Dimensional Precision Research Articles

Surface and Subsurface Quality of Titanium Grade 23 Machined by Electro Discharge Machining.

Electrical Discharge Machining (EDM) is a non-traditional cutting technology that is extensively utilized in contemporary industry, particularly for machining difficult-to-cut materials. EDM may be used to create complicated forms and geometries with great dimensional precision. Titanium alloys are widely used in high-end applications owing to their unique intrinsic characteristics. Nonetheless, they have low machinability. The current paper includes an experimental examination of EDM’s Ti-6Al-4V ELI (Extra Low Interstitials through controlled interstitial element levels) process utilizing a graphite electrode. The pulse-on current (IP) and pulse-on time (Ton) were used as control parameters, and machining performance was measured in terms of Material Removal Rate (MRR), Tool Material Removal Rate (TMRR), and Tool Wear Ratio (TWR). The Surface Roughness (SR) was estimated based on the mean roughness (SRa) and maximum peak to valley height (SRz), while, the EDMed surfaces were also examined using optical and SEM microscopy and cross-sections to determine the Average White Layer Thickness (AWLT). Finally, for the indices above, Analysis of Variance (ANOVA) was conducted, whilst semi-empirical correlations for the MRR and TMRR were given using the Response Surface Method (RSM). The results show that the pulse-on time is the most significant parameter of the machining process that may increase the MRR up to 354%. Pulse-on current and pulse-on time are shown to have an impact on the surface integrity of the finished product. Furthermore, statistics, SEM, and EDX images on material removal efficiency and tool wear rate are offered to support the core causes of surface and sub-surface damage. The average microhardness of the White Layer (WL) is 1786 HV.

Dimension Precision and Uniformability Depending on the Interpass Distance Variation of Automated-Wire Arc Additive Manufacturing using 5 Cr-4 Mo Tool Steel Alloy

Die casting molds for aluminum are fabricated using machining billets of tool steels, such as Cr-Mo tool steel. However, this approach has several limitations, including significant material loss and a long lead time. Wire arc additive manufacturing (WAAM) is an alternative fabrication method that yields low material loss and has a short lead time. However, WAAM involves the repetitive stacking of layers based on designed tool paths using CAD/CAM. Thus, the predictability and uniformability of each layer are the most important factors. The interpass distance is an important parameter in a given process; however, studies on the interpass distance of the WAAM process are limited. In this study, it was determined that the interpass distance significantly influences the arc stability owing to the arc interference induced by the variation in distance from the prior deposited pass; more arc interference was observed as the interpass distance decreased. This phenomenon was validated via analysis using a high-speed camera and the variation in the amount of spatter. Furthermore, it was observed that the interpass distance influences the dimensional precision and uniformability. The interpass distance influences the arc interference unless it is greater than 100%. Thus, it is important to determine a point of balance based on the arc stability, dimension predictability, and uniformability of each layer.

Structuring wheat dough using a thermomechanical process, from liquid food to 3D-printable food material

In extrusion printing, the printability of food materials depends on the rheology of the food under shearing when extruded, and at rest, post-deposition. Piloting food microstructure to provide rheological properties compatible with 3D extrusion printing is a major challenge. Microstructure, rheology, and printability of wheat-flour based materials with varying concentrations of flour, sugar, oil, and water were studied. Materials were obtained by heating and shearing doughs with a moisture content above 55% (wb). The processed doughs were structured as closely-packed particles made of swollen gelatinized starch granules glued in a denatured proteins network. These materials were easily extruded in self-supporting layers by a 3D food-printer and formed stable objects with precise dimensions. The water/flour ratio played a crucial role in the structure of the wheat materials, impacting the storage modulus (G’), tan δ and printability. This work highlights the importance of tan δ in predicting the ability of food materials to hold its 3D structure. • Thermomechanical processing of doughs produced wheat-based printable materials. • Dough particles were made of swollen starch glued by denatured proteins. • In excess of water, oil and sugar had no effect on the rheology or printability. • The water/flour ratio is an important parameter to pilot a material's printability. • Tan δ is a relevant indicator to predict the self-supporting ability of materials.

