To alleviate the operator from the repetitive riveting process and increase product throughput a collaborative application incorporating the KUKA LBR iiwa has been developed. The application works alongside the operator, fixing rivets into place as the operator continues to work on the assembly. The operator would first load the crash-can components onto the work bench and slot the rivets into place, the cobot would then secure the rivets on one side of the crash-can whilst the operator works on the other side. The operator does not wait for a single second during the cycle even though the robot is working in the same workspace at the same time, making this process design unique to MINI’s Oxford plant.
Where operators previously had to empty their rivet guns after every 20 studs or so, the cobot now automatically dispenses of the studs into a KLT box, eliminating process down time. MINI are also able to keep track of how many rivets have been fixed through the integration of the cobot into their production system which supplies them with factory reports and machine status. In instances where rivets can’t be fixed, the cobot is able to utilise its tactile search function which senses tolerance build up allowing it to understand that a rivet may not be in a 100% repeatable position. When these instances occur, the operator can use their discretion to influence the cobot, either moving the arm away through its impedance mode, or alternatively instruct it to try again if they think the rivet is in the correct position, this gives the operator total control.
The focal point of this solution was to ensure maximum human robot collaboration within a tight working space, which meant developing a sophisticated safety concept to allow for both safe operation and efficiency. When the crash-can program was produced an additional function was created for the safety configuration of the system. The configuration utilises the KUKA’s ability to be self-aware of its location by placing itself in a virtual cage with several predetermined areas. Each area can be defined individually, for example one area could be a working space and another could be a protected space. This function, along with the ability to monitor the spaces, provides the cobot with information which tells it where it can and can’t operate, thereby preserving the safety of the operator and meeting HRC requirements ISO/TS 15066:2016.
Integration of this cobot provided MINI with a system that encompasses human robot collaboration with its unique process design. The system has enabled MINI to significantly improve their cycle times, taking them from a takt time of 64 seconds to 52. This time saving has enabled operators to attend other processes within production, ultimately providing an increase in product throughout.