Precision Parts Research Articles

Technical evaluation of additive manufacturing technologies for in-situ fabrication with lunar regolith

In-Situ Fabrication and Repair can significantly reduce the construction cost of a permanent Moon base by using additive manufacturing (AM) and exploiting local resources instead of bringing all the required materials from Earth. In this article, we evaluate alternative additive manufacturing technologies for building a lunar base and maintaining it across its lifecycle. We compare alternative 3D-printing techniques, already tested for manufacturing with simulants of lunar regolith, using energy, Earth-deliverables consumption, and compressive strength of the produced samples as figures of merit. Based on our analysis, we conclude that Cement Contour Crafting and Stereo-lithography AM techniques are the most promising solutions for the construction of outdoor lunar infrastructure and small precise parts and instruments, respectively.

АЛГОРИТМИЧЕСКИЙ МЕТОД РАСЧЕТА ОТРАЖЕНИЯ И ПРОХОЖДЕНИЯ ВОЛНЫ ЧЕРЕЗ МНОГОСЛОЙНУЮ СТРУКТУРУ. ЧАСТЬ 2. ПАДЕНИЕ ВОЛНЫ НА НАКЛОННЫЙ БАРЬЕР

On the foundation of calculation matrix algorithm of single-dimension wave reflection and passage through multi-layer structure the task about incidence of wave on the inclined barrier is solved. The barrier is presented in the form of step-structure which is consisted of uniform parts divided by boundaries. As a most parameter which determines the wave properties on the single uniform part it is established the wave number. The inclined barrier corresponds to linear increasing of wave number by step way. It is shown that the reflection coefficient by maxima length of barrier is sufficient small and increases to maxima when the length of barrier goes to zero. In this case the dependence of passing coefficient from the barrier length has mirror-symmetrical character relatively the level of 0,5 relative units. The sum of reflection and passage coefficients in all cases is equal to unit. By the character of reflection coefficient dependence from wave number value it is selected three regions: first – when the dependence is regular without the oscillations; second – when dependence is regular and oscillating; third – when dependence has non-regular oscillating character which approach to chaotic so much the high of step is more. As the parameter which divides the regions it is found two critical values of wave number: first – which correspond to transition from smooth dependence to oscillating; second – which correspond to transition from oscillating dependence to chaotic. It is found that the first critical value of wave number step correspond to equality between middle length of wave and whole length of barrier. The second critical value of wave number step correspond to equality between middle length of wave and length of unit step along the barrier length. Fir the interpretation of observed phenomenon the supposition is voiced about its interference origin. It is investigated the dependencies both critical step wave number values from initial length of barrier. It is shown that both dependencies in the high precision (parts of percent) follow inverse ratio to initial length of barrier and different level of curves is determined by the alignment of barrier length and length of its unit step along the barrier length. The connection between initial barrier length and value of unit step along the barrier length. It is found the invariant which is equal to half of relation of initial barrier length to whole length of structure multiplied to value of wave number step. The reflection and passage of wave by large length of structure is investigated. It is found the periodic character of reflection and passage dependencies from length of barrier. On the dependencies is found the sharp peaks which high is approach to maximum corresponding to zero length of barrier. It is found that the distance between peaks along the barrier length corresponds to inverse ratio to wave number step. It is found that the value of barrier length period which correspond to different peaks to a great extent (about two orders) exceeds the middle wave length which is determined the whole over-fall of wave number in the region of whole barrier. For the interpretation of periodic character these dependencies of reflection and passage coefficients from barrier length the model of successive re-reflections is proposed. It is found that the specific of out-coming from structure waves is achieved by coincidence of doubled barrier length with length of propagating wave.

Analysis and System Design of Mechanical Fault Diagnosis Based on Deep Neural Network

The operating environment of mechanical equipment is complex, and it is in high-intensity working conditions for a long time. The condition monitoring and fault diagnosis of equipment are very important. As a kind of precision part commonly used in mechanical equipment, the healthy operation of the rolling bearing is a necessary condition to ensure the reliable operation of the whole equipment. This research takes rolling bearing as the research object and is devoted to mechanical fault diagnosis analysis and system design. This paper studies the structure and working principle of rolling bearing, analyzes the types and locations of rolling bearing faults, and puts forward the overall framework of the fault diagnosis system and the workflow of the fault diagnosis system. This paper also studies the relevant theory of deep learning, proposes a neural network model framework for rolling bearing fault diagnosis, and preprocesses the rolling bearing vibration data. It uses a dropout algorithm and GRU to reduce the model parameter size and reduce the risk of overfitting.

