Abrasive Flow Finishing Research Articles

Wire electrical discharge polishing of additive manufactured metallic components

Additive manufacturing (AM) is a rapidly developing technology in biomedical, aerospace and automobile industries. However, adoption of this technology on a larger production scale remains limited. This is primarily due to the drawbacks of present AM processes associated with achievable dimensional accuracy and surface integrity of the fabricated component. The average surface roughness (Ra) of the component ranges from 3 μm to 10 μm with stair-stepping effects, balling on surfaces resulting in poor dimensional accuracy. Therefore, post-processing methods like abrasive flow finishing, laser polishing, chemical polishing and traditional finish machining is often used to meet the desired surface integrity and accuracy. However, some of these post-processing methods are quite expensive leading to overall increase in the production cost of the component. On the other hand, methods like etching and sand blasting are time consuming and not suitable for component with intricate geometries. In this paper, low energy wire electrical discharge polishing (WEDP) has been employed to achieve the desired surface integrity and finish. Initially, experiments were conducted to analyse the finishing achieved on planer additive manufactured stainless steel (SS316L) specimens. A significant reduction in roughness of maximum 80 % was obtained at various settings for pulse on time and servo voltage. In addition, SEM and EDS analysis were also carried out to study the microstructure and composition after WEDP. From the study, it was found that the WEDP process is a promising method to finish metallic AMed components.

Magnetic abrasive flow finishing: A review

In these decades, there has been an increasing demand for magnetic field-assisted surface finishing processes in the industries. It is due to specific features available in the magnetic assisted surface finishing process; these are contactless and effectively controlling of magnetic forces in the intricate passage. These processes are hybridized by modification in the existing conventional surface finishing process or by clubbing two or more unconventional surface finishing processes. Magnetic Abrasive Flow Finishing (abbreviated as MAFF) process is an unconventional process used for internal cylindrical surface finishing, intricate and complex inside profile geometry. It is a hybrid process that gives a combined effect of AFM and the MAF process. MAFF was developed by the researchers Sahijpal Singh and H.S. Shan in the 2000s. They modified the AFM by applied an electromagnet around the workpiece. The main drawbacks of AFM’s process were low material removal rate and time-consuming process. MAFF was an advancement of AFM, in MAFF process material removal and surface finishing both considerable optimize. MAFF has a broader range of applications in electronics manufacturing of aerospace, semiconductor, automotive components, and medical components like biopsy needle.

Experimental investigations into magnetic abrasive flow finishing process on aluminium 6061-T6

The magnetic abrasive flow finishing (MAFF) process has been developed and investigated as an advanced fine finishing process. It is used for a surface finish (SF) of the straight and complex intricate profile using the ferromagnetic nature of abrasive media. This article presents an experimental investigation on the newly developed MAFF attachment, which was mounted on a shaper machine. A custom design workpiece fixture was used in MAFF attachment for the finishing of a straight hollow cylinder shape workpiece, which can easily modify based on workpiece shapes. A curved workpiece seat was prepared and fasting with two brass plates by nut and bolts arrangement. Taguchi design of experiment approach applied for experimentation on aluminium 6061-T6 workpiece material by MAFF setup. The main process parameters considered for experimentation are magnetic flux density (MFD), number of cycles, abrasive concentration, and piston speed while responses are material removal (MR) and surface finish (SF). The results found after finishing by MAFF were also compared with the AFF. It was identified that remarkable enhancements observed in MAFF responses. The finished surfaces were also observed by scanning electron microscope (SEM) and X-ray diffraction (X-RD).

