Development of magnetorheological finishing process for external cylindrical surfaces

The recent increase in demand for functional and technological requirements of the component results in the development of complex geometrical shapes and that too with close tolerances and fine surface quality. To fulfill the needs for finishing the external cylindrical surfaces such as groove, taper, step surfaces, and threads, an advanced finishing process based on magnetorheological (MR) fluid has been developed. The developed process can finish the external cylindrical surfaces with controlled magnetic field as likely similar to turning operation. Fine finishing of external cylindrical surfaces is a significant requirement in many functional applications. The wide applications of this present process can be valuable in automotive, machine tool production, valves manufacturing, and aerospace. A modified new MR finishing tool with flat and curved tip surface has been made to perform finishing on external cylindrical surfaces. The present cylindrical finished workpiece is useful in macaroni manufacturing machine. The surface roughness values Ra, Rq, and Rz are reduced to 54.41%, 51.65%, and 40% with flat tool tip surface and 80.88%, 81.32%, and 82.5% with curved tool tip surface in 90 min of finishing time. The overall results reported that the present process with curved tool tip surface is comparatively more useful in finishing the external cylindrical surfaces.     

Magnetorheological nanofinishing of BK7 glass for lens manufacturing

BK7 is a high-quality crown glass which is used where additional benefits such as temperature sensitive applications of fused silica glass are not required. Due to very low inclusion content with extremely low bubbles, BK7 glass can find its application in lens manufacturing. The present work focuses on nanofinishing of the BK7 glass specimen for ratifying its utility in practical application. A programmable logic controlled 3-axis motions are fed to the magnetorheological (MR) rotating tool for finishing the glass specimen. MR polishing fluid used for nanofinishing consists of deionized water, magnetic iron particles, and cerium oxide powder. Under the influence of magnetic field, the stiffened MR polishing fluid is assisted in reducing the surface roughness of glass up to nanolevel range. Optical properties such as transmittance, absorbance, and reflectance of finished BK7 glass are analyzed and found suitable for lens manufacturing. Results of higher surface quality with excellent finishing are obtained by the present MR finishing process. After 90?min of finishing, the surface roughness values R_a and R_q are reduced to 17 and 27?nm from the initial values of 41 and 57?nm, respectively. To study the surface morphology, scanning electron microscopy is performed on BK7 glass.     

Improved magnetorheological finishing process with rectangular core tip for external cylindrical surfaces

Finishing of the external surface of cylindrical components at nano-level using magnetorheological process has witnessed for rising demand in the manufacturing industries to improve its functional applications. In this paper, the best required shape of the tool core tip surface in the magnetorheological finishing process is attempted to design for improving the efficiency of the process on external cylindrical surfaces. The different shapes of the tool core tip surface are designed, and their performance was analysed with the help of magnetostatic finite element analysis. The design of a rectangular shaped tool core tip surface is found more effective for uniform and higher flux density. The experiments are conducted on the cylindrical external surface using the recently developed rectangular and existing circular shaped tool core tip surfaces. After the magnetorheological finishing with rectangular and circular shaped tool core tip surfaces, the final surface roughness values get reduced to 18 nm and 45 nm from the initial value of 310 nm. Surface waviness, characteristics and mirror images are also found better while magnetorheological finishing performed using the rectangular core tip surface. Hence, the rectangular shaped design of the tool core tip surface is found to be more useful in improving the effectiveness of the present process.     

Magnetorheological finishing of ferromagnetic blind-hole type surfaces

Products having blind-hole type surfaces such as bottle caps are being manufactured in today’s industry and are of great use. Such products are made in permanent blind-hole type mold cavities. At present, these cavities are being finished by internal grinding operations. After grinding, surface defects such as deep-seated groove, cavity, axial scratch, and ploughed material are induced because of uncontrollable finishing forces applied by grinding pins onto the workpiece surface. To obtain a better quality on final-made products, the blind-hole type mold cavities should be made defect-free. In the present process, two different tools based on magnetorheological fluid are developed to finish the lateral and bottom surfaces of cylindrical blind-hole type mold cavities. The workpiece used for finishing is the hardened EN31 die steel. The finite element studies determined the variation in magnetic field within the working gaps. The change in surface roughness (R_a) values of both inner lateral and bottom surfaces reduced by 67.7% and 69.5%, respectively, and found significant improvement in surface characteristics as compared to the initial grind surfaces. The results revealed the usefulness of present process to finish the blind-hole type mold cavities in manufacturing industries for producing a better quality of final-made products.     

