Polishing Parameters Research Articles

Towards collaborative robotic polishing of mould and die sets

Dies and moulds are fundamental elements in the manufacturing of a wide variety of products. The surface polishing of dies and moulds with complex features largely relies upon time-consuming manual work of skilled workers and, as a result of the diminishing availability of skilled people, has become the most costly step in the manufacturing system. Robot-assisted polishing (RAP) technology has been investigated as an alternative or supplement to the conventional manual polishing process in the manufacturing of dies or moulds because of its high efficiency, improved reliability and robustness. This paper presents the preliminary work investigating RAP as a collaborative technique to complete the major finish a die or mould. Including a brief review of current approaches and methodologies to support automated polishing. A classification of common feature types currently polished in moulds and dies, to allow targeted research on the most appropriate surfaces and functional relevant edges. A set of preliminary testing and analysis to allow the setting up robotic polishing parameters in order to reach a desired final roughness of the dies.

Modeling and experimentation of dynamic material removal characteristics in dual-axis wheel polishing

CCOS (computer-controlled optical surfacing) approach is widely used in different optical polishing processes for making ultra-precision components with high surface form accuracy requirements. Under the polishing mode using complex tool motions, middle-spatial-frequency errors (MSF, i.e., residual ripples) tend to be generated on the workpiece surface, which would deteriorate the functional performance of the parts. In this paper, a dynamical removal model (DRM) based on the spatial kinematic analysis and polishing material removal theory is proposed, to investigate the actual material removal characteristics in dual-axis wheel polishing (DAWP). The model is developed to calculate the overall material removal profile (low-spatial-frequency error, LSF) and the middle-spatial-frequency errors, simultaneously. The shape and the stability of the tool influence function (TIF) are firstly investigated. A series of straight line path polishing tests on BK7 glass are carried out to investigate the effects of process parameters on the generated MSF errors and also check the validity of the proposed DRM. Uniform polishing tests on 50 × 50 mm BK7 samples are conducted, under different polishing parameters, the power spectral density (PSD) characteristics of the surface are also analyzed. The results show that the proposed model can effectively predict the material removal profile and especially the ripple characteristics generated on the surface, which are not reflected when using the conventional convolution algorithm typically used in a CCOS process. When increasing the ratio of feed velocity to co-rotating speed, the wavelength and amplitude of the residual ripples increase, and the ratio of ripple amplitude to total material removal depth also increases. The level of residual ripples can be effectively restrained by the appropriate setting of the speed ratio (reducing the feed velocity or increasing the co-rotating speed).

Parameter Optimization of Polishing M300 Mold Steel with an Elastic Abrasive

In order to achieve high-quality polishing of M300 mold steel curved surface, an elastic abrasive is introduced in this paper, and its polishing parameters are optimized so that the mirror roughness can be achieved. Based on the Preston equation and Hertz contact theory, the theoretical material removal equation for surface polishing of elastic abrasives is obtained, and the polishing parameters to be optimized are as follows: particle size S, rotational speed Wt, cutting depth Ap, and feed speed Vf. The Taguchi method is applied to design the orthogonal experiment with four factors and three levels. The influence degree of various factors on the roughness of the polished surface and the combination of parameters to be optimized were obtained by the range analysis method. The particle swarm optimization algorithm optimizes the BP neural network algorithm (PSO-BP), which is used to optimize the polishing parameters. The results show that the rotational speed has the greatest influence on the roughness, the influence degree of abrasive particle size is greater than that of feed speed, and the influence of cutting depth is the least. The optimum parameters are as follows: particle size S 1200#, rotational speed Wt 4500rpm, cutting depth Ap 0.25mm, and feed speed Vf 0.8mm/min. The roughness of the surface polishing with optimum parameters is reduced to 0.021 μm.

