The main functions of machine vision systems widely used in high-precision mounting machines include precise positioning of PCBs, component centering and calibration, and component inspection.
1. PCB circuit board precise positioning. The precise positioning of the PCB is the most basic function of the mounted adder vision system. Three reference marks (Mark points) are designed near the corners of the original PCB. With these three reference marks, the mounting system is based on the set reference position and the difference between the actual positions of the PCB calculates the PCB accurate positioning compensation value, and all operations are completed under the control of the system, without manual intervention. Using these three reference markers, the mounting system compensates for linear translation, quadrature, scaling, and rotation errors on the X and y axes.
2. Device centering and calibration. Due to the misalignment of the component center and the component leads center and the error of the centering mechanism, it is difficult for the mounting and installation tool to be strictly aligned with the center of the component or the center of the lead, which generally has a certain deviation, which leads to alignment errors between the component leads and the solder graphics on the PCB. For fine pitch components, due to the strict requirements for such deviations, the components must be centered and aligned by means of the vision system. The vision system centering and aligning the components can be selected according to the actual requirements of the mounting accuracy, such as mechanical centering claws, centering work stages or optical alignment systems.
3. Component testing. The mounting machine should detect whether the component has been successfully picked up from the feeder by the mounting head, whether the component orientation is correct, and whether the electrical specifications of the component meet the requirements. Completing these test items requires the mounting machine to have a complex inspection system, and when a defective component is found, the mounting machine must perform appropriate corrective actions. On a universal SMT machine, it is usually to abandon defective components and take another one to instead. On the high-speed placement machine, it is impossible to perform the corrective action immediately. It will discard the defective components and continue to install them according to the program until the completion of all the procedures, and then proceed the subsidy process for replacing the defective components.
The above are the functions of the vision system in the PCB assembly machine during the assembly process of the circuit board.