Surface topography and wettability of the metallic surface machined through abrasive flow finishing

ABSTRACTAdvanced finishing processes are becoming the cutting-edge tool of modern manufacturing system because of the increasing demand for smooth surfaces and miniaturized features. Owing to the decreased size of the features, the requirement for the surface finish of the workpiece continues to increase the complicacy and sometimes made it difficult. Abrasive flow finishing process has an irreplaceable role in advanced finishing process because it can reach any complicated internal cavities and can finish to the required accuracy on difficult to machine materials. In the present investigation, an effort has been made to finish the aluminum metallic surfaces using tailor made abrasive flow finishing process to understand the effect of process parameters on surface topography before and after finishing. A viscoelastic polymer based flexible abrasive media is developed in-house and used for finishing of workpieces. The surface characteristics are evaluated using profilometer and scanning electron microscope. The process parameters are designed based on Central Composite Design (CCD) and Response Surface Methodology (RSM) has been used to optimize the process parameters. The sessile drop technique has been used to study the contact angle between DI water and aluminum surfaces machined using the developed technique and results are reported in this paper.

Manufacturing and performance analysis of mechanically alloyed magnetic abrasives for magneto abrasive flow finishing

The final finishing of precision components possessing a high degree of surface finish has bring about the application of magneto abrasive flow finishing (MAFF) process because of the development of manufacturing technology. In MAFF process, the magnetic abrasives play the role of cutting tool in MAFF process. This investigation highlights a novel technique of manufacturing magnetic abrasives with mechanical alloying followed by heat treatment. The performance of these magnetic abrasives was analysed in terms of percentage surface finish improvement (PSFI) of aluminum tubes. The experiments were planned and conducted according to response surface method (RSM) on aluminum tubes to check the effects of several parameters/limits such as magnetic flux density (MFD), no. of cycles and extrusion pressure (EP) on surface finishing. The experimental results revealed that the best PSFI of 72.7 % has been obtained at optimal processing conditions. The best surface finish (Ra) of 0.27 μm was acquired in this investigation. The scanning electron microscopy (SEM) images have been obtained to show the surface finish improvement after MAFF process.

Analysis of finishing forces and surface finish during magnetorheological abrasive flow finishing of asymmetric workpieces

Magnetorheological abrasive flow finishing (MRAFF) is an advanced hybrid process for producing ultrafine finished surfaces. Such surfaces reduce frictional forces and thereby minimize wear and tear to increase functional lifetime of the components. In the present research work, a model has been developed for simulating the results of MRAFF process. First, magnetic field is simulated and then a detailed study on the rheology of the magnetorheological polishing (MRP) fluid is conducted to develop a viscosity model for the flow of non-Newtonian shear thinning fluid. To calculate the forces acting in the process of material removal, the flow of MRP fluid around an asymmetric workpiece (knee joint) in a spatially varying magnetic field is simulated. Finishing forces exerted by the abrasive particles on the workpiece surface are analysed to develop a model for predicting surface roughness. A methodology has been proposed to evolve a variable correction factor to determine active abrasive particles at different locations on the workpiece surface for accurate simulation of surface finish operation. It is found that the magnetic field greatly influences the process performance by governing the viscosity of the MRP fluid and the distribution of the abrasive particles in the medium. During finishing of an asymmetric workpiece, the surface finish obtained at different locations on the workpiece surface is different. The developed model is capable to predict final surface finish within the acceptable accuracy when compared with the experimental results.

Study of Media in Abrasive Flow Machining and its Hybrid Processes

Abstract Abrasive flow finishing (AFF) is used to radius, polish, deburr and confiscate recast layer of components in an extensive variety of components. Surface finishing achieved by flowing a semi-viscous media through the target surface for finishing. There is a need for economic media because commercial media cost is too high (Rs2.5 lakhs/kg), available only in three standard forms and supplied by only one company (Extrude Hone Corporation). So, the researchers developed alternate media at low cost, easy availability. In this article, various types of media discussed from the past works have done by researchers. The selection of media depends on various testing as thermogravimetric analysis, flow capability, mechanical and rheological properties. Effective media prepared by mixing abrasive particles, binding materials and hydrocarbon oil in a fixed proportion, usually abrasive particles and binding materials ratios vary between 1:4 to 4:1 depends on the processes. The performance of the media calculated by its finishing property on an AFM and various hybrid setup. This review provides a vision into the various media in AFM and creates an improved understanding of finishing processes, to help in the selection of optimal machining limitations for the surface finishing of wide-ranging workpieces in practice.

