Manually torquing wheel lug nuts during the assembly process is a labor intensive operation. Nut runners are typically large and heavy and are manually presented to each wheel to apply the necessary torque. Maneuvering these heavy pieces of equipment presents safety issues for workers. Additionally, vehicles arriving in the torquing stations are not always in the same position and vehicle wheels are often allowed to rotate and tilt. This variation, along with the size and weight of the nut runner, presents a major challenge to automating the process.
A Cognex 2D vision system recognizes the type of wheel and locates the axle’s center using geometric pattern matching tools. The vision system also inspects the wheel’s rim to determine its angle of rotation and measures the difference between two laser cross hairs to calculate the angle the wheel is turned and tilted. The vision system data is sent to the robot controller and the robot swivels its wrist to match how the wheel is tilted and turned, and rotates to match the nut runner’s angle of rotation. The robot then guides the nut runner onto the lug nuts and the nut runner provides the necessary torque. Automating this application offers significant process efficiencies and eliminates safety concerns associated with repeatedly manipulating heavy nut runners.