Machine vision in robotic welding
Joint finding, arc tracking and inspection: what each technology solves and its limits on real materials.
In welding, vision can find the joint, correct the path or inspect the bead. These are three different problems and are not always solved with the same camera. Feasibility depends on material, fit-up and access.
Three different problems
Joint finding: where the joint starts and ends. Tracking: correct while welding. Inspection: evaluate the bead afterward. Each has its own requirements and limits.
| Criterion | When it is used | Limit |
|---|---|---|
| Joint finding | Before welding, with variable parts. | Needs access and laser contrast. |
| Arc tracking | During the bead, to correct deviation. | Does not compensate for a poorly prepared joint. |
| Inspection | After welding, to detect defects. | Does not replace code-required testing. |
Materials and reflections
Carbon steel is usually easier to read than aluminum or galvanized steel. Reflections can confuse the sensor. If the material cannot be read, vision is not the solution; another method is assessed.
Fit-up, tolerances and fixturing
Vision corrects variation within a range, not out-of-tolerance fit-up. Fixturing must present the part and leave sensor access. Without it, the best algorithm does not weld.
Data and validation
Test pieces and real parts, a range of gaps and deviations, and an acceptance criterion are needed. Validation uses the real material and welding process, not a demo on clean steel.
When vision is not a good fit
When the joint is not visible, the material reflects too much, access is impossible or variation exceeds what the system can correct. In those cases, work on fixturing, preparation or process.
Frequently asked questions
What is the difference between joint finding and tracking?
Joint finding locates the joint before welding; tracking corrects the path while welding. They solve different problems.
Does vision compensate for out-of-tolerance fit-up?
No. It corrects within a range. If the part is out of tolerance or the gap is excessive, the problem is fixturing or preparation.
Does it work on aluminum or galvanized steel?
It may fail due to reflections. Feasibility is tested with the real material; if the sensor cannot read the joint, another method is assessed.
Does vision inspect the bead?
It can detect visible defects, but does not replace tests required by code or customer. Visual inspection and testing are different.
What data is needed to assess it?
Parts and joints, material, range of gaps and deviations, access, fixturing and quality criterion. Testing uses the real process.
When is it not a good fit?
When the joint is not visible, access is impossible, the material reflects too much or variation exceeds system capability.
