Inspection technology and its use in the manufacture of spirits
What is possible today? - observations regarding costs / uses
The quality of a product is an important aspect to be considered when in competition with other products. Commercial success can depend on this. Therefore all the measures taken to monitor quality can have a decisive influence upon the appearance and image of the finished product. However these measures are not always popular with production managers because their implementation is always associated with a loss in productivity. Not only faulty products are identified and sorted but due to the tolerances of the procedures employed and above all due to the materials used (e.g. glass bottles) there are always "false detections" to be reckoned with. These frequently play a not inconsiderable part in reducing the output.
When employing control procedures it is precisely automatic control devices which require operating conditions to be as constant as possible (e.g. a stable supply of products, ambient conditions which do not fluctuate), as much work time per product as possible and a uniform as possible appearance of the products. Due to competition there is the pressure of costs and therefore lines are becoming faster, the diversity of products is increasing and the material used has to be acquired at better prices. As a result the demands made on quality controls are becoming rather more difficult and the risk of more "false detections" increases.
In this market situation the manufacturer of control devices has to therefore confront the increasing demands and optimise the capabilities of the devices for the tasks. He cannot rely upon the fact that the user will meet his requirements regarding the environment. Otherwise a comparison between the costs and uses of a control function can easily speak against him.
The HEUFT SYSTEMTECHNIK GMBH company is active in meeting this market requirement and has analysed in detail for example the demands made on optical control procedures with camera techniques in the glass and PET bottle filling industry using a complex development process.
The actual problems regarding the bottle material were evaluated on the one hand. The typical problems regarding glass bottles for returnable lines are to some extent very different from those for disposable lines. PET bottles again present additional inspection tasks.
On the other hand the disturbances possible were studied with great care. These are essentially points which in general do not cause the producer to have any doubts about the quality of the bottle but can to some extent strongly impair the optical display and as a result the ability to carry out an examination using automatic image processing methods. This includes e.g. glass thickness fluctuations, shape defects (e.g. very developed moulding seams) and drops of water however all desired structures as well (e.g. glass emblems and alignment marks). In accordance with latest technological developments such influences on the evaluation are faded out either with special masks or inhibited over an area by reducing the sensitivity so that the disturbances do not result in false results and so that the costs are not insupportable for the producer.
Different evaluation methods and their suitability for the results in the bottling hall were tested by the HEUFT company in order to improve this situation. It quickly emerged that very complex methods alone can produce positive results. However with these too much is demanded of the calculating capacity of existing image processing processors on the market. Even very fast commercial processors (e.g. very fast Pentium processors) can only do justice to the demands when the production output is low.
Therefore the HEUFT company developed a special processor chip specialized exclusively for the requirements in a bottling hall. In this way the basic processing stages of the individual camera pictures can already be processed by the hardware of the new HEUFT reflexx image processing card in a very short time. The process can be controlled by programmable parameters and optimised for individual applications.
An important area of use for this new image processing is in the empty bottle inspection section. Here it is easy to assess the additional advantages of the technique. Whilst an increase to the detection reliability in practice does not produce any direct differences which can be counted (statistically there are fewer faults which were and are identified relatively reliably) the reduction in the false rejection rate is immediately clear. The false rejection rate can until now, according to how a machine is equipped, be over 1% of the output. If it is reduced by at least half, which is possible by using HEUFT reflexx technology, then the expenditure for additional bottle material, the disposal of rejected containers and the frequently associated manual work of the operator are all reduced.
HEUFT reflexx technology can also be used to inspect filled containers, that is finished products. In this case detection reliability and low false rejection rates have more significance because the amount of goods which can be sold is influenced. The inspection techniques available for the areas mentioned are an X-ray inspection for the detection of solid objects (e.g. glass fragments) as well as an optical examination of the complete container surface for monitoring the visible quality of the finished product.
The HEUFT eXaminer XA X-ray inspection makes it possible to monitor the filling process as an extension of the empty bottle inspector installed before the filler. Glass fragments can enter disposable glass containers during the filling process due to breakages or the fault of the glass manufacturer. metal foreign objects or stones can according to the product be transported in the product and enter the containers. Using X-ray technology and downstream image processing in a special, very compact arrangement these foreign objects can be detected with a very small dose of X-rays and the faults reliably rejected.
An optical all-round monitoring of the container view after the labelling machine is part of the HEUFT FinalView quality concept. The position of the closures is checked, that is the screw closures for the quality of the rolling on process, whilst travelling on the conveyor. The positioning and alignment of the labelling is checked. The containers can show all alignments whilst travelling on the conveyor and therefore the image processing has to produce a compilation of the different views during the first stage where the original bottle orientation does not play a part. The contents of the pictures with quality features which are of interest to the producer can only be examined during the second stage. HEUFT reflexx technology has also proved itself in this area of use on the basis of its processing speed and stable efficiency so that it can be used as an effective and useful quality control at an output of 72,000 containers per hour.
CONCLUSION: automatic quality checks are only meaningful if they do not impair the effectiveness of the production process too strongly due to false rejections. A new technology specially developed for the filling area optimises the empty bottle inspection area and makes an efficient check of the finished products possible.
A talk given by Dr Thomas Jahnen at the 1st IFGB Forum "Spirits and Distilling" on 25 June 2003 in Minden, Germany.