Development of inverse replica fixture for nano-finishing of knee joint using R-MRAFF process

Rotational-Magnetorheological Abrasive Flow Finishing (R-MRAFF) process is a technique of nano-finishing in general and free-form/sculptured surfaces in particular. Knee joint is one such example of free-form surface which is used by orthopedic surgeons. Knee joints are usually made of cobalt chromium alloy which is bio-compatible material, and it is difficult to finish. The present work deals with the development of an inverse replica for a knee joint. This inverse replica is used as a fixture so that the fluid can flow with constant velocity within the confined gap between the workpiece and inner surface of the fixture in order to achieve uniform nano-level finish. Using this technique, variation in the surface roughness ( Ra) over the knee joint surface can be minimized and productivity can be enhanced. The finishing efficiency of the R-MRAFF process depends on the input parameters such as extrusion pressure, number of finishing cycles, rotational speed of the magnet, etc. These parameters should be controlled and optimized for precision finishing which is the main objective of the present research work. The minimum average Ra of 52 nm is achieved from the initial average Ra of 194 nm on the knee joint surface. The percentage change in Ra (73.20%) was achieved using the proposed method.

Study of laser texturing assisted abrasive flow finishing for enhancing surface quality and microgeometry of spur gears

This paper reports on study of laser texturing assisted abrasive flow finishing (LT-AFF) process of the hobbed spur gear (HSG) to further improve their microgeometry, surface finish, micohardness, microstructure, wear resistance, and material removal rate (MRR) as compared to AFF process. Preliminary experiments were conducted to identify optimum values of power and focal length of the continuous fiber laser of 1064-nm wavelength, and number of passes for laser texturing of the HSG made of 20MnCr5 alloy steel. Identified optimum values were used to produce homothetic texture on flank surfaces of HSG in a direction perpendicular to the lay profile generated by hobbing. Influence of laser texturing was studied by comparing deviations in microgeometry, average and maximum surface roughness values, microhardness, wear resistance, and MRR of HSG directly finished by AFF and laser-textured hobbed spur gears (LTHSG) finished by AFF. Previously optimized value of viscosity of AFF medium was used during finishing of HSG and LTHSG. Deviations in total profile, total lead and total pitch, and radial runout were used to indicate deviation in microgeometry of the spur gears. Results reveal that AFF of LTHSG reduced surface roughness and errors in microgeometry and improved microhardness, microstructure, wear resistance, and MRR than direct of AFF of HSG. Improved microgeometry and surface quality of spur gears will lead to their increased operating performance and service life thus reducing their running noise and vibrations and preventing their premature and failures. This research proves that productivity of AFF process can be improved significantly by laser texturing for finishing the spur gears.

Abrasive Flow Finishing of Stainless Steel 304 Biomedical Devices

Abrasive Flow Finishing of Stainless Steel 304 Biomedical Devices

Abrasive Machining Techniques for Biomedical Device Applications

Abrasive machining and finishing processes are techniques of material removal that are introduced in order to cut workpiece materials with the nominal mechanical and thermal residual stresses. These processes utilize continuous material removal by abrasive medium that can be in forms of water, abrasive particles or a mixture of these two. The benefit of eliminating excessive mechanical cutting force results in enhanced cutting of brittle or soft materials. On the other hand, removal of thermal cutting source provides a capability of cutting plastics and diminished the chances of thermal cracking in workpiece. Abrasive finishing processes have been introduced as complementary to abrasive cutting techniques in order to increase the precision and surface quality of manufactured parts. The most common of these techniques are water jet machining (WJM), abrasive jet machining (AJM), abrasive water jet machining (AWJM) and magnetic abrasive machining processes such as magnetic abrasive finishing (MAF), magneto-rheological abrasive finishing (MRF) and magneto-rheological abrasive flow finishing (MRAFF).

