bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Process Parameters Modifications on Directed Energy Deposition Manufactured Parts Obtained in a Hybrid Additive Manufacturing Machine
Authors: Henriques Ana Beatriz B. , de Aguiar Paola L. , dos Santos Raphael G. , Miagava Joice
Published: September 2022

In order to combine advantages of both additive and subtractive manufacturing, hybrid machine tools have been developed. In the hybrid process, directed energy deposition (DED) is the most used additive manufacturing technology due to its adaptability to CNC milling centers. However, in order to assure the integrity of a printed part, several process parameters must be set appropriately. Not only there are several parameters, but also some of these parameters influence different variables — e.g.: scan speed influences both the energy input per unit area and the powder volume that is deposited. In addition, another fact that complicates the achievement of a good quality in a workpiece is that some relevant parameters for additive manufacturing cannot be controlled due to CNC milling center constraints (e.g.: atmosphere). In this work, laser power (280 to 340 W) and scan speed (5 to 7 mm/s) were systematically varied to print 316L test samples with the aim of building a quality matrix. In the future, this matrix will be used to create strategies to optimize the quality of printed parts. Optical stereoscopy shows that the higher the laser power, the higher the sample, indicating that more powder is melted and deposited with an increasing laser power. By fixing the laser power and increasing the scan speed, printed samples were lower, indicating that less powder was deposited. Other parameters were preliminarily tested — e.g.: sample size and shield gas flow. Decreasing the sample size from 9 to 6 mm was sufficient to double the sample height, showing that the heat transfer rate was dramatically changed. Findings of this study shows that all process parameters act together and are determining factors for a good quality printed part. Moreover, it was noted that sample integrity is very sensitive to minimal changes in some process parameters.
Improving Geometric Accuracy in Wire and Arc Additive Manufacturing With Engineering-Informed Machine Learning
Authors: Ruiz Cesar , Jafari Davoud , Subramanian Vignesh Venkata , Vaneker Tom H. J. , Ya Wei , Huang Qiang
Published: September 2022

Wire and arc additive manufacturing (WAAM) is a promising technology for fast and cost-effective fabrication of large-scale components made of high-value materials for industries such as petroleum and aerospace. By using robotic arc welding and wire filler materials, WAAM can fabricate complex large near-net shape parts with high deposition rates, short lead times and millimeter resolution. However, due to high temperature gradients and residual stresses, current WAAM technologies suffer from high surface roughness and poor shape accuracy. This limits the adoption of these technologies in industry and complicates process control and optimization. Since its conception, considerable research efforts have been made on improving the mechanical and microstructural performance of WAAM components while few studies have investigated their geometric accuracy. In this work, we propose an engineering-informed machine learning (ML) framework for predicting and compensating for the geometric deformation of WAAM fabricated products based on a few sample parts. The proposed ML algorithm efficiently separates geometric shape deviation into deformation and surface roughness. Then, the predicted shape deformation of a new product is minimized by applying optimal geometric compensation to the product design. Experimental validation on cylindrical shapes showed that the proposed methodology can effectively reduce product shape deviation, which facilitates the widespread adoption of WAAM.
Enhanced Three-Dimensional Surface Profiling Technique Based on a Feature-Selective Segmentation and Merging
Authors: Guo Xiangyu , Lee ChaBum
Published: September 2022

This paper introduces an imaging technique to enhance three-dimensional (3D) surface profiling of the machined part by using a feature-selective segmentation (FSS) and merging technique. Spatially-resolved 3D stereoscopic images were achieved compared with those of the conventional filtering-based imaging process. Two identical vision cameras simultaneously take images of the parts at different angles, and 3D images can be reconstructed by stereoscopy algorithm. High-pass and low-pass filtering of the images involves data loss and lowers the spatial resolution of the image. In this study, the 3D reconstructed image resolution was significantly improved by automatically classifying and selectively segmenting the features on the 2D images, locally and adaptively applying super-resolution algorithm to the segmented images based on the classified features, and then merging those filtered segments. Here, the features are transformed into masks that selectively separate the features and background images for segmentation. The measurement system scanned the machined part with various shape and height information. The experimental results were compared with those of a conventional high-pass and low-pass filtering method in terms of spatial frequency and profile accuracy. As a result, the selective feature segmentation technique was capable of spatially-resolved 3D stereoscopic imaging while preserving imaging features. The proposed imaging method will be implemented with strobo-stereoscopy for in-process 3D surface imaging.
An Intelligent Switching Method of Multi-Resolution Models Oriented for Complex System Co-Simulation
Authors: Liu Wenzheng , Zhao Chun , Zhang Heming
Published: September 2022

