A study on the application of newly developed magneto-elastic abrasive to improving the surface roughness of the bore

Spiral polishing mechanism refers to the technology of applying a high-speed turning screw rod in the process of workpiece surface polishing. For the purpose of increasing the machining effect, a powerful ring magnet was installed around the workpiece. In this study, the new self-developed magneto-elastic abrasive would be used to polish the inner wall of the bore, the so-called workpiece surface, under the attraction of the surrounding magnet and the drive of the turning rod. The new magneto-elastic abrasive not only eased the polishing force by its flexibility but also avoided deep scratches on the workpiece surface. The control of machining parameters on surface roughness and material removal were discussed to look for the best combination of the parameters; at the same time, the effects of each parameter on the workpiece surface topography after the polishing were also examined. The results of the experiment indicated that magnetic flux density and magneto-elastic abrasive concentration affected the surface roughness the most. In addition, the newly developed magneto-elastic abrasive significantly improved the polishing effect of the workpiece surface, at the rate of 94 %.     

Two-dimensional vibration-assisted magnetic abrasive finishing of stainless steel SUS304

Traditional magnetic abrasive finishing (MAF) involves unidirectional polishing of surface but suffers the drawback of forming deep scratches, resulting in poor surface quality. This study attempts to enhance the polishing efficiency of MAF by adding vibration to the platform, focusing on the fabrication of the two-dimensional vibration-assisted MAF (2D VAMAF) setup. Experiments are conducted with variations in parameter levels of 2D VAMAF. Comparison of finished surface results shows superiority of 2D VAMAF in obtaining lower surface roughness and mirror surface quality. In addition, this study uses the Taguchi experimental design method to obtain the optimal parameter combination of 2D VAMAF for surface roughness improvement. The optimal combination obtained includes working gap (1 mm) and weight of SiC, steel particles, and machining fluid (1 g, 1.5 g and 3 g, respectively); frequency of vibration along X and Y directions (16.67 Hz); rotational speed of magnet (500 rpm); and size of SiC and steel particles (8000 and #120, respectively). With 5-min 2D VAMAF under optimal parameter combination, the surface roughness of a stainless steel SUS304 workpiece can be reduced from 0.13 to 0.03 μm, an improvement of 77 %. Experimental results reveal that 2D VAMAF can indeed improve surface quality with a shorter processing time and a smaller amount of abrasives required, both of which contribute to cost reduction. With less pollution incurred, 2D VAMAF is a more environmental friendly machining method in industry.     

Parametric investigation into accommodate-sinking effect of cluster magnetorheological effect pad

Based on magnetorheological (MR) fluid, a viscoplastic cluster MR effect pad was formed between the surface of the polishing plate and workpiece. Then an accommodate-sinking effect (AS effect) of MR effect pad on abrasives was presented. A set of experiments were conducted by adding the rogue particles to polish the damage-free K9 glasses and to study the influence of the rogue particles and carbonyl iron particles (CIPs), and the machining parameters on AS effect. The surface roughness of the machined surface was measured and adopted as the parameter of evaluating the AS effect, and a Keyence VHX-600 microscope was used to investigate the machined surface. Experimental results indicated that when the size and concentration of rogue particles were no more than the threshold value, a well AS effect on abrasives aided in obtaining a super smooth surface. The maximal contribution was made by a machining gap on AS effect, followed by the rotational speeds of workpiece and polishing plate, while the least contribution was from the flow rate of MR fluid. The recommended machining parameters for obtaining a super smooth surface (Ra 1.4 nm, Rv 4.6 nm) are a machining gap of 1.2 mm, rotational speeds of 60 and 350 rpm for polishing plate and workpiece respectively, and MR fluid flow rate of 1,000 ml/min.     