Theory and practice of diagnostics of fire hazardous modes of operation of catalytic converters

Introduction. The wide-scale use of catalytic converters and particulate filters in automobile engines has aggravated the problem of their ignition and updated the research and methodological framework for the examination of causes of fire emergency modes (FEMs) of operation of fuel catalytic units (FCUs). The relationship between the FEMs of the FCU operation and failures of the fuel equipment, wear of the cylinder-piston group of engines and deviations in fuel compositions was confirmed. The goal was to develop a diagnostic method for fire hazardous modes of operation of FCUs of vehicles.Methodology. A model of oxidative catalysis underway in the FCU has been proven rational. The model is used to calculate the thermo-catalytic efficiency and heat generation in the active layer of the γ-Al2O3 platinum catalyst depending on the temperature of exhaust gases (EG), concentrations of CO, CH and soot. It has been found out that catalysis can theoretically develop in four limit domains: internal kinetic domain, internal diffusion domain, external diffusion domain, and external kinetic domain.Results and discussion. Experimental and computational studies have shown the probability of emergence of breakdown vehicles with a multiple excess of soot emissions and thermal stresses. A 10‑fold increase in CO, CH and soot in EG rises the thermal performance of the catalytic reaction from 17,282 to 491,907 kJ/h, creating a fire hazard in a KamAZ engine. To identify a FEM, the diagnostic method based on the «free acceleration» (FA) mode according to GOST 33997–2016 is proposed. The procedure is supplemented with maximum revolutions and restrictions (0.5 s) of the FA mode time. The latter is necessary for the guaranteed operation of the engine in the «full load mode». The method was applied in the course of the fire engineering studies on a Ford Mondeo car having a TDCi (Common Rail System) diesel engine and a catalytic particulate filter. Laboratory examination and analytical studies have found that the main reason for the operation of FCU in emergency (due to environmental and fire hazards) modes is the corrosion of precision parts of the fuel equipment accumulated during its long-term operation. Progressive corrosion is caused by excessive sulfur and moisture content in fuel and oil.Conclusions. It’s been proven that the emergency heating of a catalytic converter causes a sharp rise in the car combustion risk. The authors have proposed an original method for the diagnostics of fire-hazardous modes of operation of catalytic converters based on procedures set in GOST 33997–2016 (ТР ТС 018/2011).

Study of citrate gold plating by different pulse modes with and without vibration

PurposeThe purpose of this paper is to explore the optimum average current density and pulse width for electrodeposition of gold in citrate electrolyte, and it is verified that the uniformity of film thickness can be effectively improved by periodic pulse reverse electroplating.Design/methodology/approachApply forward pulse current, forward group pulse current and periodic pulse reverse current to the electrolyte and compare the film quality. High-frequency group pulses are used in both forward and reverse directions of the periodic pulse reverse current.FindingsIt is verified by experiments that periodic pulse reverse plating is superior to forward pulse plating and forward group pulse plating in terms of particle size, compactness, impurity content and thickness uniformity of the film. Add low-frequency vibration to the cathode under the same pulse electrical parameters as a comparative experiment to prove the beneficial effect of vibration on the allowable limiting current density and plating rate.Originality/valueGold film is often used as the sealing layer of precision parts. Increasing the thickness uniformity and improving the compactness of gold film will help to reduce the size error, improve the subsequent assembly accuracy and increase the service life of wear-resistant layer. Citrate gold plating electrolyte combines the advantages of cyanide electrolyte and cyanide-free electrolyte. Hence, this research focuses on the characteristics of periodic pulse reverse plating in terms of particle size, compactness, impurity content and thickness uniformity of the film and compare it with forward pulse plating and forward group pulse plating.

VR/AR Environment for Training Students on Engineering Applications and Concepts

Modern technologies in virtual reality (VR) and augmented reality (AR) provide unique features that can be used to facilitate tasks in everyday life. Several courses can be built using augmented reality, such as engine maintenance, computer maintenance, chemistry lab, etc. Augmented reality technologies provide dynamic and interactive instructions to resolve a problem or present required concepts. Building an educational system based on augmented reality is not an easy task due to some difficulties and challenges, such as the cost of augmented reality tools and other hardware and software required. Also, training students with engineering concepts and precise parts involves a lot of analysis and practice to know problems and then design solutions. The paper aims to develop a virtual educational environment for training students in engineering sectors in practical laboratory sessions based on AR/VR techniques. The proposed system provides a safe and low-cost environment to train the student different concepts in engineering sector, such as basic concepts in electrical, mechanical and renewable energy engineering.