With the development of Cyber-Physical Systems (CPS) technologies, many multi-disciplinary collaboration of complex systems that are difficult to solve in a single field can be addressed by simulation in the cyber world. Co-simulation is a typical solution to collaboration of distributed heterogeneous models for complex system. However, the problem of how to select proper simulation models with multi-resolution remains a technical gap for heterogeneous collaboration, which needs more intelligent simulation support provided in the cyber world. In this paper, an intelligent switching method of multi-resolution heterogeneous models oriented for co-simulation of complex systems is proposed. Timing advancing of models with more than one resolution level of simulation resources are incorporated in this architecture. Simulation resources in the form of plug-in-play function blocks can be scheduled by intelligent decision, which can extend the diversity of simulation tasks. After experiments of typical collaborative simulation of a robotic arm in an automatic cruise application scenario, analysis and results show that the proposed method can switch the multi-level simulation resources and trade off well between simulation efficiency and accuracy effectively.
Separation Process Comparison of Hydrogel Film and PTFE Film in Vat Photopolymerization
Authors: Yang Feimo , Kazi Aamer , Liu Caleb , Tai Bruce L.
Published: September 2022

In constrained surface vat photopolymerization, the separation process between a newly printed layer and the vat film has long been a limiting factor for printing speed and feature size. This paper aims to compare the performance of a hydrogel film and a conventionally used polytetrafluoroethylene (PTFE) in terms of separation forces, vertical separation distances, and dimensional accuracies of the printed parts. PTFE is commonly adopted because of its low surface energy and thus low separation force, while the hydrogel film is hypothetically effective because of its repelling nature to the non-polar characteristic in most photopolymers. A custom-designed building platform with an integrated sensor is used to continuously sample the force at 1,000Hz with 0.1N resolution. The separation distance is calculated based on the ascending and descending force profiles. The results show a 26% reduction in separation forces and a 60% reduction in vertical separation distances, with 95% statistical significance when comparing the hydrogel film to the PTFE film. The dimensional accuracies of produced parts in both films are similar.
Characterization of the Direct Write Inkjet Printing Process for Automated Fabrication of PEDOT: PSS Thin Films
Authors: Morice Sara , Sherehiy Andriy , Wei Danming , Popa Dan O.
Published: September 2022

Direct write Inkjet Printing is a versatile additive manufacturing technology that allows for the fabrication of multiscale structures with dimensions spanning from nano to cm scale. This is made possible due to the development of novel dispensing tools, enabling controlled and precise deposition of fluid with a wide range of viscosities (1 – 50 000 mPas) in nanoliter volumes. As a result, Inkjet printing has been recognized as a potential low-cost alternative for several established manufacturing methods, including cleanroom fabrication. In this paper, we present a characterization study of PEDOT: PSS polymer ink deposition printing process realized with the help of an automated, custom Direct Write Inkjet system. PEDOT: PSS is a highly conductive ink that possesses good film forming capabilities. Applications thus include printing thin films on flexible substrates for tactile (touch) sensors. We applied the Taguchi Design of Experiment (DOE) method to produce the optimal set of PEDOT:PSS ink dispensing parameters, to study their influence on the resulting ink droplet diameter. We experimentally determined that the desired outcome of a printed thin film with minimum thickness is directly related to 1) the minimum volume of dispensed fluid and 2) the presence of a preprocessing step, namely air plasma treatment of the Kapton substrate. Results show that an ink deposit with a minimum diameter of 482 μm, and a thin film with approximately 300 nm thickness were produced with good repeatability.
Cutting Process in Slot Milling of AISI420 Stainless Steel Manufactured in Additive Process
Authors: Tamura Shoichi , Ishikuri Takeru , Inazawa Katsufumi , Matsumura Takashi
Published: September 2022

Hybrid manufacturing involving additive and subtractive process in the same platform has been attracted to produce complex shaped parts with excellent surface finish and accuracy in surgical, aerospace, tool and die industries. The microstructures of metals fabricated by laser powder bed fusion are different from the wrought material. The machining of the material hardened in situ locally heat treated due to laser scanning is conducted without lubrication in the hybrid manufacturing. The paper discusses the milling process of AISI 420 martensitic stainless steel manufactured in additive process with comparing to a quenched wrought material and a quenched-tempered material. The cutting tests were conducted in slotting with a helical square end mill. The chip and the burr formations are discussed with the measured cutting forces. Then, the cutting forces are analyzed in a chip flow model, in which the three-dimensional chip flow is interpreted as a piling up of orthogonal cuttings in the planes containing cutting and chip flow velocities. The shear angle and the shear stress on the shear plane during chip formation are associated with the cutting force.
Learning the Temporal Effect in Infrared Thermal Videos With Long Short-Term Memory for Quality Prediction in Resistance Spot Welding
Authors: Guo Shenghan , Wang Dali , Chen Jian , Feng Zhili , Guo Weihong “Grace”
Published: September 2022