A precision polishing method for Wolter-I type optical mandrel

In the application of the 13.5-nm extreme ultraviolet (EUV) collector optics of the discharge produced plasma (DPP) source, the Wolter-I structure based on the X-ray grazing incidence optical design is usually adopted. The requirement of the surface roughness of this collector optics is demanding, which should reach to several nanometers. Currently, the mandrel replication is the main fabrication technology of this collector optics. Obviously, the requirement of the surface roughness of the mandrel used for the replication process should reach to the same level of the collector optics. However, the fabrication of the Wolter-I mandrel with high surface quality requirement still faces great challenge. In this paper, we propose a method that applies an elastic spherical tool to polish the surface of the Wolter-I mandrel, in which the shape of the elastic sphere can be changed relatively easily to accommodate the aspherical surface of the Wolter-I mandrel. A mathematical model regarding the movement trace of the polishing tool was established. Based on this model, the contact force between the polishing sphere and the aspherical surface can be controlled to point from the center of the polishing sphere in the normal direction to the polishing point. The influence of the polishing parameters on the material removal thicknesses is simulated and analyzed. The polishing experiments of ellipsoid and hyperboloid are carried out considering the difference of the diameter of each radial section on the Wolter-I mandrel surface. The proposed method is proved to reduce the surface roughness of the mandrel coated with chemically deposited nickel-phosphorous (NiP) alloy after diamond turning effectively. The root mean square (RMS) roughness of the mandrel surface after polishing can be reduced to 1.56 nm. It indicates that this method is suitable for further polishing of nickel-plated Wolter-I mandrel after ultra-precision turning. As a result, the manufacturing precision and efficiency of the Wolter-I mandrels can be improved by using the proposed polishing approach in this study, and the manufacturing cost can be reduced accordingly.

Fabrication and polishing of chalcogenide glass optical fiber connectors

In this paper, we described the fabrication and polishing characteristics of the end-faces of highly stable physical contact type chalcogenide optical fiber connectors. The effects of downforce pressure, polishing duration, and polishing fluid on the polishing process with abrasive grit size of 0.02 μm were investigated, and the final polishing parameters were determined. The surface roughness Ra was approximately 20 nm in the fiber area, and the average fiber roughness of the core region (10 μm × 10 μm) was about 3 nm, which were measured by the profilometry and atomic force microscope. Finally, the optical performance was analyzed in terms of the insertion loss of 1 dB and return loss of -18 dB.

Modeling of pad surface topography and material removal characteristics for computer-controlled optical surfacing process

Computer-controlled optical surfacing (CCOS) technology is an advantageous polishing process for producing optical surfaces with high convergence rates and high form accuracy, especially for fabricating hard and brittle materials. However, the optimum control of polishing parameters depends critically on the understanding of polishing mechanisms and modeling of material removal characteristics to achieve a deterministic process with high polishing efficiency. Removal analysis still requires further enhancement due to the multi-disciplinary, multi-scale complexity of the material removal mechanism involved in CCOS. Thus, this study presents a novel statistical asperity model and a material removal model to provide scientific and quantitative knowledge of the material removal mechanisms in CCOS. The model is developed on the basis of the research on statistical method, contact mechanics, iterative algorithm, abrasive wear mechanism, and cumulative removal process in CCOS. Practical experiments with different polishing parameters are performed to verify the theoretical model. Simulation results reasonably agree with measured data. Simulation experiments also show that the proposed model helps clarify the effect of pad surface topography on the micro-contact behavior and the material removal characteristics in CCOS and thus forms the theoretical basis for optimizing the polishing process.

Modeling and prediction of surface topography and surface roughness in dual-axis wheel polishing of optical glass

Abstract It is rather difficult to achieve uniform surface texture and high convergence rates of surface roughness (CRSR) at the same time in the conventional optical polishing process. The dual-axis wheel polishing (DAWP) technology, which uses a semi-rigid wheel with combined dual-axis rotational movements, shows a strong capability directly changing the rough ground surface status down to mirror status with nanometer level surface roughness, and achieving a uniform and smooth surface texture. In order to provide a better scientific understanding of the surface texture generation in DAWP process, in this paper, two comprehensive mathematical models are proposed. The first model is to predict the generation of micro-topography and roughness within single-axis TIF (tool influence function) area, based on the abrasive wear theory, abrasives distribution investigation and accumulative removal theory. On the basis of this model, another surface micro-topography generation model is also built to predict the micro-topography and roughness generated on workpiece surface in actual DAWP process (both for single and dual-axis modes). A series of fixed spot polishing tests and uniform polishing tests on BK7 glass were carried out to analyze the influence of polishing parameters and motion modes on the generated surface texture and roughness. The measurement results show that the surface micro-topography and roughness within TIF area and on polished surface can be well predicted by the two models. After actual polishing process, the dual-axis mode tends to produce much lower surface roughness with uniform texture. The single-axis mode tends to generate directional surface textures with relatively higher surface roughness. Under the dual-axis mode, the variation of co-rotating speed has less influence on the polishing quality, very high CRSR and uniform texture can be achieved under different co-rotating speeds.