An investigation into superficial embedment in mirror-like machining using abrasive jet polishing

This study performs experimental investigation into the application of abrasive jet polishing (AJP) to the surface finishing of electrical-discharge-machined SKD61 mold steel workpieces. The results indicate that the AJP processing conditions which optimize the surface quality of the SKD61 workpiece when polishing using #2000SiC abrasives are as follows: an abrasive material to additive ratio of 1:2, an impact angle of 30°, a gas pressure of 4 kg/cm² (0.4 MPa), a nozzle-to-workpiece height of 10 mm, a platform rotational velocity of 200 rpm, and a platform travel speed of 150 mm/s. Under these processing conditions, a polishing time of 20 min is sufficient to reduce the surface roughness from an initial value of Ra?=?1.7 μm to a final value of Ra?=?0.27 μm, corresponding to an improvement of 84.12%. The experimental results demonstrate that the maximum attainable improvement in the surface quality of the polished workpiece is limited by a surface-hardening effect caused by the ball-impact phenomenon and the embedment of #2000SiC fragments in the workpiece surface.     

磁性液体研磨加工机理

在以前研究的基础上,改磁性液体悬浮研磨为流性液体堆积研磨,并在研磨中附加振动,大大地提高了加工效率和加工精度,加工出表面粗糙度只有Ra0.005～0.006μm的钢试件和Ra0.005～0.010μm的铜试件表面。还就这种新研磨方法中各种因素的影响以及其研磨作用机理进行了深入的研究探讨。     

Optimization of sandblasting process of complex 3D surface polishing using variable viscoelastic diamond particles abrasive

This article reports a novel and efficient diamond particles abrasive with tunable viscoelasticity for sandblasting polishing. Controlling the rust inhibitor content can change its viscoelasticity to adhere diamond particles on polymer materials. Using the sandblasting mechanism, the abrasive deform and slide on the workpiece surface, so that the diamond particles can cut onto the surface peaks of the workpiece. Thus, the complicated morphology can be rapidly and precisely polished. The friction generated by the abrasive on the surface of the workpiece will cause the rust inhibitor solution to evaporate, resulting in reduced viscosity, which makes the diamond particles gradually fall off from the abrasive. Applying Taguchi method, the optimal parameters for viscosity and injection angle were identified. The surface roughness was found to decrease from Ra?=?1.47?μm to Ra?=?0.2?μm in 3?min. The two kinds of complex concave surfaces of different materials were polished by this innovative composite diamond particles abrasive with the optimal parameter values, which has been verified to have 40 times higher efficiency than the traditional manual polishing.     

Experimental study on the effect of varying focal offset distance on laser micropolished surfaces

Laser micropolishing (LμP) is an innovative part-finishing process that reduces machining roughness by melting a thin layer of material on the micromilled surface using a focused laser beam. The quality of the final polished surface is dependent upon the part material, initial surface topography and roughness, and the energy density of the beam. The focal offset distance (FOD) is one critical parameter that controls the amount of energy delivered to the workpiece. The impact of varying the FOD on final laser-polished surface quality is investigated by performing a series of experiments on carefully prepared AISI H13 test samples with known initial surface roughness and waviness due to the milled track periodicity. Three well-defined polishing regimes were observed when adjusting the FOD for a Q-switched Nd/YAG LμP system between 1.3 and 2.9 mm. Given the same initial micromilled surface geometry, each LμP regime (i.e., short FOD, <1.8 mm; long FOD, >2.2 mm; and intermediate FOD) reduced the surface roughness and periodic waviness in a distinct manner. For a micromilled sample with a 33-μm periodicity, the LμP with FOD of >2.2 mm was determined to be the most effective regime by improving surface quality by 39.7 %. The affects of repetitive exposure to the beam and increasing the applied laser power on improving surface quality are also investigated for the 3 LμP regimes.     

