Abrasive Lapping Research Articles

Research on the generation mechanism of surface and subsurface damage in loose abrasive lapping of RB-SiC ceramics

Reaction-bonded silicon carbide ceramics (RB-SiC) are extensively utilized in aerospace, space optics, and other fields due to their superior physical and chemical properties. Loose abrasive lapping plays a crucial role in the optical manufacturing of large-diameter RB-SiC mirrors. Previous research predominantly focused on grinding processes and overlooked the removal mechanism during lapping and their impact on surface and subsurface damage. In this study, a three-body brittle fracture removal model was established to explore the removal mechanisms of RB-SiC. Additionally, experiments were carried out to investigate the influence of abrasive particle size on the surface and subsurface damage. Experimental results confirm the theoretical model and indicate that for RB-SiC, different particle sizes correspond to distinct removal mechanisms, causing abrupt changes in surface roughness, while the layer under SiC acts as a buffer against the propagation of subsurface damage. These findings help optimize the manufacturing process, improve lapping efficiency, and enhance mirror performance.

Surface evolution and subsurface damage mechanism in fixed abrasive lapping of Silicon carbide

Surface evolution and subsurface damage mechanism in fixed abrasive lapping of Silicon carbide

Simulation and experimental research on the abrasive trajectories of plane lapping based on rotary swing drive

In the pursuit of achieving exceptional surface shape accuracy for MPCVD (Microwave Plasma Chemical Vapor Deposition) polycrystalline diamond wafers during the free abrasive lapping process, plane lapping based on rotary swing drive was employed in this study. The crux of this study lay in the development of a comprehensive kinematic model, scrutinizing the motion behavior of abrasive particles, and probing the influence of parameters on the uniformity of abrasive trajectories. The results show that the eccentricity, arc chord length and speed ratio affect the probability of track coincidence rate, and then affect the distribution uniformity. And then the verification experiments solidifying the reliability of our kinematic model and affirming the veracity of simulation results. The best surface shape accuracy ( PV) of the MPCVD polycrystalline diamond wafer was 2.3 μm under optimal parameters, representing a substantial advancement compared to the original lapping method, which only yielded a PV value of 8.4 μm. This study provides a promising method for high surface shape accuracy of MPCVD polycrystalline diamond wafers with large sizes.

Ultra-precision lapping of H2O(g) plasma-treated CaF2 by porous diamond grits

The calcium fluoride (CaF2) component has excellent light transmission and a high laser damage threshold in the UV band, and thus is a potentially ideal material for high-power laser facility. However, the low-damage surface is difficult to attain via the existing processing technologies due to its brittleness, especially the dissociation property of the (111) surface. We innovatively propose H2O(g) plasma-assisted porous diamond abrasive lapping technology to achieve low-damage and high-precision surface processing of CaF2 component, which means that the CaF2 component is modified first and then the softened modified layer is removed by the porous diamond abrasive lapping. The H2O(g) plasma modification mechanism was elucidated through a combination of molecular dynamics simulation and experiment and comparison with H2O(g) plasma etching. The modification layer including an oxide layer and a phase change layer was produced by adjusting the plasma processing process (power of 25 W and H2O(g) content of 10 ml). Then the modified CaF2 component was lapped by the porous diamond abrasive tool on the ductile domain layer which is more than the modified layer and less than the sum of the modified layer and plastic domain. When the lapping process parameters were 200 rpm platen rotation speed and 20 N lapping pressure, a surface accuracy of 15.34 nm PV, 2.29 nm RMS (φ1 mm) was obtained. This study provides technical support for the low-damage processing of CaF2 component.