Medium rheological characterization and performance study during rotational abrasive flow finishing (R-AFF) of Al alloy and Al alloy/SiC MMCs

Abrasive flow finishing (AFF) is one of the advanced finishing processes and rotational AFF (R-AFF) is one of its variant wherein workpiece is provided with additional rotational motion. Polymer rheological abrasive medium used in R-AFF process perform an important role in reducing the workpiece surface roughness. In the present paper, different types of in-house medium are prepared by varying composition of the silicon-based polymer, rheological additives, and abrasive particles. Later rheological characterization (static and dynamic) medium is carried out to understand the flow and deformation properties. Fourier transform infrared spectroscopic analysis of the medium is performed to find the new functional groups in the medium. To study the effect of various medium constituents on its rheological properties and finishing abilities, experiments are designed as per central composite rotatable design and analyzed using response surface methodology. The rheological study shows that, as the wt.% of silicon polymer and abrasive particles increases, maximum shear stress as well as complex viscosity also increases. Increase in wt.% of plasticizer and abrasive particles increases medium % viscous component. Viscous properties are dominant in soft silicone based medium and ΔRa increases with an increase in wt.% of silicone polymer. ANOVA analysis shows that wt.% of abrasive particles has highest effect on ΔRa and followed by wt.% of plasticizer. Better surface finish is achieved when 43.75% of silicone polymer, 36% SiC, 5% plasticizer, and remaining rheological additives-based medium are used. Among three workpiece materials, the best surface roughness is achieved on Al alloy/SiC (10%) metal matrix composite.

A critical review of past research and advances in abrasive flow finishing process

Abrasive flow finishing (AFF) is an advanced nano-finishing process using abrasive-laden self-deformable putty for finishing, deburring, radiusing, chamfering, stress-relieving, and mirror-like polishing of the complicated components and inaccessible areas which are difficult or impossible to finish by other processes. Since its inception during 1950s, continuous research and advances in AFF are being reported globally. This paper presents comprehensive and critical review of the past research and developments on process modeling, rheological characterization of the AFF medium, development of finishing medium, development of various hybrid, derived, and hybrid-derived processes of AFF, and some novel applications of AFF for complicated shapes and difficult-to-finish materials. Major findings and observations, details of the workpiece material, finishing medium, process parameters, and responses have been presented in a tabular format for quick reference. It also covers some novel applications of AFF in the field of avionics, automobiles, biomedical, gears, additive manufacturing, cutting tool inserts, die and mold manufacturing, and recast layer removal. Finishing results for various materials such as mild steel, brass, aluminum, and its alloys, tool steel, copper, metal matrix composite, and photopolymer resin are also included. It also identifies directions for future research and provides an invaluable list of literature on past research works on AFF process. This review article will be very useful for the researchers working in micro- and nano-finishing applications and the industries involved in manufacturing of the automobiles, aero-engines, avionics components, biomedical implants, gears, impellers, dies and molds, and defense equipment.

Abrasive flow finishing of FDM printed parts using a sustainable media

PurposeThe purpose of this paper is to study the integration between fused deposition modeling (FDM) technology and abrasive flow machining process to improve the surface quality of FDM printed parts. FDM process has some limitations in terms of accuracy and surface finish. Hence, post-processing operations are essential to increase the quality of the part.Design/methodology/approachInitially, a sustainable polymer abrasive gel-based media (SPAGM) using natural polymer and natural additives (waste vegetable oil) was prepared using different combinations of (abrasive mesh size, percentage of abrasives and percentage of liquid synthesizer); then the characterization of media was done to check various properties. As media is an essential part in the process which helps in increase the surface finish, it needs to have some desired characteristics such as the following: the developed SPAG needs to hold the abrasives; its viscosity has to be medium so that it can easily flow through the machine; and its thermal stability caused by the increase in the temperature during various cycles of operation. For that, it is characterized rheologically as well as thermally to find its various properties.FindingsExperiments were performed on FDM-printed parts using an L9 orthogonal array with different parameters to find their effect on the workpiece. Scanning electron microscope images of SGAPM showed sharp edges of abrasive particles and bonding pattern between polymer chain molecules. Good surface finish and material removal rate (MRR) was observed at high pressure and long finishing time with 50 per cent abrasive concentration.Originality/valueThe authors confirm that this work is original and has neither been published elsewhere nor is it currently under consideration for publication elsewhere.