Alloy design strategy to improve fluidity of Zr-based bulk metallic glass for near-net-shape manufacturing

The near-net-shape manufacturing via casting has great potential to commercialize bulk metallic glasses (BMGs) for the complex-shaped structural material. However, it is difficult to cast BMGs with the excellent glass-forming ability (GFA) into the precise dimensions of complex shapes, because the slow kinetics of crystallization of the BMG is related to the high viscosity and low fluidity of the melt. In this study, to overcome this limitation, Zr-based BMG with excellent GFA, hardness, and significantly improved fluidity compared to Vitreloy 106 was systematically developed. Utilizing the ZrCuNi liquidus projection, it is possible to design BMG-forming alloy compositions with a low liquidus temperature (TL) by compositional tuning in the ZrCuNiAl quaternary alloy system. We also propose an alloy design methodology that can simultaneously improve the key properties of Zr-based BMGs by minor addition. Interestingly, Ag can be added instead of Zr in ZrCuNiAl alloys, resulting in higher hardness and lowest TL without deterioration of GFA. Thus, the addition of Ag can lead to a significant increase in flow length of about 40% compared to that of Vitreloy 106, because the TL is a dominant factor that determines fluidity under various casting conditions. This study shed light on how to simultaneously improve the dimensional accuracy of BMG products and life span of casting facilities when manufacturing through various conventional casting methods, which should be important to fabricate macro to nano-sized industrial parts through BMGs.

Insights on the Molecular Behavior of Polypropylene in the Process of Ultrasonic Injection Molding.

Product miniaturization is a constant trend in industries that demand ever-smaller products that can be mass produced while maintaining high precision dimensions in the final pieces. Ultrasonic micro injection molding (UMIM) technology has emerged as a polymer processing technique capable of achieving the mass production of polymeric parts with micro-features, while still assuring replicability, repeatability, and high precision, contrary to the capabilities of conventional processing technologies of polymers. In this study, it is shown that the variation of parameters during the UMIM process, such as the amplitude of the ultrasound waves and the processing time, lead to significant modification on the molecular structure of the polymer. The variation of both the amplitude and processing time contribute to chain scission; however, the processing time is a more relevant factor for this effect as it is capable of achieving a greater chain scission in different areas of the same specimen. Further, the presence of polymorphism within the samples produced by UMIM is demonstrated. Similarly to conventional processes, the UMIM technique leads to some degree of chain orientation, despite the fact that it is carried out in a relatively small time and space. The results presented here aim to contribute to the optimization of the use of the UMIM process for the manufacture of polymeric micro parts.

A Simple and Low-Cost Method for Fabrication of Polydimethylsiloxane Microfludic Chips.

The conventional fabrication methods for enrichment microfluidic devices require cleanroom, which are costly and time-consuming. Developing a facile and low-cost method to fabricate microfluidic chips could stimulate the progress of the applications of those chips. Here, we present an easy method for fabrication of a complete PDMS (Polydimethylsiloxane) microfluidic chip used for ion and protein enrichment. The method consists of three main fabrication steps: PDMS microchannels ablation by co₂ laser, nation membrane deposition, and oxygen plasma assist bonding under pressure. To fabricate a desired microchannel, the laser ablation parameters, containing laser power and ablation speed, were analyzed. The parameters for oxygen plasma assist bonding were also investigated to improve the bonding quality of the chips (low dimension loss and high bonding strength). The following Rhodamine B enrichment tests demonstrate that the presented method allows fabrication of microfluidic chips with precise dimensions and leakage free.

