Material Removal Model Research Articles

Material removal model for magnetorheological polishing considering shear thinning and experimental verification

To establish a more accurate magnetorheological polishing material removal model, the shear thinning effect of magnetorheological polishing solution under high shear rate conditions was analyzed based on magnetic dipole theory, and the two-particle chain junction model was used to analyze the force of magnetic particles in magnetorheological polishing solution, and the shear yield stress of magnetic chain under tilted condition was obtained, and the magnetorheological polishing material removal model considering shear thinning was established by combining the modified Preston equation. The effect of shear thinning on the magnetorheological polishing material removal model was analyzed. The calculated results of the model are compared with the experimental data of magnetorheological polishing material removal, and the results show that the material removal model considering shear thinning can accurately predict the material removal rate of magnetorheological polishing, especially the trend of decreasing material removal rate of magnetorheological polishing at high shear rate is effectively predicted.

Grain shape-protrusion-based modeling and analysis of material removal in robotic belt grinding

The accurate prediction of material removal (MR) remains a persistent challenge in the field of robotic belt grinding, particularly with the consideration of the stochastic nature of abrasive grains. Starting from the characteristics that abrasive grains with different shapes participate in grinding, this work presents a novel MR model that extends from microscopic grain-workpiece interaction to macroscopic wheel-curved surface contact. Specifically, the irregular shapes of single abrasive grains are generalized into four typical types, namely, semi-sphere, cone, equilateral-triangular pyramid, and square pyramid. Based on the effective abrasive grains determined by stochastic grain protrusion heights, the microscopic contact force and material removal volume shared by different effective individual abrasive grains are modeled and analyzed subsequently. Together with the macroscopic contact pressure solved by the Hertzian contact theory, the material removal model is derived by considering the geometrical characteristics of different-shaped abrasive grains. Finally, the grinding experiments on the Ti–6Al–4V test block and aero-engine blade were conducted under controllable grinding parameters, through which the effectiveness and applicability of the proposed model were validated, and the material removal characteristics with different structured abrasive belts were investigated.

Innovative Refrigeration Technology for Machine Tools with Sustainable Refrigerants and Digital Twins

This article investigates the trend of assessing energy efficiency, sustainability and greenhouse gas emissions in the operation of 5- axis milling machine tools. This research aims to predict the cooling load by thermal models control within the main spindle system to ensure that cooling devices are dimensioned adequately and to keep it running under optimal conditions leading to improve the overall efficiency. In order to achieve this goal, a digital twin approach is currently being developed utilizing commercial software which consists of four primary models. A simulation model for material removal is used to predict the mechanical load required for the milling process to finish the CAD model. The second model is the spindle control model to determine the electric currents needed to operate the induction motor at the specified mechanical power. This model provides the electric current data to the lumped-parameter thermal networks (LPTN) model, which is proposed to accurately represent the heat dissipation from the motor and spindle systems towards the cooling channel in the main spindle system. Subsequently, the task at hand involves making an estimate of the necessary outlet temperature derived from the refrigeration unit model, which is essential for effectively covering the thermal energy produced by the spindle system.

Prediction of quadratic cylinder surface morphology for ultrasonic assisted polishing

Aluminum alloys with light weight and excellent performance in processing are widely used in different kinds of optical reflector elements. In this paper, An innovative model for predicting the surface morphology of ultrasonic assisted polishing quadratic cylinder surfaces was developed based on the material removal model and calculation of the trajectory methods. Experimental verification was accomplished. By analyzing the simulation and experimental surface roughness analysis and two-dimensional power spectral density, the maximum error between the roughness experiment and the simulation is 9.3%, and the maximum error between the peak two dimensional power spectral density of experimental and simulation results is 9.8%. Surface properties can be enhanced and errors of medium and high frequency in the polished surface region can be diminished with the ultrasonic assisted polishing. This study provides important guidance for ultrasonic assisted polishing of different types of quadratic cylinder surfaces including without limitation cylindrical, elliptic, and parabolic surfaces.

