Grinding Tool Research Articles

Improvement of centerless grinding process. Part 1. Problem and methodological justifi cation of its solution

The need to process hard-to-process corrosion-resistant stainless steels such as steel grade 12Kh18N10T is growing sharply due to the growing demand for such steels. There was a demand for high-performance grinding of blanks of parts made of such steels. The paper discusses the features and results of the development of an abrasive tool for centerless grinding of one of these parts. The possibility of designing and/or selecting abrasive tools for rational and efficient grinding without cauterization with the required accuracy and roughness of processing has been established. Appropriate recommendations have been developed that reduce the complexity of designing (selecting) an abrasive wheel from 1.5 hours to 2 minutes and reduce the defect of parts to 0.1 % due to surface burns and the error of the obtained part dimensions.

Improvement of centerless grinding process. Part 2. Initial data and design stage

The need to process hard-to-process corrosion-resistant stainless steels such as steel grade 12Kh18N10T is growing sharply due to the growing demand for such steels. There was a demand for high-performance grinding of blanks of parts made of such steels. The paper discusses the features and results of the development of an abrasive tool for centerless grinding of one of these parts. The possibility of designing and/or selecting abrasive tools for rational and efficient grinding without cauterization with the required accuracy and roughness of processing has been established. Appropriate recommendations have been developed that reduce the complexity of designing (selecting) an abrasive wheel from 1.5 hours to 2 minutes and reduce the defect of parts to 0.1 % due to surface burns and the error of the obtained part dimensions.

Study of the Electrostatic Method of Applying Abrasive Grains to the Grinding Tool Backing

Study of the Electrostatic Method of Applying Abrasive Grains to the Grinding Tool Backing

A novel 3D printed compliant ball-end grinding tool with crystal structure: Feasibility and performance analysis

During grinding complex components with difficult-to-machine materials, compliance grinding tools often experience shortened life and weakened performance due to intense temperature rise. This paper presents a novel solution strategy of preparing crystal-structured compliance tools using multi jet fusion (MJF), and five structures were selected to evaluates its feasibility and grinding performance. The macro and micro elastic deformation of the tools were analyzed by combining finite element and experiment. The results show that the crystal structure provides similar macroscopic stiffness of the tools and introduces microscopic compliance anisotropy. The crystal structure resulted in a reduction of the grit pull-out ratio by more than 82.60 %, while also alleviating the adhesion of flexible substrates adhesion and the prevention of abrasive layer fall-off, leading to prolonged tool life. Furthermore, compliant grinding tools with a crystal structure achieved comparable material removal capacity, lower surface roughness, and higher energy efficiency. In addition, they used only 29.06 % to 36.22 % of the material consumed in manufacturing. Notably, the material removal rate (MMR) of the star-structure tool can reached 94.72 % of the solid-structure tool. The diamond-structure tool exhibited the lowest ground Ra, accompanied by a reduction in grinding temperature of 19.4 °C.

EIS offset-cell measurements on epoxy-based coating systems over mechanically and thermally rounded cut edges

Based on electrochemical impedance spectroscopy (EIS) measurements with a specially designed offset-cell, the protection performance of epoxy-based coatings in terms of coating resistance over cut edges was investigated. The edges were rounded with different mechanical and thermal tools, including CO2-laser, solid-state laser, plasma beam, grinding and milling tools. Two coating systems for ballast water tank environments and two rounding radii were considered. The samples were investigated by means of a specially designed EIS offset-cell suited for applications to edge geometries. The target parameter for the assessment of the protection performance of the coatings was a critical exposure time for RC < 106 Ω, whereby RC is the coating resistance. The critical exposure time could be linked to various coating defects, namely to blistering. Results of statistical investigations revealed statistically insignificant effects of the edge rounding radius.