Research on unbounded abrasive polishing process with assisted ultrasonic vibration of workpiece

Ultrasonic-assisted machining was an effective method to improve the material removal quality especially to difficult-to-cut metal materials. The ultrasonic vibration was usually superimposed on the machining tool but seldom on the workpiece, although the ultrasonic vibration of workpiece could improve the processability of material more effectively. In this paper, a rectangle hexahedron ultrasonic sonotrode with optimized slots was developed as a platform to realize the assisted ultrasonic vibration of workpiece and the ultrasonic-assisted polishing process of austenitic stainless steel was also studied. The unbounded abrasive was selected as polishing medium, and the path compensation strategy of soft polishing tool was carried out for getting uniform polishing force. The orthogonal experiments were designed to study the optimization of ultrasonic polishing parameters and the relation between different types of ultrasonic polishing path and polishing quality. The results appear that the horizontal ultrasonic vibration of workpiece can reduce polishing force and improve polished surface roughness, which can also reinforce the proportion of plastic shear effect in the material removal process. The ultrasonic polishing path keeping consistent with workpiece vibration direction can get more uniform polishing force and better surface roughness. And the 45° oblique crossing ultrasonic path can get the maximum average polishing force reduction by 75.2 %.     

集群磁流变变间隙动压平坦化加工试验研究

为了提高光电晶片集群磁流变平坦化加工效果,提出集群磁流变变间隙动压平坦化加工方法,探究各工艺参数对加工效果的影响规律。以蓝宝石晶片为研究对象开展了集群磁流变变间隙动压平坦化加工和集群磁流变抛光对比试验,通过检测加工表面粗糙度、材料去除率,观测加工表面形貌、集群磁流变抛光垫中磁链串受动态挤压前后形态变化,研究挤压幅值、工件盘转速、挤压频率以及最小加工间隙等工艺参数对加工效果的影响规律。试验结果表明：集群磁流变平坦化加工在施加工件轴向微幅低频振动后,集群磁流变抛光垫中形成的磁链串更粗壮,不但使其沿工件的径向流动实现磨粒动态更新、促使加工界面内有效磨粒数增多,而且在工件与抛光盘之间的加工间隙产生动态抛光压力、使磨粒与加工表面划擦过程柔和微量化,形成了提高材料去除效率、降低加工表面粗糙度的机制。对于2英寸蓝宝石晶电（1英寸=2.54 cm）集群磁流变变间隙动压平坦化加工与集群磁流变抛光加工效果相比,材料去除率提高19.5%,表面粗糙度降低了42.96%,在挤压振动频率1 Hz、最小加工间隙1 mm、挤压幅值0.5 mm、工件盘转速500 r/min的工艺参数下进行抛光可获得表面粗糙度为Ra0.45 nm的超光滑表面,材料去除率达到3.28 nm/min。证明了集群磁流变变间隙动压平坦化加工方法可行有效。     

A new integrated polishing process design for plastic mold steel to mirror-like surface

This paper aims to propose the design of a new polishing tool, a clamp with a flexible polishing head (or CFPH) for polishing plastic mold steel. The investigation/evaluation of this new tool’s performance in polishing is also included in this paper. The design of this brand new flexible clamp with a polishing head is, first of all, based on the application of the concept of weakening gap in the study of Fuh [1] increase in the freedom of micro-movement of the clamp is available. Second, various analyses and tests are done by the finite element method (FEM). Then, through the spectrogram, we analyze this tool’s machining characteristics. Furthermore, by the performance on large waves, medium waves, and small waves of the workpiece, we evaluate the working efficiency and set up a set of polishing strategies. This module of machining strategy process contains the combination of cutting and polishing one kind or multi-kind machining modes and the complementary precision processing methods. Finally, we propose a set of polishing integration process skills specifically on S-STAR*. We also verify our analysis with 3D profiles and the surface roughness measurement instrument. These verified analyses show that roughness and shape precision can be reached to Ra0.006, Rmax0.08, and PV0.084 μm respectively. This new invention, by the spectrum analysis, can significantly improve large wavelength accuracy up to 83.9 %, medium wavelength accuracy 82.5 %, and small wavelength accuracy 80.2 %. To conclude, we aim to set up a mirror-like surface polishing tool for plastic mold steel. This proposal is prudentially verified and should be considered theoretically and practically successful.     