Viscoelastic medium modeling and surface roughness simulation of microholes finished by abrasive flow finishing process

Surface roughness is one of the critical parameters that affect the component performance during its working life. To develop any process to its full potential, it is necessary to understand the physics of that process. Abrasive flow finishing (AFF) is one of the advanced finishing processes. In the current research work, an effort is made to understand physics and mechanism of surface roughness improvement during the AFF process. This research paper is divided into two sections. Firstly, the amount of finishing stresses and forces generated during the finishing of microholes fabricated on surgical stainless steel (316L) workpieces are computed by using the finite element method. Finishing stresses are generated in the viscoelastic medium. So, to compute finishing stresses, finite element analysis of the viscoelastic medium is carried out by incorporating its experimentally measured rheological properties. Finishing stresses are calculated along the circumferential direction of the microhole. Later, at the same workpiece surface location, simulated and experimentally measured surface roughness value are compared. Secondly, a new simulation model is proposed to predict the surface roughness on the microhole wall surface for various AFF input parameters. Maximum percentage change in surface roughness error of 8% is observed between simulated and experimental results after AFF process.

Nanofinishing of Microslots on Surgical Stainless Steel by Abrasive Flow Finishing Process: Experimentation and Modeling

Miniaturization of components is one of the major demands of the today's technological advancement. Microslots are one of the widely used microfeature found in various industries such as automobile, aerospace, fuel cells and medical. Surface roughness of the microslots plays critical role in high precision applications such as medical field (e.g., drug eluting stent and microfilters). In this paper, abrasive flow finishing (AFF) process is used for finishing of the microslots (width 450 μm) on surgical stainless steel workpiece that are fabricated by electrical discharge micromachining (EDμM). AFF medium is developed in-house and used for performing microslots finishing experiments. Developed medium not only helps in the removal of hard recast layer from the workpiece surfaces but also provides nano surface roughness. Parametric study of microslots finishing by AFF process is carried out with the help of central composite rotatable design (CCRD) method. The initial surface roughness on the microslots wall is in the range of 3.50 ± 0.10 μm. After AFF, the surface roughness is reduced to 192 nm with a 94.56% improvement in the surface roughness. To understand physics of the AFF process, three-dimensional (3D) finite element (FE) viscoelastic model of the AFF process is developed. Later, a surface roughness simulation model is also proposed to predict the final surface roughness after the AFF process. Simulated results are in good agreement with the experimental results.

On simultaneous improvement of wear characteristics, surface finish and microgeometry of straight bevel gears by abrasive flow finishing process

Improvement in operating performance, service life and transmission efficiency and reducing the noise of straight bevel gears (SBG) requires their better wear resistance, surface finish and microgeometry. Viscosity of the medium used in abrasive flow finishing (AFF) process and finishing time play very important role in achieving these objectives. This paper reports on simultaneous improvement of wear characteristics, surface finish and microgeometry of SBG by abrasive flow finishing (AFF) process by studying the effects of viscosity of AFF medium and finishing time so as to identify their optimum values through twenty experiments. Average and maximum surface roughness were used to study improvement in surface finish while, microgeometry was evaluated in parameters of pitch deviation and runout. Friction force, coefficient of friction, specific wear rate coefficient, wear volume, microhardness and microstructure of the worn surfaces were used to study the wear characteristics and wear mechanism of the best finished SBG. Use of AFF has significantly improved the wear characteristics, surface finish and microgeometry and quality of SBG. Reduced wear characteristics will reduce the frictional heating which will result in lower operating temperature of the bevel gears. Lower wear volume will improve their service life and mechanical efficiency. Microstructure study of the AFF best finished bevel gear flank surfaces revealed that they are free from hobbing cutter marks, cracks, burrs, pits, surface roughness peaks, thermal distortion. The worn flank surface of the best finished bevel gear have shown very less amounts of worn debris, pits and displacement of material and indicate scuffing mode of wear. This work helps in establishing AFF as an economical, sustainable and productive alternative process for finishing the gears made of any material which can simultaneously improve surface finish, wear characteristics, microgeometry and quality of the bevel gears.

