Electrolytic In-process Dressing Research Articles

Dynamic solid-liquid mixing mechanical model of contact surfaces and experiment of M50 aviation bearing steel by using ultrasonic-assisted electrolytic in-process dressing grinding

The mechanical contact properties of M50 aviation bearing steel surfaces by using ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding greatly influence the machined surface's quality. However, in wet grinding conditions, there are three contact forms on the grinding surface: the micro-cutting contact between the diamond abrasive particles of the grinding wheel and the workpiece surface, the sliding contact between the oxide film asperities on the grinding wheel surface and the asperities on the workpiece surface, and the hydrodynamic liquid film contact of the electrolytic grinding solution. The existing research on the mechanical behaviour of the grinding contact surfaces mainly focuses on the influence of one of the contact forms on the normal force. Therefore, calculation models of the dynamic solid-liquid mixing normal force of the UA-ELID grinding contact surfaces that with three contact forms are constructed in this paper to accurately understand the mechanical contact properties of the grinding surface. The relationship between the three contact forms under different process conditions, such as wheel speed, feed depth, and feed speed, and their influence on the normal force of the grinding contact surfaces are revealed. Finally, the accuracy and versatility of the calculation models in this paper are verified through comparative analysis with other normal force calculation model and experimental measurement.

A grinding force model considering the arc-track feeding unit device in ELID grinding of the non-standard ultra-precision bearings

Bearings play an important role in the national defense industry. The demands for the ultra-precision non-standard bearings are increasing year by year. Correspondingly, the requirements for the surface roughness of bearing raceways are getting higher and higher. The surface roughness Ra value of the bearing groove raceway has been significantly improved by the ELID (Electrolytic In-Process Dressing) grinding assisted by the arc-track feeding unit. In this research, a grinding force model for the ELID groove grinding assisted by the arc-track feeding unit is established. The modelling of the swing speeds, swing angles and duty ratios of the arc-track feeding unit are carried out as the basis for the predicting of the tangential and the normal forces. For the first time, the equivalent elastic modules are used to characterize the variation of the ELID oxide layer in the new model. Validated by the linear-groove ELID grinding with varying swing speeds, swing angles and duty ratios of the arc-track feeding unit, the predicting results of the force capture well the fluctuation of different force components due to the changing of the variables. The new grinding force model involving the arc-track feeding device is able to give accurate predictions to the tangential and normal forces. The maximum error between the predicting tangential forces and the experimental tangential force is 5 %; the maximum error between the predicting normal forces and the experimental normal forces is 6.2 %. It provides an insight into the material removal mechanism and the grinding force characteristics in the ELID grinding assisted by the arc-track feeding unit for further improving the forming accuracy of this new method.

ELID Dressing Behaviors of Non-Abrasive Iron-Based Grinding Wheels

Non-abrasive iron-based grinding diamond wheels, lacking abrasive particles, negate the concern of detached passivated abrasives scratching the polished surface. During the Electrolytic In-Process Dressing (ELID) polishing process, α-Fe2O3 particles form on the oxide film surface of the iron-based grinding diamond wheel devoid of abrasives. These particles assume the role of the grinding diamond wheel for polishing. Therefore, the ELID electrolytic performance and the oxide film formation performance of the non-abrasive iron-based grinding diamond wheel significantly influence the formation of α-Fe2O3 particles and the subsequent ELID polishing performance. Our studies investigating the ELID dressing behavior of the non-abrasive iron-based grinding diamond wheel have analyzed the influence mechanism of the electric field, flow field, and pulse energy on its ELID dressing. Moreover, the roundness of the ELID dressing grinding diamond wheel, oxide film properties, and α-Fe2O3 particle content were measured, and plate glass was polished using the ELID non-abrasive iron-based grinding diamond wheel. The results illustrate that the non-abrasive iron-based grinding diamond wheel exhibits excellent ELID dressing performance. The diamond wheel’s roundness is less than 0.001 mm, the oxide film uniformly covers the surface, the content of α-Fe2O3 particles is evenly distributed, and the surface accuracy of the polished plate glass is approximately 0.5 nm. These findings provide a compelling case for the continued use and development of grainless iron-based grinding diamond wheels in precision grinding operations.

