Search

The proposed novel polishing method, hybrid electrochemical magnetorheological (H-ECMR) finishing, combines electrochemical reactions and mechanical abrasion on the workpiece surface to reduce finishing time. Moreover, H-ECMR finishing on the biomaterial surface produces a uniform, thick passive oxide layer to improve corrosion resistance. Herein, the electrolytic solution facilitates the chemical reaction and acts as a carrier medium for carbonyl iron particles (CIPs) in magnetorheological (MR) fluid. The synergic action of the two processes reduces the surface finishing time, which takes longer in the case of the conventional magnetorheological Finishing (MRF) process, as observed experimentally. The developed H-ECMR finishing process employs an electromagnet, maneuvering in situ surface quality variation by altering the magnetic field during finishing. The magnetic shield material (i.e., mu-metal) confines the bottom of the electromagnet core to restrict the magnetic field's leakage and provide a uniform and concentrated magnetic field at the polishing spot. The effectiveness of the H-ECMR process is evaluated based on various surface roughness parameters (i.e., average surface roughness (Ra), skewness (Rsk), and kurtosis (Rku)) and compared with the MRF process. A 96.4% reduction in Ra value is attained in the H-ECMR polishing compared to 49.6% in MRF for identical polishing time. Furthermore, an analytical model is developed to evaluate the final Ra attained from the developed H-ECMR polishing process and agrees well with the experimental results. The impact of different process parameters on surface roughness values is also analyzed. The electrochemical reaction forms a thick and unvarying passive layer on the Ti-6Al-4V surface as layer thickness increases to 78 nm from 8 nm. A case study on the femoral head of the Total Hip Arthroplasty (THA) for enhancement in the surface roughness and biocompatibility is performed through the developed H-ECMR polishing. The Ra value is decreased to 21.3 nm from 326 nm on the femoral head surface through the contour-parallel radial toolpath strategy. [ABSTRACT FROM AUTHOR]

Fixation plates are crucial to ensure the fracture site remains stable and prevent any movement that could widen the gap between broken bones, ultimately promoting the healing process of the bone. Topological optimization is a solution to increase the strength-to-mass ratio and produce lightweight metal implants with less stiffness to reduce stress shielding. Laser-Directed Energy Deposition (L-DED) is a 3d printing method to fabricate objects with near-net shapes. However, the manufactured implants' surface quality is still a major issue and further leads to an increase in the release of metal ions, which can cause inflammation and infection and lead to screw loosening. The current study aims to design and develop the topologically optimized fixation plate to reduce stress shielding further fabricated and polished by the L-DED and H-ECMR super polishing method, respectively. Herein, the H-ECMR super finishing method reduced the Ra value of the manufactured parts to 29.26 nm. [ABSTRACT FROM AUTHOR]

A computer numerical controlled (CNC) magnetorheological fluid assisted finishing (MFAF) process can super-finish the metallic surfaces of objects without any human intervention. In such a system, a rotating MFAF tool follows a path inside the region to be processed. An appropriate toolpath strategy can significantly reduce surface roughness. This work investigates different toolpath strategies such as Zig-Zag, Hilbert, Peano, Spiral, and Trochoidal for the MFAF process. A comparison is made among these toolpaths on the magnitude of the final surface roughness (Ra) and its variation on the finished profile on a similar domain with the same process parameters. In Zig-Zag and Spiral toolpaths, unidirectional crests are produced as polishing tool passed over the surface; this undesired orientation generates a non-uniform finished surface. The fractal curves such as Hilbert and Peano consist of significantly high numbers of sharp turns, making them unsuitable for the process. The Trochoidal toolpath, conventionally used for high-speed milling operation, is the most suitable toolpath for the MFAF process. The investigation shows that the Trochoidal toolpath reduces a mild steel plate's surface roughness (Ra) from 379 nm to 1.06 nm. [ABSTRACT FROM AUTHOR]

