Tech note: assembly checks and large parts — solder joints, nuts and washers, coil insulation
Missing, broken and unsoldered joints all show up in images; the hard part is component leads with varying shapes. Nuts, screw torque marks and part numbers on control panels can be recognised. Large coils need rotation and lifting mechanics first.
In assembly inspection the challenge is often not the defect itself, but that no two parts look exactly alike. Here are three different kinds of projects.
Solder joints: defects are visible, leads are the problem
With a 5 MP colour camera at 13.4 μm under a white dome light, insufficient solder, broken joints, unsoldered and deformed leads were all imaged. Good joints have larger solder areas, so area separates abnormal ones; leads without solder or that cannot be located are judged NG.
- Several viewing angles are needed; broken joints require both front and back
- Lead bending varies, so a separate lead-detection step is needed
- AI visual inspection is another route, but needs many sample images and a long collection and validation cycle
Control panels: presence, marks and part numbers
- Nuts: recognised from the front; washers hidden under nuts need a side view, or a washer larger than the nut
- Screw torque marks: the screw is found first, then the mark is recognised correctly
- Part search and counting and reading part markings both work; checking that sequences are correct needs a position-to-part logic list
Large coils: mechanics before inspection
For insulation-sheet position on heavy-electrical coils, exposed areas on both sides, their difference and the angle show whether a sheet has shifted. The parts are large and heavy, so the proposal included guide rods for crane loading, a coil rotation table, a camera lift with an autofocus axis and an automatic red-pen marker for NG points, checking point by point through a full rotation.
Summary
Deal with varying position first — through mechanics, alignment algorithms or both — and judgement becomes stable.
