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Hopmann C.,RWTH Aachen | Kaltbeitzel D.,IKV | Moller M.,RWTH Aachen | Zhu X.,ITMC
Kunststoffe International

Absorbable stents for treating blocked blood vessels offer advantages over commercially available stents. First a biodegradable material was developed, which combines the advantages of different materials, such as mechanical strength and good biodegradability. Subsequently, molds for injection molding a stent were developed and constructed. The injection molding simulation shows that it is possible to manufacture a delicate stent structure. The manufactured stents should then be mechanically and toxicologically tested to validate their loading strength and biocompatibility through animal tests. As the movement continues, the mold is then opened completely via a mandrel and the part can be removed. By replacing the shaping inserts, it is possible to investigate various stent designs with the new mold inserts. Source

Hopmann C.,RWTH Aachen | Lammert N.,IKV | Heinisch J.,IKV
Kunststoffe International

The results for reproducing microstructures make it clear that the laser-based process for targeted variotherm temperature control and quasi-simultaneous heating of discrete mold regions is possible. Because of the effect of the rapid laser heating close to the surface, the cavity can also be rapidly cooled with a fluid-based basic temperature control. Since the external design of the laser system unavoidably involves a cooling of the cavity, this must be very precisely matched to the process. The aim here is to reduce handling, and therefore irradiation, times. Because of the high-energy laser beam, the system requires the integration of a special protection concept. The goal of further R&D work is, against the background of system flexibility, to extend the safety concept, if possible to make the laser scanner usable from both sides, and to improve the temperature dynamics while retaining the same flexibility. Source

Becker S.,IKV | Hopmann Ch.,IKV
Progress in Rubber, Plastics and Recycling Technology

Water-assisted injection technique (WAIT) is well established for the production of plastics parts with functional hollow sections. This technique is widely used to manufacture handholds and pipes for transportation of fluids in particular. The process sequence of WAIT is characterised by the injection of water into the mould part after the filling stage. Thus, the still liquid melt is displaced and a cavity is formed in the interior of the part. Since WAIT is primarily used for the production of technical parts, a comprehensive quality control and process monitoring is essential [2, 3]. The moulding process is much more complex compared to the injection moulding of compact parts. Furthermore, internal properties (e.g. The residual wall thickness, eccentricity) or internal part defects (e.g. water inclusions) play a decisive role in the compliance with quality requirements. A promising approach in this context is the utilisation of the ultrasonic measurement technology for the analysis of the hollow space formation and for the identification of internal part properties.© Smithers Rapra Technology, 2013. Source

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