Effect of pad surface morphology on the surface shape of the lapped workpiece

Double-sided lapping is currently the mainstream manufacturing method for obtaining plane-parallel optical workpieces with high surface shape accuracy, and the fixed abrasive lapping pad is the main machining tool. However, the effect of pad surface morphology on the workpiece surface shape has rarely been studied, and its formation mechanism has not yet been revealed. In this paper, based on probabilistic statistics and contact mechanics, an analytical model that takes into account the pad surface morphology for predicting the workpiece surface shape evolution is developed. Notably, this model considers the cross-scale relationship between the formation of lapped surface shape and the scratching process of a single abrasive grain in material removal for the first time. Furthermore, the real-time dynamical contact relationship between the workpieces and the measured actual pad surface morphology is also considered. The surface shape and peak-to-valley value of the workpiece under different parameters were simulated and analyzed, and the influence mechanism of the local profile and macro shape of the lapping pad on the lapped workpiece surface shape are clarified. Moreover, the double-sided lapping trial experiments were performed to validate the theoretical model, and the experimental results demonstrated good agreement with the simulation results. The maximum error of the surface shape evolution prediction model is less than 14.6 %. This result verifies the correctness and validity of the established model. This work not only provides new ideas for controlling the workpiece surface but also forms the theoretical basis for understanding the double-sided lapping process.

Experimental studies on reflective finishing of aluminum sheet by CNC abrasive lapping

ABSTRACT This study focuses on improving the surface properties of Aluminum (Al) sheets for imaging and optical applications. To achieve high efficiency and low damage, novel CNC abrasive lapping (CNC AL) techniques were proposed and tested. The experiments investigated the impact of various parameters, such as spindle speed, feed rate, and depth of cut, using two types of abrasives (PCD and hybrid PCD with Al2O3) on the surface quality (Ra) and reflectance (R) of the Al sheets. Optimal parameters were determined using Taguchi L9 and (S/N) analysis, favoring low spindle speed, low feed rate, and high depth of cut. Surface roughness was measured with Surfcom1400G, while SEM EDX, AFM, and 3D profilometer were used to assess surface microstructures. Significant improvement of 35-96% was observed in the highly reflective Al sheets using UV-VIS spectrophotometry and texture analysis in MATLAB.

An Exploration of the Influence of Abrasive Water Jet Pressure on the Friction Signal Characteristics of Fixed Abrasive Lapping Quartz Glass Based on HHT

Abrasive water jetting is an effective dressing method for a fixed abrasive pad (FAP) and can improve FAP machining efficiency and the impact of abrasive water jet (AWJ) pressure on the dressing effect; moreover, the machining state of FAP after dressing has not been thoroughly studied. Therefore, in this study, the FAP was dressed by using AWJ under four pressures, and the dressed FAP was subjected to lapping experiments and tribological experiments. Through an analysis of the material removal rate, FAP surface topography, friction coefficient, and friction characteristic signal, the influence of AWJ pressure on the friction characteristic signal in FAP processing was studied. The outcomes show that the impact of the dressing on FAP rises and then falls as the AWJ pressure increases. The best dressing effect was observed when the AWJ pressure was 4 MPa. In addition, the maximum value of the marginal spectrum initially rises and then falls as the AWJ pressure increases. When the AWJ pressure was 4 MPa, the peak value of the marginal spectrum of the FAP that was dressed during processing was the largest.

Super hard and brittle material removal mechanism in fixed abrasive lapping: Theory and modeling

Currently, the problems of inefficient fixed abrasive lapping (FAL) for super hard and brittle material wafers (such as sapphire) with fixed abrasive pads (FAPs), restrict the development of the semiconductor industry. Most importantly, the mechanisms of FAL processes are still unclear, often analyzed based on the theoretical models of chemical mechanical polishing (CMP). However, the material removal models of CMP are specific to loose abrasives, do not effectively apply to the lapping processes for super hard and brittle material wafers with a FAP. In this paper, the spherical crown model modified by elastic-plastic mechanics and brittle-plastic transformation mechanism was applied to super hard and brittle material removal mechanism in FAL processes. In consideration of the influences of the yielding abrasives embedded in the FAP matrix and the matrix surface topography on the wafer-pad contact, a material removal model suitable for super hard and brittle material wafers lapped by FAPs was obtained. The loads applied on the fixed abrasives and the matrix asperities during the elastic-plastic-brittle deformation processes of wafers were analyzed, respectively. The model indicates that the back-off of the abrasives embedded in the FAP matrix intensifies along with the decrease of the matrix hardness and the increase of the abrasive size, respectively. The penetrating depth of the fixed abrasive can be raised by increasing matrix hardness, applied pressure, abrasive size, and decreasing abrasive number, as same as the elastic recovery of the super hard and brittle material slid by the abrasive after unloading. The pad matrix surface dressed by loose grains greatly affects the MRR of wafers. The predicted MRR of sapphire wafers based on the FAL model is consistent with experimental data. Finally, the keys to improving the processing efficiency of super hard and brittle material wafers are clarified in detail.

