Internal Finishing Research Articles

Internal surface finishing and roughness measurement: A critical review

Internal surface finishing and roughness measurement: A critical review

Experimental Investigation on Magnetic Abrasive Finishing for Internal Surfaces of Waveguides Produced by Selective Laser Melting.

To enhance the surface quality of metal 3D-printed components, magnetic abrasive finishing (MAF) technology was employed for post-processing polishing. Experimental investigation employing response surface methodology was conducted to explore the impact of processing gap, rotational speed of the magnetic field, auxiliary vibration, and magnetic abrasive particle (MAP) size on the quality enhancement of internal surfaces. A regression model correlating roughness with crucial process parameters was established, followed by parameter optimization. Ultimately, the internal surface finishing of waveguides with blind cavities was achieved, and the finishing quality was comprehensively evaluated. Results indicate that under optimal process conditions, the roughness of the specimens decreased from Ra 2.5 μm to Ra 0.65 μm, reflecting a reduction rate of 74%. Following sequential rough and fine processing, the roughnesses of the cavity bottom, side wall, and convex surface inside the waveguide reduced to 0.59 μm, 0.61 μm, and 1.9 μm, respectively, from the original Ra above 12 μm. The findings of this study provide valuable technical insights into the surface finishing of metal 3D-printed components.

Holistic design of energy-efficient temporary houses: Meeting ventilation, heating, cooling, and lighting demands

Recent disasters around the world have brought attention to the challenges faced by the homeless. Energy-efficient container houses (EECHs) offer a comfortable, sustainable, and temporary solution. A holistic design of EECH was conducted for mixed and hot climates using DesignBuilder software. The design, performed initially according to design criteria derived from ASHRAE Standards and previous studies, was subsequently examined for five passive strategies: envelope layering, WWR, windows opening ratio, glazing type, and shading. Optimal conditions were determined by the trade-off between heating and cooling demands, ventilation rate, and minimum daylight factor (DF) and uniformity (UDF). Results reveal that in mixed climates, using insulation materials and thermal mass is recommended, while in hot climates, it is advisable to avoid using them and instead rely solely on internal finishing layers. Complete reliance on natural ventilation is achieved by combining an opening ratio of 35 % with a WWR of 9%–25 % for south and north facades, and 6%–12 % for west façade. In mixed climates, argon gap double clear glazing is suitable, while a low-e layer is added for hot climates. Installing overhangs on south windows enhances UDF, unlike vertical fins on north and west windows. The designed EECHs consume 176 kWh/m2 of electricity annually.

Hydrodynamic flexible spindle (HydroFlex) polishing for internal surfaces of complex channels with high aspect ratio

Internal surface finishing of complex channels fabricated by additive manufacturing (AM) is of large consequence to the future functionality of AM components. Conventional fluid-based internal polishing methods struggle to maintain surface finish uniformity and dimensional integrity especially in long, complex channels with correspondingly high aspect ratios. In this study, we introduce a novel hydrodynamic flexible spindle (HydroFlex) polishing process, in which a fixed diamond abrasive wheel is driven by a high-speed flexible spindle and the hydrodynamic force from the flow pattern surrounding the wheel. The performance of HydroFlex polishing in long, complex channels was experimentally investigated. HydroFlex polishing was evaluated in both straight and curved channels with wheel speeds of 50,000, 70,000, and 90,000 rpm and wheel sizes of 1.75, 2.00, and 2.25 mm. Surface finish, grinding forces, dimensional integrity, and surface uniformity were quantitatively compared. This technique improved surface roughness by 88.2% with sub-micron roughness obtained. Channels with varied curvature and length were consistently polished with deviation in roughness and material removal being 7% and 11% indicating uniformity in material removal, and surface roughness improvement regardless of part geometry. Rotational speed and grinding wheel size were found to directly correlate with grinding force and cutting motion. The findings show the potential of HydroFlex polishing being used for uniform, surface roughness improvement in complex, high aspect ratio channels such as those produced by AM processes.