A novel magnetorheological honing process for nano-finishing of variable cylindrical internal surfaces

A novel magnetorheological honing process is designed and developed for nano-finishing of cylindrical internal surfaces with the help of permanent magnets. The radial movement of magnetic tool surface is adjusted as per the internal diameter of different cylindrical components and make it fixed before start of finishing so that it can maintain constant working gap while perform finishing. The present developed magnetic tool surface always constitutes higher magnetic field than the inner surface of ferromagnetic or non-ferromagnetic cylindrical workpiece. This is an important requirement to finish the internal surface of ferromagnetic or non-ferromagnetic cylindrical components because it ensures MR polishing fluid cannot stick on the workpiece surface while performing the finishing. Hence, present developed process is useful for finishing of ferromagnetic cylindrical molds, dies, hydraulic actuators, etc. for its better functional applications after the conventional honing or grinding process. The internal surface roughness of cylindrical ferromagnetic workpiece is dropped to 90?nm from its initial value of 360?nm in 100 minutes of finishing. Further scanning electron microscopy has also been done to understand the surface characteristics of finished workpiece. The results revealed that the developed magnetorheological honing process is capable to perform nano-finishing of internal surface of the ferromagnetic cylindrical components.     

Improved magnetorheological honing process for nanofinishing of variable cylindrical internal surfaces

Improved magnetorheological honing process is developed for nanofinishing of variable cylindrical internal surfaces with better surface integrity. In the present work, finishing performance of existing magnetorheological honing process is enhanced. The present improved process consists magnetorheological honing tool having curved permanent magnet end surfaces. When magnetic field is analyzed using Ansoft Maxwell, the improved magnetorheological honing process results in uniform and higher magnitude of magnetic flux density over its magnetic tool curved end surfaces as compared to the tool having magnetic flat end surfaces. Therefore, an improved magnetorheological honing process has been developed with tool having curved permanent magnet end surfaces. During experimentation, surface roughness values Ra, Rq, and Rz get decreased by 76.28%, 76.67%, and 75.20%, respectively, with improved magnetorheological honing tool having curved end magnetic surfaces, while 47.97%, 46.24%, and 47.08% decreased with tool having flat end magnetic surfaces in same 60 minutes of finishing time. This results in enhancement of finishing performance of the present improved magnetorheological honing process in terms of reduced finishing time and ability to produce good surface integrity. Hence, the present improved magnetorheological honing process performance with tool having curved end magnetic surfaces is found as comparatively better than the finishing tool having flat end permanent magnetic surfaces.     

An industrial approach of laser polishing with different laser sources

Surface finishing of dies and molds is one of the most interesting applications of laser polishing process. Because of the variety of materials used in die and mold manufacturing, as well as the different surface topographies, in each case, it is necessary to use appropriate process parameters. The presented work focuses on the study of laser polishing process on three commonly used materials in the manufacture of dies and molds, such as tool steels AISI D2 and AISI P20, ductile cast iron GGG70L and LaserForm ST‐100, a specific material developed for plastic injection mold making. Experimental studies were carried out determining the influence of the energy density on the roughness reduction rate. A key point that has a direct impact on the resulting surface roughness is the initial surface finishing of the material before laser polishing. In order to determine the degree of influence, experimental studies were conducted on two steels, AISI H13 and AISI P20, which are typically used in mold making industry. The experimental tests showed that a random distribution of peaks and valleys allows more homogenous material melting and gives as result a smoother surface after laser polishing.     

A rotating core-based magnetorheological nano-finishing process for external cylindrical surfaces

A rotating core-based magnetorheological finishing process has been developed to finish the external cylindrical surfaces at the nano-level more efficiently. The existing MR finishing process based on the stationary curved core tool tip is found to be comparatively less effective than the present process based on a rotating flat core tool tip for finishing the external cylindrical surfaces. This is due to the fact that in the present process both the workpiece and the tool rotating rather than giving rotation to the workpiece alone as in the existing process. The carbonyl iron particle (CIP) chains are rotated along with the rotation of the tool. This results in an increase in the kinetic energy of the active abrasive particles gripped by CIP chains which causes for the better finishing performance. Finishing is done by both the processes and their corresponding results are compared. The R_a, R_q, and R_z values are reduced to 71.62%, 72.53%, and 70.73% with a stationary curved core tool tip, and 94.59%, 94.51%, and 92.68% with a rotating flat core tool tip in 90 minutes of MR finishing. The overall results revealed that the present developed process using the rotating flat tool tip is more useful in finishing the external cylindrical surfaces as compared to the stationary curved tool tip.     

