This page was translated automatically using artificial intelligence (DeepL). The German version is binding. More information about automatic translation
News Intranet
This page was translated automatically using artificial intelligence (DeepL). The German version is binding. More information about automatic translation
Plastic guide rails are used as a key component in intralogistics and conveyor technology, for example in belt or chain conveyors [1]. However, friction-induced wear on these rails cannot be avoided, even with the ultra-high-molecular-weight polyethylene (PE-UHMW), which exhibit particularly high wear resistance and good friction characteristics, so that the rails must be replaced over time [2]. As the wear on these rails cannot be accurately predicted and can only be detected sporadically—and not whilst the system is in operation, or only by at least partially dismantling the system, the rails have so far been replaced at regular maintenance intervals or only after defects have occurred [3]. This results, amongst other things, in high costs and frequent, unplanned plant shutdowns.
The aim of this research project is to develop a structural health monitoring system for such guide rails, based on an electrically conductive plastic which is integrated into the structure of existing guide rails using a compression moulding process and acts as a wear sensor (see Figure 1).
The electrical resistance of the conductive plastic is indirectly proportional to wear; thus, by measuring the resistance intermittently during operation whilst simultaneously compensating for temperature variations in the results, conclusions can be drawn about the current remaining height of the slide rail, thereby determining its exact state of wear and predicting its remaining service life.
As the integrated sensor strip replaces part of the PE-UHWM, it must exhibit comparable friction and wear properties, whilst also possessing a sufficiently high level of electrical conductivity. To identify a suitable compound, samples of various mixtures of PE-UHMW (Celanese GUR®4120) and carbon blacks (CB) of different grades—with weight fractions ranging from 0% by weight% CB and 15 wt.% CB. These were examined using a tribometer at various contact pressures and sliding speeds to assess their tribological properties, and using the four-wire measurement method to assess their electrical properties at room temperature and at other temperatures within the operating range. The results to date show an expected increase in electrical conductivity with rising filler content; in accordance with classical percolation theory, a continuous conductive network forms from approximately 0.9 wt.%, a continuously conductive network forms, and filler contents between 3 wt.% and 7 wt.% are suitable for the planned sensor application.
However, both the coefficient of sliding friction – which, at filler contents of less than 3 per cent by weight, is even lower than that of the base material – and the wear rate decrease as the filler content decreases.
The studies summarised here enable the selection of a material combination that is ideally suited to the application. In order to detect wear as accurately as possible, a measurement and evaluation unit is being developed in parallel, which will subsequently be tested in endurance trials alongside the first prototypes of the slide rail.
About the person
Pascal Winkler studied Mechatronics with a specialisation in Automotive Engineering (Bachelor’s specialisation) and Electrical Engineering/Automation with a specialisation in Mechatronics (Master’s specialisation) at Mittweida University of Applied Sciences. Since April 2023, he has been working as a research assistant at the university’s Faculty Engineering Sciences, in the Design Group led by Professor Jörg Hübler, on the iSlide R&D project.
Bibliography
[1] Terbrack GmbH (n.d.): “Company: Terbrack Kunststoff GmbH & Co. KG”, [online] terbrack.de/index.php [20 February 2024].
[2] Celanese Corporation (n.d.): “Ultra-High Molecular Weight Polyethylene”, [online] www.celanese.com/products/gur-uhmw-pe-ultra-high-molecular-weight-polyethylene [20 February 2024].
[3] Kaden, H. (2008): “A Study on the Friction and Wear Behaviour of Toothed Belt Conveyors” (PhD thesis, Mechanical Engineering), Chemnitz: Chemnitz University of Technology.
Text and illustrations: Pascal Winkler
; Photographs: Johanna Wicht and Jacob Golde