A Study on Using Magnetic Abrasive Finishing with a 6-Axis Robot to Polish the Internal Surface Finishing of Curved Tubes

This study proposed a new magnetic abrasive finishing (MAF) method, in which a 6-axis robot with a magnetic machining tool was used to polish the inner surfaces of curved tubes. We have also developed a magnetic machining tool jig, which can be fixed at the front of the 6-axis robot, rotating freely and suitable for polishing the inner surfaces of curved tubes. In this study, we focused on investigating the machining parameters in the initial machining stage and precision finishing stage. Based on the characteristics of machining parameters, a multi-stage MAF process was conducted to obtain an inner surface with high quality and high efficiency. The experimental results showed that both the roughness Ra and Rz of inner surface in the initial machining stage significantly decreased with the increase in the mixed magnetic abrasives, to as low as less than 20 nm Ra in the precision finishing stage when the machining parameters were appropriately adjusted. In addition, the roughness Ra of inner surface could be further reduced to less than 10 nm Ra in the multi-stage MAF process. Finally, the magnetic flux density cloud map and the magnetic field line distribution map were analyzed in Ansys Maxwell.

An Overview of the Latest Progress in Internal Surface Finishing of the Additively Manufactured Metallic Components.

Fast progress in near-net-shape production of parts has attracted vast interest in internal surface finishing. Interest in designing a modern finishing machine to cover the different shapes of workpieces with different materials has risen recently, and the current state of technology cannot satisfy the high requirements for finishing internal channels in metal-additive-manufactured parts. Therefore, in this work, an effort has been made to close the current gaps. This literature review aims to trace the development of different non-traditional internal surface finishing methods. For this reason, attention is focused on the working principles, capabilities, and limitations of the most applicable processes, such as internal magnetic abrasive finishing, abrasive flow machining, fluidized bed machining, cavitation abrasive finishing, and electrochemical machining. Thereafter, a comparison is presented based on which models were surveyed in detail, with particular attention to their specifications and methods. The assessment is measured by seven key features, with two selected methods deciding their value for a proper hybrid machine.

Material Removal Rate Prediction Based on Broad Echo State Learning System for Magnetically Driven Internal Finishing

Material removal rate (MRR) modeling is crucial for process and quality control in abrasive finishing processes. In this paper, a novel broad echo state learning system (BESLS) is developed to predict MRR in the magnetically driven internal finishing process based on the force signal. This BESLS model employs reservoirs with echo state properties to replace the enhancement layer nodes of the conventional broad learning system. Three representative BESLS architectures are designed and experiments are conducted to validate the developed models. The effect of feature-fusion approaches on prediction accuracy is investigated. Results demonstrate that the prediction error of MRR is only 6.86% for the proposed BESLS model. The model has one reservoir with variable nodes (BESLS-III) and fuses extracted force features and process parameters as input. It also shows remarkable computational efficiency with a testing time of 0.134 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\rm s$</tex-math></inline-formula> , making it a potential candidate for online process control.

DLP 3D printing of high strength semi-translucent zirconia ceramics with relatively low-loaded UV-curable formulations

DLP 3D printing is one of the additive manufacturing techniques, which allows the fabrication of ceramic parts with a complex shape, precisely controlled internal architecture and fine surface finishing. The method is based on the layer-by-layer solidification of a photosensitive ceramic suspension via UV-light projection followed by debinding of organic components and sintering and generally requires a high solid content of the ceramic filler to achieve good sintered densification. The present article aims to explore the possibility of fabricating high strength, fully dense and semi-translucent zirconia parts with relatively low-loaded UV-curable systems using a low-cost desktop DLP printer designed for printing polymers. For the slurry preparation, tetragonal zirconia powders from three different suppliers were evaluated. It was shown that with 35 vol% of zirconia content slurries, it was possible to fabricate zirconia semi-translucent ceramics with a density of 99.6%. No cracks or pores larger than 1 μm were observed on the sintered parts. According to ball-on-3-ball mechanical tests performed on the 13 × 1 mm discs an average flexural strength of the printed zirconia ceramics was 1566 MPa and a maximum of 1964 MPa could be achieved.

