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New automation technology for rubber hose production

Troester GmbH & Co KG and Sikora AG, two Germany-based companies, present a new, jointly developed technology concept for quality assurance using an automatic wall thickness centering for the production of rubber hoses in the extrusion process.


The basis of the new system is an automatic tool centering developed from Troester in combination with Sikora’s X-Ray measuring technology X-Ray 6000. As introduced, an optimized cross head is featured for an extremely precise adjustment of the inner tool (mandrel tip) until the tool is perfectly centered. This is achieved by an automatic hydraulic servo-system. The new cross head receives the information for precise tool centering via the Sikora X-ray measuring device X-Ray 6000. The system continuously measures online the wall thickness and eccentricity of the hose. The measuring values are transmitted to an optimized PID-controller, which adjusts the eccentricity of the hose automatically within a split of a second with an impressive precision.

Among all tested production conditions the X-Ray 6000 achieves an eccentricity per axis of below one hundredth of a millimeter and maintains this value over the complete production time. “Via manual centering such a precision can only be achieved with tremendous effort and can hardly maintain over a long period,” explains Peter Hügen, Area Sales Manager at Sikora.

Besides the high accuracy that assures the continuous and precise collection of measuring values, the system has a selectable measuring rate of 1 to 3 Hz (optional 10, 100 Hz). The device is equipped with XLL (eXtra-Long-Life) X-ray tubes for high reliability and life time.

An important criterion for the success of the system is the distance between head and measuring device. In practice this means for example a distance of ca. 20cm between the die piece and measuring center. “The distance should be as short as possible under consideration of the line speed,” explained Mr Hügen. “On average, there are five to seven control steps necessary in order to for example control an eccentricity from 0.6 to 0 respectively 0.01, that is to produce the perfect hose.” A control step is the time span that is required to get from the head output to the measuring point. Generally, it takes one to two seconds until the next control step is started.

With the new automatic technology the product quality can be increased with the help of a stable online control process. In addition, due to the permanently assured precision customer can work with nominal wall thickness values without oversize. Calculated upon one year this leads to significant material savings. Thus, Sikora says that an investment in the new cross head with integrated X-ray measuring technology amortizes within one year.


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