Olmec-UK has developed a vision system to verify cable assemblies before soldering during the manufacture of instruments for the automotive industry. The system differs from many vision systems since it is used interactively by the assembly technicians rather than replacing them.
The operators present the cables in a particular colour sequence to a precise position on a PCB. The cables are clamped into position and the PCB then passes to the next station for soldering.
Operators use their fingers to slide two-wire cables along a pair of grooves in the cable block until the bare ends of the cables are positioned over the solder pads. The vision system checks the colour of the cables and tracks the position of the cables as the operators move them into position, using an edge detection method. When the bare metal ends of the cables are in within 1mm of the soldering position, the system initiates spring-loaded clamps across the grooves to hold them in position and the operators can then remove their hands.
Once the cables are clamped, the vision system makes a second positional check (since there is some variation in the speed with which operators slide the cables) to confirm that the ends are in the correct position. If they are not, the clamps are released and the process is repeated. The procedure is repeated for each of the four cable blocks on the PCB before it is released for soldering.
Although colour imaging is a standard machine vision technique, the cables used in this application are very reflective. This makes differentiating between colours such as red, orange and brown quite challenging. The traditional machine vision solution would be to use high intensity dome illumination, but this is not practical, so a large flat illumination system was designed to minimise reflections.
The interactive vision system not only acts as an aid to the worker, but also controls how they do their job, since the cameras are part of the workflow. The operator can’t move onto the next PCB unless the camera shows that everything is in the right position.