Study on Elucidation of the Roundness Improvement Mechanism of the Internal Magnetic Abrasive Finishing Process Using a Magnetic Machining Tool

The magnetic abrasive finishing process using the magnetic machining tool was proposed to finish the internal surface of the thick tube (the thickness of the tube is 5~30 mm). It has been proved that this process can improve the roundness while improving the roughness. In this paper, we mainly study the machining mechanism of roundness improvement. Firstly, the influence of finishing characteristics on the roundness improvement was discussed, including the rotational speed of the magnetic machining tool and the rotational speed of the tube. It was concluded that the roundness improvement increases with the increase in the rotational speed through the analysis of finishing force and finishing times. Furthermore, the influence on roundness improvement of different distributions of magnetic particles were experimentally compared. After finishing, due to the magnetic force generated by the magnetic machining tool and the magnetic pole unit exerting pressure on the magnetic particles, a fixed magnetic brush is formed. The experimental results show that the circumferential length of the fixed magnetic brush is different due to the different distribution areas of magnetic particles. It was concluded that the roundness improvement increases with the circumferential length of the fixed magnetic brush increases by discussing the relationship between the circumferential length of the fixed magnetic brush and the wavelength of the roundness curve. When the circumferential length of the fixed magnetic brush is 76 mm, the roundness was improved from 379 μm to 236 μm after 60 min of finishing.

Experimental Examination on Finishing Characteristics of Aluminum Pipes in Magnetic Abrasive Machining Using SiC Contained Glued Magnetic Abrasives

With the rapid development in the industry, applications of finished parts are increasing day by day. However, the surface finish of the parts fabricated by conventional processes could not readily meet the requirements of various applications. Therefore, post-processing is needed to further improve the surface quality. Magnetic abrasive machining uses a flexible magnetic abrasive brush to remove material from the workpiece surface at a controllable rate. This cutting tool sticks to the workpiece during finishing operation and exerts a small force on the surface. In magnetic abrasive machining, the cutting tool neither requires compensation nor dressing. In this paper, the internal finishing of aluminum pipes has been investigated in magnetic abrasive machining tests using silicon carbide-based glued magnetic abrasives. For evaluating the performance of these magnetic abrasives, experimental work according to the central composite design technique was carried out to finish the aluminum pipes. The results so obtained were analyzed to study the influence of process parameters like magnetic field strength, speed of workpiece, abrasive mesh size and quantity of magnetic abrasives on percentage improvement in surface finish and material removal rate. The analysis showed that magnetic field strength was the most effective parameter while finishing the aluminum pipe followed by the quantity of magnetic abrasives. The finishing at optimal condition resulted in a surface finish of 0.07 μm. Further, scanning electron microscopy of the surface before and after magnetic abrasive machining was taken to study the improvement in surface finish.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Magnetic abrasive machining (MAM) of aluminum work specimens have been performed by SiC-based magnetic abrasives&#x0D; The central composite design has been used for planning and execution of experiments&#x0D; The surface finish and material removal rate of the machined work specimens have been analysed as a performance measure of MAM process&#x0D; The high value of improvement in surface finish and material removal rate at optimum machining conditions have been observed&#x0D; Scanning electron microscopy (SEM) has been employed to study the surface topography of machined surfaces&#x0D; &#x0D; GRAPHICAL ABSTRACT

Design and development of ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process

The rotational-magnetorheological abrasive flow finishing (R-MRAFF) process, as one of the derivatives of the abrasive flow finishing (AFF) process, has a high potential for surface modification. However, the R-MRAFF process is a major challenge in terms of finishing time. The present study aims to propose ultrasonic vibration has been proposed as a technical solution to deal with the technological challenges of the R-MRAFF process. A new finishing method called the ultrasonic assisted-rotational magnetorheological abrasive flow finishing (UA-RMRAFF) process has been developed for the first time in which ultrasonic vibrations are applied to the workpiece perpendicular to the magnetorheological polishing (MRP) fluid flow direction. For this purpose, the workpiece was first kept in dynamic condition. Then, an ultrasonic horn was designed using the finite element method (FEM) to apply maximum amplitude to the workpiece. To evaluate the finishing efficiency of the UA-RMRAFF process, experiments were conducted on the internal finishing of Al2024 tubes at different finishing times for investigating and observing its effect on surface roughness (Ra) and material removal (MR). In addition, a comparative study was performed between the UA-RMRAFF and R-MRAFF processes in terms of % change in Ra (%ΔRa) and % improvement in MR. Experimental findings illustrate that the UA-RMRAFF process provides a uniform and fine surface finish without surface defects such as a mirror up to the range of 25.5 nm, in addition to increasing MR. Based on the results of the comparative study, the UA-RMRAFF process performs surface modification faster than that of the R-MRAFF process. While confirming these findings, the morphological and topographic analysis of the surface of the finished samples emphasizes that the main difference between the UA-RMRAFF and R-MRAFF processes is in the sinusoidal motion path of abrasive particles on the workpiece surface asperities, which clearly shows the effect of ultrasonic vibrations.