Theoretical and Experimental Investigation of Material Removal Rate in Magnetorheological Shear Thickening Polishing of Ti–6Al–4V Alloy

Abstract Magnetorheological shear thickening polishing (MRSTP) is a novel hybrid polishing method that combines the magnetorheological effect and the shear thickening effect. It has great potential for ultra-precision machining of complex surfaces. However, the absence of a correlation between material removal and the rheological properties of the polishing media has posed difficulties for further improvements in polishing efficiency and quality in MRSTP. In this work, a material removal model for MRSTP was established based on the principles of magneto-hydrodynamics, non-Newtonian fluid kinematics, and microscopic contact mechanics. This model combines the material removal model for a single abrasive particle with a statistical model of active grits. When comparing the experimental and theoretical results, it became evident that the developed material removal model can accurately predict the material removal depth of the workpiece under different processing parameters such as rotational speed of the rotary table and magnetic field strength. The average prediction error was found to be less than 5.0%. Furthermore, the analysis of the rheological behavior and fluid dynamic pressure of the polishing media reveals the coupling effects between the magnetic, stress, and flow fields. This provides theoretical guidance for the actual processing of MRSTP. Finally, the maximum material removal rate of 3.3 μm/h was achieved on the cylindrical surface of the Ti–6Al–4V workpiece using the MRSTP method. These results demonstrate that the MRSTP method holds great potential in the field of ultra-precision machining of difficult-to-machine materials.

Acceleration mechanism of abrasive particle in ultrasonic polishing under synergistic physical vibration and cavitation: Numerical study

Ultrasonic technology is widely applied in the engineering ceramic polishing processes without the limitation of material properties and ideally integrated into computer numerical control system. Ultrasonic-induced cavitation and mechanical vibration effect could accelerate the motion of solid abrasives. The individual behaviors of microjet/shockwave of ultrasonic cavitation in gases and liquids, and micro-abrasives with simple harmonic vibrations in solids and liquids has been extensively studied. To conduct a systematic and integrated study of abrasives behavior in the polishing contact region involving abrasive, surround-workpiece wall, ultrasonic physical vibration, and ultrasonic cavitation impact, a novel model integrating the free abrasive motion velocity and fixed abrasive indentation depth under multi-scale contact was proposed according to Hertzian contact theory, Greenwood-Williamson model, indentation deformation theory, the basic equations of cavitation bubble dynamics, cavitation impact control equations, and Newton's law of motion equation. The effects of ultrasonic amplitude, ultrasonic frequency, preloading force and particle size on the proposed model were investigated by theoretical analysis and numerical simulations. Ultrasonic physical vibration mainly influences the dynamic gap and further influence the number of different abrasives. Furthermore, the indentation depth of fixed abrasive depends mainly on the abrasive geometry. As the contact gap and abrasive size decrease, the indentation depth gradually decreases. Under the synergistic effect of cavitation-induced shock wave and microjet, the velocity of free abrasive in this paper is generally 0–150 m/s, and the kinetic energy of free abrasive increases roughly linearly with increasing frequency and approximately as a quadratic function with increasing particle size. Increasing the preloading force leads to a reduction in the abrasive kinetic energy. Besides, the kinetic energy induced by the shock wave has a cliff-like increment at an amplitude of 0.7–0.8 μm. It is revealed that the abrasive kinetic energy is suppressed by the cavitation bubble expansion and collapse at smaller ultrasonic pressure amplitude and surround-wall distance. This research provides a theoretical reference for the modeling of potential defects and material removal on the workpiece surface caused by abrasive motion during polishing, and reduces the trial cost for parameter optimization in actual polishing processing.

Numerical and experimental investigation on the material removal profile during polishing of inner surfaces using an abrasive rotating jet

Inner surface components with a high level of precision are extensively utilized in contemporary industry. Polishing of inner surfaces and precise control of profile contours are extremely difficult due to space constraints and the surface shape. To realize ultraprecision polishing of inner surfaces, this paper proposes an abrasive rotating jet polishing (ARJP) method, in which a new type of polishing process with an infinitely adjustable incidence angle is adopted to realize ultraprecision polishing of the inner surfaces of workpiece made of aluminium alloy 6061. The precision of inner surface profiles strongly depends on the accuracy of the material removal profile prediction. A computational fluid dynamics approach is used to simulate and analyse the material removal profile of the workpiece inner surface during the ARJP process for a novel polishing process and tools. A series of inner surface polishing experiments demonstrate that the average error between the actual material removal depth and model simulation results is less than 5.9% and that the roughness of the inner surface is reduced from 0.200 µm to 0.046 µm, a 77% improvement in inner surface roughness.

