High-Speed Curtain Recoating for Stereolithography

The University of Leuven uses a liquid curtain recoating system for resin deposition in stereolithography. This system deposits new liquid layers of photo-polymer by means of a liquid curtain travelling over the build vat. Experiments have been carried out to increase the speed of the liquid curtain while depositing a layer. Speeds up to 1.2 m/s, and accelerations up to 1 g have been tested successfully, meaning that it is possible to coat high-quality layers of 75 µm thickness with this recoating technique. However, the curtain restores too slowly after acceleration. This paper discusses possible reasons and tries to formulate adequate solutions. Possible solutions consist in controlling small pressure differences in the curtain’s neighbourhood. A solution to this problem is necessary, as to make the travelling length of the curtain, and so the machine length acceptable with respect to the dimensions of the build vat.Mechanical Engineerin

Mobile Robot Localization using Panoramic Vision and Combinations of Feature Region Detectors

IEEE International Conference on Robotics and Automation (ICRA 2008, Pasadena, California, May 19-23, 2008), pp. 538-543.This paper presents a vision-based approach for mobile robot localization. The environmental model is topological. The new approach uses a constellation of different types of affine covariant regions to characterize a place. This type of representation permits a reliable and distinctive environment modeling. The performance of the proposed approach is evaluated using a database of panoramic images from different rooms. Additionally, we compare different combinations of complementary feature region detectors to find the one that achieves the best results. Our experimental results show promising results for this new localization method. Additionally, similarly to what happens with single detectors, different combinations exhibit different strengths and weaknesses depending on the situation, suggesting that a context-aware method to combine the different detectors would improve the localization results.This work was partially supported by USC Women in Science and Engineering (WiSE), the FI grant from the Generalitat de Catalunya, the European Social Fund, and the MID-CBR project grant TIN2006-15140-C03-01 and FEDER funds and the grant 2005-SGR-00093

Machining of steel with sialon ceramics: influence of ceramic and workpiece composition on tool wear

At the high cutting speeds typical for machining with ceramics and the concomitant high temperatures generated at the cutting edge and the rake face of the tool, chemical interaction between tool and workpiece material becomes the predominant mode of tool wear. Commercial SiAlON and YSiAlON cutting tools are known to be unsuitable for the machining of steel because of the chemical incompatibility of these materials at elevated temperatures. in this work, the flank and crater wear behaviour in turning steel with a number of experimental ceramics, belonging to the Si3N4-SiO2-AlN-Al2O3 system, are compared with that of a commercial YSiAlON cutting tool and the influence of the workpiece composition on the wear behaviour is investigated. The relative tool wear of the different ceramics is compared with the predicted mechanical wear by abrasion, calculated from the mechanical properties of the ceramics, and the predicted chemical wear, estimated from equilibrium solubility calculations of the ceramic in pure iron. The relative crater and flank wear of the different ceramics correlates well with the predicted chemical wear. Those ceramics with a low solubility in pure iron were not sensitive towards crater formation and showed the least flank wear of the investigated ceramics, although the modest mechanical properties of these ceramics makes them more sensitive to abrasion. The relative tool wear during turning is correlated with the reactivity measured in static interaction couples.status: publishe