Centrifugal casting is a technology used for manufacturing hybrid rocket paraffin grains. This technology helps avoiding voids formation inside the solid paraffin as it cools. Voids are formed because of air bubbles being entrapped while pouring and because the liquid wax shrinks by 17–19% upon cooling. In this work, the centrifugal casting process for the manufacturing of paraffin cylinders was prototyped at two different scales considering critical casting issues. The effects of process parameters (rotational speed, melt temperature, and flow rate) on the tensile properties of the manufactured grains were analyzed. The results of the optimization conducted at the lower scale (2.5 kg) were up scaled to manufacture 25 kg grains. The resulting mechanical properties complied with the design specifications, and they were better than those characterized from the gravity cast wax. A numerical model of growth and dissolution of bubbles during the process was then developed to predict the quality of the castings. The numerical results showed how increasing the mold rotational speed up to 1800 rpm reduced the removal time. However, compared to grains solidification time, the predicted removal times were much shorter, proving the advantage of centrifugal casting in counteracting voids formation. [ABSTRACT FROM AUTHOR]
International Journal of Computer Integrated Manufacturing. Oct2014, Vol. 27 Issue 10, p901-918. 18p.
Medical equipment industry, Innovations in business, Medical instruments & apparatus manufacturing, Rapid prototyping, Industrial design, and Operative surgery
Nowadays medical devices are a fast-growing industry. Advances in design, materials and technologies have increased the potential to find better solutions for those medical problems whose remedies were, up until now, unimaginable. A broad spectrum of new solutions is available ranging from new materials to new products, tools and procedures. Medical doctors have discovered how the latest advances in engineering support their work by making surgery or treatment processes easier than ever before. For this reason, medical devices are now a hot topic of industrial and academic interest in fields such as design, prototypes or manufacturing. This paper introduces a special issue with several medical device case studies, illustrating new developments in product design, material selection and prototype methods. In addition, the paper also reviews medical device development research and depicts some case studies to better explain the relationship between technology/engineering and medical devices. The paper contributes with some data on this combination of research fields. [ABSTRACT FROM AUTHOR]
This paper first reviews manufacturing technologies for realizing air-filled metal-pipe rectangular waveguides (MPRWGs) and 3-D printing for microwave and millimeter-wave applications. Then, 3-D printed MPRWGs are investigated in detail. Two very different 3-D printing technologies have been considered: low-cost lower-resolution fused deposition modeling for microwave applications and higher-cost high-resolution stereolithography for millimeter-wave applications. Measurements against traceable standards in MPRWGs were performed by the U.K.’s National Physical Laboratory. It was found that the performance of the 3-D printed MPRWGs were comparable with those of standard waveguides. For example, across X-band (8–12 GHz), the dissipative attenuation ranges between 0.2 and 0.6 dB/m, with a worst case return loss of 32 dB; at W-band (75–110 GHz), the dissipative attenuation was 11 dB/m at the band edges, with a worst case return loss of 19 dB. Finally, a high-performance W-band sixth-order inductive iris bandpass filter, having a center frequency of 107.2 GHz and a 6.8-GHz bandwidth, was demonstrated. The measured insertion loss of the complete structure (filter, feed sections, and flanges) was only 0.95 dB at center frequency, giving an unloaded quality factor of 152—clearly demonstrating the potential of this low-cost manufacturing technology, offering the advantages of lightweight rapid prototyping/manufacturing and relatively very low cost when compared with traditional (micro)machining. [ABSTRACT FROM PUBLISHER]