Effect of Ultrasonic Electro-Chemical Polishing Parameters on Surface Roughness and Material Removal Rate of Medical Grade Cobalt Chromium Alloys

The fabrication of prosthesis from superalloys in bio-medical field is a challenging task as a result of strict tolerance requirement in surface finish. Precision surface finish is desired to avoid biocompatibility issue resulting from poor surface finish. Such surface finish requirement can be achieved by using Electro-Chemical Polishing (ECP) process. This research investigated the effect of applying ultrasonic vibration on ECP with process parameters, namely current (0.5A-2.5A) and time (2min-10min) on the surface roughness (Ra) and material removal rate (MRR) of cobalt chromium molybdenum (CoCrMo). The experiments were conducted using ECP and ultrasonic assisted ECP (UECP) processes whereby phosphoric acid (H3PO4) and SS 304 steel were used as electrolyte and electrode respectively. The result showed an increasing trend of MRR and Ra as the time and current increased in both processes. It was also found that ultrasonic assisted ECP at current (2.5A) and time (30 min) recorded the highest MRR (0.047 g/min) and the lowest Ra (2.139 µm).

Modelling and investigation of material removal profile for computer controlled ultra-precision polishing

Computer controlled ultra-precision polishing (CCUP) is widely used for high-precision surface finish processing with high form accuracy and good surface finish. CCUP is a deterministic material removal process based on the surface error-profile and the removal characteristic of the polishing tool. Material removal profile is often used to characterize the material removed in polishing process. Deviation phenomenon is a newly detected feature of the material removal profile which may contribute to the non-negligible form error of the polished surface. In this paper, the material removal model is established on the basis of Preston equation to obtain a better understanding of the characteristics of material removal in surface polishing. Firstly, contact stress model is established using Hertz contact theory. Then, relative velocity in the contact area is analyzed using geometric methods which can directly reflect the difference of the velocity of points in the contact area. Finally, single factor analysis and Taguchi method are used to investigate the influence of polishing parameters on the deviation feature of material removal profile and to provide a way for parameter optimization. The simulation and experiment results indicate that the proposed method can describe the deviation features well and parameter optimization strategies are provided in the conclusions.

Experimental investigation of the magnetorheological polishing process with roller

PurposeThis paper aims to develop a new magnetorheological polishing (MRP) device with roller and investigate the polishing mechanism of MRP fluids using this new device.Design/methodology/approachThe principle of MRP process with roller is discussed, and then the structure of the polishing device is designed in detail. The polishing experiments of K9 glass are carried out using MRP device with roller.FindingsA series of tests are performed to evaluate the effect of the excitation gaps, working gap and polishing time on the polishing characteristics, and the optimized polishing parameters can be obtained. The surface roughness Ra of the sample is reduced from 359 to 38 nm under optimized polishing parameters.Originality/valueMRP method with roller is proposed in this paper, and the MRP device with roller can reduce the surface roughness Ra significantly. After being polished, the circular ring-shaped polishing belt disappears on the workpiece surface, which means it has great potential for polishing.

Manuscript numerical simulation on ultra-precision polishing of monocrystalline silicon by SPH method

Ultra-precision polishing is an important processing method for monocrystalline silicon, in order to improve the machining efficiency and obtain good machining quality, it is necessary to investigate the material removal process and process parameters of ultra-precision polishing. Smoothed particle hydrodynamics (SPH) is a meshless method with good self-adaptability, it can be used in the simulation of ultra-precision polishing which has high speed deformation characteristics. The calculation model and SPH analysis model of ultraprecision polishing are established according to the principle of ultra-precision polishing, SPH method is used to simulate and analyze ultra-precision polishing of the monocrystalline silicon. The material removal process of ultra-precision polishing is investigated, the effects of abrasive size and indentation depth on the equivalent plastic strain (PEEQ), Mises stress and the force of abrasive is investigated. The result is that, at the different time of ultra-precision polishing, the maximum PEEQ is different, but the difference is not obvious; the X direction force of the abrasive increases with the indentation depth; the size of abrasive has a great influence on the soft coefficient of stress state in ultra-precision polishing. According to the simulation results, it is possible to optimize the technological parameters of ultra-precision polishing, and provide the theoretical guidance for practical production.

Laser polishing of additive manufactured CoCr alloy components with complex surface geometry

Laser polishing, capable of polishing selective nonplanar areas, is exploited to improve the surface roughness of additive manufactured metal components. It offers a highly repeatable, higher speed polishing process as well as low labor costs compared with traditional mechanical abrasive polishing. In spite of the fact that many studies can be found on laser polishing processes, few have reported that focus on metal components, manufactured additively by selective laser melting (SLM) technology, with geometrically different complex surfaces. This paper presents a novel method to reduce the surface roughness of Cobalt Chromium (CoCr) components with complex surface geometry by using a layered polishing method which can constantly adjust the defocusing distance of the laser along with the surface shape of the components. The optimized laser polishing parameters used were firstly obtained from the test results on planar surfaces of CoCr alloy samples and samples with complex surface geometry were then polished based on the laser parameters. Characterizations for the laser polished samples were conducted using optical profiling and scanning electron microscopy, showing that the surface roughness was reduced significantly in comparison with the as-received samples. A reduction of up to 93% in surface roughness was achieved. The mechanical hardness was also characterized by testing for Vickers hardness, which indicated the surface hardness of the laser polished samples was enhanced by 8%. Moreover, a simple and effective model was developed to illustrate the method of laser polishing on the complex surface geometry of additive manufactured CoCr alloy components. The analytical model is helpful in understanding and evaluating the underlying mechanisms of laser polishing.