Study on a grinding force model of a variable grinding contact area during knife-edge surface grinding

Abstract. ​​​​​​​In the context of non-standard blade geometries of knife-like tools with tapered cutting edges where the width of the blade surface varies with feed, there is limited research on predicting grinding forces considering the changing contact line. To enhance the accuracy of predicting grinding forces during the blade surface grinding of knife-like tools, a novel analytical-regression correction method is proposed. This method employs an analytical approach to analyze the varying contact line between the grinding wheel and the tool during grinding, enabling the determination of irregularly shaped grinding contact zones. By introducing exponential coefficients related to the grinding contact line, a regression analysis is employed to refine a variable edge-width grinding force model. In comparison to the conventional constant contact line blade surface grinding force prediction, this model is better suited for non-standard blade geometries of knife-like tools in grinding processes. Results indicate that the average relative error between the predicted values from the variable edge-width grinding force model and the actual measurements remains within 9 %, thereby validating the model's effectiveness in predicting grinding forces.

Numerical Analysis of Stress Force on Vessel Walls in Atherosclerotic Plaque Removal through Coronary Rotational Atherectomy.

Coronary rotational atherectomy is an effective technique for treating cardiovascular disease by removing calcified tissue using small rotary grinding tools. However, it is difficult to analyze the stress force on vessel walls using experiments directly. Using computational fluid dynamics is a better way to study the stress force characteristics of the burr grinding procedure from a fluid dynamics perspective. For this purpose, physical and simulation models of atherosclerotic plaque removal were constructed in this study. The simulation results show that smaller ratios between the burr and arterial diameter (B/A = 0.5) result in a more stable flow field domain. Additionally, the pressure and stress force generated by the 4.5 mm diameter grinding tool reach 92.77 kPa and 10.36 kPa, surpassing those of the 2.5 mm and 3.5 mm grinding tools. The study has demonstrated the use of computational fluid dynamics to investigate wall shear stress characteristics in medical procedures, providing valuable guidance for optimizing the procedure and minimizing complications.

АБРАЗИВНЫЙ МЕТАЛЛОРЕЖУЩИЙ ИНСТРУМЕНТ ДЛЯ БЕСЦЕНТРОВОГО ШЛИФОВАНИЯ

The paper objective: to increase the efficiency of grinding by choosing the rational characteristics of the abrasive tool, mainly according to the criterion of ensuring the necessary temperature of the tool material, without burning, ensuring the required accuracy and roughness of the treated surfaces.&#x0D; Research results: recommendations are developed on the choice of a rational abrasive tool that provides minimal softening of the part material being ground, the required surface roughness, dimensional accuracy and treatment performance.&#x0D; Conclusions:&#x0D; 1. The objective is achieved by clarifying the conceptual principles and methods of rational choice of abrasive tools.&#x0D; 2. The studies allowed to estimate the cutting temperatures during grinding depending on the combination of different pairs of tool and treated material. The research results make it possible to choose the grinding tool for various materials correctly.&#x0D; 3. The nature of temperature influence in the cutting zone on the probability of appearing burnings and, accordingly, on the softening of the surface layer of parts is confirmed. &#x0D; The paper presents the results of theoretical and experimental studies of centerless grinding of parts made of various materials, namely: corrosion-resistant steel grade 12X18N10T, nickel alloy grade HN60W, composite steel 12X2NVFA and characteristic structural steel grade 30XGSA.&#x0D; Novelty of the work: a new approach to the rational choice of an abrasive tool is formed, based on modeling the cutting process, taking into account the required quality and productivity of the treatment.

Scratch-induced surface formation mechanism in C/SiC composites

Due to the extremely complex composition of C/SiC composites, their material removal mechanisms are significantly different from those of conventional single-phase ceramic materials. Therefore, the grinding removal mechanism of C/SiC composites must be investigated so that the components based on these composites can be machined efficiently and with low damage. In this paper, nano-scratch experiments with various cutting depths are carried out along different fiber orientations to simulate the material removal process in grinding and theoretically clarify the damage failure mechanism based on different cutting thicknesses. According to the assessment of surface and subsurface morphology of the various constituents in the scratch grooves regarding different fiber orientations, the multiple brittle breakage modes and surface integrity of carbon fiber are revealed. Green’s function is applied to establish a half-space anisotropic analytic elastic stress field considering the microstructural characteristics of material, and the crack nucleation and propagation principles during micro brittle fracture regime for nano-scratch experiment are elucidated based on the fracture mechanics and the maximum principal stress criterion. The formation mechanism of machined surface morphology in macro brittle removal process is investigated under the crack deflection effect at the weak interface and based on the elastic foundation beam theory. The related findings can provide a reasonable reference framework for optimizing the grinding technology, material and tool design regarding C/SiC composites.

