QUALITY CONTROL: ADVANCEMENTS
distinguished and unimportant cosmetic flaws might be rejected or deep cracks retained. Also, as volume cannot be calculated, the levels of fill into a packet or tin cannot be confidently assessed.
STEPS IN 3D Where the height (or depth) of an object is a vital statistic, then 3D vision, which incorporates depth of profile measurement, is required. This was the next goal of vision inspection, and its introduction was beset with difficulties. It has taken a few years to
achieve full usability of the technology in the factory environment. For example, the early hardware required separate lighting equipment and multiple cameras. The robustness and applicability of the operating software, complex configuration and integration with SCADA were additional factors which had to be overcome. Then the next generation of
single unit 3D vision smart cameras, set at an angle with integrated lighting and narrow beam scanning laser profiling, was found to be an excellent way for reading depth so that, for example, a deep crack is not mistaken for a minor surface blemish. This 3D system was also able to judge fill depth of packages. At the same time, the
combination of intuitive set up and configuration, and more powerful software to process the digital image quickly, simplified operation for the production engineer. The speed and power of the
order to avoid product damage. As well as positioning, 2D
vision may be used to measure the essential dimensions of objects, which are compared with a preset dimensional profile within tolerance, and the product is rejected if not applicable. Indeed, 2D vision is still the
basis for much production inspection but, it is sometimes used more as a warning of production variability (end of batch, poor mix etc.) and supplemented by visual inspection for the QC process. 2D vision is unable to assist
where the depth or height profile of an object cannot be measured. Thus surface variation will not be accurately
image capture facilitated rapid decision making which started to match conveyor and packaging line speeds. This meant that procedures such as portion and volume control, as well as out of specification item rejection, could be added to picking position and packing capabilities.
COMPLETE 3D VISION POTENTIAL Two further advances have now redefined the technology and started to show what it could do. Introduced at the end of 2010,
camera software development resulted in full 3D data capture, and now full colour vision has added as much more quality information as the original step
from 2D to 3D. Quality control of colour
defects can now be monitored as well as shape, size and surface irregularities. For example, a line picking baked goods from a belt for packing is now able to offer control and feedback on the degree of cooking, within set shades.
DELIVERING CONSISTENT QUALITY BENEFITS 3D inspection with vision cameras is becoming the market norm, with easy to set up and use software. This is complemented by full integration with typical factory SCADA systems and communications protocols. Increasingly wider acceptance of the value of 3D and colour and more equipment available with these technologies will be the result, following the rapid changes over the last three years. Further software
developments which simplify the accessibility and applications will continue to
deliver real benefits including rapid feedback to enable adjustment for ‘instant’ fault rectification at ever faster line speeds. These improvements should enable the plant engineer to integrate the technology more completely with the factory distributed control systems. The benefits offered by the
new 3D vision systems are directly leading to food processing and packaging quality improvements and wastage savings. Reduced goods rejection rates and improved relations with customers also mean better business prospects. With the objective of the highest quality in food and packaging, vision inspection aims to maintain consistency at the same intensity level over the whole production shift. We can now match or improve on the human eye for quality and exceed it for fatigue resistance
and attention span.
“Developments in vision camera system performance have opened up new quality information potential for the production engineer. An informed insight into the progress of the technology enables the engineer to select the best mix of systems to meet a wider range of quality needs”
Even though it was essential, the introduction of 3D technology into vision inspection was not easy. It has taken a few years for the technology to become useable in factories
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