Modeling and experimental study on material removal rate of quartz wafer by fixed abrasive lapping

Modeling and experimental study on material removal rate of quartz wafer by fixed abrasive lapping

Fractal Characteristic-Induced Optimization of the Fixed Abrasive Lapping Plate in Fabricating Bipolar Plate of Proton-Exchange Membrane Fuel Cells

Purpose: A bipolar plate with fractal-characterized microstructures can realize intelligent energy transmission and obtain a high efficiency of proton-exchange membrane fuel cells. In this paper, fixed abrasive lapping technology is proposed to fabricate a surface microstructure on a bipolar plate with fractal characteristics. Methodology: The kinematics of the fixed abrasive lapping process was developed and employed to numerically investigate the particle trajectories moving on the target surface by considering the different arraying forms of diamonds on the lapping plate. Findings: It was found from an analysis of both the uniformity and the fractal characteristics that the arraying form of diamonds on the lapping plate, with the distribution of latitude and longitude with an angle of 30° and a gap of concentric circles of 40 mm with a minimum radius of 70 mm and maximum radius of 190 mm, can be used to obtain the best uniformity and fractal characteristics in the fixed abrasive lapping of a bipolar plate. Conclusions: The distribution of the latitude and longitude of 40° and 30° considered in this study is expected to realize the best machining performance in the bipolar plate and present good cell performance.

Surface Morphology Evaluation and Material Removal Mechanism Analysis by Single Abrasive Scratching of RB-SiC Ceramics

Reaction-Bonded Silicon Carbide (RB-SiC) ceramics possessing excellent mechanical and chemical properties, whose surface integrities have an essential effect on their performance and service life, have been widely used as substrates in the core parts of aerospace, optics and semiconductors industries. The single abrasive scratching test is considered as the effective way to provide the fundamental material removal mechanisms in the abrasive lapping and polishing of RB-SiC ceramics for the best surface finish. In this study, a novel single abrasive scratching test with an increasing scratching depth has been properly designed to represent the real abrasive lapping and polishing process and employed to experimentally investigate the surface integrity regarding different scratching speeds. Three typical and different material removal stages, including the ductile mode, ductile–brittle transition mode and brittle mode, can be clearly distinguished and it is found that in the ductile material removal stage by increasing the scratching speed would inhibit the plastic deformation and improve its surface integrity. It is also found that in the ductile–brittle transition and brittle material removal stages, to increase the scratching speed would inhibit the plastic deformation due to the fast scratching speed that limits the time of plastic deformation on the target, but it also results in the increased length of lateral cracks with the increased scratching speed which can reflect that the size of brittle chips, like brittle fractures and large grain fragmentations, increases as the scratching speed increases. It can provide the references for the optimization of the abrasive lapping and polishing of RB-SiC ceramics with high efficiency and surface quality.

Surface Form Accuracy Evaluation in Abrasive Lapping of Single-Crystal Silicon Wafers

Silicon-based materials still dominate the current semiconductor industry for the foreseeable years such that it is needed in continuously developing the related advanced manufacturing technologies. For the abrasive precision lapping of single-crystal silicon wafers, the surface form accuracy is very important which can significantly improve its efficiency and reduce the cost in the following ultra-precision polishing process. In this study, a novel driving system is proposed in the single-side planetary lapping process that could realize the irrational rotation speed ratio of the lapping plate to the workpiece, and it is found from the numerical qualitative and quantitative analysis that the uniformity of the particle trajectories moving on the target surface has been significantly improved using the irrational rotation speed ratio and hence resulting in the higher surface form accuracy than that driven by the rational rotation speed ratio. Moreover, an in-house developed irrational rotation speed ratio driving system has been designed for the experimental study, and it is found that the effect of the rational and irrational rotation speed ratios on surface roughness is not significant, while all the five essential values related to the surface form accuracy are better under the rotation speed ratio of i = 1.0772… than that under the rotation speed ratio of i = 1, which demonstrates that the irrational rotation speed ratio driving system has the advantage of being able to obtain a good surface form accuracy and agrees well with the numerical simulation results.