Machining performance of a grooved tool in dry machining Ti-6Al-4 V

In this paper, dry machining experiment of Ti-6Al-4 V was carried out to investigate the machining performance of a grooved tool in terms of its wear mechanisms and the effects of cutting parameters (cutting speed, feed rate, and cutting depth) on tool life and surface roughness of the machined workpiece. The results showed that chip-groove configuration substantially improved the machining performance of cutting tool. The main wear mechanisms of the grooved tool were adhesive wear, stripping wear, crater wear, and dissolution-diffusion wear. The resistance to chipping was enhanced due to the decrease of contact pressure of tool-chip interface. And the resistance to plastic deformation of tool nose was weakened at the cutting speed of more than 60 m/min. The appropriate cutting speed and feed rate were less than 70 m/min and 0.10 mm/r, respectively. With cutting speed increasing, the surface roughness of machined workpiece decreased. A high feed rate helped the formation of higher surface roughness except 0.21 mm/r. When cutting depth increased, tool nose curvature and phase transformation of workpiece material had great impact on surface roughness.     

介电泳效应磨粒流抛光中的电极形态

针对薄壁陶瓷工件内表面抛光,提出一种基于介电泳效应的磨粒流抛光方法。将非均匀电场布置于陶瓷工件外表面,极化磨粒,实现陶瓷工件内表面高效抛光。仿真分析发现:电极间隙比为2时,SiC磨粒具有最好的介电泳效应,参与抛光的磨粒最多。陶瓷工件初始内表面粗糙度值Ra为(208±5)nm时,抛光10 h后,无介电泳效应的磨粒流抛光工件内表面粗糙度值Ra为51 nm,有介电泳效应的磨粒流抛光工件内表面粗糙度值Ra为23 nm。     

Fundamental investigation on nano-precision surface finishing of electroless Ni–P-plated STAVAX steel using magnetic compound fluid slurry

Electroless nickel–phosphorus (Ni–P) plating used in a range of hot embossing metal molds/dies and injection metal molds/dies must be manufactured to nano-precision roughness for proper operation of the molds/dies. We therefore developed a novel polishing technique for mirror surface finishing of this kind of magnetic material using a magnetic compound fluid (MCF) slurry. The effects of the magnetic and gravitational forces acting on the carbonyl iron particles (CIPs) and abrasive particles (APs) within the MCF slurry were studied first, and the behaviors of the CIPs and APs in the presence of an external magnetic field were predicted. Then, experiments were performed to confirm the predictions by investigating the distribution of the CIPs and APs on the working surface of the MCF slurry. Finally, four MCF slurries containing CIPs and APs with different diameters were employed to finish the Ni–P-plated STAVAX steel specimen at different working gaps. The results revealed that for the magnetic workpiece, the resultant vertical force attracted CIPs towards the work surface, whereas APs were pushed away from the work surface. However, the CIPs and APs showed opposite behaviors with the non-magnetic workpiece. The percentage of APs distributed on the working surface increased and the distribution became more even as either the diameter of the CIPs or the working gap increased, whereas that of CIPs had the opposite tendency. The MCF slurry containing bigger CIPs and smaller APs should be employed and the working gap should be set at a smaller value in order to perform mirror surface finishing of a magnetic Ni–P-plated surface. Under the experimental conditions in this work, the Ni–P-plated surface quality improved significantly, and a mirror surface roughness (Ra) of 4 nm was successfully achieved without leaving scratches or particle adhesion when using an MCF slurry containing CIPs 7 μm in diameter and APs 1 μm in diameter, showing that MCF slurries containing commercial CIPs are applicable to the nano-precision finishing of magnetic materials.     