With the advances of sensing technology, in-situ infrared thermal videos can be collected from Resistance Spot Welding (RSW) processes. Each video records the formulation process of a weld nugget. The nugget evolution creates a “temporal effect” across the frames, which can be leveraged for real-time, nondestructive evaluation (NDE) of the weld quality. Currently, quality prediction with imaging data mainly focuses on optical feature extraction with Convolutional Neural Network (CNN) but does not make the most of such temporal effect. In this study, pixels corresponding to critical locations on the weld nugget surface are extracted from a video to form multivariate time series (MTS). Multivariate Adaptive Regression Splines (MARS) is used in MTS processing to remove noisy signals related to uninformative frames. A Stacked Long Short-Term Memory (LSTM) model is developed to learn from the processed MTS and then predicts weld nugget size and thickness in real-time NDE. Results from a case study on RSW of Boron steel demonstrates the improvement in prediction accuracy and computational time with the proposed method, as compared to CNN-based weld quality prediction.
Experimental Characterization of the Mechanical Properties of Medical-Grade Dental Implants, Fabricated Using Vat-Photopolymerization Additive Manufacturing Process
Authors: Raines Regan , Day James B. , Salary Roozbeh (Ross)
Published: September 2022

The overarching goal of this research work is to fabricate mechanically-robust and dimensionally-accurate dental implants for the treatment of dental fractures, anomalies, and structural deformities with a focus on oral and maxillofacial surgery applications. In pursuit of this goal, the objective of the work is to investigate the mechanical properties of several triply periodic minimal surface (TPMS) scaffolds, composed of a medical-grade photopolymer resin, fabricated using digital light processing (DLP) process. DLP is a vat-photopolymerization additive manufacturing process; it has emerged as a high-resolution method for the fabrication of a broad spectrum of biological tissues and constructs for tissue engineering applications. However, the DLP process is intrinsically complex; the complexity of the process stems from complex physiochemical phenomena (such as UV light photopolymerization) as well as resin (photopolymer)-process interactions, which may adversely influence the mechanical properties, the surface morphology, and ultimately the functional characteristics of fabricated dental scaffolds. Consequently, physics-based process and material characterization would be an inevitable need. In this study, several TPMS scaffolds (having complex internal geometries) were fabricated, based on a medical-grade photopolymer resin. The compression properties of the fabricated dental scaffolds were measured using a compression testing machine. In addition, the bioactivity of the scaffolds was assessed in a simulated body fluid (SBF). The outcomes of this study pave the way for the fabrication of complex dental implants with tunable medical and functional properties.
Investigation of the Influence of Hydroxyapatite and Polysaccharide Concentration on the Mechanical Properties of Bone Scaffolds, Fabricated Using Freeze Drying Process
Authors: Ekstrom Tanner , Day James B. , Salary Roozbeh (Ross)
Published: September 2022

The overarching goal of this research work is to synthesize and fabricate mechanically robust, dimensionally accurate, and porous bone scaffolds for the clinical treatment of osseous fractures, defects, and diseases. In pursuit of this goal, the objective of the work is to investigate the influence of hydroxyapatite (HA) as well as polysaccharide concentration on the mechanical properties of bone scaffolds, fabricated using freeze drying process. Freeze drying or lyophilization has emerged as a robust method for the fabrication of a broad spectrum of tissue constructs. Freeze Drying allows for multi-material fabrication of structures with complex pore morphology for soft and hard tissue engineering applications. However, the process is intrinsically complex; the complexity of the process, to a great extent, stems from complex physical phenomena (such as sublimation) as well as material-process interactions, which may adversely affect the mechanical properties, the surface morphology, and ultimately the functional characteristics of fabricated bone scaffolds. Consequently, physics-based process and material characterization would be an inevitable need. In this study, the influence of HA and polysaccharide concentration was investigated using a central composite design (CCD). The concentration of both HA and polysaccharide was changed in the range of 5%–15% with the aim to obtain mechanically robust structures. The compression properties of the fabricated bone scaffolds were measured using a compression testing machine. The outcomes of this study pave the way for the fabrication of complex, mechanically strong, and porous bone-like scaffolds with tunable medical and functional properties.
Vision-Sensor Fusion-Based Low-Cost Dimension Measurement System for Machining Shop Floor
Authors: Singh Swarit Anand , Kumar Aitha Sudheer , Sorathiya Pratik C. , Desai K. A.
Published: September 2022

