Assisted Machining Research Articles

Dynamic evolution simulation of ablation zone in water-jet assisted laser machining of Korean pine (Pinus koraiensis)

In order to solve the difficulties with the observation of the ablation zone and the many factors that affect the dynamic evolution process of the ablation zone, the structural morphology and dynamic evolution process of the ablation zone in the process of water-jet assisted laser machining Korean pine (Pinus koraiensis) were studied. Based on the DFLUX subprogram, a compound heat source model was established. Under the comprehensive consideration of heat conduction, heat convection, heat radiation, and thermal physical properties varying with temperature, the three-dimensional (3D) finite element model of the Korean pine was numerically simulated by water-jet assisted laser machining. Through numerical simulation analysis, the cross-sectional morphology of Korean pine kerf was found to be screw-shaped, and the experimental results were in good agreement with the simulation results. The dynamic evolution law of water-jet assisted laser machining of Korean pine was obtained. In addition, as the laser power increased and the cutting speed decreased, the morphology of the Korean pine kerf remained unchanged, but the structure size of the Korean pine kerf showed an increasing change.

A Review of the Preparation, Machining Performance, and Application of Fe-Based Amorphous Alloys

Amorphous alloy is an emerging metal material, and its unique atomic arrangement brings it the excellent properties of high strength and high hardness, and, therefore, have attracted extensive attention in the fields of electronic information and cutting-edge products. Their applications involve machining and forming, make the machining performance of amorphous alloys being a research hotspot. However, the present research on amorphous alloys and their machining performance is widely focused, especially for Fe-based amorphous alloys, and there lacks a systematic review. Therefore, in the present research, based on the properties of amorphous alloys and Fe-based amorphous alloys, the fundamental reason and improvement method of the difficult-to-machine properties of Fe-based amorphous alloys are reviewed and analyzed. Firstly, the properties of amorphous alloys are summarized, and it is found that crystallization and high temperature in machining are the main reasons for difficult-to-machine properties. Then, the unique properties, preparation and application of Fe-based amorphous alloys are reviewed. The review found that the machining of Fe-based amorphous alloys is also deteriorated by extremely high hardness and chemical tool wear. Tool-assisted machining, low-temperature lubrication assisted machining, and magnetic field-assisted machining can effectively improve the machining performance of Fe-based amorphous alloys. The combination of assisted machining methods is the development trend in machining Fe-based amorphous alloys, and even amorphous alloys in the future. The present research provides a systematic summary for the machining of Fe-based amorphous alloys, which would serve as a reference for relevant research.

A novel design of ultrasonic vibration system: asymmetric structure

This paper designs an acoustic system of asymmetrical structure based on the theory of wave. Firstly, the frequency equation of asymmetric structural horn (ASH) was obtained by wave theory, the structural dimension of ASH was calculated based on frequency equation. Then, the influence law of different structural parameters on the resonance frequency and amplification coefficient of ASH was obtained. Simulation results demonstrated that the minimum error of the resonant frequency of the designed horn was 0.16%, and the maximum error was 7.57%. Effect of the change of the horn geometry on the acoustic parameters of the acoustic system was analyzed, and the results manifest that the order of influence on the resonance frequency was , the order of influence on the amplification coefficient was . Finally, the variable horn was processed in segmented and integral two processing methods, and its acoustic performance was tested. Results indicated that the vibration form of the horn output was the vertical vibration accompanied by the slightly curved vibration and the longitudinal vibration amplitude of ASH with resonant frequency of 30–35 kHz can reach 5 . ASH meets the requirements of amplitude in ultrasonic assisted machining and can further expand the application field of ultrasonic machining.