Study on the effect of various machining speeds on the wafer polishing process

Silicon wafer polishing has an important role in semiconductor manufacturing; the general purpose of the polishing process is to produce a mirror-like surface. The wafer surface roughness is affected by many variables such as the carrier head unit characteristics, operation, platen and chuck speeds, pad and slurry ratios, and temperature. The optimum process conditions for the experimental temperature, down-force, slurry ratio, and processing time were determined in previous studies and used as fixed factors in this experiment. The main purpose of the present study was to determine how the different platen and chuck machining speeds influence the wafer surface roughness via the polishing process to obtain the optimum machining speed. In the results, the machining temperature appeared to differ at different machining speeds, which is a vital element with regard to wafer polishing.     

Investigation on the polishing of aspheric surfaces with a doughnut-shaped magnetic compound fluid (MCF) tool using an industrial robot

Aspheric elements have become essential optical surfaces for modifying optical systems due to their abilities to enhance the imaging quality. In this work, a novel method employing a doughnut-shaped magnetic compound fluid (MCF) polishing tool, and an industrial robot was proposed for polishing aspheric surfaces. Firstly, investigations on the MCF tool, including the formation process and geometry, were conducted to form an appropriate polishing tool. The distribution of abrasive particles was observed using SEM and EDX mapping. Thereafter, a conic workpiece constructed from 6061-aluminum alloy was selected as the workpiece, which was used to discover the effects of the parameters on the polishing ability of aspheric surfaces. Finally, a polishing experiment was conducted with an aspheric element under the optimized conditions. The obtained results are shown as follows. (1) A relatively regular MCF tool was obtained when the eccentricity (r), amount of MCF slurry supplied (V), revolution speed of the MCF carrier and magnet (n_c and n_m, respectively) were given at appropriate values. (2) Abrasive particles entrapped in or attached to the clusters were observed abundantly on the MCF tool sample. (3) The surface profile of the conic workpiece after 60 min of polishing indicated that material was removed evenly, and an annular polishing area was attained. Meanwhile, a higher material removal rate and better surface roughness were achieved with a smaller working gap (h) and larger volume of the MCF slurry supplied (V). (4) The roughness (Ra) of the aspheric surface decreased from 49.81 to 10.77 nm after 60 min of polishing. The shape retention obtained a Pearson correlation coefficient (Pcc) of 0.9981, which demonstrated that this novel method is appropriate for polishing aspheric elements.     

On the effect of relative size of magnetic particles and abrasive particles in MR fluid-based finishing process

Magnetorheological fluid-based finishing (MRFF) process is widely used for fabrication of optical material such as glasses, lenses, mirrors, etc. Performance of the process is significantly affected by the properties (size, concentration, hardness, etc.) of the constituents of MR fluid. MR fluids have been prepared by varying three abrasive particles mean sizes (4 µm, 6 µm and 9 µm) with carbonyl iron particles (CIPs) having average particles size of 6 µm. Yield stress of MR fluids is measured using a rheometer. The composition of the fluid has CIPs of 25%, abrasive 10% (by volume) and rest of the base medium (liquid). The yield stress was evaluated at magnetic flux density of 0.33 Tesla. It is observed that MR fluid having the same particle size of CIPs and abrasive particles exhibits higher yield stress as compared to other combinations. The lowest yield stress is observed in case of 9 µm abrasive particles size. A set of finishing experiments is carried out to understand the effect of relative size of magnetic particles and abrasive particles on surface roughness values.     

Application of magnetic abrasive polishing to composite materials

Magnetic abrasive polishing (MAP) is an advanced machining process that can produce smoother surfaces in many material types. The present study conducted an experimental assessment of MAP for a newly developed, non-ferrous and aluminum-based composite material. A permanent magnet was installed under the workpiece to enhance its magnetic flux density, which had proved insufficient for effective MAP. The success of the permanent magnet in improving the surface roughness of the non-ferrous material was verified.     

