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WORLD OF INDUSTRIES - Industrial Automation 4/2017

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WORLD OF INDUSTRIES - Industrial Automation 4/2017

Machine vision provides

Machine vision provides defect-free aluminium containers The machine module for quality control consists of four parallel lines with offset imaging stations About Stemmer Imaging Stemmer Imaging is Europe’s largest imaging technology provider for science and industry. The perfect combination of innovative products, intelligent consulting and extensive service helps our customers solve their imaging projects with speed and ease. In the last financial year, the company generated a total turnover of 88,7 million Euros. MACHINE VISION The Swiss company, Leuthold Mechanik makes machines for manufacturing aluminium containers which, among other things, are used for packaging pet food and foodstuffs. A core element of quality assurance is a modern and innovative machine vision solution. Unremittingly, 120 times a minute over three shifts the ram on the press in the Leuthold Mechanik AG (HLM) Competence Centre rises and falls and after every stroke spits out four finished pet food containers. A machine like this thus produces 480 high quality aluminium containers per minute, which will later be filled with pet food. “However our machines not only produce containers for pet food but also the most varied forms of aluminium receptacles for, among other things, preserves, pies or ground coffee”, explains Mathias Leuthold, who is responsible for the management of toolmaking and mechanical engineering in the family business. The company has also developed machines for entirely different substances such as fuel pastes or packaging for medical products such as inhalers. Mission worldwide “If a customer has decided on us as his machine supplier, the first step as a rule is to send us some ideas, sketches and/or 3D models of his desired aluminium container. On this basis we will then develop the whole machine, from the design of the container or casing through the tool and checking module to the stacking unit, or adapt our standard machines to the customer’s wishes”, explains the engineer describing the usual path from the idea to the finished machine. A large proportion of these machines is installed with HLM’s customers worldwide. “In addition to the domestic Swiss market, our customers are based in many European countries. But our machines are also in use, e.g., in the USA and Australia”, says Mathias Leuthold. Every defective container has been detected The prerequisite for stamping out thin-walled containers, the dimensions of which can vary between 60 and 120 mm in width and between 60 and 200 mm in length, is high quality aluminium foil. The stamped-out containers are conveyed in line to the modulebased built-in inspection and stacking machines. After the containers have been brought into the finished shape by a single stroke in the press, they are blown out and transported WORLD OF INDUSTRIES – INDUSTRIAL AUTOMATION 4/2017

in-line by means of transport belts and mechanical tracks to the modules where quality control is carried out. “Aluminium is relatively expensive as a base material, so the walls of the containers must be as thin as possible to keep the costs low. On the other hand, as the material thickness is reduced, there is an increased risk that holes will appear during the forming process as a result of inclusions in the raw material or excessive stresses during the forming. These holes will cause the container to leak and thus make it unusable”, says Mathias Leuthold, explaining why every single container must be checked. “We must detect and separate out every defective container as otherwise, using the example of pet food or foodstuffs in general, there is a risk that the contents will go bad.” Due to the high production speeds and the required 100 % inspection, machine vision is a viable tool for quality inspection. HLM has already been using this technology for over 20 years and has had positive experiences with it, Mathias Leuthold confirmed: “There are no longer any installations in which machine vision is not used as a central element of the testing stations.” a considerable amount of computing power. With this machine it must evaluate 120 images per minute and track, and forward the results to the discharge station in the shortest time possible so that defective containers can be separated out immediately. The images are evaluated using the Common Vision Blox (CVB) imaging software from Stemmer Imaging. Photographs: Stemmer Imaging GmbH Embedded systems compared to intelligent cameras For the latest generation of machines, the Swiss company is no longer relying on intelligent camera systems as before, but rather on an Embedded PC vision system. According to Leuthold, several benefits justified this decision. “With the previous architecture using intelligent cameras, a PC first had to be connected to the machine in order to display images of defects or undertake statistical evaluations. Only in this way was it possible to check, for example, whether more defects arose on one of the lines or whether a certain type of defect occurred more frequently. The operator can now detect such tendencies much more easily and more quickly via a monitor directly on the machine, and thus switch off the defect sources selectively in a shorter time. This facility is implemented by means of a ring buffer, which saves the last 20 defect images in the embedded system and displays them on demand. In addition to images of current results, the user can also view statistics about types of defects and their frequency, the distribution of rejects across the different tracks and also images of defective containers very easily, directly on the machine’s display. “This contributes significantly to faster rectification of defects by means of appropriate mechanical adjustments to the machine”, emphasises Mathias Leuthold. As a further advantage of the new embedded system compared with the previous intelligent cameras, he cites the improved connection to the users MES (Manufacturing Execution System) systems. 02 The LED lighting and the cameras on each track are triggered by a light barrier. The cameras located under the transport tracks take pictures of the containers in the transmitted light procedure 03 The Genie Nano cameras are mounted below the transport tracks, the lighting above it and the monitor can be seen on the upper edge of the picture Machine vision in use HLM does not employ its own machine vision specialists. “Although we have already been using this technology for around 20 years and have accumulated some experience in this matter, we have nevertheless been relying on the know-how of our partner, Stemmer Imaging, for many years”, Mathias Leuthold pointed out. In the new generation of machines, there is a Genie Nano camera, made by Teledyne Dalsa, installed on every line. This is triggered by light barriers. Equipped with suitable optics from Lensation, these cameras are located underneath the transport tracks. The LED lighting, which is also triggered by light barriers, is integrated above the testing stations in the machines, so that the containers can be inspected in the transmitted light procedure. It was developed by Stemmer Imaging specially for the present requirements, because there is no standard lighting that meets the requirements. The embedded PC, which undertakes the evaluation of all the images from the four lines and also handles the control of the machine by means of the so-called Real Time Manager, is a custom product from the Swiss electronics manufacturer, Worx. It has to manage 04 End products of the special machine for the packaging industry are aluminium cat food trays WORLD OF INDUSTRIES – INDUSTRIAL AUTOMATION 4/2017