Federated learning-based semantic segmentation for pixel-wise defect detection in additive manufacturing

Semantic segmentation is a promising machine learning (ML) method for highly precise fine-scale defect detection and part qualification in additive manufacturing (AM). Most existing segmentation methods utilize convolutional neural network architectures that require large quantities of training data. However, obtaining sufficient data—both in quality and quantity—to train such models is expensive and time-consuming for individual AM practitioners, which severely limits the deployment of semantic segmentation in a data-scarce production environment. Similar data may be readily available with other AM practitioners that cannot be pooled together for conventional centralized learning (CL) due to its sensitive nature or conflicts of interest. This paper develops a federated learning (FL)-based method to simultaneously alleviate the constraints of data availability and data privacy. A U-Net architecture is created for semantic segmentation and is trained under the FL framework. The effectiveness of the developed FL-based semantic segmentation approach is demonstrated using case studies on layer-wise images from the laser powder bed fusion process. Results show that the proposed technique achieves a comparable defect detection performance with CL, which shares data among manufacturers/clients but does not preserve data privacy, and significantly outperforms individual learning, where each manufacturer trains a model using its own data. Additionally, the impact of data distribution across clients, incentives to participate in FL, and the learning dynamics of FL are discussed in detail. It is found that data diversity within and across clients improves FL performance, and FL does not involve a significantly higher training cost compared to CL. Lastly, transfer learning is shown to enhance FL generalizability, thus allowing more manufacturers with heterogeneous machines or technologies to benefit from participating in a data federation. Overall, this work puts forth FL as a promising paradigm for privacy-preserving collaborative ML in AM process control.

High-precision calibration to zoom lens of optical measurement machine based on FNN.

We proposed a calibration method for high-precision zoom lenses of optical measurement machines based on Fully Connected Neural Network (FNN), using a 5-layer neural network instead of a camera calibration model, to achieve continuous calibration of zoom lenses at any zoom setting by calibrating typical zooms. From the experimental verification, the average calibration error of this method is 9.83×10-4mm and the average measurement error at any zoom setting is 0.01317mm. The overall calibration precision is better than that of Zhang's calibration method and can meet the application requirements of a high-precision optical measurement machine. The method proposed in this paper provided a new solution and a new idea for the calibration of zoom lenses, which can be widely used in the fields of precision parts inspection and machine-vision measurement.

Anti-apoptosis and anti-inflammation activity of circ_0097010 downregulation in lipopolysaccharide-stimulated periodontal ligament cells by miR-769-5p/Krüppel like factor 6 axis

Background/purposePeriodontitis is a prevalent infectious inflammatory disease. Growing evidence has revealed important roles for circular RNAs (circRNAs) and circRNA sponge activity in periodontitis. Here, we elucidated the precise part of circ_0097010 in periodontitis pathogenesis. Materials and methodsHuman periodontal ligament cells (hPDLCs) were exposed to lipopolysaccharide (LPS). Cell viability, proliferation and apoptosis were evaluated by CCK-8 assay, EdU incorporation assay and flow cytometry, respectively. Circ_0097010, microRNA (miR)-769-5p and Krüppel like factor 6 (KLF6) were quantified by qRT-PCR and Western blot. Interleukin 6 (IL-6) level, tumor necrosis factor-α (TNF-α) secretion, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were detected by enzyme-linked immunosorbent assay (ELISA). Dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays were used to confirm the direct relationship between miR-769-5p and circ_0097010 or KLF6. ResultsOur data showed that LPS repressed cell proliferation and induced cell apoptosis and inflammation in hPDLCs. Circ_0097010 was upregulated in periodontitis samples and LPS-exposed hPDLCs. Downregulation of circ_0097010 exerted anti-apoptosis and anti-inflammation functions in LPS-exposed hPDLCs. Mechanistically, circ_0097010 acted as a miR-769-5p sponge, and reduced abundance of miR-769-5p reversed the anti-apoptosis and anti-inflammation effects of circ_0097010 suppression. KLF6 was a direct miR-769-5p target, and miR-769-5p-mediated inhibition of KLF6 possessed anti-apoptosis and anti-inflammation functions in LPS-induced hPDLCs. Moreover, circ_0097010 controlled KLF6 expression by miR-769-5p. ConclusionThese data identify circ_0097010 as a key regulator of LPS-induced inflammation and apoptosis in hPDLCs and highlight a novel mechanism of circ_0097010 regulation through miR-769-5p/KLF6 axis.