Understanding of highly-oriented 3C-SiC ductile-brittle transition mechanism in ELID ultra-precision grinding

Highly-oriented 3C-SiC possesses good out-of-plane orientation uniformity, and has more potential to obtain uniform surface quality during ultra-precision machining, compared with randomly-oriented SiC (such as RB-SiC and S-SiC, et al.). Through ultra-precision machining of highly-oriented 3C-SiC under electrolytic in-process dressing (ELID), the oxide film formed on the grinding wheel enhances the contact stiffness between the grinding wheel and the workpiece during the process. Further, compressive residual stress of 0.29 MPa on highly-oriented 3C-SiC surface conducive to the removal of material ductile was generated. It enabled ELID to perform better material ductile removal ability than conventional grinding (CG) does. On the other hand, numerous stacking faults (SFs) in highly-oriented 3C-SiC promoted the migration of dislocations in the material and generated more dislocations in the material under the shear stress of ELID grinding wheel. In addition, the accumulated dislocations at the grain boundary continued to slip to the next grain rather than resulting in dislocation pile-up and material crack due to the consistency of grain orientation. This phenomenon has the materials been ductile removal rather than brittle fracture. All above findings would provide a beneficial reference for the control of grinding process and the analysis of material removal mechanism of highly-oriented materials.

Effect of vibration dimensionality on ultrasonic vibration-assisted electrolytic in-process dressing (ELID) grinding of zirconia ceramics

Effect of vibration dimensionality on ultrasonic vibration-assisted electrolytic in-process dressing (ELID) grinding of zirconia ceramics

Investigations on a hybrid chemo-magnetorheological finishing process for freeform surface quality enhancement

Surface roughness improvement of the freeform surfaces is essential for the enhanced functionality of the components, including implants, turbine blades, microchannels, etc. The exclusion of human involvement during the finishing of freeform surfaces prevents hazardous exposure to particulate and provides uniform surface quality. Different surface finishing techniques, including vibratory finishing, Abrasive Flow Finishing (AFF), Electron Beam (EB) Irradiation, Electrolytic in-process Dressing (ELID) grinding, etc., have been developed to automate the finishing operation. However, some limitations are associated with the preexisting techniques, e.g., the process controllability of AFF and vibratory finishing, recast layer formation during EB irradiation, and low productivity of ELID grinding. Hence, a novel method for surface improvement, namely, Hybrid Chemo-Magnetorheological Finishing (HC-MRF), is proposed in the present study to reduce the surface roughness (Ra) (~up to a few nanometer) without affecting the surface topography of the workpiece. HC-MRF simultaneously utilizes the synergic action between Magnetorheological Finishing (MRF) and chemical etching to reduce surface finishing time and escalate process efficiency. Herein, the carrier medium of the Magnetorheological (MR) fluid is replaced by a reagent to facilitate the chemical etching process, and its synchronized action with mechanical abrasion reduces surface irregularities. Furthermore, the design of the developed apparatus to enable the HC-MRF process, where permanent magnets are used to produce the desired external magnetic field, is also discoursed. A case study on the surface roughness enhancement through the HC-MRF on the WC-Co (tungsten carbide in a cobalt-rich matrix) is investigated using Response Surface Methodology (RSM). Herein, Murakami's reagent is used as the carrier medium in the MR fluid, and a reduction in surface roughness (Ra) from an initial value of 312.87 nm to a final value of 34.50 nm is noticed. Moreover, the inclusion of Murakami's reagent enhances the process efficiency. The change in surface roughness with and without Murakami's reagent in the MR fluid is 88.97 % and 43.12 %, respectively, for a constant finishing time.

Surface Properties of Ultrasonic Vibration-Assisted ELID Grinding ZTA Ceramics.

This study aimed to explore the evolution of surface properties of nanocomposite ceramics during ultrasonic vibration-assisted electrolytic in-process dressing (UVA-ELID) grinding. First, the trajectory of the grain was analyzed, and the motion was simulated using MATLAB to demonstrate the mechanism of UVA-ELID grinding. The critical grinding depth was also calculated under the effect of ultrasonic vibration. Then, the conventional ELID (C-ELID) and UVA-ELID grinding were compared. The surface properties, including surface residual stress, surface microstructure, surface roughness, and surface morphology, were used to evaluate the effectiveness and feasibility of UVA-ELID grinding. Whether it was conventional C-ELID or UVA-ELID grinding, the residual compressive stress was introduced into the machined surface, while the former was lower than the latter. The microstructure of the UVA-ELID grinding was evenly distributed, and the ductility removal occurred during material removal. The surface roughness of Ra and Rz was reduced by 14.5% and 20.6%, respectively, during the UVA-ELID grinding. The surface morphology was dramatically changed with the help of ultrasonic vibration. In a word, for nanocomposite ceramic, the UVA-ELID grinding can significantly improve surface performance and achieve a better machining effect.