Evolution mechanism of flip-fold removal behaviour through crossed scratching of glass-ceramics

In this study, a novel flip-fold removal model was established to reveal the ductile–brittle mixed removal phenomenon in the grinding process of glass-ceramics. This flip-fold model proposed for the ductile–brittle mixed removal mode differs from conventional brittle or ductile removal mechanisms. Using the theoretical exploration method, a theoretical model of flip-fold removal is established based on the analysis of different scenarios of the relationship between the depth of the stagnation region and pile-up height of the interference zone. Through an experimental verification method, the approach of crossing double scratches with a continuously variable scratch distance is proposed to observe the evolution progression and verify the flip-fold removal model. Using the analytical analysis method, the amplitude and direction cosine distributions of the interference stress field were analysed to reveal the internal mechanism of the flip-fold removal model. The results of the three scientific research methods were in good agreement with those of the proposed model. The flip-fold material removal model supports the comprehension of the ductile–brittle mixed removal mode during the grinding of hard-brittle materials. This model provides an approach to controlling the material removal mode from the perspective of regulating the flip-fold behaviour by adjusting the scratch distance.

Process parameter analysis of ultrasonic vibration-assisted polishing of SiCp/Al ceramics based on optimized Hilbert trajectories

As an important ceramic matrix composite material, SiCp/Al ceramics have found extensive applications across several domains. However, the intricate nature of their material properties has resulted in a scarcity of scholarly investigations pertaining to the topic of ultrasonic vibration-assisted polishing (UVAP) of SiCp/Al ceramics. To solve this problem, a theoretical derivation of the material removal model (MRM) for UVAP SiCp/Al ceramics is presented in this paper. The selection of UVAP feeding speed is analyzed and discussed. The process parameters of UVAP of SiCp/Al ceramics are optimized based on the improved Hilbert's trajectory characteristics. According to the experimental results, high-quality machined surfaces can be obtained and the “fish scale” phenomenon can be avoided when the feeding speed is 0.015 m/s. Compared with the traditional trajectory, the improved Hilbert trajectory is easier to achieve uniform surface polishing. The introduction of ultrasonic amplitude (UA) can increase the material removal rate (MRR) by more than 21.6 % compared with the conventional polishing method. The maximum removal depth (MRD) increased by more than 27.76 % and the surface roughness (SR) is reduced by more than 76.45 %. The research results have an important application value for realizing efficient and high-quality polishing of SiCp/Al ceramics.

Evolution of the Interelectrode Gap during Co-Rotating Electrochemical Machining

A new co-rotating electrochemical machining method is presented to machine the complex structure inside annular parts such as flame tubes and aero-engine casings. Due to the unique shape and motion of electrodes, it is difficult to accurately compute the electric field intensity in the machining area. In this paper, the complex electric field model is simplified by conformal transformation, and the analytical solution of electric field intensity is exactly calculated. A material removal model is built on the basis of the electric field model, and the dynamic simulation of the material removal process is realized. The effects of the cathode radius, applied voltage, feed rate and initial interelectrode gap on the interelectrode gap (IEG) and material removal rate (MRR) are analyzed. The simulation results indicate that the MRR is always slightly less than the feed rate in a quasi-equilibrium state, resulting in a slow reduction in IEG. In addition, the final machining state is not affected by the initial IEG, and the MRR in a quasi-equilibrium state is determined by the feed rate. Several comparative experiments were carried out using the optimized processing parameters, in which the MRR and IEG were measured. The convex structures were successfully machined inside the annular workpiece with optimum machining parameters. The experimental results are in good agreement with the theoretical results, indicating that the established model can effectively predict the evolution process of MRR and IEG.