Product contamination during mechanochemical synthesis of praziquantel co-crystal, polymeric dispersion and cyclodextrin complex

This paper aims to evaluate the product contamination by elemental impurities during the mechanochemical synthesis of praziquantel (PZQ) co-crystal, polymeric dispersion and cyclodextrin complex by grinding. To assess that, PZQ was co-ground with malic acid (MA), Poloxamer F-127 (F-127) and hydroxypropyl-β-cyclodextrin (HPβCD) in high-energy vibrational mills using stainless steel and agate grinding tools, applying different processing time (30 and 90 min). Differential scanning calorimetry and X-ray powder diffraction confirmed the formation of the targeted products, regardless of applied processing time and grinding tool type. After digestion of the solid powder products, the levels of selected elemental impurities were analysed by inductively coupled plasma mass spectrometry (ICP-MS). The analysis revealed that the content of Mg, Ca, and V are below the limit of quantification in all samples analysed. The contents of P and Na are not related to the type of ball mill and reaction time, but to the starting materials themselves, considering that Na is found in HPβCD and MA, while P was found in F-127. The detected Si impurities in the co-ground products can be related to the use of the agate balls and jars, while the presence of Cr and Fe can be related to the use of the stainless steel grinding tools. The risk assessment showed that the oral administration of the prepared co-ground products in quantities corresponding to regular PZQ oral doses resulted in only insignificant exposure to Cr. Finally, the use of agate grinding tools should be preferred, as administration of such products results in lower Cr exposure. The presented elemental impurities did not lead to any significant drug degradation as PZQ content at the end of the six-month testing period was still in the range of 95–105 % of the initial content. Regardless, ICP-MS analysis of the elemental impurities should be considered in regular quality control procedures in the development and production of novel pharmaceutical products prepared by grinding.

A multi approach study of grinding artefacts recovered at the north of the Hualfín valley (Catamarca, Argentina)

This paper aims to characterise the lithic technology associated with food processing at the Villavil 1 site (northern Hualfin Valley, Argentina), inhabited during both the Middle period (ca. 7th – 9th centuries AD) and Late-Inka period (ca. 10th – 16th centuries AD). We conducted this study by following different approaches on grinding tools: at the macroscopic scale, we carried out techno-morphological studies, while at the microscopic scale we identified botanical residues and use-wear traces.These different lines of evidence allowed us to recognise upper tools that could have been used for grinding vegetables. We detected starch grains of three taxa: Zea mays, Neltuma sp., and Phaseolus vulgaris. Also, wear traces (dimples, micro-striations, micro-polishing) pointed out an intense or prolonged percussion on the surface of another rock and the contact with plant material. The results match with the functions of the site Villavil 1, related to agricultural production, which was fundamental to the diet of pre-Columbian populations that inhabited the valley.

Optimizing Energy Efficiency of Dielectric Materials’ Electrodischarge Dispersion as One Sustainable Development Green Trend

Increasing the energy efficiency of production processes is closely related to minimizing the impact on the environment and is one of the priorities of the concept of sustainable development. Electric discharge is an effective tool for multilevel grinding of non-metallic materials in various working fluids and obtaining coarse and fine suspensions. We introduce the technique for calculating the electrotechnological parameters necessary for energy-efficient electric discharge dispersion. This technique considers the strength characteristics of the crushed material (dispersed phase) and the electrical conductivity of the working fluid (dispersed medium). It is also essential to consider the energy stored in the capacitor bank, the energy criterion, the critical value of the working fluid’s electrical strength, the radius of the high-voltage electrode point, and the distance from the discharge channel axis to the disintegration object. All this allows obtaining a given granulometric composition of the dispersed phase with minimal energy consumption. Experiments confirmed the validity of the proposed calculation technique. We obtained the water-brown coal suspension with a given dispersion two times faster and consumed four times less energy in comparison with the known methods that did not take into account the electrical conductivity of the working liquid and the mechanical strength of the crushed material.