The majority of industrial inspection activities across the globe involve considerable human efforts due to the requirements of robust detection abilities under varying lighting conditions, large field of view, higher speeds, and dynamic range of operation. In recent years, the motivation for integrating inspection and manufacturing operations on the shop floor has grown considerably to maximize the potential benefits of implementing Industry 4.0 initiatives. It is essential to digitize and integrate inspection of raw materials, in-process inventory, and finished components with manufacturing operations for achieving autonomous manufacturing goals. Machine vision offers an excellent alternative to manual inspection at a reduced cost, increased productivity, digital output, and negligible errors. However, its utility is restricted to the finished component inspection currently due to exorbitant equipment costs, requirements of specific lighting conditions, and a controlled operating environment. This paper presents the development of an integrated system combining a camera and ultrasonic sensor to develop a low-cost dimensional measurement system for inspection of raw material and in-process machined components in the shop floor setting. An indigenous inspection system is developed by integrating a camera, ultrasonic sensor, power source, and interactive user interface with onboard processing abilities. The augmentation of the ultrasonic sensor serves a dual purpose of eliminating the need for image calibration and dimensions measurement in the system. An interactive graphical user interface with acquisition trigger abilities and results display is developed using an open-source TkInter framework of the Python environment. A set of dimension measurements are performed for common raw material and in-process machined shapes using the developed setup. The comparison of results obtained using developed inspection setup and commercial machine vision system showed good agreement for common shapes. The efficacy of the developed system is validated for inspection of simple shapes with machining operations on the shop floor in the present work. The proposed system can be easily extended to inspect complex shapes such as gear profiles or camshafts as subsequent research work.
Process Temperatures and Material Flow in Friction Stir Welding of High Density Polyethylene (HDPE)
Authors: Sheikh-Ahmad Jamal , Rehman Razi Ur , Deveci Suleyman , Almaskari Fahad
Published: September 2022

In this study we investigate the effect of material temperatures on material flow and weld quality in the friction stir welding of bi-modal high density polyethylene (HDPE). The heat input to the process was controlled by varying the tool rotational speed, welding speed and the material initial temperature. Preheating of the HDPE blanks on the bottom surface of the weld was incorporated in order to increase the material flow in this relatively colder region. Temperatures on the boundary surfaces of the HDPE blanks were measured using an infrared camera and thermocouples. Material flow patterns were observed by welding two different colors of the polymer blanks, white on the advancing side and black on the retreating side. Joint quality was assessed using optical microscopy and joint strength was measured by tensile testing. It was found that material temperatures greatly affect the material flow in the weld zone, which in turn affects the tendency to form defects and the overall joint quality. High joint efficiencies and large elongations in excess of 100% were obtained when the material temperatures across the thickness were in excess of 100 °C.
Dynamic Simulation Analysis of Multi-Support Rotary Shaft System
Authors: Mei Jiangnuo , Zheng Yinhuan , Lu Hong , Li Zhangjie , Zhang Wei , Peng Di , Lin Huang , Liu Qiong
Published: September 2022

The multi-support rotary shafting system, represented by the ship propulsion shafting, is widely used in the power transmission device of the ship, and its working condition has a great influence on the operational safety of the ship. Therefore, it is necessary to conduct a dynamic analysis of the ship propulsion shafting. The ship propulsion shafting is used as a prototype to design a transmission shaft system fault detection platform based on the dual-engine parallel transmission mode. In order to accurately simulate the load loaded by the magnetic powder brake in the fault detection platform of the transmission shaft system, the control strategy of the magnetic powder brake loading is studied, including conventional PID control, Smith control, fuzzy Smith control and fuzzy Smith with integral action. The control realizes the ideal control effect of the magnetic powder brake. On the basis of the accurate load control effect, use the Adams software to conduct dynamic simulation analysis on the rigid-flexible hybrid model of the ship propulsion shafting. The dynamic characteristics of the shaft system under normal and fault conditions are studied, the research shows that the occurrence of collision and friction faults will increase the force fluctuation range of the shaft system, the shafting vibration will become more complex, and the characteristic frequency will have a large number of high-multiplication frequencies. The above analysis results have certain significance for the fault analysis of the transmission shaft system.
A Novel Objective Function for the Inverse Problem of Simultaneous Identification of Unknown Youngs Modulus and Boundary Conditions With Noisy and Partial Observation
Authors: Xu Tian , Du Shilun , Li Murong , Hu Yingda , Wang Zhen , Lei Yong
Published: September 2022

The biomechanical models of the surgical navigation systems need patient-specific elastic properties and boundary conditions to calculate the deformation of soft tissues. However, these information cannot be directly obtained in a real endoscopic surgical scenarios. Many studies have been carried out focusing on identification of unknown elastic parameters and boundary conditions. But they rarely estimate these unknown parameters together. For the convergence of unknown parameters with observation error, some methods add regularization terms to the objective functions which are complex and sometimes rely on experience. In this paper, a novel objective function based on the gradient of displacement field is proposed, which can ensure the convergence of unknown Young’s modulus and boundary conditions without additional regularization terms. A “two field” construction method, which can convert this ill-posed inverse problem to two well-posed problems, is introduced to construct this objective function. The sensitivity analysis is conducted based on approximate differential method and the Gauss-Newton (GN) method is applied to minimize the objective function and update unknown parameters. The proposed objective function is compared with a few classical objective functions in a series of numerical experiments based on the linear elastic finite element model. The results of numerical experiments show the advantages and feasibility of the proposed objective function.
3D Printing and Mechanical Behavior of Anisogrid Composite Lattice Cylindrical Structures
Authors: Stan Felicia , Sandu Ionut-Laurentiu , Fetecau Catalin
Published: September 2022