A novel tool wear suppression method for polycrystalline diamond by applying magnetic field in turning of ferrous materials

Ferrous materials are widely used in the mould industry because of their excellent properties. However, ferrous materials are regarded as difficult-to-cut materials for diamond turning due to their affinity for diamond. The resulting catastrophic tool wear leads to high machining costs in ultraprecision turning. The unpaired d-electrons in the workpiece are regarded as the dominant element causing catastrophic diamond wear during the turning. However, an insightful method for unpaired d-electrons in existing assisted machining schemes is still lacking. As a type of diamond tool, polycrystalline diamond (PCD) tools are inexpensive to appropriately carry out wear experiments. Therefore, in this study, a novel assisted method based on a magnetic field (MF) was applied to suppress the PCD tool wear. Experimental results demonstrated that the MF-assisted machining can reduce the flank wear of PCD tools by 30.6%. The spin polarisation of d-electrons by the MF was the dominant mechanism inhibiting the chemical reaction and graphitisation, and thus suppressing the PCD tool wear. Simultaneously, the suppression of machining system vibration by the Lorentz force also had a positive effect on the suppression of the PCD tool wear. The innovative method provides an assisted machining scheme to inhibit the catastrophic wear of PCD tools.

Artificially Intelligent, Interactive, and Assistive Machines: A Definitional Framework for Intelligent Assistants

Intelligent assistants have proliferated across various settings spurring research and ideas. However, there is a lack of clarity on how they can be defined and identified. This definitional and terminological incoherence manifests in narrow and misinformed understanding of technology and thus, poses threats to theoretical and empirical endeavors in AI. To overcome these challenges, this paper presents a definitional framework that defines intelligent assistants and distinguishes them from other technologies. This framework is informed by tracing the historical evolution of this technology in the past 70 years which saw the rise of three constitutive features in machines: AI, interaction, and assistance. A review of technology’s definitions published since 2010 and associated terminologies was also conducted to unpack their conceptual limitations and support the framework. A new definition is then presented which contends that a technology can only be characterized as an intelligent assistant if it is AI-enabled, interactive, and assistive.

Towards understanding the ploughing friction mechanism in ultrasonic assisted grinding with single grain

Despite the widespread use of ultrasonic vibration in machining (i.e., grinding) due to friction reduction, the friction mechanism at the tool-workpiece contact is still unclear. Most of the explanations focus on the kinematic analysis, but few attempts have been made to understand the deformation process of the tool-workpiece contact under ultrasonic vibration. This work presents a novel prediction model to calculate the ploughing friction coefficient with the two-dimensional ultrasonic vibration assistance (imposed transverse vibration and additional normal vibration). Considering the ploughed surface generation, the actual contact area and the distribution of friction stress could be predicted. Particularly, the instantaneous contact area with a complex motion path was solved by generating the ploughed surface and calculating the overlapping area of the particle geometry engaged with the generated groove. Experimental results agree well with the predicted results. In addition to the deflection of resultant velocity, the friction reduction is also attributed to the change in friction stress distribution due to three special contact states. This research can deepen the understanding of tool-workpiece friction reduction mechanism in ultrasonic assisted grinding and might provide an important reference for studying other ultrasonic assisted machining processes.

A Review of CO2 Coolants for Sustainable Machining

In many machining operations, metalworking fluids (MWFs) play an invaluable role. Often, proper application of an intelligent MWF strategy allows manufacturing processes to benefit from a multitude of operational incentives, not least of which are increased tool life, improved surface integrity and optimised chip handling. Despite these clearly positive implications, current MWF strategies are often unable to accommodate the environmental, economic and social conscience of industrial environments. In response to these challenges, CO2 coolants are postulated as an operationally viable, environmentally benign MWF solution. Given the strong mechanistic rationale and historical evidence in support of cryogenic coolants, this review considers the technological chronology of cryogenic MWF’s in addition to the current state-of-the-art approaches. The review also focuses on the use of CO2 coolants in the context of the machining of a multitude of material types in various machining conditions. In doing so, cryogenic assisted machining is shown to offer a litany of performance benefits for both conventional emulsion (flood) cooling and near dry strategies, i.e., minimum quantity lubrication (MQL), as well as aerosol dry lubrication (ADL).