Experimental calibration and compensation for the continuous effect of time, number of layers and volume of material on shape deformation in small-scale additive manufacturing of concrete

Additive manufacturing (AM) of cementitious material is a multidisciplinary effort that depends on multiple aspects such as printing system, toolpath design and material properties. Although each of these aspects are important individually, their combined effect must also be considered. For instance, the rheological and physical properties of fresh cementitious material affect the printing system, and in turn the toolpath design. More importantly, the properties of printed material and its deformation behavior affect the dimensional and geometric precision which requires modification of the toolpath to compensate for such a deformation. The deformation of fine aggregate concrete is a time related issue that is directly related to the scale of printed specimens. In larger parts the time to print each layer is bigger and the material will have more time to harden and keep its shape, whereas in smaller parts it does not have enough time to harden and will deform under the weight of subsequent layers. As a result, shape accuracy of the printed specimen will be compromised. Previous experimental research determined the effect of the number of layers and beads on deformation and the time interval after which printed concrete stops deforming. This study investigates the effect of the number of layers and beads on layer width and layer height deformation as a function of extrusion rate and time before that time interval. The result is a model relating all the relevant variables that can be used to compensate for deformation in toolpath design of small scale printed concrete specimens.

Research on reliable sealing technology of spacecraft rectangular hatch based on boundary control

In view of the large size of the sealing surface of the space large diameter rectangular cabin door, the large number of locking mechanisms and long service life, it is difficult to adjust the multi degree of freedom attitude in the assembly process, the complex assembly and adjustment of the mechanism, the synchronization accuracy is not easy to ensure, the consistency of the multi-point seal compression rate is high, and it is not easy to control. Based on the rotation law of the spatial linkage mechanism, the precise dimension chain control of the hatch is carried out, and the attitude of the multi degree of freedom linkage is adjusted to realize the synchronous compression of multiple compression units of the compression mechanism; Based on the minimum and maximum operating force as the boundary, through the sealing stress simulation, the “boundary control” coupling assembly and adjustment technology is proposed to optimize the sealing structure and realize rapid and efficient assembly. The results show that the vacuum leakage rate is still less than 2.5×10−3 PaL/s after 2000 door opening and closing tests and sealing compression ratio are better than 15%. The long-life test verifies the feasibility and effectiveness of this method, and forms a set of high reliable and long-life sealing assembly and adjustment method of space hatch, which provides technical guidance and reference for the subsequent assembly of similar space hatch mechanisms.

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.

Use of multiple linear regression to compensate for diametrical deviations in machined components due to thermal errors

Computer Numeric Control (CNC) machine tools such as CNC milling machines and CNC turning centers produce components with a higher dimensional precision and accuracy when compared to traditional machine tools. The precision, accuracy of the dimensions are still governed by factors such as geometric errors, cutting forces induced errors and thermal errors. Thermal errors are a major contributing factor to dimensional deviations of the machined component. The heat generating sources of the machine tool which include spindle ball bearings, spindle motor, the axes motors, transformer pack, coolant pump, lubricant pump among others. The ambient temperature and weather also play a role in inducing thermal errors in a machine tool. The heat generated at these sources gets transferred to the adjacent elements of the machine tool causing them to distort or deform. These distortions or deformations of the various machine tool elements produce a cumulative effect which leads to the increase or decrease of the gap between the tool and work piece resulting in dimensional deviation in the final machined component. In the current work an attempt has been made to compensate for these thermal errors by building a prediction model based on experimentally measured diametrical and temperature data. Multiple linear regression has been used to create the prediction model, where the diametrical deviations were considered as dependent variables and temperature data was considered as independent variables. Least squares method is employed in multiple linear regression to obtain regression coefficients which would then be used in a mathematical equation to determine the deviation between tool point and work piece, which can be compensated to maintain the dimensions of the machined components. Four case studies were carried out in this work. Logarithmic transformation was used in the final case study to transform non-linear data into linear data which lead to consistent model behaviour when applied to several hours of test data.

