Robotic welding without programming each part: how it works
Laser scanning, 3D model and arc tracking: how a robot welds beams and structures that are never the same without anyone teaching it every point.
The classic welding robot repeats a path someone taught it point by point. That pays off with thousands of identical parts, but not in a fabrication shop that makes different beams, columns or chassis every week with fit-up that is never exact. For that case there are systems that generate the path themselves: they start from the part's model, measure it with a laser and correct while welding.
Why point-by-point programming does not pay off in structures
In steel structures almost no two parts are alike, and cutting and fit-up carry errors of several millimeters. If every new part needs hours of programming and the real part does not match the taught one, the robot spends more time stopped than welding. That is why most of this industry still welds by hand even when it is short of welders.
Step 1: the 3D model builds the path
The software takes the part's model, identifies the joints and generates the paths, torch angle and seam order from a process library. Before welding, a technician reviews the simulation to confirm the robot reaches every joint without colliding.
Step 2: the laser finds the real joint
A laser scanner mounted next to the torch scans the part and locates each joint where it really is, including where it starts and ends. That lets the system tolerate up to about 30 mm of difference between the fitted part and the model, and seams that came out longer or shorter than planned.
Step 3: the arc corrects while welding
During welding, arc tracking reads the current while the torch weaves and corrects the path in height and sideways, with up to 8° of angle deviation. That makes it possible to weld multi-pass bevels, follow corners and go around through-holes without reprogramming.
Where it does not work
The laser needs to see the joint: galvanized parts, aluminum and polished surfaces reflect and confuse it, and aluminum has no arc tracking either. It also does not solve hidden joints the laser or torch cannot reach, or fit-up with gaps wider than the weave. For carbon steel from 6 to 30 mm, on the other hand, it is the most direct way to robotize parts that are welded by hand today.