ELID Mirror Surface Grinding for Concave Molds by Conductive Elastic Wheel Containing Carbon Black

Elastic grinding wheels have previously been adopted for the development of the mirror surface finishing method for concave spheres. In this study, new conductive elastic grinding wheels, to which electrolytic in-process dressing (ELID) can be applied, are developed; the aim of the study is to address the challenge of maintaining a constant removal rate for rubber bond wheels. When ELID grinding is performed using a non-diene (isobutane isoprene rubber, IIR)-based wheel, a larger removal amount is achieved, and a higher-quality surface is also achieved compared to a diene (acrylonitrile-butadiene rubber, NBR)-based wheel. In addition, to investigate the effect of grinding wheel bond hardness on the removal amount and ground shape accuracy, grinding wheels with various levels of hardness are prepared by controlling the amount of carbon black contained in them, and grinding experiments are conducted. Thus, a larger removal amount is achieved using a harder grinding wheel, but the roughness of the ground surfaces deteriorates. Therefore, in practice, it is necessary to select an appropriate grinding wheel that can achieve both productivity and surface quality. Finally, to obtain a high-quality mirror finish on a concave spherical surface, ELID grinding is performed on the workpieces as is done for spherical lens molds. Thus, high-quality mirror surfaces with roughness Ra < 10 nm were generated. When the work pieces are ground using a grinding wheel of the same radius, excessive removal occurs at the edge of the concave spherical profile, decreasing the form accuracy. Numerical simulation demonstrates that chamfering of the grinding wheel is effective for improving the shape accuracy. The results of this study are expected to contribute to automation and cost reduction in the mirror-finishing process for concave molds.

Cavitation Effect in Ultrasonic-Assisted Electrolytic In-Process Dressing Grinding of Nanocomposite Ceramics.

Ultrasonic-assisted electrolytic in-process dressing (UA-ELID) grinding is a promising technology that uses a metal-bonded diamond grinding wheel to achieve a mirror surface finish on hard and brittle materials. In this paper, the UA-ELID grinding was applied to nanocomposite ceramic for investigating the cavitation effect on the processing performance. Firstly, the ultrasonic cavitation theory was utilized to define the cavitation threshold, collapse of cavitation bubbles, and variation of their radii. Next, the online monitoring system was designed to observe the ultrasonic cavitation under different ultrasonic amplitude for the actual UA-ELID grinding test. A strong effect of ultrasonic cavitation on the grinding wheel surface and the formed oxide film was experimentally proved. Besides, under the action of ultrasonic vibration, the dressing effect of the grinding wheel was improved, and the sharpness of grain increased by 43.2%, and the grain distribution was dramatically changed with the increase of ultrasonic amplitude. Compared with the conventional ELID (C-ELID) grinding, the average protrusion height increased by 14.2%, while the average grain spacing dropped by 21.2%. The UA-ELID grinding reduced the workpiece surface roughness Rz and Ra by 54.2% and 46.5%, respectively, and increased the surface residual compressive stress by 44.5%. The surface morphology observation revealed a change in the material removal mechanism and improvement of the surface quality by ultrasonic cavitation effect. These findings are considered instrumental in theoretical and experimental substantiation of the optimal UA-ELID grinding parameters for the processing of nanocomposite ceramics.

A Review of Ultrasonic Assisted Electrolytic In-Process Dressing (UA-ELID)

This paper presents previous research work of researchers on electrolytic in-process dressing and its ultrasonic-assisted system variant. This paper also contains information about the ELID system and applications of ultrasonic-assisted ELID. This technique enables continuous dressing of wheels made using metallic bond in the grinding process itself while retaining sharp grits from the super abrasive wheels. An ultrasonic-assisted setup requires an ultrasonic power generator, piezoelectric transducer (PZT), horn assembly. An ultrasonic generator generates ultrasonic pulses, which are supplied to the piezoelectric transducer. The piezoelectric transducer then converts electrical energy to mechanical energy and vibrates either in longitudinal mode or in transverse mode. The horn system then amplifies these vibrations, and amplified vibration is supplied to the grinding tool. The relevance of research papers referred to regarding setup development of ultrasonic-assisted electrolytic in-process dressing, effect of process parameters and modeling of the ultrasonic-assisted ELID process is described in this paper.