Anisogrid cylindrical lattice (ACL) structures have been successfully used in space applications, demonstrating high mechanical performance and weight efficiency. However, the manufacturing process for the composite ACL structures is very complex and, traditionally, involves different technologies, including winding of filaments or prepregs and curing. Tacking the advantage of the fused deposition modeling (FDM) to manufacture completely integral composite parts with complex shape, in this paper, the FDM-3D printing of ACL structures using carbon fiber (CF) and glass fiber (GF) reinforced polyamide 12 (PA12) composites has been investigated. The mechanical behavior of 3D printed ACL structures has been analyzed in terms of the static stiffness, specific load, and failure mode through axial and transverse compression tests, as a function of the geometrical parameters of the lattice structure.

It was observed that, under transverse compression, after the initial linear elastic response, the applied load changed its slope and continued to increase with increasing displacement up to a specified displacement (inner radius of the ACL structures) without visible fracture or delamination between layers, demonstrating that the 3D printed composite ACL structures are robust and highly efficient in the nodes. Under axial compression, the applied load increased with displacement up to a maximum load and then decreased until fracture, mainly, due to local buckling and material failure of the helical ribs. The 3D printed CF/PA12 ACL structures were found to be more efficient than either the GF/PA12 or PA12 ACL structures taking into account both the axial and transverse specific load and stiffness. The increase in the shell thickness, helical rib width or number of helical ribs resulted in a remarkable increase in the stiffness and load-bearing capacity of the 3D printed composite ACL structures. From the manufacturing perspective, it was shown that the FDM-3D printing technology holds promise for the development of mechanically robust composite ACL structures with excellent reliability.
Precision Evaluation of Large Payload SCARA Robot for PCB Assembly
Authors: Nimon Andrew S. , Sherehiy Andriy , Alqatamin Moath , Wei Danming , Popa Dan O.
Published: September 2022

The placement of SMD components is usually performed with Cartesian type robots, a task known as pick-and-place (P&P). Small Selective Compliance Articulated Robot Arm (SCARA) robots are also growing in popularity for this use because of their quick and accurate performance. This paper describes the use of the Lean Robotic Micromanufacturing (LRM) framework applied on a large, 10kg payload, industrial SCARA robot for PCB assembly. The LRM framework guided the precision evaluation of the PCB assembly process and provided a prediction of the placement precision and yield. We experimentally evaluated the repeatability of the system, as well as the resulting collective errors during the assembly. Results confirm that the P&P task can achieve the required assembly tolerance of 200 microns without employing closed-loop visual servoing, therefore considerably decreasing the system complexity and assembly time.
Research on Positioning Error of Dual-Drive Feed System Based on Virtual Axis-Electronic Cam Strategy
Authors: Deng Zhanyun , Lu Hong , Liu Qi , Meng Lanqi , Dai Jiashun , Liu Qiong
Published: September 2022

The dual-drive feed system (DDFS) is widely used in highspeed, high-precision and heavy-duty applications due to its good vibration resistance, high rigidity and rapid response. Positioning accuracy is an important performance index characteristic of CNC (Computer Numerical Control) machine tools, which can directly determine the processing quality of the workpiece, but the existence of positioning errors always damages the performance and processing accuracy of CNC equipment. This paper firstly analyzes the source of the positioning error of the DDFS. Then, according to the structure of the DDFS, the multi-body system (MBS) theory and the modeling method of homogeneous transfer matrix (HTM) is used. The error modeling of the DDFS is carried out, and the positioning error model is obtained. According to the positioning error model, a reasonable positioning error detection program is designed. And the experimentally measured positioning error values are fitted. Finally, by using the virtual axis-electronic cam error compensation function in the TwinCAT software of the German BECKHOFF control system, the error compensation method of virtual axis-electronic cam is used on the built DDFS platform to carry out error compensation experiments. The experimental results show that the error compensation method of virtual axis-electronic cam can effectively reduce the positioning error.
Acoustic Emission Sensors to Monitor Early Onset of Necking During Uniaxial Tension
Authors: Baral Madhav , Al-Jewad Ali , Breunig Alexander , Ha Jinjin , Groche Peter , Korkolis Yannis P. , Kinsey Brad L.
Published: September 2022