Optimization of process parameters with Taguchi method for nano machining CaF2 crystal

ABSTRACTOwing to the outstanding optical characteristics of calcium fluoride (CaF2) crystal, this material is a great choice for ultraviolet lenses and windows. Due to its softness and brittleness, it is difficult to nano machining CaF2 crystal. Fixed abrasive polishing technology, one of nano machining directions, was adopted to process CaF2 crystal. Experiments were designed using Taguchi method to explore the effect of pressure, plate speed, slurry flux and slurry pH on material removal rate and surface roughness in fixed abrasive polishing of CaF2 crystal. The optimum polishing parameters for material removal rate are discovered to be pressure 10 kPa, slurry pH 11, plate speed 50 rpm and slurry flux 40 ml/min. And they are pressure 6.7 kPa, slurry pH 9, plate speed 40 rpm and slurry flux 60 ml/min for surface roughness. The analysis of variance shows that pressure 52.6% and plate speed 25.4% are the most significant parameters that affect material removal rate, while plate speed 51.3% and slurry flux 32.0% are the two main factors for surface roughness. The most significant factor and the contribution of each parameter for MRR and surface roughness were obtained in nano machining process, respectively.

Development of hydrophobic cupronickel surface with biofouling resistance by sandblasting

The paper focuses on a novel method for enhancing the biofouling resistance of cupronickel (90-10 Cu-Ni) alloy by surface modification involving sand blasting, pickling and coating with silane. After optimizing the experimental parameters for polishing, pickling and sandblasting in order to develop a hydrophobic surface, the surface morphology and the wetting properties of the modified surface were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and contact angle meter. The enhancement in resistance to bacterial adhesion was demonstrated by adhesion studies on Pseudomonas sp., the major biofilm former in marine environment. The silane based coating on the sand blasted surface of cupronickel alloy brought about two order reduction of bacterial attachment as compared to the control sample.

Use of chemical oxidizers with alumina slurry in Double Disk Magnetic Abrasive Finishing for improving surface finish of Si (100)

The present communication emphasizes on the polishing of monocrystalline silicon wafer Si (100) using Double Disk Magnetic Abrasive Finishing (DDMAF) under the influence of oxidizer i.e., Marshall’s acid salt (K2S2O8,1%wt/wt), Caro’s acid salt(KHSO5,1%wt/wt)) and Hydrogen peroxide (H2O2, 0.05% wt/wt) mixed with 1200 mesh alumina slurry. The alumina slurry under the influence of these oxidizers for aforesaid weight percent was allowed to flow in the finishing gap ranging between (2–10) ml/min. The polishing with DDMAF was simultaneously executed at different polishing speeds and working gaps. A set of 20 experiments were planned using Response Surface Methodology (RSM) and surface roughness data of polished silicon wafers were recorded for each experimental trial. Analysis of Variance (ANOVA) was used to obtain the significant process parameters on the surface roughness. Statistical model for surface roughness in terms of process parameters was developed. The pooled model after neglecting the insignificant terms was optimized using fmincon for constrained non-linear minimization tool box available with MatLab13 software package. The optimization of the pooled surface roughness model could firmly determine the optimum polishing parameters for obtaining the desired minimum surface roughness. Confirmatory experiment was carried out at optimum polishing parameters and it was found that the theoretical results agreed well with the experimental findings. The work further focused into the study of surface integrity of unpolished Si (100) sample and the polished sample obtained at optimum parameter using SEM and AFM images.

Research on effect of parameters in Rotation & Revolution Type Polishing Method

The Rotation and Revolution Polishing method which can stably maintain polishing tool shapes and uniformly generate the surface roughness by through optimum polishing velocity distribution, was applied here as a replacement of conventional methods. Relationship of the various polishing parameters was analyzed for improving polishing stability. Experiments were conducted to determine and prove the effectiveness of mathematic formula on polished profiles based on the Preston equation and geometry under diverse conditions.

