Extrusion International 5-2022

79 Extrusion International 5/2022 HOSE PRODUCTION HEADS truder heads. During production, the system keeps the wall thickness distribution within a range of less 1/100 mm. Conditions The hose layers’ wall thickness must be measured con- sistently online in a defined plane. X-ray meters are suit - able for this purpose, some of which are already avail- able for quality assurance and can be integrated into the closed-loop control system. However, without reliable recognition of each of the layers, this isn’t possible. This depends on the physical properties of the compounds, i.e. the attenuation of the X-rays. Prior testing is advisable, particularly where multi-layer hoses are concerned. Limitations of the system In addition to limited detectability, the system might not work as well if the hose twists. Measurement and adjustment data will then differ. The cause usually lies in reinforcements applied to the hose using spiralling or knitting machines. As long as the degree and direction of rotation don’t fluctuate too abruptly, this can be compensated for by the control system. Too great a distance between the me- ter and the head amplifies this effect and leads to slower control. Compensating for mirror-image errors (ellipses) is also impossible. Benefits to the customer In addition to guaranteed and documented quality, hose manufacturers benefit from saving compound when using the automatic TROESTER extrusion heads on their production lines. The savings achieved during start-up (due to the scrap saved) and by reduction of wall thicknesses, especially where compounds are expensive, also lead to a very fast ROI of less than one year when a combination of an ex - truder head, X-ray meter and control is used. The environ- mental aspects - better utilization of resources and raw materials - are other bonuses on top. Author: Wieland Hoffmann, Head of rubber machinery and equipment development/TROESTER TROESTER GmbH & Co KG Am Brabrinke 1-4, 30519 Hanover, Germany www.troester.de Controlling the wall thickness difference