Smartphone-enabled 3D printing of medicines

3D printing is a manufacturing technique that is transforming numerous industrial sectors, particularly where it is key tool in the development and fabrication of medicinees that are personalised to the individual needs of patients. Most 3D printers are relatively large, require trained operators and must be located in a pharmaceutical setting to manufacture dosage forms. In order to realise fully the potential of point-of-care manufacturing of medicines, portable printers that are easy to operate are required. Here, we report the development of a 3D printer that operates using a mobile smartphone. The printer, operating on stereolithographic principles, uses the light from the smartphone’s screen to photopolymerise liquid resins and create solid structures. The shape of the printed dosage form is determined using a custom app on the smartphone. Warfarin-loaded Printlets (3D printed tablets) of various sizes and patient-centred shapes (caplet, triangle, diamond, square, pentagon, torus, and gyroid lattices) were successfully printed to a high resolution and with excellent dimensional precision using different photosensitive resins. The drug was present in an amorphous form, and the Printlets displayed sustained release characterises. The promising proof-of-concept results support the future potential of this compact, user-friendly and interconnected smartphone-based system for point-of-care manufacturing of personalised medications.

Bottom‐Up versus Top‐Down Strategies for Morphology Control in Polymer‐Based Biomedical Materials

The size and shape of polymer materials is becoming an increasingly important property in accessing new functions and applications of nano‐/microparticles in many scientific fields. New synthetic methods have allowed unprecedented capability for the facile fabrication of anisotropic and shape‐defined nanomaterials. Bottom‐up approaches including: emulsion polymerization techniques, amphiphile self‐assembly, and polymerization‐induced self‐assembly, can lead to polymer particles with precise dimensions in the nanoscale. Top‐down methods such as lithographic templating, and 3D printing, have increased the access to unique particle shapes. In this review, these recent developments are appraised and contrasted, with future research directions providing that focus on biomedical applications. Finally, the opportunity available for synergistic combinations of top‐down and bottom‐up fabrication approaches in realizing previously unattainable architectures and material properties is highlighted.

Intelligent Solutions in Chest Abnormality Detection Based on YOLOv5 and ResNet50.

Computer-aided diagnosis (CAD) has nearly fifty years of history and has assisted many clinicians in the diagnosis. With the development of technology, recently, researches use the deep learning method to get high accuracy results in the CAD system. With CAD, the computer output can be used as a second choice for radiologists and contribute to doctors doing the final right decisions. Chest abnormality detection is a classic detection and classification problem; researchers need to classify common thoracic lung diseases and localize critical findings. For the detection problem, there are two deep learning methods: one-stage method and two-stage method. In our paper, we introduce and analyze some representative model, such as RCNN, SSD, and YOLO series. In order to better solve the problem of chest abnormality detection, we proposed a new model based on YOLOv5 and ResNet50. YOLOv5 is the latest YOLO series, which is more flexible than the one-stage detection algorithms before. The function of YOLOv5 in our paper is to localize the abnormality region. On the other hand, we use ResNet, avoiding gradient explosion problems in deep learning for classification. And we filter the result we got from YOLOv5 and ResNet. If ResNet recognizes that the image is not abnormal, the YOLOv5 detection result is discarded. The dataset is collected via VinBigData's web-based platform, VinLab. We train our model on the dataset using Pytorch frame and use the mAP, precision, and F1-score as the metrics to evaluate our model's performance. In the progress of experiments, our method achieves superior performance over the other classical approaches on the same dataset. The experiments show that YOLOv5's mAP is 0.010, 0.020, 0.023 higher than those of YOLOv5, Fast RCNN, and EfficientDet. In addition, in the dimension of precision, our model also performs better than other models. The precision of our model is 0.512, which is 0.018, 0.027, 0.033 higher than YOLOv5, Fast RCNN, and EfficientDet.

Experimental Study on the Influence of TiN/AlTiN PVD Layer on the Surface Characteristics of Hot Work Tool Steel

It is desirable to improve tool steel wear resistance to produce pieces with precise dimensions and increase the lifetime of tools. The aim of this work was to modify the surface of 1.2344 (X40CrMoV5-1) hot work tool steel to improve the wear properties. Surface modification was achieved in three steps: first, hardening was applied, followed by plasma nitridation and, finally, physical vapor deposition (PVD) was employed to produce a TiN/AlTiN multilayer coating. The microhardness and the wear coefficient of the surfaces were measured. PVD coating showed the highest hardness value, 2938 HV0.01, whereas plasma nitridation followed by PVD resulted in 2679 HV0.01. The surface modification resulted in an increase in surface roughness in all cases compared to the hardened sample. However, the wear coefficient showed a significant decrease for the surface treated samples. The lowest wear coefficient of K = 1.47 × 10−10 mm3/Nm, which is a magnitude lower than the reference hardened sample (K = 6.32 × 10−9 mm3/Nm), was achieved employing both plasma nitridation and PVD. The results confirm that the use of a combined surface modification of plasma nitridation and PVD significantly improve the wear resistance of the treated samples.