Investigation of Technological and Load Intensity Parameters of the Finishing Process of Materials on Equipment with Tools Translational Kinematics.

The regularities of the formation of the resulting raster tool trajectories based on Lissajous figures for the lapping process of planes are established. This makes it possible to maximize the cutting ability of the tool, which contributes to its more uniform wear and increased productivity and processing quality. Optimal parameters of productivity and roughness of the treated surface during lapping of zirconium ceramics are achieved through the use of ASM paste 28/20 µm. Based on Preston’s hypothesis, an exponential dependence of the change in the contact area during the lapping of planes of different initial shape of the macrorelief is obtained. The obtained theoretical and practical results of the study of the process of flat lapping with constant and variable clamping force of the treated surface to the surface of the tool. The influence of the force factor on the formation of the surface in the process of abrasive lapping has been established. Studies have been carried out and the main technological recommendations of precision surface treatment of workpieces based on hard, brittle ceramic material and bronze samples on equipment with a raster trajectory of the tool movement are presented. The optimal pressure value when processing ceramics should be considered 203–270 kPa (2.1–2.8 kg/cm2).

Tribological effects of loose alumina abrasive assisted sapphire lapping by a fixed agglomerated diamond abrasive pad (FADAP)

The tribological effects between a fixed abrasive pad (FAP) and a workpiece can effectively maintain the self-conditioning process of the FAP in real time. However, the FAP is easy to be glazed along with the long-term lapping processes of hard-to-process ceramic materials. This paper proposed a novel method of loose abrasive assisted fixed agglomerated diamond abrasive lapping (LA-FADAL) to achieve efficient and stable lapping processes of sapphire. LA-FADAL tests with a fixed agglomerated diamond abrasive pad (FADAP) were carried out by changing the particle size and volume fraction of loose alumina abrasives in lapping slurries. The influences of the different alumina abrasives on the processing performance of the FADAP were discussed. Material removal mechanisms in the LA-FADAL processes were proposed based on the tribological effects of loose alumina abrasive assisted sapphire lapping by the FADAP. The loose alumina abrasives with the similar size as the diamond grains embed in the surface of the fixed AD abrasive could not remove sapphire materials directly and effectively by mechanical actions, mainly played a role of dressing the FADAP to enhanced the self-sharpening ability of AD abrasives, and further improved the self-conditioning ability of FADAPs.

Investigation on surface evolution and subsurface damage in abrasive lapping of hard and brittle materials using a novel fixed lapping tool

Novel fixed abrasive lapping (NFAL) is used in this study to quickly remove the surface damage layer and control the depth of subsurface damage (SSD), thus saving overall machining time and reducing the costs of large-aperture optical manufacturing. The influence of lapping parameters on the surface and subsurface state is studied through a series of experiments to better understand the material removal and damage mechanisms during NFAL. A surface evolution model for NFAL was established based on indentation fracture mechanics, mathematical statistics, abrasive wear theory and convolution iteration principle. Experimental results show that the model can predict the surface topography well. Further simulation experiments were also conducted to study the effects of the tool load and particle size on the microscopic removal characteristics of the NFAL process. The results show that NFAL can quickly produce submicron-level surface roughness and restrain SSD with the reasonable selection of lapping parameters.