Performance Analysis of Ball End Magnetorheological Finishing Process with MR Polishing Fluid

A ball end magnetorheological finishing (BEMRF) process was developed for finishing a flat as well as 3D workpiece surfaces. The BEMRF process has a wide scope in today's advanced manufacturing systems for finishing 3D complex surfaces. Magnetorheological (MR) polishing fluid is used as finishing medium in BEMRF process. The constituent of MR polishing (MRP) fluid includes ferromagnetic carbonyl iron powder, abrasives, and base fluid medium. The workpiece surface is mainly finished by abrasives contained in MRP fluid. Therefore, the different mesh size from 400 to 1200 and volume percent concentration from 5% to 25% of abrasives in MRP fluid were chosen as factors to study their effects on the developed process performance in terms of percent change in roughness values. Silicon carbide abrasives were chosen in the present experimental investigation. Experiments were performed on the ferromagnetic ground surfaces whose initial roughness values (R_a) were measured in the range of 0.428 to 0.767 µm. The experimental results revealed that the MRP fluid with 15 vol % abrasives of mesh number 400 demonstrated better improvements in surface texture of finished surface as compared to other MRP fluid compositions. The finished surface characteristics and textures were studied at microscopic level using scanning electron microscopy and atomic force microscopy.     

油基磁流变液的开发及抛光性能研究

磁流变抛光技术可用于具有超光滑要求光学元件的超精密制造。在明确磁流变抛光机理的基础上,开发了油基磁流变抛光液,其体积比配方是:33.84%的羰基铁,57.34%的硅油,6%的氧化铈,2.82%的稳定剂。抛光液初始粘度达到0.5Pas,流变性具有较大范围的稳定性能。实验中,利用磁流变液在外磁场作用下形成的强剪切应力对一平面K9玻璃进行了可控抛光,结果证明其具有良好的抛光特性,抛光23分钟后工件表面粗糙度降低到0.6739nm。     

Manipulating mechanics and chemistry in precision optics finishing

Deterministic processing is critical to modern precision optics finishing. Put simply, determinism is the ability to predict an outcome before carrying out an activity. With the availability of computer numerically controlled (CNC) equipment and sophisticated software algorithms, it is now possible to grind and polish optics from a variety of materials to surface shape accuracies of ∼20 nm peak-to-valley (p-v), with surface roughness values (measured on white light interferometers over 250 μm×350 μm areas) to sub-nm root-mean-square (rms) levels. In the grinding phase the capability now exists to estimate removal rates, surface roughness, and the depth of subsurface damage (SSD) for a previously unprocessed material, knowing its Young's modulus, hardness, and fracture toughness. An understanding of how chemistry aids in the abrasive-driven removal of material from the surface during polishing is also critical. Recent polishing process research reveals the importance of chemistry, specifically slurry pH, for preventing particle agglomeration in order to achieve smooth surface finishes with conventional pad or pitch laps. New sub-aperture polishing processes like magnetorheological finishing (MRF) can smooth and shape flat, spherical, aspheric and free-form surfaces within a few process iterations. Difficult to finish optical materials like soft polymer polymethyl methacrylate, microstructured polycrystalline zinc sulfide, and water soluble single-crystal potassium dihydrogen phosphate (KDP) can be finished with MRF. The key is the systematic alteration of MR fluid chemistry and mechanics (i.e. the abrasive) to match the unique physical properties of each workpiece.     

Nanofinishing of FDM-fabricated components using ball end magnetorheological finishing process

Fused deposition modeling (FDM) is among the extensively used and the most economical additive manufacturing processes. Currently, the surface finish obtained for FDM additive manufactured parts are not at par with the current industrial application. To overcome the limitation of high surface roughness of 3D printed parts, a novel finishing technique has been proposed which includes primary and secondary finishing processes. While facing and lapping has been used as primary finishing technique, the secondary finishing involves the use of ball end magnetorheological finishing (BEMRF) process. BEMRF process is an unconventional finishing process which utilizes an advanced approach to impart finish on magnetic as well as non-magnetic materials that may be flat or freeform in shape. This article presents the experimental and analytical study to finish a polylactic acid (PLA) workpiece material manufactured by FDM process and finished using the BEMRF technique. The surface roughness of the FDM component has been reduced from initial surface roughness Ra = 20 µm to final value of Ra = 81 nm by combined primary and secondary finishing processes. The effect of magnetorheological polishing (MRP) fluid’s composition and finishing time is discussed and is followed by optimization of MRP fluid for maximum percentage reduction in surface roughness.     

A Comprehensive Experimental Study on Finishing Aluminum Tube by Proposed UAMAF Process

In this paper, a new noncontact ultrasonic magnetic abrasive finishing mechanism is presented. An ultrasonic vibration producer is used to vibrate the permanent magnets. The ferromagnetic steel grits in the created magnetic field form a flexible finishing tool. To take advantage of cavitation collapse pressure, the finishing zone components are immersed in water. The present work also studies the effect of parameters, i.e., time duration for finishing and working gap between magnetic poles and the workpiece on the surface roughness (Ra). The microscopic pictures and the roughness profile diagrams demonstrate the advantages of the proposed method.     