Environmental, technological and economical aspects of cryogenic assisted hard machining operation of inconel 718: A step towards green manufacturing

It is critical in today's modern manufacturing era to have a machining system that is both environmentally and economically beneficial. It is therefore necessary in many ways to illustrate a relationship between technological, economic and sustainability measures in the machining of Inconel 718. In present investigation, the experimental studies are incorporated by the use of the dry and MQL (minimum quantity lubrication) environments, as well as cryogenic-LN2 and cryogenic-CO2 environments. In terms of technological, sustainability, and economic metrics, the results show that cryogenic-LN2 performed better, followed by cryogenic-CO2, MQL, and dry conditions. As turning Inconel 718, LN2 assisted machining reduce total machining costs and energy usage considerably when compared to dry, MQL, cryogenic-CO2 environments. In addition, the LN2 cooling environment has been shown to significantly reduce machining outputs such as cutting force, tool wear, and surface roughness. LN2 conditions was found to be most promising as it has decreased the cutting force by 32.1%, tool flank wear by 33.33% and total energy consumption by 18% compared to dry machining conditions. It's worth noting that modern lubri-cooling technologies help the aerospace sector be more sustainable by decreasing resource consumption, enhancing environmental advantages, and improving machining features.

Improving machining stability of AISI-4140 with magnetic field

Several methods have been developed in order to improve the traditional machining processes and machining outputs. In this study, the effect of the magnetic field on the turning process was investigated. AISI-4140 was machined with different cutting speeds and magnetic flux density magnitudes. The magnetic field was generated with neodymium magnets. Machining stability, surface roughness, and maximum cutting temperature were measured. Additionally, chip shapes were examined. The machining stability was determined by measuring the vibration amplitude and other vibrational parameters (natural frequency, stiffness, and damping coefficients). Conventional turning and magnetic assisted turning were performed under the same cutting parameters consecutively, and the results were compared. According to the results, it was observed that neodymium magnets attached to the cutting tool improve machining stability and damping properties. Surface roughness was decreased between 6%–10% in magnetic assisted turning. Furthermore, it has been observed that the maximum cutting temperatures have been increased between 10%–45% in the magnetic assisted machining. Besides, it can be said that magnets contribute to improving chip control by collecting the chips on them while machining AISI-4140 steel.

Development and Preliminary Evaluation of a New Apple Harvest Assist and In-Field Sorting Machine

HighlightsA new, improved apple harvest assist and in-field sorting (HAIS) machine was developed.The HAIS machine has several major innovations for enhanced harvesting and infield sorting efficiencies.Laboratory tests showed superior performance in fruit grading and sorting and bin filling and handling.Field tests showed only 0.4% of harvested fruit downgraded due to harvest-induced bruising.Abstract. Apples are still manually harvested in the U.S. and other countries, which contributes to high labor and production costs. Currently, no presorting is performed at harvest or in the field, which could incur significant postharvest costs or even economic loss to growers, when a high percentage of culls are present in harvested apples. Hence, technologies that integrate harvest assist and in-field sorting (HAIS) functionalities would be greatly beneficial to the apple industry by enhancing both harvest efficiency and postharvest cost savings. A new apple HAIS prototype machine was recently developed, which includes adjustable picking platforms with fruit receiving conveyors covering the entire height of trees, a computer vision-based grading and sorting system that is capable of sorting apples for color and size at a speed of up to 12 apples s-1, an automatic bin filling system for discharging graded fruit to bins, and a computer-controlled hydraulic system for automatic handling of empty and full bins. Inhouse developed operating software is fully integrated with the HAIS machine for automatic control of fruit grading and sorting and bin filling and handling. Laboratory tests showed superior performance of the machine in fruit grading and sorting and bin filling and handling. Field tests and demonstration (https://www.youtube.com/watch?v=21SB9FJjf2M) conducted in a commercial apple orchard in 2019 harvest season, showed that only 0.4% of harvested fruit were downgraded due to bruising, which exceeded the industry’s requirement for harvest-induced apple bruising. With further improvements, the HAIS machine can be commercially used for harvesting and infield presorting of apples. Keywords: Apple, Bin filling, Bruise evaluation, Bin handling, Computer vision, Harvest, In-field sorting.