Elastic waves are generated and propagate when a material undergoes plastic deformation and can be detected by acoustic emission (AE). In this work, AE measurements are obtained during a uniaxial tension (UT) test using a custom-made sensor employing piezoelectric crystals. The UT tests are performed on an MTS machine with two AE sensors clamped on each end of the specimen gage section. A low pass Butterworth filter is designed to attenuate the high frequency noise from the AE signals. Also, full-field strain measurements on the specimen surface are acquired using the 2-D digital image correlation (DIC) method. A typical result from a UT test reveals, as the plastic deformation increases, the AE signals from each sensor increase until they reach a maximum value followed by a drop of signal until the specimen fractures. It is found through interrogation of the DIC images that the maximum amplitude from the AE signals corresponds to the early onset of localized necking. The goal of this work is to implement the UT findings in an actual forming process (e.g., cup drawing) and monitor the event in real time using closed loop control to achieve improved formability.
Effect of Inherently Porous Structure Produced by Metal Fused Filament Fabrication on the Tribological Behavior of Lubricated Steel-Steel Contact
Authors: Liu Rui , Greeley Andrew , Zhang Shuhuan , Cormier Denis , Iglesias Victoria Patricia
Published: September 2022

By introducing local depressions, as small reservoirs for lubricants and wear debris, on a flat surface, the surface texture has been proven to positively affect the friction and wear behavior of lubricated sliding surfaces. However, the effectiveness of the surface texture diminishes and disappears eventually as wear develops at the contact interface. In order to achieve a longer-lasting beneficial effect on the sliding surface, this work develops an approach to print an inherently porous structure up to a certain depth beneath the contact surface to retain the benefits associated with surface texture. A test structure was created from 17-4 PH stainless steel using a metal fused filament fabrication system. The performance of the printed porous structure was evaluated using a steel ball in a ball-on-flat reciprocating tribometer under lubricated conditions with mineral oil. By comparing with the solid sample, it was found that the printed structure with inherent porosity improved the tribological performance by reducing the friction up to 20% and the wear rate up to 90%. The experimental results also indicate that the effectiveness of the printed texture is strongly correlated to the shape and the distribution of the pores on the wear track, which requires further research in the following studies.
Synthesizing and Printing of Tin Oxide Nanoparticles Using a Single Ultrafast Laser System: A Feasibility Study
Authors: Contreras Lopez Enrique , Ahmed Farid , Li Jianzhi
Published: September 2022

In laser-based manufacturing, processing setup customization is one of the popular approaches used to enhance diversity in material processing using a single laser. In this study, we propose setup design modification of an ultrafast laser system to demonstrate both Tin Oxide (SnO2) nanoparticle synthesis from bulk metal, and post printing of said nanoparticles using Laser Induced Forward Transfer (LIFT) method. Using the Pulse Laser Ablation in Liquid (PLA-L) method, nanoparticles were synthesized from a bulk tin metal cube submerged in distilled water. Such nanoparticles dispersed in water can form colloidal ink that can be used for different printed electronics applications. Pulse energy was varied to investigate the influence on morphological properties of the nanoparticles. It was observed that a decrease in average particle size, and an increase in the number of particles synthesized occurred as the pulse energy was increased. In our study, we adapted the same laser system to enable LIFT operation for printing of the SnO2 nanoparticles. The colloidal ink prepared was then used in LIFT method to study feasibility of printing the synthesized nanoparticles. By varying not only the laser parameters but process parameters such as coating thickness and drying time, printed results can be improved. Experimental results show great potential for both synthesizing and printing of the nanoparticles using a single laser system. This study serves as a proof of concept that a single laser system can turn bulk metal into nanoparticles-based applications without the need for extra processing from other machines/systems, opening the door to highly customizable prints with reduced lead times.
Extracting the In-Process Structural Dynamics Parameters in Micro-Milling Operations
Authors: Hashemitaheri Maryam , Mittal Rinku , Cherukuri Harish , Singh Ramesh
Published: September 2022

Stability properties of micro-milling operations are characterized by the Stability Lobe Diagram (SLD). The material removal rates during micro-milling operations depend on the optimal values chosen for the depth of cut and also spindle speed. Theoretically, the stability boundary is calculated having the structural dynamics and the cutting parameters. However, some discrepancies are usually observed between the empirical results and the expected results that the theory supports. The driver of such a gap is that the dynamics is affected during machining operation by parameters such as the spindle speed, cutting loads, thermal changes, feed rate, etc whereas the theory is based on the structural dynamics parameters in the idle state of the machine (zero speed). Consequently, the selection of chatter-free values for cutting depth and spindle speed based on SLD in the idle state of the machine is not reliable. In addition, measuring structural dynamics parameters under cutting conditions is difficult. In this study, a novel approach is introduced to determine in-process structural dynamics parameters based on a multivariate Newton-Raphson method. Having the empirical SLD characterized by experimental data, our method tries to find the structural parameters under which the theory can support the given empirical SLD. Note that the theoretical SLD is usually characterized as a function of the cutting and structural dynamics parameters. Here our method follows the inverse flow and utilizes the empirical SLD to return the underlying parameters. The parameters returned by our method are those supported by the physics-based theories. Therefore, our approach is a hybrid method where the physics-based model is combined with the experimental results. For any given empirical SLD, with the cutting parameters fixed, the in-process structural dynamics parameters are determined using the proposed inverse approach. We use a multivariate Newton-Raphson method approach where through the iterations, an initial guess selected for the set of the parameters is adjusted step-by-step until the final set of the parameters can justify the empirical SLD based upon physics-based models.
Size-Based Filtration of Poly-Disperse Micro-Particle by Dipping
Authors: Khalil Md Ibrahim , Khoda Bashir
Published: September 2022