Development and characterisation of 3D printing finishing process applying recycled plastic waste

In recent years, additive manufacturing technologies have been playing an important role in the global economy. Consequently, low-cost 3D printers rose in the domestic environment, accelerating the development of startup companies and new market segments. Nevertheless, with regard to 3D printing based on fused filament fabrication, several challenges still need to be overcome, such as those related to surface finishing and mechanical strength. Moreover, 3D printing in the domestic environment also generates untreated plastic waste, which can cause environmental problems. For these reasons, the main goal of this work is to introduce and characterise 3D printing surface finishing post-processing using recycled plastic waste. As the main results of this work, the proposed recycling process was confirmed to improve object properties. Whereas surface roughness was reduced from 27 to 3?µm, while mechanical strength was increased in 20 times. The application of recycled material for chemical welding was also seen to be feasible.     

Improvement of Flat Surfaces Quality of Aluminum Alloy 6061-O By a Proposed Trajectory of Ball Burnishing Tool

Burnishing is a profitable process of surface finishing due to its ability to be automated, which makes burnishing method more desirable than other finishing methods. To obtain high surface finish, non-stop operation is required for CNC machine and we can attain that by choosing a suitable trajectory of the finishing tool. In other words, burnishing paths should be multidirectional rather than monotonic, in order to cover uniformly the surface. Indeed, the burnishing force is also a key parameter of the burnishing process because it determines the degree of plastic deformation, and that makes determining the optimum burnishing force an essential step of the burnishing process a success. Therefore, we consider the strategy of ball burnishing path and the burnishing force as variable parameters in this study. In this paper, we propose a new strategy of burnishing tool path with trochoid cycles that achieves a multidirectional burnishing of the surface according to various patterns. Taking into consideration the optimum burnishing force, to improve flat surface finish of AL6061-O samples by reducing the surface roughness parameter (Rz). Experiments carried out on 3-axis milling machine show that the proposed trochoidal path is more effective than the conventional one.     

扇形及一种四边形塑性区的上限解的极限解法——平面应变问题

本文采用将扇形及四边形塑性区分为三角形和四边形刚性块的有限方法,得到平底模平面正挤压及园冲头压入半无限体的上限解法的极限解,此结果与滑移线法所得结果相符合。     

A new magnetorheological finishing process for ferromagnetic cylindrical honed surfaces

In today’s industries, the internal surface finishing of cylindrical objects is highly demanded to improve their functional performance in various engineering applications. During the traditional honing operation, the finishing forces produced by abrasives on the workpiece surface are not easily controllable and also produce various surface defects. Therefore, to further improve the surface integrity of the traditionally cylindrical honed surface made of ferromagnetic or non-ferromagnetic materials, a new magnetorheological (MR) finishing process has been used with a controlled magnetic field. The experimentation is performed on the honed surface made of gray cast iron, which is generally used as a cylinder liner. The percentage change in surface roughness values, i.e., Ra, Rq and Rz, reduced by 77.44%, 70.16% and 72.16%, respectively, with better improvement in surface after 90 minutes of finishing. The experimental results demonstrated the effectiveness of present process for improving the functional applications of ferromagnetic cylindrical honed surface after removing the various surface defects such as deeper grooves, honing grooves with shaper edges, torn and folded metals, and cavities or holes. The applications of new MR finishing process can also be useful in the internal finishing of injection barrel of a molding machine, cylindrical molds and dies, hydraulic cylinder, etc.     

传动轴冲方凸模的改进

采用冲方加工工艺加工传动轴方孔,由于原冲方凸模端面为平端面,切削力较大,零件的表面粗糙度达不到图纸要求。每加工一件传动轴,需要更换7次冲方凸模和冲方加工7次,生产效率低,劳动强度大。通过改进冲方凸模结构,只需更换4次冲方凸模和冲方加工4次,就能生产出尺寸精度高,表面粗糙度低的传动轴零件,而且提高了生产效率,降低了生产成本。     

Analysis and Experiment on Incremental Forming Process for the Spiral Plate of Continuous Screw Conveyer

An incremental press-forming method was newly developed for the fabrication of spiral plates of a continuous screw conveyer, boring screw, screw pump and so on. In this method, a pair of V-shaped punches and dies with two opposite inclined edges are used instead of punch and die with spiral surfaces. The experiments on incremental forming were carried out on aluminum alloy and steel disks with a hole and a slit, and the deformation process of the plate during and after the press-forming was simulated by a finite element method (FEM). The press-forming shows that the spiral plate has a correct shape and smooth surface, i. e. the gradient of the surface along the internal, central, and external spiral curves of the deformed disk is constant. In addition, the spiral pitch and the amount of spring back obtained by the FEM simulation agree well with the experimental values for the different die or punch angles, the disk thicknesses and the disk materials. The FEM calculation also indicates that the equivalent stress during the press forming as well as the residual stress after the spring back takes a maximum value at an internal diameter position where the die or punch makes first contact to the disk.