Laser seam finding and tracking replace manually taught welding trajectories by using a laser to identify the weld seam for welding — effectively giving the robot a pair of "eyes".
During manual teaching, weld seams are susceptible to deformation, varying gaps, and assembly errors, causing significant seam deviations during welding. To improve weld quality, the welding robot needs real-time control to correct these deviations.
How the Laser Detects the Weld Seam
A laser diode projects a laser onto the workpiece surface; the reflected light forms an image on a CCD or CMOS sensor. In communication with the controller, the controller processes the image position to determine the weld seam location, then guides the robot to track or find the seam.
In fact, most welding robots currently in service work in "teach-and-replay" mode, with a few working in trajectory-planning mode. In other words, whatever the product, welding must follow the design data — a predetermined theoretical program is compiled and then executed. When large batches of identical workpieces are involved, laser seam finding or tracking is used to establish the trajectory; since large batches inevitably introduce errors, the laser compensates for them, keeping the welding pass rate above 90%.
Laser Calibration
The calibration steps are illustrated and described in text, making it relatively easy — as long as you can read the weld detection image on the host PC, you can perform the calibration.
Laser Seam Finding
Refer to the following video
or iNexBot Technology's demo video
Dedicated Laser Seam Finding Instructions
iNexBot laser seam finding is mainly divided into static and dynamic seam finding, seam-finding offset, and — most importantly — seam-finding calculation. For users, programming is simple and requires no complex logic; a single algorithm can serve an entire line producing the same workpieces.
Laser Seam Finding Algorithm
Laser seam finding can be used to correct the position of identical workpieces on a line or to determine the weld start and end points. Because seam finding detects before welding, it cannot be used for seams that deform severely from heat during welding or for irregular seams.
iNexBot offers multiple seam finding and tracking algorithms, including arc seam finding for irregular shapes, enabling weld detection in a wide range of working conditions. Depending on the laser vendor, detectable seam types include inside fillet joints, outside fillet joints, left lap joints, right lap joints, and butt joints.
When using the laser, as long as the tool center point accuracy is kept under 2mm, laser seam finding can achieve an accuracy of ±0.5mm, ensuring the precision of the calculated points.
Seam finding is typically used to determine the start point when it is unknown, or for large batches of regular workpieces requiring welding. As long as the workpiece is within the laser's detectable range, any offset or rotation in any direction can be compensated by calculating the shifted seam via the user coordinate system or offset values.
Dedicated Parameters
The iNexBot system supports up to 99 sets of process parameters, freely switchable and copyable between sets. The laser task number corresponds to the vendor's parameter number. Parameter setup is minimal and simple, and parameters can be fully customized.
Laser Seam Tracking
Laser tracking uses a laser vision sensor mounted ahead of the welding torch to perform detection; using the pre-calibrated positional relationship between the sensor and the torch, it calculates the coordinates of the measured points.
During welding, the robot's taught position is compared with the sensor's detected position to compute the position deviation at each point. When the torch — lagging behind the laser line — reaches the corresponding detection position, the deviation is compensated onto the current welding trajectory to correct it.
Dedicated Laser Tracking Instructions
Laser tracking requires very few instructions: after using a line or point-to-point instruction to set the start point, simply insert the trajectory to be tracked between the laser tracking start and end commands. It supports straight-line tracking, irregular trajectory tracking, curves, and arc tracking — anything within the laser's detection range can be tracked with high accuracy of ±0.5mm.
Seam finding and tracking can also be combined, using seam finding to establish a precise tracking start point.
Laser tracking is generally used when the seam is irregular rather than a single straight line: line instructions define the start and end points, and as long as the laser can detect the seam during the process it keeps tracking; if detection is lost, the robot pauses.
Dedicated Laser Tracking Parameters
Laser tracking also has its own independent parameters. Up to 99 sets are supported, freely switchable and copyable between sets. All commonly used parameters are included, and offset values, scanning parameters, and more can be customized to ensure tracking stability.
