Information on other interesting applications can be found at:
www.eutist-imv.com
and
www.automaatioseura.fi
Applications
The following applications indicate the diverse nature to which machine vision technology can be put.
Inspection of bandsaw blades
made easy
A leading UK Bandsaw blade manufacturer has utilised a novel adaptation of a standard product for the inspection of the quality of bandsaw blades, while being manufactured.
The requirement was to install a vision system to allow operators to easily check the quality of the teeth on bandsaw blades.
The problem was that the blades are produced on a moving belt and the detail of observation that was required meant that the operator could only inspect the teeth quality if the belt was stopped. This obviously was not possible, as this was a continuous production line.
After consultation with Alrad Imaging the client decided to install an electronically shuttered, CCD camera fitted with a Macro lens above the moving belt. The output from the camera is sent to a stand-alone frame grabber box to which is attached a remote timer control. The operator via this remote control is able to freeze the image either manually or automatically at pre-set intervals, to inspect the blades. The resulting video output is sent to a standard video monitor mounted close to where the operator is positioned.
Such a system could be used in many industrial applications on moving belts where just a visual inspection is required, and no saving or further processing of images is needed.
Accurate
labeling for 70,000 bottles per hour with
the F10 sensor from Omron
When German brewers Emil Petersen GmbH & Co needed to ensure its bottle labels were applied correctly, the Omron F10 mini vision advanced sensor proved to be an ideal, cost effective and accurate solution.
Founded in 1888 the Flensburg-based brewery is responsible for producing the full-bodied 'Flensburger Pilsner', the German market leader in bottled beer. Since its inception, the company has brewed its premium products according to the strict German purity regulations of 1516, and currently has an annual output of around 55,000,000 litres.
In order to increase efficiency at the brewery, a complete automation system was installed in 1999 under the supervision of Werner Sauer, technical Director at Emil Petersen. Using two Krones production machines set up in a mirror configuration, Emil Petersen were able to expand output capability to 70,000 bottles per hour.
One particular constituent of the new Krones machines, the Multimatic is responsible for receiving the beer bottles once they have been packed, cleaned, filled and sealed with a plastic stopper. The Multimatic is then responsible for both labeling the bottles and applying a wire clamp over the stopper to ensure it does not discharge under the build up of pressure in the bottle, this also ensure the bottle is in pristine condition.
Each bottle enters the Multimatic, is fed into a forty -bottle capacity magazine and placed on a separate plate in such a way that the clamp faces in one of two orientations. These plates are equipped with a servo motor providing the means for 360deg rotation to accurately position each bottle prior to labeling, two retro-reflective sensors are used to recognise the orientation of the clamp on the bottleneck.
Each bottle must be in exactly the right position to ensure uniform labeling; to do this each sealing clamp must be accurately located and identified. Previously, proximity switches were used for this purpose, but the introduction of a new refined steel clamp material meant that the sensing distance was reduced, resulting in mechanical problems.
Further experiments with the latest sensor technology, such as laser displacement sensors repeated resulted in errors with label positioning. The main problems were extraneous light impinging on the sensors, different bottle pressure caused by different sealing rings and also, surprisingly, the amount of foam present in the bottle.
The solution came in the form of the Omron F10 pattern matching advanced sensor which has the capability of recognising the position of the clamp and compensating for errors, cost effectively. The F10 is a compact and low cost pattern matching advanced sensor, consisting of two parts; firstly the camera head, which projects the area which is taught to the sensor and the area in which the sensor searches for the taught image and secondly; the evaluation unit which receives the resulting readings and gives a yes/no output.
The F10 projects the measurement window over the bottle neck area containing the clamp and compares this with the 'good' pattern taught by the user.
The clamp is in the correct position, the bottle will not rotate and the label will be successfully placed. If however, the sensor does not detect the clamp, the bottle will be rotated until the F10 identifies the correct pattern after which labeling is executed, the F10 is triggered by an Integral Rotary Shaft Encoder.
The F10 has an inbuilt light source and consequently is unaffected by extraneous light interference. Furthermore the F110 features an easy teach function (also available remotely), which enables fast and simple installation and implementation and typical evaluation times are only 3.6ms for a normal field scan and 10.8ms for a wide field scan.
Crack Detection for Medicinal
Tablets
Sugar coated medical tablets, like all pharmaceutical products,
have to conform to high quality standards and this includes excellent
visual appearance.
Based on ideas from a successful student project, for which the
York undergraduate won a commendation from the Design Council, a
major pharmaceutical company commissioned the York
Electronics Centre to design and build an inspection
system for small surface cracks in sugar coated tablets. Such cracks
can develop occasionally due to powder compaction variations.
The presentation system consists of three parallel chutes from which
the pills are dispensed at regular intervals onto grooved, rotating
rollers. A line camera scans the circumference of each tablet in
a batch of three as they rotate. By comparing successive scans,
sharp edged cracks can be detected by differential techniques whereas
gentle modulations in the sugar coated surfaces are ignored. The
resolution of the camera system is such that 20 micron width cracks
can be detected.
After two rotations of the tablets, the high speed electronic signal
processing determines if any tablets have cracks, the rollers open
and the tablets are sucked downwards, in one direction if unblemished
and in another if found to be cracked. As the rollers reclose, another
three pills descend from the delivery chutes and the inspection
process continues.
The system operates at ten tablets per second. A batch of 750,000
tablets takes about 21 hours. Previously the task would have required
a team of 5 inspectors to accomplish the same task in that time,
assuming they could work continuously and effectively on such a
tedious but necessary job.
2D Code Reading
The latest two-dimensional coding techniques, applied to industrial products for process control and traceability, are being read by machine vision techniques.
Such codes are able to store considerably more data in a far smaller physical space; typically more than 100 numeric digits can be encoded in a 5mm x 5mm area. They are far more robust than bar codes, due to in-built error correction and detection algorithms and can be reliably read in any orientation.
These features make it possible to apply the codes to a range of packaging material, including paper, plastic, glass, foil or film by ink-jet, laser or thermal transfer printers. It is not surprising, therefore, that leading companies are now adopting the code to enhance their operations.
Thermometer Calibration
Vision systems do not just check for faulty products. They can also control processes. A major producer of thermometers uses vision systems as part of the production process. Thermometers are produced for consumer, scientific and medical applications. These thermometers can work over very different temperature ranges and contain either mercury or alcohol. There is a natural variation in the response of each product. To overcome this, the thermometers are tested and accurately sorted before having the correct calibration print applied.
The vision system performs the testing and sorting process to the tight tolerances required. Each thermometer is immersed in two different temperature baths at which the height of the fluid is measured by the vision system. The twin camera vision system then communicates the results to two linear drives holding the scribing mechanisms and with 32 sorting bins where the calibrated thermometers are stored prior to printing.
Windscreen Wiper Development
Vision systems are not always used in production solutions. They can play an important part too in the development process. A windscreen wiper manufacturer has developed a special test rig incorporating a vision installation, which was designed to give information on the efficiency of a wiper blade in an objective and repeatable way. The test rig comprised a specially lit screen, water spray jets and a wiper blade assembly. Water is sprayed onto the screen, which is then inspected after each wipe for streaks and smears. A succession of efficiency co-efficients is then recorded for each wiper assembly tested on the rig.
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