Study on the characteristics of zirconia ceramic in three-dimensional ultrasonic vibration-assisted ELID internal grinding

Three-dimensional (3D) ultrasonic vibration-assisted ELID grinding, which combines 3D ultrasonic vibration-assistance with electrolytic in-process grinding wheel dressing (ELID), is a compound process that is designed to achieve high-efficiency precision machining. A grinding force model of 3D ultrasonic vibration-assisted ELID grinding was first developed on the basis of the kinematics of a single grit particle and was verified through experimentation. The surface quality then was observed using white light interference profiling. It was demonstrated during the present investigation that the grinding force during 3D ultrasonic vibration-assisted ELID grinding was approximately 20 %~30 % lower than that of two-dimensional (2D) ultrasonic vibration-assisted ELID grinding. In addition, the surface roughness (Ra) achieved during 3D ultrasonic vibration-assisted ELID grinding was approximately 40 %~50 % smoother than was achieved under 2D ultrasonic vibration-assisted ELID, and thus 3D ultrasonic vibration-assisted ELID grinding can achieve better surface quality.

Experimental study on the characteristic and function of oxide film formed on grinding wheel in ELID precision grinding

PurposeThe purpose of this study is to investigate the characteristic and function of oxide film formed on grinding wheel in electrolytic in-process dressing (ELID) precision grinding and improve the quality of ELID grinding.Design/methodology/approachDynamic film forming experiments were carried out with a simulation device close to the actual processing conditions. Then, the ELID grinding experiments of bearing rings were performed using grinding wheels with good film forming effect. The experiment was designed by quadratic regression general rotation combination method. The influence of grinding depth, electrolytic voltage, duty cycle and grinding wheel linear speed on grinding effect is analyzed.FindingsA mathematical model for the formation rate of oxide film was established. The experiments show that the composition of grinding wheel and grinding fluid, as well as the electrical parameters, influence the film forming effect. Thus, the oxide film plays an important role in ELID grinding.Originality/valueThis study provides a reference for the design and selection of grinding wheel and grinding fluid and the setting of process parameters in ELID grinding.

Effects of O2 Fine Bubbles on ELID Grinding Using Conductive Rubber Bond Grinding Wheel

This study proposes a new grinding system using grinding fluid containing oxygenic fine bubbles (O2FBs) to realize high-performance electrolytic in-process dressing (ELID) using a conductive rubber bond grinding wheel. It was found that grinding fluid containing O2FBs dramatically increases the dissolved oxygen in the grinding fluid. In addition, the O2FBs in the fluid are drawn to the conductive rubber bond grinding wheel, which is the positive pole, during ELID. These effects are thought to enhance the dressing performance of the conductive rubber bond grinding wheel. Grinding of pure titanium using the proposed grinding system was found to realize mirror surface finishing while increasing the amount of removed workpiece material, compared to when ELID was not applied and to when ELID grinding was conducted using a normal grinding fluid. Effects of ELID grinding on surface modification were also observed, confirming that the proposed grinding system is able to form a thick oxidized film on pure titanium.

Properties of α-Fe2O3 in Oxide Film of α-Fe Grinding Wheel Without Abrasive Particles

The properties and the formation mechanism of α-Fe2O3 in oxide film on α-Fe bonded grinding wheel without abrasive grains were researched. The content of α-Fe2O3 in oxide film was measured by XRD and XPS, the results show that there are more α-Fe2O3 in the oxide film of the α-Fe bonded grinding wheel without abrasive grains than that of the iron bonded grinding wheel with abrasive grains. The microstructure of oxide film of α-Fe bonded grinding wheel without abrasive grains was measured by SEM and TEM, the results show that the oxide film formed on the surface of α-Fe bonded grinding wheel without abrasive grains was more smooth, uniform, continuous and it’s granularity is finer, which was beneficial to ultra-precision polishing. The experimental results show that the α-Fe bonded grinding wheel without abrasive grains is more suitable for ELID (Electrolytic In-process Dressing) ultra-precision polishing.