Development of magnetorheological fluid-based process for finishing of ferromagnetic cylindrical workpiece

A magnetorheological fluid-based process is developed for the internal surface finishing of ferromagnetic cylindrical workpiece. The existing finishing processes based on magnetorheological fluid are not equipped to finish the internal ferromagnetic cylindrical surface significantly as it obtained higher magnetic flux density than the MR polishing fluid. At present, magnetorheological fluid-based finishing tools are designed to ensure the maximum magnetic flux density always present on the outer finishing tool core surface as compared to internal surface of ferromagnetic cylindrical workpiece surface. To validate this present principal idea, the magnetostatic finite element analysis has been performed on the newly designed finishing tools. The preliminary experiments have also been conducted to evaluate the finishing performance with the two newly designed finishing tools. The percentage reduction in surface roughness (R_a) values with I-shaped tool core is found as 65–78% after 150 min of finishing, whereas, with rectangular shaped tool core is found as 78–81% after 90 min of finishing. The results clearly revealed that the present finishing tool with rectangular shaped core is more suitable for uniform significant finishing of ferromagnetic cylindrical internal workpiece than the I-shaped core. The developed process can be useful in finishing of cylindrical mold and dies, hydraulic cylinder, barrel for injection molding, etc.     

Effect of the components of Magnetic Compound Fluid (MCF) slurry on polishing characteristics in aspheric-surface finishing with the doughnut-shaped MCF tool

For the aspheric optical surface finished with a doughnut-shaped MCF (magnetic compound fluid) polishing tool, the performance of the polishing tool depends mainly on the properties of the MCF slurry. Therefore, understanding the effect of each MCF slurry component on the polishing characteristics is crucial to developing novel polishing techniques. In this paper, the polishing principle was depicted and the corresponding polishing jig was constructed with a six-degree-of-freedom manipulator. The conical surfaces, which were considered as special aspheric surfaces, were experimentally polished under proper polishing conditions to examine the effects of the carbonyl iron particles (CIPs) concentration and the sizes of the abrasive particles (APs) on the polishing ability to remove material/tool marks and improve work surface qualities. Theoretical analyses were also performed to gain a more comprehensive understanding of the behaviors of CIPs and APs in the magnetic field. The results were shown as follows: (1) The CIPs concentration affected positively the magnetization of the MCF slurry, leading to better performance in the removal rate of material/tool marks when a higher CIPs concentration of was applied. The best surface quality was attained with a CIPs concentration of 45 wt%. (2) Larger APs were beneficial for obtaining higher removal rates of material/tool marks. The APs with 1 μm in diameter were preferred for achieving a better surface quality. (3) Ferric clusters were formed along the magnetic line of force and their orientations changed periodically to stir the APs with the magnet revolution. (4) The Aps, at a given working gap, can squeeze the work-surface. The squeezing action was much more intense when larger APs and the MCF slurry with a higher magnetization were employed. (5) The material removal model suggested that the material was removed due to the APs and the relative motion between the work-surface and APs.     

Effect of machining parameters on surface roughness and tool wear for 7075 Al alloy SiC composite

In the present study, an attempt has been made to investigate the influence of cutting speed, depth of cut, and feed rate on surface roughness during machining of 7075 Al alloy and 10 wt.% SiC particulate metal-matrix composites. The experiments were conducted on a CNC Turning Machine using tungsten carbide and polycrystalline diamond (PCD) inserts. Surface roughness of 7075Al alloy with 10 wt.% SiC composite during machining by tungsten carbide tool was found to be lower in the feed range of 0.1 to 0.3 mm/rev and depth of cut (DOC) range of 0.5 to 1.5 mm as compared to surface roughness at other process parameters considered. Above cutting speed of 220 m/min surface roughness of SiC composite during machining by PCD tool was less as compared to surface roughness at other values of cutting speed considered. Wear of tungsten carbide and PCD inserts was analyzed using a metallurgical microscope and scanning electron microscope. Flanks wear of carbide tool increased by a factor of 2.4 with the increase of cutting speed from 180 to 240 m/min at a feed of 0.1 mm/rev and a DOC of 0.5 mm. On the other hand, flanks wear of PCD insert increased by only a factor of 1.3 with the increase of cutting speed from 180 to 240 m/min at feed of 0.1 mm/rev and DOC 0.5 mm.