An experimental investigations on effects of cooling/lubrication conditions in micro milling of additively manufactured Inconel 718

The demand for additive manufacturing (AM) technology is recently increased in the aerospace, biomedical, and automobile sectors due to the capability of producing complex components with zero tolerance. However, the small or precise part manufactured by AM process needs post-processing such as machining, polishing, etc. because of the poor surface quality characteristics. Therefore, in this paper, the micro-milling was performed on additively manufactured Inconel-718 alloy under different sustainable cooling conditions. The tool wear, surface roughness, and burr generated during micro-milling experiments were investigated under the effect of air, minimum quantity lubrication (MQL), and flood cooling conditions. The results demonstrated that the MQL conditions provide the proper cooling and lubrication effect, and this results in improved tool life (which is almost 45% higher compared to dry conditions. MQL also improved the product quality in terms of surface roughness (almost 65% less surface roughness). Other machining characteristics, such as burr width and cutting forces, were also improved in MQL and flood environments. However, it was noticed that milling with a chilled air environment has not given any significant improvement in terms of machining characteristics.

Reverse Engineering Algorithm for Cutting of Ruled Geometries by Wire

Abrasive wire cutting (AWC) and wire electric discharge machining (WEDM) are efficient and economical processes for the fabrication of precision parts from bulk material. Operating costs and manufacturing lead times are low compared to more general methods such as 5-axis CNC milling, turning, or electro-discharge machining. In this paper, an algorithm based on differential geometry in Euclidean space is proposed for reverse engineering of ruled geometries. The algorithm can determine whether a given geometry is producible by wire cutting, and can also derive the associated wire trajectories. Implementation is demonstrated by producing complex turbine blade geometries on 4-axis wire cutting machines with an overall shape accuracy of 20–40 μm peak-to-valley.

Using additive manufacturing technologies in high-field accelerator magnet coils

Recent advances with additive manufacturing (AM) technologies using various materials allow them to be considered for the manufacture of precise and complicated metal parts of the magnet coils of high field accelerator magnets from aluminum bronze, titanium alloy, stainless steel, etc. The 3D printing technology is also being used to fabricate prototype models of real parts to test and optimize their geometry. This paper discusses the designs of the complex stress-management coil parts developed at Fermilab, their fabrication using AM technologies, and quality control methods and results.

Reliability optimization of micro-milling cutting parameters using slime mould sequence algorithm

An optimal selection of cutting parameters is of great significance for increasing machining efficiency, improving accuracy, and reducing the cost of micro-milling. An accurate description of the machining mechanism and the cutting process is the premise of obtaining high-precision cutting parameter optimization results. In this work, a framework is presented for analyzing cutting forces, tool deflection and workpiece surface roughness, considering size effects, tool runout and minimum cutting thickness in micro-milling. Moreover, the novel slime mold sequence algorithm is proposed based on the feedback effect of slime mold on food propagation waves and the decoupling of the optimization process and reliability evaluation. Based on the proposed algorithm, to improve the efficiency of optimization, the material removal rate, machining cost and time are selected as objective functions while the cutting forces, tool deformation, workpiece surface roughness, and parameter uncertainty are considered as optimization constraints. The accuracy of the developed model is verified by micro-milling experiments. Furthermore, the reliability optimization results show that the material removal rate is increased by 12.6%, the processing cost is reduced by 6.94%, and the processing time is reduced by 9.74%, which provides theoretical guidance for optimizing the cutting processes of precision parts.

A Study of the Design Method of Miruk-Jõn Hall Kumsan-Sa Temple in Korea—Through a Comparison with the Kiwari Method

It is considered that it is difficult to build a well-constructed building without proportional or dimensional relationships of precise parts, so it is estimated that Korea has some sort of numerical determination method now. Also, in China there is “Ying Zao Fa Shi: 営造法式” of technical books and it is doubtful that there is no similar technology in Korea with the same architectural flow, given that there are ways to decide “Kiwarisho: 木割書” in Japan. Therefore, focus on this point and aim to clarify the dimension determination method of Miruk-jõn Hall Kumsan-sa Temple using analysis method of each proportional method in Japan.