Toward an Integrated Context-Based Design Approach for Dementia Residential Care Homes: A Review of Key Operational Design Problems.

This article seeks to develop a context-based management system focusing on assessing key operational and design problems and affecting wayfinding in dementia residential care homes. Dementia is multifaceted neurocognitive impairments largely attributed to cognitive deterioration manifested in memory loss and visuospatial deficit which have wider practical implications to both environmental safety and wayfinding and navigation of dementia user. Two key questions were addressed in this context: (1) How can cognitively facilitating assistive technology (AT) be made more user-focused to mitigate the impacts of cognitive impairments on environmental safety and wayfinding? (2) How can design intervention and changes in design topology, colors and texture, and internal finishing aid wayfinding, navigation, and orientation in dementia residential care homes? A systematic literature review and analysis was undertaken to assess the efficacy of key cognitively-related AT to support activities of daily living and environmental safety of dementia sufferers in a care home and aid wayfinding, navigation, and orientation. Several key design variables to facilitate wayfinding and spatial orientation were identified which include design topology, floor finishing, signposting, and use of color and texture strengthened by meaning, emotional connection to places and cognitively focused intervention via memory cueing and objects-centered recognition. Key operational and design guidelines were proposed to assist built environment, care home developers, clinicians and healthcare professionals, and care services providers. There is a need to move toward a dementia-centered design to address the challenges facing people living with dementia in care homes. This should be based on the interrelated behavioral, cognitive, and communication factors.

A Magnetic Abrasive Finishing Process with an Auxiliary Magnetic Machining Tool for the Internal Surface Finishing of a Thick-Walled Tube

This paper proposes a novel magnetic abrasive finishing (MAF) process that uses an auxiliary magnetic machining tool for the internal surface finishing of a thick-walled tube. The auxiliary magnetic machining tool and external poles form a closed magnetic field circuit. Thus, a stronger magnetic force can be generated during the process. In the current study, we focus on analyzing the distribution of the magnetic field and magnetic flux density and investigating the finishing characteristics of a mixed magnetic abrasive finishing process and speed of relative revolutions. Based on the finishing characteristics, we also conduct a stage-by-stage finishing process by changing the combinations of the mixed magnetic abrasive finishing process. The finishing quality of the internal surface was mainly evaluated by the measured roundness and surface roughness. The experimental results show that the roundness and surface roughness Ra are affected when the total amount of WA abrasive and iron powder is too much; a better surface roughness could be obtained when the difference in the speed of relative revolutions is considerable, but the roundness is the worst. Furthermore, the original roundness measurement of 270 µm can reach 10 µm, and the surface roughness Ra can increase from an original surface roughness of 4.1 µm to reach 10 nm after 105 min of the stage-by-stage finishing process.

THE INFLUENCE OF CLIMATIC FACTORS ON THE CHANGE IN THE ELASTIC-STRENGTH INDICATORS OF EPOXY POLYMERS BINDERS USED IN LIQUID THERMAL INSULATION COATINGS

