The final stage of making electronic connectors is the assembly of finished products. There are two methods to connect the plated pin with the injection box base: single pair insertion or combined pair insertion. Single pair insertion refers to inserting one pin at a time; For combined pair insertion, multiple pins are connected with the box base at one time. No matter what kind of plug-in method is adopted, the manufacturer requires to check whether all pins are missing and correctly positioned in the assembly stage; Another kind of routine testing mission is related to the measurement of the spacing on the joint surface of the connector.
Like the stamping stage, the assembly of connectors also poses a challenge to the automatic detection system in terms of detection speed. Although most assembly lines have a beat of one or two pieces per second, the visual system usually needs to complete multiple different inspection items for each connector passing through the camera. Therefore, detection speed has once again become an important system performance index.
After assembly, the appearance dimension of the connector is much larger than that allowed by a single pin. This also brings another problem to the visual inspection system. For example, the dimensions of some connector box seats exceed one foot and have hundreds of pins. The detection accuracy of each pin orientation must be within the scale range of one thousandth of an inch. Obviously, the detection of a one foot long connector cannot be completed on one image, and the visual detection system can only detect the quality of a limited number of pins in a small field of view at a time. There are two methods to complete the detection of the whole connector: using multiple cameras (increasing the system consumption); or when the connector is connected in front of a lens to trigger the camera, the vision system "stitches" the successive single frame images to judge whether the quality of the whole connector is qualified. The latter method is usually used by ppt visual inspection system after connector assembly.
The test of "practical orientation" is another requirement for the test system of connector assembly. This "practical orientation" refers to the distance between the top of each pin and a specified planning datum line. The visual inspection system must make this imaginary reference line on the inspection image to measure the "practical orientation" of each pin vertex and judge whether it reaches the quality standard. However, the reference point used to delimit this reference line is often invisible on the practical connector, or sometimes appears on another plane and cannot be seen at the same time of the same lens. Even in some cases, the plastic on the connector box has to be ground off to confirm the orientation of this reference line.
