN EN-ISO 10218-1, DIN EN-ISO 10218-2 as well as the technical specifications of the trade association TS 15066 are considerable and are adhered to.
The exact current position of the screwing unit is determined by the camera system and offset against the current robot position so that the respective screw position is defined. Then the screw is screwed. The robot moves to the calculated screw position and repeats the process for all screws. An image recording is definitely conceivable with which all screw positions can be determined immediately. This saves additional time during the subsequent screwing. However, the screws are always tightened in the correct order and with the correct torque.