Systematic Review on Investment Casting

The Investment casting (IC) method is now used to make all precision components in the medical, hydropower, defence, car, and other sectors. IC has a wide range of applications and is well-known for its ability to make complex near-net form items with great dimensional precision and surface polish. Various scholars are making ongoing efforts to investigate the topic of investment casting. This publication offers a comprehensive survey of the studies in this vast topic. It emphasises improvements in the earliest stages of the investment casting process. It focuses on pattern creation improvements, mould composition, casting materials, and typical flaws, as well as preventative actions. Keywords: Investment casting, Pattern modelling, Mould, TiAl alloys, defects

A metrological approach for multispectral photogrammetry

<p>This paper presents the design and development of a three-dimensional reference object for the metrological quality assessment of photogrammetry-based techniques, for application in the cultural heritage field. The reference object was 3D printed, with nominal manufacturing uncertainty of the order of 0.01 mm. The object was realized as a dodecahedron, and in each face, a different pictorial preparation was inserted. The preparations include several pigments, binders, and varnishes, to be representative of the materials and techniques used historically by artists.</p><p>Since the reference object’s shape, size and uncertainty are known, it is possible to use this object as a reference to evaluate the quality of a 3D model from the metric point of view. In particular, verification of dimensional precision and accuracy are performed using the standard deviation on measurements acquired on the reference object and the final 3D model. In addition, the object can be used as a reference for UV-induced Visible Luminescence (UVL) acquisition, being the materials employed UV-fluorescent. Results obtained with visible-reflected and UVL images are presented and discussed.</p>

Using Stereolithographic Printing to Manufacture Monolithic Microfluidic Devices with an Extremely High Aspect Ratio

Stereolithographic printing (SL) is widely used to create mini/microfluidic devices; however, the formation of microchannels smaller than 500 μm with good inner surface quality is still challenging due to the printing resolution of current commercial printers and the z-overcure error and scalloping phenomena. In the current study, we used SL printing to create microchannels with the aim of achieving a high degree of dimensional precision and a high-quality microchannel inner surface. Extensive experiments were performed and our results revealed the following: (1) the SL printing of microchannels can be implemented in three steps including channel layer printing, an oxygen inhibition process, and roof layer printing; (2) printing thickness should be reduced to minimize the scalloping phenomenon, which significantly improves dimensional accuracy and the quality of inner microchannel surfaces; (3) the inclusion of an oxygen inhibition step is a critical and efficient approach to suppressing the z-overcure error in order to eliminate the formation of in-channel obstructions; (4) microchannels with an extremely high aspect ratio of 40:1 (4000 μm in height and 100 μm in width) can be successfully manufactured within one hour by following the three-step printing process.

Translating Movement into Architectural Form

This work seeks to define original ways of creating architectonic forms using kinesiology studies. A series of methodologies are devised to record subjects in motion, with analogue and digital modelling techniques rigorously used independently and in combination to transpose these into sculptural figures with differing levels of formal fidelity and dimensional precision. Surface structures, and in particular thin shells, are found to have great potential for moving from abstract figures to structural forms. Such structures are traditionally problematic in terms of ‘constructional energy’, which has limited their usefulness and application. In response, the ‘hanging cloth reversed’ modelling technique devised by Heinz Isler is investigated to capitalise on the ambiguity between large-scale models and small structures. A construction method is devised that accords with the principles of structural art which, significantly, suggests that (small-span) shell structures could be liberated from the strictures of formwork to create economic, efficient and elegant minimal structures.

Geometric Accuracy and Mechanical Behavior of Polymer-Based Composite Curved Tubes produced by Fused Filament Fabrication (FFF)

The present study aims to assess and characterize the effect of processing parameters including infill pattern and reinforcement type on the dimensional accuracy of products manufactured by Fused Filament Fabrication (FFF) process as well as on the mechanical properties of the printed components. The reinforcements used were carbon, Kevlar and glass fibers supplied by MarkForged®; they were utilized to manufacture the PA6 matrix composite. The mechanical properties of the stated composites were compared. Finally, the results obtained confirmed that the selection of the appropriate type of the reinforcements and infill patterns among the several available types during the printing process is effective in improving the mechanical properties and also in providing a better geometrical quality of the surfaces and the consequent dimensional precision improvement of the parts printed by FFF process.

Development of a vibration free machine structure for high-speed micro-milling center

The demand of ultra-precision micro-machine tools is growing day by day due to exigent requirements of miniaturized components. High accuracy, good dimensional precision and smooth surface finish are the major characteristics of these ultra-precision machine tools. High-speed machining has been adopted to increase the productivity using high-speed spindles. However, machine tool vibration is a major issue in high-speed machining. Vibration significantly deteriorates the quality of micro-machining in terms of dimensional precision and surface finish. This paper describes a design methodology of a closed type machine structure for vibration minimization of a high-speed micro-milling center. The rigid machine structure has provided plenty of stiffness and the damping capability to the machine tool without utilizing vibration absorbers . The models of the machine structures have been generated and assembled in AutoCAD 3D . The performances of the integrated micro-milling machine tools were determined by finite element analysis. The best model has been selected and proposed for manufacturing. Additionally, simulation results were validated by comparing with experimental results. Eventually, after manufacturing and assembly, experiments have been performed and determined that the amplitude of vibration was approaching towards nanometer level throughout the working range of the high-speed spindle. The machine tool was capable to fabricate miniaturized components with fine surface finish.