In manufacturing industries, spherical micro-particles are commonly used as (e.g., brazing powder, metal filler, and 3D printing powder) which are produced with droplet-based particle fabrication techniques. Such processes create spherical morphology but introduce polydispersity and follow a continuous exponential pattern commonly expressed with Rosin-Rammler expression. Sorting those micro-particles in a narrower size range is an important but difficult, costly, and challenging process. Here we demonstrate the successful separation of the particles from a poly-disperse mixture with a particle volume fraction of 10% by dipping process. Nickel-based micro-particles (avg. dia. 5.69 μm) are added in a binder-based liquid carrier system. To encounter the gravitational force, external kinetic energy in the form of agitation is applied to ensure the uniform dispersion of the particles. The cylindrical substrate is prepared and dipped in the ‘pseudo suspension’ to separate the particles by adhering to it. The substrate is dried, and images are taken to characterize the separated particles using image J software. A clear size distribution can be observed which is also plotted. Additionally, a relationship between the process parameter and sorted particles has been established. The proposed method is quick, controllable, and easy to implement, which can be a useful tool for sorting wide-range poly-disperse particles.
3D Co-Printability of PCL and Hybrid Hydrogels
Authors: Quigley Connor , Habib Md Ahasan
Published: September 2022

3D bioprinting has recently gained popularity due to its inherent capability of releasing cell-seeded and cell-laden biomaterials in a defined location to fabricate patient-specific scaffolds. Multi-nozzle extrusion-based 3D bio-printing allows the fabrication of various natural and synthetic biopolymers and the investigations of material to material and cell to material interactions, and eventually with a high percentage of cell viability and proliferation. Although natural hydrogels are demanding candidates for bio-printing because of their biocompatibility and high-water content, ensuring the scaffold’s fidelity with only natural hydrogel polymers is still challenging. Polycaprolactone (PCL) is a potential synthetic bioprinting material that can provide improved mechanical properties for fabricated scaffolds, especially bone and cartilage scaffolds. In this paper, application-oriented structural viability such as 3D printability, shape fidelity, and mechanical properties of the scaffolds fabricated by PCL and other natural hydrogel materials will be investigated. Scaffolds will be fabricated using various natural hybrid hydrogels such as Alginate-Carboxymethyl Cellulose; Alginate-Carboxymethyl Cellulose-TEMPO NFC, and PCL simultaneously using various infill densities, applied pressures, print speeds, and toolpath patterns. Shape fidelities of printed scaffolds will be analyzed. This research can help identify optimum natural-synthetic polymer combinations based on the materials interaction, external and internal geometries, and mechanical properties for large-scale multi-material bio fabrication.
A Study on the Effect of Nozzle Geometrical Parameters on Supersonic Cold Spraying of Droplets
Authors: Akin Semih , Wu Puyuan , Nath Chandra , Chen Jun , Jun Martin Byung-Guk
Published: September 2022

Supersonic cold spraying of droplets containing functional nanomaterials is of particular interest in advanced thin-film coating, that enabling high-adhesion strength particle deposition. In this method, coating occurs when the particles are accelerated to supersonic velocities in a converging-diverging nozzle, and then impact onto a target surface. Here, the optimum design of the nozzle is essential to deal with low-inertia particles like droplets. In particular, nozzle geometrical parameters (i.e., throat diameter, exit diameter, divergent length) determine droplets’ acceleration and deposition characteristics under supersonic flow conditions. To this end, we thoroughly investigate the influence of nozzle geometrical parameters on droplets acceleration by numerical modeling followed by experimental validation, and a case study on surface coating application. Two-phase flow modeling was used to predict droplets’ behavior in continuous gas flow for different nozzle configurations. The results show that the nozzle expansion ratio — a function of throat and exit diameters — has a significant influence on droplet velocity, followed by divergent length. In particular, to correctly accelerate low-inertia liquid droplets, optimum nozzle expansion ratio for an axisymmetric convergent-divergent nozzle is found to be in a range of 1.5–2.5 for various sets of parameters, which is different than the recommended expansion ratio (i.e., 5–9) for cold spraying of micro-scale metal particles. The findings can help determine the ideal design of a supersonic nozzle to minimize turbulent velocity fluctuation and shock wave formation that in turn assist to effectively spray low-inertia particles like micro-scale droplets. Based on the simulation results, an optimal design of supersonic nozzle is selected and prototyped for the experimental studies. Numerical modeling results are validated by particle image velocimetry (PIV) measurements. Moreover, coating experiments confirm the adaptability of the optimized nozzle for supersonic cold spraying of droplets containing nanoparticles, which thereby has the potential for rapid production of advanced thin films.
Effect of Withdrawal Velocity on Particle Entrainment From Density Mismatched Mixture
Authors: Shovon S. M. Naser , Khalil Ibrahim , Alam Adeeb , Khoda Bashir
Published: September 2022

