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Laser seam locating and laser tracking apply a laser sensor to identify the weld seam after manual teach-programming of the welding trajectory — essentially giving the robot an extra pair of "eyes."

In manual teach welding, the seam is easily affected by deformation, dimensional variations, and assembly tolerances, which causes significant deviations during welding. To ensure welding quality, the welding robot must be controlled in real time to correct seam deviations.

Laser-Based Seam Detection Principle

The laser emitter projects a laser line onto the workpiece surface; the reflected light forms an image on the CCD or CMOS sensor. Through communication with the controller, the controller processes the image to determine the seam position, which then drives the robot to track or locate.

In fact, most welding robots currently in service run in the "teach-and-replay" mode, with only a small fraction working in trajectory-planning mode. In other words, regardless of the product, welding always follows design data: a predetermined theoretical program is first written, then welding runs. For high-volume runs of identical workpieces, laser locating or tracking is needed to determine the trajectory; for batches with deviations, the laser sensor compensates for those deviations — keeping the qualified rate above 90%.

Laser Sensor Calibration

The calibration step is shown with figures and described in text. It is straightforward — once you can read the seam-detection image on the host, you can complete calibration.

Laser Seam Locating

Refer to the videos below.

Or an iNexBot demonstration:

Dedicated Locating Instructions

iNexBot laser locating is mainly divided into static, dynamic, locating-offset, and most importantly, locating-calculation categories. For users, programming is simple — no complex logic is needed; a single set of algorithms can be applied to a whole assembly line of identical workpieces.

Locating Algorithm

Laser locating can be used on the assembly line for identical workpieces to perform locating correction, or to determine welding start and end points. Because locating detects the seam first and then welds, it cannot be used for welds that undergo significant thermal deformation during welding or that are highly irregular.

iNexBot has multiple locating and tracking algorithms to support the locating of irregular contours such as circular arcs, handling various seam-identification scenarios. Depending on the laser sensor vendor's supported seam types: inside corner, outside corner, left-lap, right-lap, butt, and more.

When using the laser sensor, as long as tool-hand precision is < 2 mm, laser-locating precision can reach ±0.5 mm, guaranteeing accuracy at the post-calculation points.

Locating is typically used to determine the starting point when it is unknown, or when large-volume, regular workpieces require robotic welding. As long as the workpiece is within the laser's identifiable range, regardless of the direction or rotation of deviation, the offset can be computed via the user coordinate system or offset variables to recover the seam after deviation.

Dedicated Parameters

The iNexBot system supports up to 99 process parameter sets. Parameter sets can be freely switched and copied. The laser-sensor job number corresponds to the laser-sensor vendor's parameter index; parameter setup is minimal and intuitive, and you can fully self-define the parameters you need.

Laser Tracking

Laser tracking uses a laser-vision sensor mounted ahead of the welding torch to detect, and computes the sensor-measured-point coordinates from the pre-calibrated positional relationship between the sensor and the torch.

During welding, the robot's teach position is compared against the sensor's detected position, and the deviation at each point is computed; when the welding torch trailing the laser line reaches the relevant detection position, the deviation is overlaid onto the current welding trajectory, achieving weld-trajectory correction.

Dedicated Tracking Instructions

Tracking instructions are minimal. After defining the start point via a line instruction or point-to-point instruction, simply insert the trajectories to track between tracking start and tracking end. Straight-line tracking, irregular-trajectory tracking, curves, and circular-arc tracking are supported — any seam within the laser's identifiable range can be tracked with ±0.5 mm precision.

Locating and tracking can also be used together to determine a precise tracking start point via locating.

Laser tracking is generally used when the seam is irregular rather than a single straight line. Straight-line start and end points can be defined, and as long as the laser can identify the seam, tracking continues; if not, the robot pauses.

Dedicated Tracking Parameters

Tracking also has its own independent parameter set. Ninety-nine (99) sets are supported; each can be freely switched and copied. All common parameters are included, and offsets, scanning parameters, etc., are user-definable, ensuring stable tracking.