Microscopic characterization and modeling of oxide layer for electrolytic in-process dressing (ELID) grinding with focus on voltage, electrode-wheel gap, and coolant flow

Electrolytic in-process dressing (ELID) is a grinding technique used to generate high-quality surfaces on hard and brittle material. Oxide layer formed on grinding wheel during ELID grinding heavily influences the surface roughness of the workpiece. To study the microscopic structure of the oxide layer and model the thickness of it, we conducted a previously reported study on metallic-bonded prism samples with major adjustments and implementations. The parameter studied are voltage, electrode-grinding wheel gap, and coolant flow rate. Scanning electron microscopy (SEM) images of cross-section of the oxidation sites were captured and compared and oxide layer thickness was accurately measured. All three parameters are found to significantly affect the formation of the oxide layer.

Research on ELID Grinding Mechanism and Process Parameter Optimization of Aluminum-Based Diamond Composites for Electronic Packaging

Abstract Aiming at the problem of poor processing performance and difficult processing in the process of aluminum-based diamond composites for electronic packaging, this paper uses electrolytic in-process dressing (ELID) grinding technology to grind the aluminum-based diamond composites. The quadratic orthogonal rotation combination method was used to investigate the influence law and degree of grinding depth, grinding wheel linear velocity, duty cycle and electrolysis current on surface roughness. The ELID grinding optimization process parameters of aluminum-based diamond composites obtained by LINGO software are: grinding depth 9.3μm, grinding wheel linear speed 36m/s, duty cycle 63.7%, electrolysis current 11.5A. The surface of the aluminum-based diamond composite with a surface roughness of 125 nm was machined by this optimized process parameter combination.

Research on Generation and Polishing Mechanisms of Nano Grain α-Fe2O3 in Precision Electrolytic in process dressing (ELID) Grinding

Electrolytic in process dressing (ELID) grinding holds tremendous promise for ultra-precision grinding on hard and brittle materials. Besides oxide films on the grinding wheels it is important to study the content generation and transformation of α- Fe2O3 inside the oxide film and its effect on polishing process. In this study, X-ray diffractometer (XRD) measurement, SEM, TEM was performed in ELID grinding with different grinding wheels in order to investigate the content and transformation procedure of α- Fe2O3. Results shown, transformation of α- Fe2O3 is bound up with grinding temperature, the grain size of α- Fe2O3 5-10nm, the α- Fe2O3 in oxide film formed membrane structure.

Mechanical Properties of Oxide Films on Electrolytic In-process Dressing (ELID) Copper-based Grinding Wheel

The mechanical properties of oxide films on copper based grinding wheel were studied by nanoindentation technique. The analysis of load displacement shows that the creep phenomenon occurs during the loading stage. Results show that the oxide film and the matrix have different characteristics, and the rigidity of the copper based grinding wheel is 0.6-1.3mN/nm, which is weaker than that of the matrix; the hardness of the oxide film is 2000-2300MPa, which is higher than the matrix; and the elastic modulus of the oxide film is 100-120GPa, also higher than the matrix.

Wear life characterization of the grinding wheel for electrolytic in-process dressing (ELID) grinding of ball bearing raceways: a new perspective based on a moving normal distribution curve of the grit state variation

Many advantages make electrolytic in-process dressing (ELID) grinding desirable for cutting hard and brittle material with high surface requirements. The self-electrolytic in-process dressing property in ELID grinding is also largely responsible for the shorter wear life and lower forming accuracy of the grinding wheel. In ELID grinding, except for traditional mechanical wear, the electrolytic oxidation wear also adds more uncertainties to the wear velocity of the grinding wheel. To date, few investigations focused on the grinding wheel wear life characterization in ELID cut-in grinding of ball bearing raceway. In this study, the wear life characterization of the grinding wheel during ELID grinding was quantitatively simulated by a moving normal distribution curve of the grit state variation. As all types of cutting grits wear out, so did the normal distribution curve, showing movement towards the grinding wheel center. With the normal distribution curve moving towards the grinding wheel center, a local acceleration and local deceleration in moving velocities occurred. It is the diversity of the moving speed of the normal distribution curve that provides a quantitative description to understand the wear life characterization of the ELID grinding wheel. Some experimental results can easily explain this new proposed perspective. This new perspective can also be extended to predict the forming accuracy and surface topography of the bearing raceway during ELID grinding.

Precision Grinding of Ultra-fine Cemented Carbide Based on Electrolytic In-process Dressing of a Multi-layer Brazed Diamond Wheel

Precision Grinding of Ultra-fine Cemented Carbide Based on Electrolytic In-process Dressing of a Multi-layer Brazed Diamond Wheel