SuZhou Tonkida Electromechanical Technology Co., Ltd Professional SMT whole line supplier

Visual alignment system is widely used in high performance placement machines. The visual alignment system uses digital image processing technology. When the nozzle on the patch head absorbs the component, the camera fixed on the patch head or fixed on a certain position of the fuselage acquires the image during the process of moving to the patch position, and the optical density distribution of the component is detected through the image. These optical densities are digitally passed through the CCD photocoupler array composed of many small sensitive elements on the camera, and the grayscale values of 0 ~ 255 are output. The gray value is proportional to the optical density, and the larger the gray value, the clearer the digital image. The digital information is stored, encoded, amplified, sorted and analyzed, and the results are fed back to the control unit, and the processing results are output to the servo system to adjust the position deviation absorbed by the compensation element, and then the mounting operation is completed.

So, after the machine takes photos of the reference points and components on the PCB, how to realize the automatic correction of the mounting position and achieve accurate mounting? In this process, the machine locates the mounting target of the component through a series of transitions between coordinate systems. We illustrate how the system works through the mounting process. First of all, the PCB is transmitted to a fixed position through the transmission device and is fixed by the splint mechanism, the sticker head is moved above the PCB reference point, and the head camera takes photos of the reference point on the PCB. At this time, there are four coordinate systems: the substrate coordinate system (Xp, Yp), the head camera coordinate system

Principle of confirming the compensation value of component mounting deviation

(Xca1, Ycal), image coordinate system (Xi, Yi) and machine coordinate system (Xm, Ym). After the reference point is photographed, the machine converts the substrate coordinate system to the machine coordinate system by associating with the camera and image coordinate system, so that the target mount position is determined. Then the sticker head picks up the component and moves to the position of the fixed camera, and the fixed camera takes a picture of the component. There are also four coordinate systems: the patch head coordinate system is also the mouthpiece coordinate system (Xn, Yn), the fixed camera coordinate system (Xca2, Yca2), the image coordinate system (Xi, Yi) and the machine coordinate system (Xm, Ym). After the component is photographed, the machine calculates the core position coordinates of the component features in the image coordinate system, and converts them to the machine coordinate system by association with the camera and image coordinate system. At this time, the core coordinates of the component and the core coordinates of the nozzle are compared in the same coordinate system. The difference between the two coordinates is the required position deviation compensation value. The machine control unit and servo system can then control the machine for mounting according to the target mounting position determined in the same coordinate system.