Design and evaluation of a control system for two-dimensional metric validation of metal screws used in osteosynthesis

The metal screws used in osteosynthesis are fabricated with precise dimensions in order to prevent complications in the surgical procedure and to optimize costs and production time. This research work proposes a control system comprised of a digital microscope, a lighting base, and a graphical user interface developed in ImageJ (open-source software). The main objective in this work is to validate metrologically the screws dimension’s quality. In the results, the length and width of the screws obtained with the interface and the same measurements obtained with a caliper were compared as a metrological validation procedure.

Overcoming Environmental Stress Cracking of FDM 3D Printed Formwork for Counter-Pressure Casting of Concrete.

The rapid growth of interest toward concrete digital fabrication reflects the current aspiration for better, smarter, faster, and greener construction means. Among a broad variety of techniques developed by our community, digital casting presents clear advantages regarding dimensional precision, geometrical freedom, and surface finish of the produced elements. In contrast to robotic slip forming, the usage of digitally fabricated formworks requires simpler equipment. It, however, calls for easily shaped formworks, typically best three-dimensional (3D) printed, for example, by fused deposition modeling. While such molds can be easily fabricated with a wide range of commercially off-the-shelf available 3D printers, a shortcoming is the susceptibility of many polymers to environmental stress cracking, particularly when in contact with high pH solutions typical for cementitious materials. This article confirms the problem posed by this type of environmental stress cracking and presents two very effective means of circumventing it: A silicone coating and cyclic olefin copolymer. Apart from this, in the specific case of counterpressure casting (CPC), hydrostatic pressure must be resisted by a powder bed surrounding the formwork. The efficiency of such beds is examined and a particular mixture of sand and lead is shown to be particularly effective, provided its density is regulated to balance stress principles derived from soil mechanics. Presented applications include the successful CPC of thin prismatic formworks with a concrete height up to 3 m as representative of typical interfloor load-bearing elements. The combination of counterpressure and stress control is shown to be essential for such achievement, highlighting the potential of this approach as a viable member of the concrete digital casting family.

An investigation on cutting of the cold work steel X153CrMoV12 by WEDM

Purpose Wire electric discharge machining (WEDM) is a non-conventional machining process, which is used for cutting parts of civil and military aircraft, rotorcraft, satellites and spacecraft. The cold work steel X153CrMoV12 is used in molds that are needed to produce plastic and metal parts used in these areas. It is only possible to produce parts with precise dimensions and quality with the use of mold steels with sensitive surfaces. The purpose of this study is to analyze X153CrMoV12 material by cutting it with WEDM method in precise dimensions. Design/methodology/approach The effects of varying cutting parameters on the size of the finished product, surface roughness (SR) and surface hardness were determined by making rough in one pass and precision cuts in different passes. Nikon SMZ745T, Mitutoyo micrometer, Mitutoyo SJ-210 and Insize ISHL-P100 were used for macro-analysis, dimensional control, SR and surface hardness, respectively, to determine the cut qualities. Findings According to the hardness measurement results obtained from the steel surface before cutting and from the cut surfaces after cutting, there was no significant change in the surface hardness owing to the use of heat-treated steel. Increasing the wire tension as a result of the increase in the number of cutting passes and the decrease in the amount of rough stock left for the final cut increased the cut quality. Cutting precision has increased by preventing vibration of the wire with zero upper and lower water pressure required for slag cleaning. Originality/value There are many studies on WEDM in the literature, but there is no similar study emphasizing the importance of the processing parameters such as the number of cutting passes and rough stock amount. In this study, cold work steel with a hardness of 56–60 HRC was machined as rough cut in one pass, rough and fine cut in double pass, double fine cut after one roughing in three passes. As a result of the cuts, 3 µm measurement precision and 0.998 Ra SR were obtained as well as there was no hardness change in the cut surfaces.