Introduction: Thermal insulating coatings are increasingly being introduced into construction practice for internal and external finishing enclosing structures and pipelines. Thermal insulation coatings are usually made based on polymer binder and mineral fillers. The durability and stability of the properties of heat-insulating materials depend on the type of binder. As a rule, polymers are used as a binder: epoxy resin; silicone rubber; urea-formaldehyde resins; aqueous dispersed polymers - styrene-butadiene, polyvinyl acetate, and acrylate (acrylic and styrene-acrylic). The quality indicator of binders can be assessed by the influence of the seasonality of climatic impact, and as a result, the best elastic strength characteristics of binders can be established after one month to a year of field tests. Aim: To determine the influence of climatic factors on the change in the elastic-strength indicators of epoxy polymers binders used in liquid thermal insulation coatings. Methods: A tensile testing machine of the AGS-X series with the TRAPEZIUM X software was used for mechanical tests. The tests were carried out in accordance with GOST 11262-2017 (ISO 527-2: 2012) "Plastics. Tensile test method". Results and Discussion: The paper discusses the results of experimental studies of the compositions of polymer binders and their resistance to various climatic factors, which will later be used as a polymer binder for thermal insulation coatings based on fine mineral granular systems. Conclusions: When analyzing the changes in the characteristics of polymer samples after exposure to climatic factors, it was found that compositions based on Etal-247 epoxy resin, cured with amine hardeners Etal-1440N, Etal-1460, Etal-1472, and Etal-45M, demonstrate the best elastic strength characteristics after one year of full-scale tests. The high stability of the indicators under consideration allows us to conclude that the use of Etal-247 resin as a base leads to creating of the most climate-resistant epoxy coatings.

Experimental investigations into the nano-finishing of Al2024 tubes using the rotational-magnetorheological abrasive flow finishing (R-MRAFF) process

Aluminum alloy 2024 (Al2024) tubes have extensive applications in the aerospace industry; however, finishing their interior surfaces is a big challenge. In this case, many traditional and advanced machining processes are inefficient due to the limitations of machining tools. To overcome these challenges and limitations, rotational-magnetorheological abrasive flow finishing (R-MRAFF) process has been proposed. In this process, magnetorheological polishing (MRP) fluid, experiences a rotational motion in addition to the reciprocating motion on the workpiece surface asperities. In the present work, the effect of the R-MRAFF processing time on the internal finishing of Al2024 tubes has been investigated experimentally in terms of two essential parameters; surface roughness and material removal. In this regard, an industrial prototype of the R-MRAFF process has been developed. Experimental results express the efficiency of the R-MRAFF process for nano-finishing of Al2024 tubes. The surface roughness and material removal values at a processing time of 15 min are 26.3 nm and 41 mg, respectively. In addition to the morphological observations, the surface topography results emphasize the removal of peaks by the R-MRAFF process, besides creating deep scratches with negative skewness on the surface texture of Al2024 tubes, which results in increased oil holding capacity.

Effects of various reinforcing intra-module connection details on seismic behavior of corner-supported steel modular buildings

The rib stiffeners are usually used to reinforce the intra-module connections in corner-supported modular steel buildings; however, may be conflicted with the internal wall panels. There is a lack of relevant understanding of the effects of reinforcing intra-module connections on the seismic behavior of corner-supported steel modular structures. Therefore, this study investigated the effect of the intra-module connections reinforcing details on the seismic behavior of such modular structures. Such proposed reinforcing measures comply well with the architectural internal finishing demand, including vertical stiffeners or cover plates and an enlarging ceiling beam section. Four full-scale two-story plane frame structures were designed and experimentally examined under lateral cyclic loading to investigate and compare their seismic performance, such as the hysteretic performance, skeleton curves, and strain distribution. The experimental results showed that these reinforcing measures were helpful for the development of plastic deformation of such corner-supported modular structures through effectively moving local buckling away from the beam ends. Moreover, the reinforcing intra-module connection details were able to enhance the force resisting capacity and initial lateral stiffness of the overall structures. Additionally, the nonlinear finite-element (FE) modeling was developed and validated against the corresponding experiment. It showed satisfactory agreement with the failure responses and load–displacement curves. The plastic strains at reinforcing intra-module connection were further analyzed through the validated FE models, and the design suggestions were given accordingly.