Investigation of in-situ cryogenic assisted machining of 2205 duplex stainless steel in AWJM

An experimental investigation on Abrasive Water Jet Machining (AWJM) of duplex steel at cryogenic temperatures is discussed in this work. Material removal takes place in AWJM by abrasive induced fracture. The lowering of temperature during machining induces brittleness in metallic material. Hence, by reducing the temperature of the work piece, the occurrence of abrasive induced fracture can be promoted and the MRR will be increased. In this study, a 2205 duplex stainless steel block of thickness 20 mm and diameter 70 mm was selected as a work piece for the investigation due to its high toughness at normal temperature. Piercing experiments were conducted at three different pressures (254, 271, and 302 MPa) and three different stand-off distances (SOD) (2, 3, 4 mm). The work piece is machined at non-cryogenic temperatures between 28 °C and 35 °C. Subsequently, it is repeated at cryogenic conditions with the temperature ranges below −50 °C and their respective piercing times are noted. Comparison of machining at the normal and cryogenic temperatures, with a high pressure of 302 MPa and SOD of 4 mm, revealed 28.57% reduction in piercing time while machining under cryogenic temperature. Where-as, at low pressure of 254 MPa and SOD of 2 mm, the reduction in piercing time for machining at cryogenic temperature is about 5.84% only.

PCM assisted reverse electro discharge machining process for pattern generation

ABSTRACT This research work reports about pattern generation using the photochemical machining (PCM) assisted reverse electro discharge machining (EDM) process on an aluminum 6061 workpiece. A mixture of fine powder of copper and tungsten is used to fabricate a green compact tool. A complex shape is generated onto the tool surface and is further implemented to migrate the shaped tool particle onto the work surface. The output parameters are the material deposition rate (MDR), tool wear rate (TWR), edge deviation (ED), and surface roughness (Ra). The pattern is characterized by Field Emission Scanning Electron Microscopy (FESEM) and Energy Disperse Spectroscopy (EDS) analyses. The presence of tungsten particles increases the microhardness of the substrate material. The surface microhardness of the pattern is found to be 362Hv.

Enhancement of machining and surface quality of quaternary alloyed NiTiCuZr shape memory alloy through ultrasonic vibration coupled WEDM

NiTiCuZr shape memory alloys (SMA) outperform ternary and binary SMA alloys in terms of functional fatigue and higher temperature performance due to their high cyclic stability and transformation temperatures. Owing to the impairment of the shape memory effect during processing, it is difficult to select a manufacturing process for obtaining design functionality with the required dimensions and surface roughness. In this work, a high-temperature NiTiCuZr SMA was machined using an ultrasonic vibration assisted wire electric discharge machine (USV-WEDM). The machining was conducted using various parameters with a constant ultrasonic vibration of 20 kHz provided on a wire-electrode to evaluate surface roughness (Ra) and material removal rate (MRR). Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray analysis (EDX) were utilized to examine the surface integrity and chemical composition of the machined surfaces. MRR increased by 62% with a steady increase in pulse-on time ( Ton) and applied current ( I), whereas increasing levels of parameters such as pulse-off time ( Toff) and servo voltage (SV) reduced surface roughness ( Ra) by 69%. The results reveal that tool vibration at ultrasonic frequency reduces the surface roughness and improves the material removal rate of the machined NiTiCuZr SMA as compared to that of non-ultrasonic assisted machining conditions. SEM-EDX investigation reveals that the formation of re-solidification and oxide layers during NiTiCuZr machining at high machining parameters results in increased hardness and surface roughness. USV-WEDM is a suitable process for machining SMA alloy without adversely impacting SMA properties.