Novel insights into abrasive flow machining uniformity for SLM channels

Selective laser melting (SLM) has emerged as a transformative technology for fabricating intricate parts. However, a deteriorated as-built surface remains an Achilles’ heel due to the inherent layer-wise building features, driving the demand for post-finishing processes like abrasive flow machining (AFM) for internal channel refinement. Despite AFM's potential to improve surfaces, a significant research gap exists in ensuring uniform material removal and consistent surface quality. This challenge is accentuated by the complex geometry of SLM channels and the lack of a detailed material removal model considering wall slip velocity and interaction forces. To address this challenge, this study delves deep into the post-finishing process uniformity of AFM for internal channels made by SLM. Investigating the impacts of building orientation angle, abrasive media viscosity, and internal channel geometry on finishing uniformity, the nuances of material removal, surface morphology, and roughness were explored with specially designed rectangular right-angle tubes as samples. The proposed method introduced a CFD simulation model that captures complex abrasive media behaviors, including wall slip and shear thinning. Furthermore, the innovative approach of the study is highlighted by the development of a modified Preston material removal model, which for the first time utilizes the concentrated suspensions theory to reveal the physical mechanisms underlying material removal in AFM. Our exhaustive research demonstrates that experimental outcomes harmoniously resonated with our modified Preston model's predictions, offering robust validation. This significant finding reveals a direct positive correlation between material removal and several parameters, notably particle phase normal stress but not pressure effects. Moreover, geometric variations in the flow channel significantly impact non-uniform removal in AFM, with the challenge escalating as abrasive media viscosity increases. Contrarily, the role of the building orientation angle is less pronounced. Insights into surface quality indicate that a steeper build orientation angle diminishes the initial surface quality of SLM channels. However, this disparity lessens as AFM progresses, underscoring AFM's potential to achieve uniform surfaces of high quality. Therefore, this study offers exceptional insights into AFM uniformity for SLM channels, highlighting pivotal parameters and their effects.

Modeling of material removal in copper blanket wafer polishing based on the hard polishing pad microstructure

Modeling of material removal in copper blanket wafer polishing based on the hard polishing pad microstructure

The Polishing of Inner Wall on Medical Device Hole by Shear Thickening Abrasive Flow

To improve medical device hole inner wall quality and overcome issues of traditional abrasive flow methods—limited fluidity in small holes causing deformation due to high inner wall pressure, and slow processing with low viscosity abrasives—a new method called shear thickening abrasive flow polishing is suggested. It uses shear thickening fluid as the medium. By leveraging the Preston equation and fluid dynamics theory, this study establishes both an abrasive flow dynamics model and a material removal model for the shear thickening abrasive flow machining of small titanium alloy hole workpieces in medical instruments. Utilizing the COMSOL software, the flow field state of shear thickening fluid within small holes is examined under varying flow behavior indexes and flow velocities. The findings demonstrate that shear thickening fluid yields superior polishing effects compared to Newtonian fluid. Elevating the flow behavior indexes facilitates a higher material removal rate on the inner wall surface; however, excessively large flow behavior indexes diminish the uniformity of material removal, thereby hindering the attainment of a high-quality polished surface. Furthermore, excessively large flow behavior indexes can reduce fluidity and consequently lower the efficiency of the polishing process. Conversely, while maintaining a constant flow behavior index, increasing the flow velocity contributes to an enhanced material removal rate and improved polishing efficiency. Nevertheless, as the flow velocity rises, the uniformity of inner wall surface roughness diminishes, posing challenges in achieving a high-quality polished surface.

Nano-Precision Processing of NiP Coating by Magnetorheological Finishing.

NiP coating has excellent physicochemical properties and is one of the best materials for coating optical components. When processing NiP coatings on optical components, single-point diamond turning (SPDT) is generally adopted as the first process. However, SPDT turning produces periodic turning patterns on the workpiece, which impacts the optical performance of the component. Magnetorheological finishing (MRF) is a deterministic sub-aperture polishing process based on computer-controlled optical surface forming that can correct surface shape errors and improve the surface quality of workpieces. This paper analyzes the characteristics of NiP coating and develops a magnetorheological fluid specifically for the processing of NiP coating. Based on the basic Preston principle, a material removal model for the MRF polishing of NiP coating was established, and the MRF manufacturing process was optimized by orthogonal tests. The optimized MRF polishing process quickly removes the SPDT turning tool pattern from the NiP coating surface and corrects surface profile errors. At the same time, the surface quality of the NiP coating has also been improved, with the surface roughness increasing from Ra 2.054 nm for SPDT turning to Ra 0.705 nm.