In this work, the physical phenomenon of the polydisperse micro-particle entrainment process from density mismatch mixture is investigated with the variation of substrate withdrawal speed. A liquid carrier system (LCS) is prepared by a polymer-based binder and an evaporating solvent. Nickel-based inorganic and spherical particles with a. moderate vol%. of 35% are added to the LCS solution. The cylindrical AISI 1006 mild steel wire substrate is dipped at different withdrawal speed ranging from 0.01 mms-1 to 20 mms-1. The binder vol%. is varied between 6.5% and 10.5%. Once the cylindrical substrate is extracted from the mixture, the surface coverage and the particle size are measured following the image analysis technique. The average particle size, coating thickness and the surface packing coverage by the particles are increasing with the higher withdrawal speed of the substrate. We observed relatively low size of particles (< 10 micrometers) as well as low surface coverage (∼33%) when the withdrawal speed remains at 0.01 mm/s. However, with high withdrawal speed (20 mm/s), we found all sizes of particles present on the substrate with a surface coverage of over 90%. The finding of this research will help to understand the high-volume solid transfer technique and develop a novel manufacturing process.
An Investigation Into Multi-Track Deposition in Laser Powder-Bed Fusion: Transient Regions Analysis and Scan Length Effects
Authors: Rauniyar Santosh , Shrestha Subin , Chou Kevin
Published: September 2022

Laser powder bed fusion (L-PBF) additive manufacturing has been used to fabricate complex-shaped structures, which often consist of fine features. Due to transient process phenomena, there are differences in terms of the melt pool formation and the surface morphology depending upon the feature area and scan parameters. This study investigates the scan length effect on the surface morphology and the presence of transient length and width that may have a significant effect as the layer addition continues. For this purpose, four scan lengths (0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm) are used to fabricate six tracks with back-and-forth scanning. A full factorial design of experiments is used to form multi-track depositions with three levels of power (125 W, 160 W, and 195 W), two levels of scan speed (550 mm/s and 1000 mm/s), and four levels of hatch spacing (80 μm, 100 μm, 120 μm, and 140 μm). A white light interferometer is used to acquire the surface data, and MATLAB is used for surface topographical analysis. The results indicated that the scan length has a significant effect on the surface characteristics. The average height of multi-track deposits increases with the decrease of the scan length. Moreover, the transient length and width can be approximated based on the height variation along both the scan and transverse directions, respectively.
Immersive Virtual Reality Training With Error Management for CNC Milling Set-Up
Authors: Ryan Matt , Wang Yiwen , Xiao Qinqin , Liu Rui , Zhang Yunbo
Published: September 2022

In order to address the demand for skilled machinists and limitations with current training programs, we introduce an immersive Virtual Reality (VR) CNC machining training environment for CNC machine setup processes with a novel error management based training curriculum. Current machinist training programs are several years long requiring active mentorship from a skilled individual and are very costly due to the materials and tools required. Mistakes and errors made during the set up process can create safety risks, waste material and break equipment requiring additional time to reset. Existing VR CNC milling training environments fail to address mistakes that can occur during the setup process. In order to address these operational challenges, a novel error-management based training in VR is proposed which allows trainees to learn the set up procedure,learn the common errors & mistakes and practice identifying errors in addition to practicing activities for the setup. The training first introduces students to the setup procedure, followed by demonstrations of error cases and identification and management strategies culminating in practice opportunities. Trainees witness a spatial demonstration of the procedure, guided by auditory and text instructions. Users are able to actively explore the spatial teaching environment while controlling a virtual CNC milling machine. A preliminary user training test is performed comparing the VR method to a video training and a video training with error management curriculum.
Modeling Maximum Stresses in Each Layer for Layer-by-Layer Deposition of the Direct Metal Laser Sintering Process for Different Scanning Patterns
Authors: Tang Joseph , Sezer Hayri , Ahsan Nazmul , Ahmed Hossain , Kaul Sudhir
Published: September 2022

In this paper, maximum stresses from the Direct Metal Laser Sintering (DMLS) process are numerically calculated for each layer using a novel computational model that has been developed to capture the layer-by-layer deposition. The computational domain with all layers is modeled numerically with conduction, while using convection and radiation on the model boundaries. The phase change of the material between liquid and solid states is accounted for and the residual thermal stresses are obtained from the temperature gradient data in conjunction with Hooke’s law. The resulting maximum stress versus time behavior and maximum stress distribution patterns on each layer are complex and do not always match the scanning path. However, there is direct correspondence between the stress distribution and the scanning patterns.