Optimal Design and Verification of Standing-up Motion Assistant Machine

Standing-up motion assistant machine is a new type of assistant device for the care and motion of the semi-disabled, which can replace the manual motion mode to a great extent and reduce the workload of the care-givers. After a detailed analysis of shortcomings of the structural design of the existing standing-up motion assistant machine in the practical application in elderly institutions, this paper proposes a design scheme and mechanical structure of the hanger. The optimized product is verified based on ergonomics theory. Results show that the design scheme and structure of the hanger of the motion assistant machine proposed in this paper can satisfy the requirements of occupant comfort on the premise of ensuring safety, as well as effectively expand the application of the standing-up motion assistant machine in elderly institutions of varied facility levels.

A Fuzzy Logic Model for the Analysis of Ultrasonic Vibration Assisted Turning and Conventional Turning of Ti-Based Alloy.

Titanium and its alloys are largely used in various applications due its prominent mechanical properties. However, the machining of titanium alloys is associated with assured challenges, including high-strength, low thermal conductivity, and long chips produced in conventional machining processes, which result in its poor machinability. Advanced and new machining techniques have been used to improve the machinability of these alloys. Ultrasonic vibration assisted turning (UVAT) is one of these progressive machining techniques, where vibrations are imposed on the cutting insert, and this process has shown considerable improvement in terms of the machinability of hard-to-cut alloys. Therefore, selecting the right cutting parameters for conventional and assisted machining processes is critical for obtaining the anticipated dimensional accuracy and improved surface roughness of Ti-alloys. Hence, fuzzy-based algorithms were developed for the ultrasonic vibration assisted turning (UVAT) and conventional turning (CT) of the Ti-6Al7Zr3Nb4Mo0.9Nd alloy to predict the maximum process zone temperature, cutting forces, surface roughness, shear angle, and chip compression ratio for the selected range of input parameters (speed and depth-of-cut). The fuzzy-measured values were found to be in good agreement with the experimental values, indicating that the created models can be utilized to accurately predict the studied machining output parameters in CT and UVAT processes. The studied alloy resulted in discontinued chips in both the CT and UVAT processes. The achieved results also demonstrated a significant decline in the cutting forces and improvements in the surface quality in the UVAT process. Furthermore, the chip discontinuity is enhanced by the UVAT process due to the higher process zone temperature and the micro-impact imposed by the cutting tool on the workpiece.

The Impact of Control Interface on Features of Heart Rate Variability.

Shared human-robot control for assistive machines can improve the independence of individuals with motor impairments. Monitoring elevated levels of workload can enable the assistive autonomy to adjust the control sharing in an assist-as-needed way, to achieve a balance between user fatigue, stress, and independent control. In this work, we aim to investigate how heart rate variability features can be utilized to monitor elevated levels of mental workload while operating a powered wheelchair, and how that utilization might vary under different control interfaces. To that end, we conduct a 22 person study with three commercial interfaces. Our results show that the validity and reliability of using the ultra-short-term heart-rate variability features as predictors of workload indeed are affected by the type of interface in use.

Using nominal group technique to advance power assisted exercise equipment for people with stroke

BackgroundPower assisted exercise is accessible and acceptable for people with stroke. The potential for technological advancement of the equipment to improve the user experience has been identified. Involvement of end users and service providers in the design of health technologies is essential in determining how said technology is perceived and adopted. This project invited people with stroke and service providers to influence design features and determine machine selection in the preliminary stages of a codesign research programme.AimsTo capture the perspectives of people with stroke and professionals working with people with stroke about proposed digitalisation of power assisted exercise equipment and select machines for prototype development.MethodsNominal group technique was used to capture the perspectives, ideas, preferences and priorities of three stakeholder groups: people with stroke (n = 3, mean age 66 years), rehabilitation professionals (n = 3) and exercise scientists (n = 3). Two questions underpinned the structure of the events; ‘What does an assistive exercise machine need to do to allow the person with stroke to engage in exercise?’ and ‘Which machines would you prioritise for use with People with Stroke?’ Attendees were invited to cast votes to indicate their preferred machines.FindingsSynthesis of the data from the NGT identified four domains; software and interface, exercise programme, machine and accessories, setting and service. Three preferred machines from a range of nine were identified through vote counting.ConclusionNominal group technique directed the selection of machines to be included in the development of the proposed technology. The vision shared by users during the structured discussion shaped the subsequent steps in the design and testing of the new technology.Patient and service provider contributionThe opinions and preferences of people with stroke, rehabilitation professionals and exercise scientists were central to key decisions which will shape the digitalisation of power assisted equipment, influence future research and guide implementation of the new technologies.

