Optical sorting machines are generally set up to measure specific external features such as lengths, head heights, outside diameters and alike. It works with an angled laser and light comparators that break and release beams on parts that are out of tolerance. Optical sorting is highly effective on a certain range of parameter parts and can generate under 50PPM results and in some case below 20PPM.
In some instances light can be used as an indicator for the presence of internal threads and used with a combination of cameras, the number and pitch of internal threads can be successfully identified.
The use of multiple lasers can be highly successful at measuring multiple points and on given parameters results better than 20PPM can generally be attained.