Kompozit materialdan olan presizion maşın hissələrinin ekstruziya üsulu ilə alınmasının texnoloji xüsusiyyətləri Ə.G. Huseynov, V.A. Abbasov, Ç.M. Məmmədov, Ş.N. Əsədov

In the article, in order to increase the efficiency and productivity and accuracy of the extrusion process in the production of precision machine parts made of composite material, in pressure casting machines (extruders) and thermoplastic machines, the working principle and technological losses of nozzles made of brass and copper alloys, equipped with a straight flow nozzle, are revealed. the causes of these losses have been determined. Keywords: composite material, extrusion process, precision parts, injection molding machines, thermoplastic automaton, screws.

Research on assembly clearance of precision spherical coupling parts by point cloud analysis

Abstract Assembly clearance has a great influence on the performance of precision parts. Improper assembly clearance affects the working state and induces failure of parts. A method to analyze the assembly clearance of the precision spherical coupling parts by analyzing the points cloud was proposed. The least square center was used to find a rough center. Accurate center was searched near the least square center by the particle swarm optimization (PSO) algorithm based on the minimum zone method. Radical clearance and Z clearance of precision spherical coupling parts were calculated. Furthermore, the dynamic change of assembly clearance was also calculated by rotating the parts. The sphericity error evaluation results were improved obviously compared with other results. The accuracy of the evaluation results improved 4.51%∼28.97%.

Numerical simulation and experimental analysis for evaluating warpage of a 3D thin-walled polymeric part using the injection compression molding process

Abstract Injection compression molding (ICM) is a nontraditional hybrid injection molding (IM) process that has been utilized to mold a wide range of the latest and difficult-to-manufacture precision parts that require high dimensional accuracy and no residual stresses. This paper introduces the accurate calculation of warpage for ICM by numerical simulation via Moldflow software, and a comparison of results with products produced experimentally by ICM. To begin with, the process parameters of ICM were discussed based on the numerical simulations. The effects of process parameters, namely melt temperature, mold temperature, compression pressure, and compression distance, on warpage behavior of a molded 3D BJ356MO polypropylene (PP) (100MFI) part were investigated using Taguchi analysis. The obtained warpage results with optimum process parameters were compared with experimental measurements to test the validity of the simulation model of ICM. It was found that the numerical simulations of the ICM show good agreement with experimental measurements.

Effects of sandblasting and HIP on very high cycle fatigue performance of SLM-fabricated IN718 superalloy

Additive manufacturing (AM) has a bright application prospect because of its ability to efficiently manufacture complex and precise parts. However, defects such as pores and surface roughness produced in the manufacturing process severely restrict its application. Here ultrasonic fatigue test is conducted to evaluate the effects of sandblasting and hot isostatic pressing (HIP) on the VHCF performance of IN718 fabricated by selective laser melting (SLM). X-ray computed tomography (CT) and a 3D-optical profiler are used to characterize the defects, including size and location. After sandblasting, the crack initiation sites transfer from surface to interior, which is attributed to the improved surface state. Kurtosis, rather than the often-employed arithmetical mean height, is used to evaluate the contribution of sandblasting on surface state due to its ability to characterize surface defect morphology. With the elimination of defects and the introduction of the compressive residual stress under the combination of sandblasting and HIP, the potential initiation sites are transferred from the locations of defects to the weak microstructure, which still significantly improves the fatigue resistance. The tensile test reveals that the VHCF performance was more sensitive to small defects than the tensile properties. Finally, the influence of defects on fracture behavior is analyzed in the framework of fracture mechanics.

Three-dimensional measurement of precise shaft parts based on line structured light and deep learning

Line structured light is widely used in three-dimensional measurement of metal parts. The large curvature and specular reflection on the surface of precise shaft parts make the intensity of laser stripes captured at some different positions too weak or too strong to extract the center accurately. To extract the center of the stripes from the disturbed image, a center extraction algorithm based on deep learning is proposed. The deep neural network with good feature learning ability can extract the overall distribution and bending characteristics of laser stripes. The region of laser stripe is accurately detected and segmented from the interference. Then the center of the segmented stripe can be well extracted. Experiment verifies the noise suppression ability of the proposed method. Three-dimensional measurement of the precise shaft parts is implemented with light plane calibration. The diameter of the shaft parts is calculated and the measurement error is less than 0.017 mm.

3D printing produces sealant parts that are ESD safe

Germany's Hänssler Group, which specialises in sealing and plastics technology, is using 3D printing to produce precise sealant parts from a material that protects against electrostatic discharge. Here we look at the materials and additive manufacturing system that are employed, and focus on the benefits of using this production process