Magnetically driven internal finishing of AISI 316L stainless steel tubes generated by laser powder bed fusion

Internal surfaces generated by additive manufacturing (AM) are finding their wide applications in aerospace, automobile, and medical industries. Nevertheless, the poor surface quality resulting from the intrinsic melting and solidification process of laser powder bed fusion (L-PBF) is still a common issue for the full functionality of the fabricated components. Though conventional abrasive-based and chemical-based finishing methods have been recently deployed to improve the surface finish of the AM-ed internal surfaces, they may have limitations and unresolved issues such as low material removal rate, uneven removal and chemical hazards. In this study, magnetically driven internal finishing (MDIF) with magnetic polishing tools is developed to finish the AISI 316L stainless steel tube printed by selective laser melting (SLM), one of the most typical L-PBF processes. Results demonstrate that the surface roughness in single-point polishing and section-polishing experiments can be reduced from the as-printed level of 11.599 μm Ra to 0.385 and 0.808 μm Ra, respectively, within tens of minutes of polishing time. Benchmarking experiments with conventional magnetic abrasive finishing (MAF) shows that the MDIF outperforms MAF in terms of both the final surface finish and efficiency. Besides, a material removal model based on the Abbott-Firestone curve is developed to predict the material removal in mass for the SLM-ed workpiece and the average predicting errors are only 7.9% and 13.4% in the single-point polishing experiment and section-polishing experiment, respectively. This paper provides an efficient alternative to the existing surface finishing methods addressing the poor surface finish of L-PBF internal surfaces.

Internal magnetorheological finishing of a typical outer race of ball bearing

ABSTRACT The outer race is an important component of the ball bearing that supports heavy load from the attached spindle shaft to the inner race via the bearing balls. The machinery that uses bearing for revolving the shaft, their performance depends on the internal surface condition of the outer-race. A typical outer-race of ball bearing (ORBB) of EN-31 steel has been considered to fine-finish its inner surface using the rotational magnetorheological honing (RMRH) in this work. In this research, the response surface methodology approach was used to find out the best finishing variables. From an initial surface roughness of 0.39 µm, a significant surface finish of 0.06 µm was reached after 40 min of RMRH finishing. Furthermore, the surface waviness on the finally finished surface is lessened to 0.08 µm from 0.38 µm on the traditionally honed interior surface of the ORBB, resulting in a substantial increase in straightness. In addition, a circularity test is carried out to see whether the finished surface’s circularity has improved. The change in the surface appearance of the ORBB’s interior surface is explored using a scanning electron microscope test done on its initial honed and finally finished surfaces using the RMRH technique.

Study on Mechanism of Roundness Improvement by the Internal Magnetic Abrasive Finishing Process Using Magnetic Machining Tool

An internal magnetic abrasive finishing process using a magnetic machining tool was proposed for finishing the internal surface of the thick tubes. It has been proved that this process is effective for finishing thick tubes, and it can improve the roundness while improving the roughness. However, the mechanism of improving the roundness is not clear, so it is necessary to study it theoretically. In this research, firstly, the roundness curve expression was derived using the principle of roundness measurement by the assumed center method, and the expression of roundness curve expanded by Fourier series was obtained. The influencing factors of roundness improvement were then analyzed. Secondly, the experiments were carried out on SUS304 stainless steel tubes. By confirming the mechanism analysis results and the experimental results, it was concluded that the internal magnetic abrasive finishing process using the magnetic machining tool was effective for improving the roundness of the thick tubes whose thickness is from 10 mm to 30 mm. As the thickness of the tube increased, the improvement in roundness decreased.

Magnetic field assisted finishing (MFAF) process for internal finishing of alumina ceramic tube

Nowadays, fine surface finish is in great demand for many industrial applications. An MFAF process is discussed in this conference paper to achieve a highly finished internal surface of non-ferromagnetic Alumina ceramic tube. Conventional grinding and polishing techniques cannot be used to finish this material because they cannot achieve high surface precision and produce surface defects like micro cracks. Therefore, MFAF process is an alternative method as it minimizes the surface damage because of flexible finishing conditions. MFAF Process, has flexible abrasive brush which can easily finish complex geometry of the workpiece. The workpiece material is alumina ceramic which is in higher demand as a substrate in electronic device applications. The MFAF process was done on alumina ceramic tube and 3 parameters, each having 2 different levels was selected. The parameters considered in the study are chuck speed (rpm), quantity of Diamond abrasive and iron power, machining time. 4 experiments with different levels of parameters were conducted. After finishing experiment using MINITAB 19 software, optimum parameters were determined. From the results of experiment, it was concluded that quantity of diamond abrasive and iron powder did not have much influence on finishing time compare to the chuck speed (r.p.m).