Sustainability-based holistic assessment and determination of optimal resource consumption for energy-efficient machining of hardened steel

Advance cooling/lubrication (lubricooling) approaches are getting fame in industry and academia due to their excellent performance. A significant amount of work has been conducted to investigate the effect of various lubricooling approaches on the machinability of the hardened steel. However, sustainability-based performance evaluation of lubricooling assisted machining is missing. Thus, this paper presents 3E-based (Energy, Economics, Environment) analysis to compare the performance of various lubricooling approaches.Initially, preliminary experiments were performed to achieve optimal flow rates of various cutting fluids used in Minimum Quantity Lubrication (MQL), cryogenic cooling, and conventional emulsion (Flood) approaches. Later, optimal flow rates were used to achieve equal cutting-tool life under all machining environments. Results showed that with the same tool life method (STLM), Cryogenic-MQL(CryoMQL) could withstand aggressive cutting speeds and produce the highest productivity among all lubricooling approaches. In addition, it yielded 50% lower-priced specific production cost as compared to dry machining. However, 44.3% more specific-CO2 emitted in CryoMQL as compared with dry machining. In summary, the hybrid CryoMQL assisted machining process is sustainable economically but not environmentally. The outcomes of the present study provide useful information, and it can help machinist to enhance the process performance.

Sulfuric Acid Etching for Surface Modification and Improved Polishing of Magnesium Aluminate Spinel

Magnesium aluminate spinel is a material with high optical transparency and great potential for optical applications. However, its high hardness, high strength and chemical inertness make obtaining the required surface quality quickly through traditional processing a challenge. Existing assisted machining methods are complicated and costly, which limits their application to high-efficiency and ultra-precision manufacturing. In this study, etching was employed as a polishing preprocess owing to its obvious advantages of simplicity, practicality and low cost. Sulfuric acid was applied to etching spinel, and the influences of the etching temperature and time on the surface morphology and mechanical properties of the spinel were evaluated. Surface analytical techniques were performed to clarify the mechanism for improved polishing. Experimental results indicated that sulfuric acid etching significantly reduced the surface hardness. The surface quality and efficiency were significantly improved with the etching pretreatment compared with traditional chemical mechanical polishing. Thus, the proposed method of sulfuric acid etching-assisted polishing can reduce the difficulty of spinel machining to realize the high-efficiency and precision manufacturing for a wider range of applications.

Numerical investigation on subsurface damage in nanometric cutting of single-crystal silicon at elevated temperatures

Achieving nanometric surface on single-crystal silicon is important for semiconductor and optoelectronics industries. In recent years, thermal assisted machining (hot machining) raises as an effective technique for high-quality surface fabrication of single-crystal silicon. However, the formation mechanism of the subsurface damage at elevated cutting temperatures is still unclear. In this paper, molecular dynamics simulation and cutting experiments were conducted to study the subsurface damage evolution in single-crystal silicon at elevated cutting temperatures. The cutting mechanism and behavior of the amorphous phase were investigated. The results indicate that with an increase of the cutting temperature, the subsurface damage can be greatly suppressed and the cutting mechanism can be distinct with ordinary cutting. Furthermore, the lubricant effect of the amorphous layer and the recrystallization process are determined as two important reasons for suppression of the subsurface damage at high cutting temperature. The lubricant effect reduces the deformation of the crystal substrate and decreases the frictional coefficient during cutting. While the recrystallization mainly occurs before the compressive stress decrease to zero, which causes point-like subsurface damage and thinner amorphous layer on the machined surface.