Residual stress of belt polishing for the micro-stiffener surface on the titanium alloys

Titanium alloys are widely used in the key parts of aero-engine, such as blade, blisk and so on, and the belt polishing process is proved to be a good method to creating optimal surface integrity to improving the fatigue life and service performance for titanium alloys parts. The method of micro-stiffener belt polishing was presented, based on the influence rule of thin-plate stiffener on the bending life and the principle of micro-crack, to forming characteristically and clearly surface texture to further improving the fatigue life with new belt polishing method. This paper provides a comprehensive characterization of residual stresses produced in micro-stiffener belt polishing for heat-resistant titanium alloys bearing steel using aluminum oxide abrasive belt. There are two method to analyzing the residual stresses generated by this method: the X-ray projector was used to measure the surface residual stress to revealing the formation rule of residual stress with different belt polishing parameters (reciprocating frequency, feeding speed and contact force), and a finite element model of the belt finishing operation in order to bring an further understanding the belt polishing process and the residual stress distribution in different depth. The results show that, the contact force is the main parameters to influencing the forming of residual stress, and the same time, the bigger residual stress would be obtained under the conditions of smaller feeding speed and faster reciprocating frequency, the influenced layer thickness of residual stress is nearly 10μm, and the maximum residual stress is 1.2μm under the surface. Therefore, the new method can be used to improve the surface residual stress of titanium alloy parts.

Experimental Optimization of Annular Polishing Parameters for Silicon Carbide

Machined surface quality has a strong impact on the functionality of silicon carbide‐based components and devices. In the present work, we first analytically investigate the complex coupling of motions in annular polishing based on the Preston equation, which derives the influential parameters for material removal. Subsequently, we conduct systematic annular polishing experiments of reaction‐bonded silicon carbide to investigate the influence of derived parameters on polished surface quality, which yield optimized polishing parameters for achieving ultralow surface roughness of reaction‐bonded silicon carbide.

Granite polishing: Effects of polishing parameters and tool paths on part quality and dust emission

Machining is necessary to shape parts but it is also an important source of pollution (such as dust and aerosols) and this constitutes hazards for machine-tools operators. The emission of dust depends on machining conditions, processes, tooling, and machining strategies. The shop floor air quality is thus of great concern when shaping dusty materials such as granite as this process generates harmful dusts. In recent times, the occupational health and safety regulations have become more severe. On the 24th of March 2016, the US department of Labor’s, occupational Safety and Health Administration (OSHA) announced the reduction of the exposure limit for inhalable crystalline silica dust by half. To quickly comply with these new regulations, engineers and researchers must help industries in developing strategies to limit workers risk of exposure to the silica. This paper investigates the emission of fine and ultrafine particle emission when polishing granite as a function of machining conditions and parameters. The main goal is to determine machining conditions leading to less dust emission while maintaining acceptable part quality and productivity.

Vibration-assisted micro-ECM combined with polishing to machine 3D microcavities by using an electrolyte with suspended B4C particles

Three-dimensional (3D) microcavities can be machined by micro-electrochemical machining (micro-ECM) using a 3D microelectrode. However, with increasing machining depths, it becomes challenging to renew electrolyte and remove the electrolytic products from the machining gap. Therefore, 3D microcavities are usually shallow and the machined surfaces are of poor quality. To address these problems, this paper proposed performing 3D microelectrode vibration-assisted micro-ECM in combination with polishing to machine 3D microcavities by using an electrolyte containing suspended B4C particles. First, a 3D microelectrode with rectangular holes on both of its undersurfaces was fabricated by means of bending-and-avoiding mode wire electrical discharge machining in combination with vacuum thermal diffusion bonding. Second, the prefabricated microelectrode was applied in vibration-assisted micro-ECM to machine deep 3D microcavities using an electrolyte containing suspended B4C particles. Thereafter, the machined surfaces of the deep 3D microcavities were polished to improve the surface quality. Furthermore, the effects of vibration amplitude and frequency, polishing time, and B4C particle concentration on the microcavity surface quality were investigated in detail. The experimental results indicate that the electrochemical reaction attachments on the microelectrode surface were removed by polishing of the particles during processing, ensuring satisfactory processability of the microelectrode, as well as a highly efficient and stable micro-ECM process. Moreover, when the vibration amplitude was set to 10 μm, vibration frequency to 30 Hz, polishing time to 30 min, and B4C particle concentration to 5 g/L for the 300 μm deep microcavity machined by the proposed method, the microcavity bottom surface roughness was minimized (Ra = 0.223 ± 0.021 μm) and the sidewall roughness was improved. Finally, based on the proposed method and optimized polishing parameters, 3D microcavities of more than 800 μm deep with rectangular and semi-cylindrical islands were obtained.