Differential finishing of freeform surfaces (knee joint) using R-MRAFF process and negative replica of workpiece as a fixture

ABSTRACTIt is difficult and challenging to achieve uniform nanoscale surface finish in the contact zone, particularly on freeform (or sculptured) surfaces having different curvatures at different locations. Femoral (or, Knee joint component) is one of such biomedical freeform component which has complex profile along its curvature. Surface conditions of a femoral decide the life of the implant and they play a crucial role in its functionality. The variation in surface roughness of the femoral should be minimum in the contact zone. For this purpose, a special tooling is being proposed for rotational magnetorheological abrasive flow finishing (R-MRAFF) process. A negative replica of the workpiece (knee joint) as a tool (or a fixture) is used so that the medium flow velocity in the fluid flow channel is almost constant (or minimum possible variations) along the medium flow direction. It is able to do differential finishing also along the curvature. In addition, pulsating magnetic field has been used to generate vibrations in the medium in the finishing zone so that the possibility of fresh abrasive particles interacting with the surface of femoral is high. The surface finish has been achieved ranging from 26 nm to 62 nm using the proposed finishing technique and negative replica of the workpiece (femoral) as a fixture.

Nano-finishing Studies Using Elastically Dominant Polymers Blend Abrasive Flow Finishing Medium

Abrasive flow finishing (AFF) process is one of the advanced finishing processes that uses polymer rheological abrasive medium to finish simple to complex surface features. AFF process comprises of machine set-up, tooling and medium. Among these three AFF process components, medium plays an important role. Depending on medium constituents and its quantity, the rheological property as well as its finishing abilities varies. In the current research work, soft styrene polymer and silicone polymers are blended along with additives and silicon carbide abrasive particles to make medium. The viscous and elastic properties of base polymers blend are varied using softeners (stearate), plasticizers (hydrocarbon oils) and abrasive particles. Finishing experiments are conducted on Al alloy/SiC (10%) metal matrix composites using central composite rotatable design as well as the responses are modeled using response surface methodology. The best surface finish achieved with optimally blended abrasive medium on Al alloy/SiC (10%) metal matrix composite (MMC) is 110nm.

A review on magnetically assisted abrasive finishing and their critical process parameters

Magnetically assisted abrasive finishing (MAAF) processes are the precision material removal processes that have been applied to a large variety of materials from brittle to ductile and from magnetic to non magnetic. The MAAF process relies on a unique “smart fluid”, known as Magnetorheological (MR) fluid. MR fluids are suspensions of micron sized magnetizable particles such as carbonyl iron, dispersed in a non-magnetic carrier medium like silicone oil, mineral oil or water. The MAAF processes overcome the limitation of abrasive flow machining by deterministically control the abrading forces by applying magnetic field around the workpiece. MAAF process is divided into two parts; one is magnetorheological finishing (MRF) and another is magnetorheological abrasive flow finishing (MRAFF). The MRAFF process gives better results as compared to results of MRF because it has additional reciprocating motion of MR fluid. In this article the attempt has been made to review various technical papers related to MRF and MRAFF. The experimental setups, process parameters, MR fluid, modeling & optimization and applications are discussed in this paper. This review article will be useful to academicians, researchers and practitioners as it comprises significant knowledge pertaining to MAAF.