A novel specialized material removal rate model considering the synergistic effect of dynamic pressure and shear stress for the permanent-magnet small ball-end magnetorheological polishing

Permanent-magnet small ball-end magnetorheological polishing is often used to process small glass workpiece. During polishing, the pressure and shear stress are generated by magnetorheological fluid on the workpiece surface. When conducting fixed-point polishing experiment on fused silica plane workpiece, it was found that the polished pits were mainly distributed on one side of the polishing head's rotation axis. However, the available material removal model considering only a single force cannot explain the cause of polished pit offset phenomenon. It is speculated that the synergistic effect of the two forces on material removal may lead to the offset phenomenon. In order to accurately describe the material removal mechanism of this polishing method, a novel material removal rate model is established in this research. First, a group of actual polished pits are obtained through fixed-point polishing experiment. Then, a novel pressure-shear stress synergistic material removal rate model with unknown coefficients is established. Based on this model, the fixed-point polishing process is simulated by finite element method. The simulated polished pits under different model coefficients are obtained, and the influence rules of model coefficients on the polished pit contour is analyzed. Finally, by seeking the minimal fitting error between the simulated and actual contours, a group of optimal model coefficients are determined, namely, the shear stress coefficient is 1, the dynamic pressure coefficient is 1.2, and the weight coefficient of polishing velocity is 1.9. Through verification, the relative error between the simulated and actual contours can be as low as −9.12 % to 7.13 %. The novel model reveals that the material removal is caused by both shear stress and dynamic pressure. The dynamic pressure is distributed on one side of the polishing head axis and plays a leading role in material removal, which can well explain the cause of offset phenomenon. This research fills the blank of material removal mechanism of this polishing method, and the novel model provides a theoretical basis for process optimization research.

Robotic Belt Finishing with Process Control for Accurate Surfaces

The aerospace industry still relies on manual processes for finish applications, which can be a tedious task. In recent years, robotic automation has gained interest due to its flexibility and adaptability to provide solutions to this issue. However, these processes are difficult to automate, as the material removal rate can vary due to changes in the process variables. This work proposes an approach for automatically modeling the material removal process based on experimental data in a robotic belt grinding application. The methodology concerns the measurement of the removed mass of a test part during a finishing process using an automatic precision measurement system. Then, experimental models are used to develop a control algorithm for continuous material removal that maintains a uniform finishing process by regulating the robot’s feed rate. Next, the results for various experimental material removal models under different process conditions are presented, showing the process parameter’s influence on the removal capacity. Finally, the proposed control algorithm is validated, achieving a constant material removal rate.

A material removal model considering the effect of anisotropy on the processing of laser metal deposition Ti-alloy

A material removal model considering the effect of anisotropy on the processing of laser metal deposition Ti-alloy

Experimental Investigation and Modeling of the Kerf Profile in Submerged Milling by Macro Abrasive Waterjet

Abstract Toward achieving control over the kerfing through macro abrasive waterjet submerged milling, there is a need (i) to understand the influence of the water column height on the kerf quality and (ii) to develop a model for the prediction of the kerf characteristics. This study performs detailed experimentation to assess the kerf quality enhancement in submerged milling relative to the in-air milling on Al-6061 alloy. From the modeling perspective, there are very limited efforts in developing a comprehensive model that includes both the jet flow dynamics and material removal models—this is the missing link. Toward this, a comprehensive model is proposed and validated for the prediction of kerf in in-air and submerged conditions by considering (i) jet dynamics and (ii) jet–material interaction. From the experimental results, it is observed that by adopting the submerged milling, the damaged region, top kerf width and edge radius got reduced by 20.3%, 13.53%, and 22.7%, respectively. However, this enhancement in the kerf quality is associated with a reduction in the centerline erosion depth (hmax) by 12.33% and a material removal rate by 24.52%. The material removal mechanism is more uniform and directed in the submerged milling, whereas in-air is random. The proposed model predicted the kerf cross-sectional profile in submerged milling and in-air with a mean absolute error of 60 µm and 57 µm, squared Pearson correlation coefficient of 0.97 and 0.99, and the hmax with a maximum error of 1.3% and 1.4%.

