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| Simatic S7-200 and Siwarex MS weighing module in barrel testing systems | | Tight with the Ideal Weight | There are no compromises in terms of ideal weight and 100% tightness for yoghurt cups, canisters, barrels and the like. Manufacturers of these articles confess an increasing demand for test systems like those made by Steffes Prüf- und Messtechnik GmbH which have an eagle eye on the quality of the end products.
Hollow bodies are the packaging for many different products such as food, chemicals, paint, detergents, petrol etc. But no matter what the application, the quality must be right. On the one hand, they may not have any holes, so that nothing escapes and is lost or may even harm the environment if they are used for packing and transporting hazardous substances. On the other hand, the material thickness of the hollow body should be as thick as necessary and as thin as possible. This means: Safety for and from the contents yes; waste of material no. The market therefore calls for more and more test systems, which carry out reliable safety inspections with regard to tightness and weight of hollow bodies and therefore ensure a uniform quality, but also unnecessary production costs or even costs for settling damages.
The answer from St. Augustin
The Steffes Prüf- und Messtechnik GmbH in St. Augustin has its finger on a pulse. The Simatic S7 200 has been the heart of their test systems for many years. In addition to the good price-performance ratio with small dimensions and high processing speed, there are other factors in favor of its use. The modular system of this controller, Uwe Krotsch, Head of Development and Process Technology and Rene Erdmann, Head of Technology and Sales Consulting report, enable us to integrate frequently used functions, such as analog value processing, modem linking for telemaintenance and teleprogramming as well as a data logging memory module for recipe management, easily in the automation. Another advantage is the worldwide availability of Simatic S7-200 in view of the fact that the company has a percentage export of almost 80%. The Steffes company swears by Siwarex MS as a second leg of the automation scope so to speak. With the compact weighing module, we can now integrate our weighing tasks cheaply and easily in the automation concept. The previously expensive and care-intensive coupling software to connected systems is omitted. Low-cost, fast, efficient, easy to understand in the handling these are the properties which wee admire, Erdmann praises. The weighing module is designed as an extension module for the Simatic S7-200 micro-controller. The access of the control program to the currently measured weight data is gained directly via the Simatic CPU without an additional interface. The Siwatool MS software is used for the parameterization. The measuring results can be saved and archived with the S7-200 data logging function. By using Siwarex MS, the installation, commissioning and maintenance is reduced considerably.
Siwarex MS will therefore be an important part of Steffes systems in the future. The system automation concept is completed by the use of different Touch Panels such as TP 270, TP 177 and TP 170 for data entry, changing the process parameters and clear display of the measured values.
Weighed and found to be too light
Years of experience in plastics technology and quality assurance, technical knowledge, great creativity and work are the reasons for the companys worldwide success. Steffes only reveals this much about its test systems: Air is pumped into the containers to test the tightness of the hollow bodies. If no air escapes, they are tight. The weight is also checked. If the hollow body is too heavy, material could be saved which could amount to several thousand euros over the year. If it is too light, however, this will affect its stability. The companys scope of delivery includes standard tightness test systems for bottles, canisters, barrels and technical parts up to a capacity of 2,000 liters. Special designs can be supplied even without restrictions to the volume. The systems have up to 16 test heads. Here again, the number of test heads in special designs is unlimited. Quad-test systems, for example, achieve a test rate of up to 5,400 half liter hollow bodies per hour.
One example from the Steffes machine park is the S-P-300-1-DSPW quality control center. The system controlled by a Simatic S7-200 takes over the final quality inspection of 300 liter plastic barrels. It can handle 120 barrels per hour. The barrels are fed into the machine, turned into punching and testing position to have two rain holes punched in. After then being transported to the test station, they are tested for leaks. Leaking barrels are ejected from the machine, the others move to the test position for weighing inspection on a scales. The preconfigured Siwarex MS weighing module determines the sensor voltage, converts it into a weight value and transfers this to the controller. Barrels which correspond to the nominal weight are passed on for sale, the others are rejected. The trend display integrated in the machine allows article weights to be displayed exactly to the gram up to approx. 15 kg barrel weight over a period of one hour on the TP 270. The freely programmable limit values such as lower/upper waste limit, lower/upper control limit and nominal value are subject to continuous monitoring. An acoustic and visual alarm is triggered in case of deviations. Thanks to Siwarex MS, barrel manufacturers are able to increase the productivity of their blowing machine which produces the barrels and ensure a consistent level of quality, Erdmann explains. Deviations in weight are signaled in good time so that the operator of the blowing machine can intervene accordingly. This saves cash at the end of the day!
GO! 1 / 2007 | |
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