In today's manufacturing sector, it is required to manufacture products that have an exceptionally low tolerance. The desired high precision (or low tolerance) can be obtained through various finishing processes, which consist of bonded (honing, grinding, lapping, etc.) or unbonded (abrasive flow finishing) forms of the tool. An unbonded form of tool is more reliable and beneficial because it helps to achieve a highly polished surface without affecting the material topography of the product. The literature survey shows that an effective unbonded form of finishing tool can be produced through the assistance of Magnetorheological (MR) Fluid, as it has in-situ control on its rheological properties. The MR fluid is mainly composed of abrasives and ferromagnetic powder mixed in a viscoplastic base medium. The unbonded multipoint cutting tool is generated during the finishing operations, which produces a mirror-like polished surface. Several MR fluid-assisted finishing processes have been developed in the last few decades. This article explores the evolution of MR fluid-assisted finishing processes, along with their development, applications, influencing process parameters, the composition of MR fluids, and governing analytical models. The key capabilities and limitations of different MR fluid-assisted finishing processes are also discussed, and a comparison is made to provide an overview at a glance. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) processes have ample advantages compared to traditional manufacturing processes, including mass customization, material efficiency, bioprinting, and fabrication of complex geometries with reduced lead time. Despite such benefits, it suffers most from staircase effects that deteriorate the fabricated part's surface quality. Nowadays, additively manufactured aligners are suitable for treating malocclusion and temporomandibular defects of teeth. F used Deposition Modelling (FDM) is one of the best substitutes for clear aligners production to reduce per-unit cost. Glycol-modified Polyethylene Terephthalate (PETG) is opted as the material to fabricate the clear aligners due to its biocompatibility and non-toxicity. However, the poor surface quality of the additively manufactured is a major challenge in developing clear aligners with the FDM. A novel experimental setup is designed and developed to enable Chemical Vapor Smoothing (CVS) to enhance the surface quality of the clear aligners. Furthermore, based on the Surface roughness, the comparison is made between the surface quality polished with various chemicals (namely methylethylketone (also known as 2-butanone), toluene and, cyclohexanone). Moreover, Response Surface Methodology (RSM) is used to analyze the impact of different process parameters (i.e., the chemical volume, exposure time, and workpiece orientation) on the surface quality of the clear aligners. Moreover, RSM shows that the impact of the clear aligners orientation on %ΔR a during the CVS is higher than other process parameters. Results demonstrate that cyclohexanone produces more uniform surface quality with a 92.73% reduction in surface roughness compared to methylethylketone and toluene on PETG, i.e., 89.66% and 88.63%, respectively. The developed surface finishing method is capable of producing uniform, smooth surfaces over the FDM -fabricated PETG clear aligners. [Display omitted] • Clear aligners are fabricated through FDM, followed by chemical Vapor Smoothing to improve surface quality. • Chemicals, i.e., methylethylketone, toluene, and cyclohexanone, are used to improve surface quality of PETG clear aligners. • Cyclohexanone produces uniform surface quality as compared with other chemicals. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) is recently used to manufacture biomedical implants as the customized fabrication of the desired complex shapes is easily achievable with reduced manufacturing time and material waste. However, the poor surface quality of additively manufactured products is a major concern over biomaterials' functionality. Magnetorheological Fluid Assisted Finishing (MFAF) process is an advanced surface finishing process used to improve the workpiece surface quality without altering surface topography. Selective Laser Melting (SLM) is utilized in the presented study to fabricate biomaterials using SS316L powder, and surface quality is further enhanced through the MFAF process. However, average surface roughness (R a) only delivers the details regarding the average altitude of peaks and depth of valleys from the central line. Therefore, kurtosis (R k u) and skewness (R sk) analysis of the polished surface are also carried out to determine detailed surface characteristics. The bio-tribology analysis of the polished surface of the AM implant determines its sustainability inside the human body. Hence, a wear test utilizing the pin-on-disc process is performed on the finished surface to determine the efficiency of the polishing process during tribological contact of the biomaterials with the bone. Further, the improved surface roughness parameters (R a , R k u , and R sk) after the MFAF of AM implant's surface are also investigated with an optical profilometer and scanning electron microscope. The MFAF process produced a highly polished surface on the biomaterial and a final R a value of 32.46 nm is attained after polishing from its initial value of 8.32 μm with a decrease in wear rate (i.e., from 9.86 × 10−5 mm3/min to 0.46 × 10−5 mm3/min). The value of kurtosis less than three (i.e., 0.79) indicates that the flat peaks are generated on the surface irregularities after MFAF. Similarly, the negative skewness (i.e., Rsk = −0.28) represents that the number of peaks is less than the valleys. It indicates that the chances of wear out of the surface irregularities from the workpiece on their tribological contact are very low. • Surface characteristics improvement of Selective Laser Melted biomaterial (SS316L). • A mirror-like polished surface is achieved through Magnetorheological Fluid Assisted Finishing process on the biomaterial. • A final R a value of 32.46 nm is attained after polishing from its initial value of 8.32 μm. • The wear rate is reduced on the polished surface from 9.86 × 10−5 mm3/min to 0.47 × 10−5 mm3/min. [ABSTRACT FROM AUTHOR]