Integration of CFD simulated abrasive waterjet flow dynamics with the material removal model for kerf geometry prediction in overlapped erosion on Ti-6Al-4V alloy

Complex surfaces in difficult-to-machine materials can be milled by maneuvering the abrasive waterjet (AWJ) according to the local part geometry by suitably overlapping the kerf cross-sectional profiles (CPs). The CP of a kerf milled in a single pass (i.e., trench) and overlapped pass (i.e., cavity) erosion by the AWJ are the building blocks that need to be known apriori for developing a jet path strategy to achieve a complex surface. This demands an efficient model for the kerf CP prediction. The present work proposes a novel framework for overlapped kerf CP prediction, wherein the jet characteristics of the AWJ exiting the focusing tube are evaluated from the two-phase flow computational fluid dynamics simulation coupled with the material removal model developed based on energy conservation principles. Towards incorporating the non-linearities observed in the kerf formation from the overlapped experimental trials into the model for CP prediction enhancement, the following are considered: (i) a hypothesis: ‘secondary erosion by the jet on the previously eroded kerf increases material removal’, (ii) the varying jet-material property of the ductile material (Ti-6Al-4V alloy), and (iii) local particle impact angles. Furthermore, the variation in the above mentioned non-linearities is incorporated into the model under the change in the AWJ conditions. From the results, it is observed that the proposed models predicted (i) the trench CP with a mean absolute error (MAE) of 27 μm, and the maximum erosion depth (hmax) with an error < 2%, and (ii) cavity at different overlaps (7% – 82%) and jet traverse rate (3000 mm/min – 5000 mm/min) with a MAE of 47 μm, and the hmax with an error < 6%. The predicted geometry of the CP correlates well with the experimental ones, with an average R2 of 0.98 and 0.95 in single- and overlapped- pass erosions.

The use of Preston equation to determine material removal during lap-grinding with electroplated CBN tools

Grinding executed in a lapping configuration is an alternative finishing process benefiting from both grinding and free-abrasive machining, while minimizing the heat effect impact. Electroplated tools can be effectively used in different abrasive processes, including high-speed grinding, however, the assessment of machining performance over time is a key factor in their correct use to achieve satisfactory technological results. In conventional grinding, bigger grain-coverage provides better results due to the higher bonding strength of grains. In lap-grinding, fracturing and crushing of the abrasive particles initially covered by the plating result in a suspension which is typically dosed continuously in free-abrasive machining. Due to this, the process transforms from two-body (grinding) to three-body abrasion (free abrasive machining) which may result in reduced grinding performance approaching asymptotically a specific value while improving surface finish. The main aim of the presented study is the evaluation of electroplated CBN tools used in lap-grinding of 40H alloy steel workpieces whose hardness was 54 HRC. The obtained results and observations of the working surface of CBN wheels and workpieces allowed for the identification of the wear characteristics for three nickel plating thicknesses corresponding to 35%, 50% and 65% of the nominal CBN crystal size and for specific process parameters. The surface roughness Ra parameter decreased gradually from the initial value 1.9 μm to the values below 0.7 μm for bigger B107 grains and for all plating thicknesses. For smaller B64 grains, the surface roughness and waviness parameters reached similar values to those obtained for the larger B107 grains at corresponding processing times. The lowest value of Ra parameter below 0.4 μm was obtained for B64 grains and for the thinnest plating but with a 50% reduction in material removal comparing to B107 grains. The Preston equation was employed to calculate the material removal as a function of time under variable process conditions in the machining zone due to the tool wear. This attempt extended the range of the material removal modeling, despite the fact that the electroplated wheels were subject to wearing down resulting in the gradual reduction in the efficiency, as well as in the change of the working conditions in the workpiece-tool contact zone.