Fast calculation of the welding gun posture for spot welding using octrees and CPU parallel processing

Spot welding is widely used for the lightweight and rigid bonding of metal parts. To plan the spot welding, the welding engineer should check the posture of a welding gun to ensure that it does not collide with the welding objects and fixtures. Although commercial programs can check the posture range of a welding gun, it requires a long calculation time, infeasible for industrial applications with hundreds or thousands of welding points. This study proposed a method for automatically calculating the weldable posture range for given welding points. The proposed method detects the possible collision areas between the welding objects and the welding gun in advance by the octree method, drastically reducing the calculation time. It used the central processing unit (CPU) parallel processing to calculate the exact weldable posture to shorten the calculation time further. The proposed method uses the stereolithography (STL) model as input for versatility for welding objects and guns. It also developed several algorithms to overcome the limited information available with the format. As a result, the program could calculate the weldable posture range within 4 s per single welding point with a one-degree resolution. The proposed method is intended for spot welding but may be utilized for other welding applications.