Prediction analysis of subsurface damage of work-part ZnS in fixed abrasive lapping

Prediction analysis of subsurface damage of work-part ZnS in fixed abrasive lapping

Theoretical and experimental investigation on surface generation and subsurface damage in fixed abrasive lapping of optical glass

Fixed abrasive lapping (FAL) is a promising technology increasingly used for finishing optical mirrors and molds in a number of materials due to its high finishing efficiency, environmental friendliness, and relatively better surface and subsurface quality. A theoretical model for fixed-abrasive lapping of optical glass was developed in this paper by using indentation fracture mechanics, contact mechanics, mathematical statistics, lapping kinematics, and convolution iterative principle to provide an enhanced scientific understanding of the surface microtopography generation and subsurface damage (SSD) control mechanisms. In the modeling, the influence of the shape, size, and spatial distribution of abrasive particles and the ductile and brittle removal mechanisms of the material were considered. A series of lapping experiments on fused silica glass was carried out to quantitatively analyze the feasibility and accuracy of the model and study the influence mechanism of process parameters on the surface and subsurface state. Results indicated that the models could well predict the surface micromorphology and the SSD depth, and the range of sharpness angle of abrasive particles and tool load affected the predicted SSD range. In addition, the material removal mechanism and lapping tool wear characteristics were revealed by the surface structure and element component analysis. Finally, the FAL process was optimized by the evaluation indices of material removal rate (MRR), surface roughness, and SSD.

Effect of material structure on spinel machinability in its fixed abrasive lapping

Clarifying the effects of material properties on the lapping performance is helpful in optimizing the lapping processing and revealing the lapping mechanisms. In this study, the microstructures of single-crystal spinel (SS) and polycrystalline spinel (PS) were observed by a microscope after being etched with H3PO4 at high temperature. Automatically controlled micro-hardness testing and analysis systems were used to measure the hardness and crack length of SS and PS wafers. On this basis, the fracture toughness and critical cutting depth were estimated. And, a series of lapping tests were conducted to evaluate the effects of crystals on its machinability with a fixed abrasive pad (FAP). After lapping, the size distribution of collected debris was measured by using a laser particle analyzer. The debris and selected posts of FAP were observed by using a scanning electron microscope. Experimental results indicate that the different microstructures and hardness characteristics between SS and PS result in different average cutting depths, which finally affect the lapping debris sizes, FAP surface conditions, and its machinability.

Surface Quality Improvement by Using a Novel Driving System Design in Single-Side Planetary Abrasive Lapping.

For the traditional single-side planetary abrasive lapping process particle trajectories passing over the target surface are found to be periodically superposed due to the rational rotation speed ratio of the lapping plate to workpiece that could affect the material removal uniformity and hence its surface quality. This paper reports on a novel driving system design with combination of the tapered roller and contact roller to realize the irrational rotation speed ratio of the lapping plate to workpiece in the single-side planetary abrasive lapping process for the improvement of surface quality. Both of the numerical and experimental investigations have been conducted to evaluate the abrasive lapping performance of the novel driving system. It has been found from the numerical simulation that particle trajectories would theoretically cover the whole target surface if the lapping time is long enough due to their non-periodic characteristics, which can guarantee the uniformity of material removal from the surface of workpiece with relatively high surface quality. The encouraging experimental results underline the potential of the novel driving system design in the application of the single-side planetary abrasive lapping for the improvement of the surface quality in terms of surface roughness and material removal uniformity.

Novel Abrasive-Impregnated Pads and Diamond Plates for the Grinding and Lapping of Single-Crystal Silicon Carbide Wafers

In this study, special ceramic grinding plates impregnated with diamond grit and other abrasives, as well as self-made lapping plates, were used to prepare the surface of single-crystal silicon carbide (SiC) wafers. This novel approach enhanced the process and reduced the final chemical mechanical planarization (CMP) polishing time. Two different grinding plates with pads impregnated with mixed abrasives were prepared: one with self-modified diamond + SiC and a ceramic binder and one with self-modified diamond + SiO2 + Al2O3 + SiC and a ceramic binder. The surface properties and removal rate of the SiC substrate were investigated and a comparison with the traditional method was conducted. The experimental results showed that the material removal rate (MRR) was higher for the SiC substrate with the mixed abrasive lapping plate than for the traditional method. The grinding wear rate could be reduced by 31.6%. The surface roughness of the samples polished using the diamond-impregnated lapping plate was markedly better than that of the samples polished using the copper plate. However, while the surface finish was better and the grinding efficiency was high, the wear rate of the mixed abrasive-impregnated polishing plates was high. This was a clear indication that this novel method was effective and could be used for SiC grinding and lapping.