How Do We Assess How Agentic We Are? A Literature Review of Existing Instruments to Evaluate and Measure Individuals' Agency

The importance and centrality of the construct of agency is wellknown amongst social scientists. Yet, there is still little agreement on how this construct should be understood and defined, as demonstrated by the diversity of instruments that are used to investigate it. Indeed, there is no current consensus or standardized methodology to assess agency. This paper provides a synthetic overview of the studies that have evaluated and measured individuals' agency. More specifically, the purpose is to review research that quantitatively investigates the agency of adults, as well as children and youth, across different social contexts. In the process, it offers recommendations to inform future research, practice, and policy. We identified published peer-reviewed studies relating to the assessment of agency across countries and across age through a narrative literature review. The findings were grouped according to whether agency was measured in its most comprehensive conception or in a precise single domain or dimension, which was then discussed separately for children, adults, and women. Of the 3879 studies identified from online searches of the literature and the five additional sources gathered through bibliography mining, 106 qualified for full review, with 34 studies included in the final synthesis. Multiple different instruments were found to be currently adopted or developed to assess agency. The present review offers an exhaustive overview of the different conceptualizations of agency and of the available instruments to assess it, providing critical information for researchers and policymakers to improve intervention and empowerment programs.

Reducing the geometrical machining errors incurred during die repair and maintenance through electric discharge machining (EDM)

The importance of geometrical accuracy can never be overruled in dies and molds which governs the dimensional precision of the parts being manufactured. The continuous use of such tooling requires repair and maintenance. Among the different processes used to upkeep the dimensional consistency of the tooling, machining is essentially required in most cases. The intricacy of the dies and molds’ cavities requires the use of electric discharge machining (EDM). However, in EDM it is challenging to develop control over the machined dimensions owing to the inherent issues of overcut/undercut. This aspect was not comprehensively investigated so far which is the core focus of this research. Three electrode materials, namely, copper, graphite, and tungsten carbide, which belong to the category of metals, nonmetals, and ceramics, respectively, have been compared for the said perspective on the comprehensive list of parametric variables. The results revealed that the average value of the axial errors is 2.5 times lesser in comparison to lateral dimensional errors. In the case of lateral dimensional errors, the electrode of graphite has proved to be a promising choice in comparison to the other two types of electrode materials, namely, copper and tungsten carbide. The copper electrode is noticed to be the most appealing option for reducing axial error (A.E). The mean A.E obtained with Cu electrode is 80.9% and 47.6% lower than that achieved in case graphite and tungsten carbide, respectively. Furthermore, the optimal parametric combination based on 7 variables has also been proposed using desirability analyses whose validity is proved during confirmation trials.

Surface, microstructure, and tensile deformation characterization of LPBF SS316L microstruts micromachined with femtosecond laser

Considerable surface roughness, dimensional deviation, and non-uniform microstructure are a few of the characteristics found on thin or micro-scale features fabricated via laser powder bed fusion (LPBF) that yield inferior and/or inconsistent mechanical properties. Femtosecond laser micromachining can aid in fabricating micro-scale parts with ultra-high dimensional precision. In this work, the surface and tensile behavior of microstruts of 500μm nominal diameter micromachined with Gaussian laser pulses of <100fs duration are characterized. Roughness parameters such as Ra=0.9±0.2μm and Rz=3.4±1.3μm are achieved on the micromachined faces. Surface-associated grains are successfully ablated with negligible microstructural damage to the microstruts. As a result, the average uniform strain under quasi-static tensile loading is measured as 0.54±0.02 compared to 0.42±0.01 for the as-built microstruts. Uniform and non-uniform deformation strain portions are separated analytically and characterized primarily via in-situ imaging. Progressive degradation of the surface and dimensional variance is observed on the micromachined test specimens. Post necking initiation, ablation-associated asperities on the micromachined surfaces evolve into notches, leading to tensile failure.