2020 Vol. 2, No. 2
Due to the rapid development of precision manufacturing technology, much research has been conducted in the field of multisensor measurement and data fusion technology with a goal of enhancing monitoring capabilities in terms of measurement accuracy and information richness, thereby improving the efficiency and precision of manufacturing. In a multisensor system, each sensor independently measures certain parameters. Then, the system uses a relevant signal-processing algorithm to combine all of the independent measurements into a comprehensive set of measurement results. The purpose of this paper is to describe multisensor measurement and data fusion technology and its applications in precision monitoring systems. The architecture of multisensor measurement systems is reviewed, and some implementations in manufacturing systems are presented. In addition to the multisensor measurement system, related data fusion methods and algorithms are summarized. Further perspectives on multisensor monitoring and data fusion technology are included at the end of this paper.
In the past decades, Moore's law drives the semiconductor industry to continuously shrink the critical size of transistors down to 7 nm. As transistors further downscaling to smaller sizes, the law reaches its limitation, and the increase of transistors density on the chip decelerates. Up to now, extreme ultraviolet lithography has been used in some key steps, and it is facing alignment precision and high costs for high-volume manufacturing. Meanwhile, the introduction of new materials and 3D complex structures brings serious challenges for top-down methods. Thus, bottom-up schemes are believed to be necessary methods combined with the top-down processes. In this article, atomic level deposition methods are reviewed and categorized to extend Moore's law and beyond. Firstly, the deposition brings lateral angstrom resolution to the vertical direction as well as top-down etching, such as double patterning, transfer of nanowires, deposition of nanotubes, and so on. Secondly, various template-assisted selective deposition methods including dielectric templates, inhibitors and correction steps have been utilized for the alignment of 3D complex structures. Higher resolution can be achieved by inherently selective deposition, and the underlying selective mechanism is discussed. Finally, the requirements for higher precision and efficiency manufacturing are also discussed, including the equipment, integration processes, scale-up issues, etc. The article reviews low dimensional manufacturing and integration of 3D complex structures for the extension of Moore's law in semiconductor fields, and emerging fields including but not limited to energy, catalysis, sensor and biomedicals.
Precision measurement tools are compulsory to reduce measurement errors or machining errors in the processes of calibration and manufacturing. The laser interferometer is one of the most important measurement tools invented in the 20th century. Today, it is commonly used in ultraprecision machining and manufacturing, ultraprecision positioning control, and many noncontact optical sensing technologies. So far, the state-of-the-art laser interferometers are the ground-based gravitational-wave detectors, e.g. the Laser Interferometer Gravitational-wave Observatory (LIGO). The LIGO has reached the measurement quantum limit, and some quantum technologies with squeezed light are currently being tested in order to further decompress the noise level. In this paper, we focus on the laser interferometry developed for space-based gravitational-wave detection. The basic working principle and the current status of the key technologies of intersatellite laser interferometry are introduced and discussed in detail. The launch and operation of these large-scale, gravitational-wave detectors based on space-based laser interferometry is proposed for the 2030s.
Projection micro stereolithography (PµSL) is a high-resolution (up to 0.6 µm) 3D printing
technology based on area projection triggered photopolymerization, and capable of fabricating
complex 3D architectures covering multiple scales and with multiple materials. This paper
reviews the recent development of the PµSL based 3D printing technologies, together with the
related applications. It introduces the working principle, the commercialized products, and the
recent multiscale, multimaterial printing capability of PµSL as well as some functional
photopolymers that are suitable to PµSL. This review paper also summarizes a few typical
applications of PµSL including mechanical metamaterials, optical components, 4D printing,
bioinspired materials and biomedical applications, and offers perspectives on the directions of
the further development of PµSL based 3D printing technology.
Three types of scanning strategies, including the chessboard scanning strategy, the zigzag scanning strategy and the remelting scanning strategy, were conducted to study the effects of scanning strategies on surface morphology, microstructure, mechanical properties and the grain orientation of selective laser melted pure tungsten. The results showed that the pores and cracks were main defects in SLM-processed tungsten parts. The pores could be eliminated using the remelting scanning strategy. However, the cracks seemed to be inevitable regardless of the applied scanning strategies. The microstructures of SLM-processed tungsten were columnar grains and showed strong epitaxial growth along the building direction. A compressive strength of 923 MPa with an elongation of 7.7% was obtained when the zigzag scanning strategy was applied, which was the highest among the three scanning strategies. By changing the scanning strategies, the texture of SLM-processed tungsten in the direction of processing could be changed.
Novel water-based nanolubricants using TiO2 nanoparticles (NPs) were synthesised by adding sodium dodecyl benzene sulfonate (SDBS) and glycerol, which exhibited excellent dispersion stability and wettability. The tribological performance of the synthesised nanolubricants was investigated using an Rtec ball-on-disk tribometer, and their application in hot steel rolling was evaluated on a 2-high Hille 100 experimental rolling mill, in comparison to those without SDBS. The water-based nanolubricant containing 4 wt% TiO2 and 0.4 wt% SDBS demonstrated superior tribological performance by decreasing coefficient of friction and ball wear up to 70.5% and 84.3%, respectively, compared to those of pure water. In addition to the lubrication effect, the suspensions also had significant effect on polishing of the work roll surface. The resultant surface improvement thus enabled the decrease in rolling force up to 8.3% under a workpiece reduction of 30% at a rolling temperature of 850 °C. The lubrication mechanisms were primarily ascribed to the formation of lubricating film and ball-bearing effect of the TiO2 NPs.
Laser-induced forward transfer (LIFT) is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer (LIDT) technique. To deposit a single nanodot in a single shot of laser irradiation, a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid–liquid–solid (SLS) process. In conventional LIDT experiments, multi-shots with step scanning have been used to form array structures. However, interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot. In this study, a femtosecond laser interference pattern was first applied to LIDT, and an array of nanodots was successfully deposited in a single shot, producing the following unit structures: a single dot, adjoining dots, and stacking dots. The diameter of the smallest nanodot was 355 nm, and the narrowest gap between two adjoining nanodots was 17.2 nm. The LIDT technique produces high-purity, catalyst-free that do not require post-cleaning or alignment processes. Given these significant advantages, LIDT can expand the usability of nanodots in a wide range of fields.
The dynamic performance of an ultraprecision fly cutting machine tool (UFCMT) has a dramatic impact on the quality of ultraprecision machining. In this study, the dynamic model of a UFCMT was established based on the transfer matrix method for multibody systems (MSTMM). In particular, the large-span scale, flow field mesh model was created; and the variation in linear and angular stiffness of journal and thrust bearings with respect to film thickness was investigated by adopting the dynamic mesh technique (DMT). The dynamic model was proven to be valid by comparing the dynamic characteristics of the machine tool obtained by numerical simulation with the experimental results. In addition, the power spectrum density estimation method was adopted to simulate the statistical ambient vibration excitation by processing the ambient vibration signal measured over a long period of time. Applying the dynamic model, the dynamic response of a tool tip under ambient vibration was investigated. The results elucidated that the tool tip response was significantly affected by ambient vibration, and the isolated foundation had a good effect on vibration isolation.