Machine Vision & Web Inspection

Machine vision creates ‘factory of tomorrow’ By Earl Yardley, director at Industrial Vision Systems


ndustries continue to be driven by innovative developments in automation, which have enabled

manufacturers to create new ways to deploy virtual labour to oversee automated knowledge-based tasks. As a result, not only are these organisations saving on the costs of manual work, but they are also witnessing increased accuracy and higher levels of safety. Machine vision technologies are used in

virtually all manufacturing industries, and typical applications include type verification, part defect detection, surface inspection, product traceability, ID and code reading. These methods are also used to precisely

inspect components and for identifying and automatically sorting out defective parts. Vision system technology can also be used for completeness and type detection for Just-In-Time manufacturing sequencing. A significant feature of machine vision is its high speed compared to a human operator - the algorithms require just milliseconds to detect and process image data. Consequently, large quantities of products can be inspected automatically at rapid speed, with the added advantage of data being stored automatically.

CONFORMAL COATING In the fabrication of PCBs, electronics manufacturers apply coatings using automated systems that consist of an X-Y-Z platform that moves a dispensing head to key points on the surface, in a process known as selective conformal coating. To allow operators to manually inspect

PCBs, many of the standard conformal coating materials are available with a 365nm wavelength UV trace. Using standard UV lamps, inspectors can then manually check individual boards to see if the coating is placed correctly around the component,

whether it has migrated into incorrect areas of the board and whether the correct amount of coating has been applied. Due to the different levels of trace versus

raw material within the compound, the fluorescent nature of such coatings can vary widely. Because of this, inspectors must be properly trained to understand the nature of both the compound used and its fluorescent properties to properly inspect each board. As with all manual inspections, such checks are subject to the individual accuracy and reliability of each operator. IVS have developed intelligent vision systems to automatically check PCB boards for this coating.

UV INSPECTION In the design of its conformal coating checking systems, IVS uses a standard 1000mm PCB conveyor system and canopy. In this way, the system can be adapted for any size of board and multiple PCB types. PCBs are individually stepped along the systems conveyor and into the inspection station using the SMEMA standard machine interface. This equipment interface specification standardises the communication mechanism for single transfer manufacturing systems of surface- mounted PCBs and allows equipment from a number of different manufacturers to be integrated more easily. Because of the nature of the UV traces

added to the conformal coating, IVS use two custom industrial lighting rigs to illuminate both sides of the PCB. To image each board, two IVS digital cameras are mounted above and below the conveyor belt.

COLOUR LEVELS To compute the colour level of each coating, the UV trace within each ROI is colour matched using Colour Matching. Each colour value is represented by three values

28 May 2019 Launched in 2000, IVS manages the

design, installation and commissioning of quality control vision systems for manufacturing companies. Their vision systems are used for inspection, guidance, identification, measurement, tracking and counting around the world.

for the three basic colours of red, green and blue. These values fall into the standard grey level range from 0 to 255. Taking an RGB colour image as input, the

software creates a grey level image of the same size as its input image. The grey level of every pixel in this image indicates the similarity of the corresponding pixel in the original image to one or more known reference colours. In the design of the IVS system, the Distance Mode function is used. In this mode, the brightness of the resulting grey level pixel indicates its similarity to a single reference colour. For each pixel in the source image, the similarity of its colour to the reference colour is computed. The grey level of the corresponding pixel in the result image indicates the degree of similarity.

HUMAN INTERFACE To supply the system’s operator with information regarding each PCB inspection, IVS have a graphical user interface to display images and the results of each inspection. As each board is inspected, the operator is presented with an image of the board and the highlighted ROIs. The results of each pass or fail on each board is displayed as well as a running total of the number of boards inspected and passed by the IVS machine.

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