Research on design and milling performance of unequal gradient helix and variable pitch end mill

It is difficult to obtain excellent surface quality and dimensional accuracy of the low-rigidity frame and beam parts made by titanium alloy, due to the obvious vibration and large elastic deformation during side milling. The variable helix and pitch cutting tool is usually used to reduce vibration, which does not consider the unequable stiffness in the milling area. Therefore, the concept of Unequal Gradient Helix and Variable Pitch (UGHVP) is proposed in this research. The helix angles of the UGHVP vary with the stiffness of the milling area position, which will lead to milling forces and vibration decreasing as the stiffness weakens. As a result, the surface quality and dimensional accuracy will be increased, of which the advantages are analyzed. The mathematical models of the UGHVP circumferential cutting edges and groove sections are derived, which provide theoretical support for tool grinding. The models are visualized by numerical simulation. Finally, the comparison experiment with the conventional variable helix and pitch end mill was completed by side-milling the designed feature samples. The results showed that the milling forces perpendicular to the milling surface by the UGHVP were smaller and less fluctuating, which could obtain less elastic deformation theoretically. The milling vibration was smoother, especially when cutting in and out. Besides, the larger the axial depth of cut, the more obvious the superior performance of the UGHVP tool. Better surface quality and dimensional accuracy were obtained, which proved the excellent performance of the UGHVP.

Plant, pigment, and bone processing in the Neolithic of northern Arabia-New evidence from Use-wear analysis of grinding tools at Jebel Oraf.

Archaeological sites with surface hearths are a ubiquitous feature across the arid zones of the Arabian interior. At Jebel Oraf, in the Jubbah basin of the Nefud Desert of northern Arabia, numerous grinding stone fragments were found in association with hearths, though the original purpose of these stones was unclear owing to the poor preservation of faunal and botanic remains. Here we describe results from use-wear analysis on five grinding tools at Jebel Oraf, demonstrating that such artefacts were used during the Neolithic for plant processing, bone processing, and pigment production. Grinding stones were often broken up after initial use and fragments were subsequently re-used for alternative purposes, before finally being placed on hearths or discarded. More specifically, plants were ground or prepared and possibly cooked in the hearths, and bones were processed as well. The analyses also highlight the importance of pigment processing at Neolithic sites and provide a link to painted rock art. The frequent use of pigment in the archaeological record suggests that pigment was widely used, and that Neolithic painted art may have been more common than the surviving images suggest.

Dry Grinding by Means of Additively Manufactured Toric Grinding Pins

AbstractThe dry grinding process is challenging due to the induced thermal loads into the workpiece, which leads to a reduction of the workpiece quality. One approach to reduce the thermal loads is to adjust the grinding tool geometry by inserting a porous structure for dry grinding. This porous structure can be implemented, for example, by additively manufactured grinding tools. For this purpose, the suitability of additively manufactured vitrified cubic boron nitride grinding tools for dry grinding of tempered AISI M3:2 was investigated and compared with conventionally manufactured grinding tools to investigate the possibility of reducing the high temperatures and to verify the advantage of additively manufactured grinding tools. For this the resulting topographies and residuals stress states as well as wear of the grinding tools were analyzed. Additively manufactured grinding tools generated constant surface roughnesses of below 1 µm as well as contant compressive residual stress states. These results were attributed to a continuous self-sharpening of the grinding tools, which was shown qualitatively and quantitatively on the basis of the tool surfaces. Additively manufactured grinding tools with a porous structure thus have the potential to increase the possibilities of dry grinding.

Influence of the process parameters on the grinding result in continuous generating grinding of cutting tools

Continuous generating grinding processes have largely replaced discontinuous profile grinding processes in gear manufacturing due to their higher productivity. On order to transfer the advantage of the productivity benefits of this process to tool grinding, the continuous generating grinding was adapted to the manufacture of cutting tools. However, this novel approach of using continuous generating grinding processes for tool grinding has not been widely investigated. Therefore, the aim of this study is to investigate the influence of cutting speed, feed and radial depth of cut on the process result and thus to generate initial knowledge for the process design. Subsequently, the influence of these parameters on the grinding worm wear as well as on the cutting edge quality and surface properties of the ground milling tools are investigated. The results show that an increase of the radial depth of cut leads to a reduction of the process time by the factor of four without significantly influencing the wear of the grinding worm tooth. Furthermore, an increase of the cutting speed only leads to an increase in the initial wear of the grinding worm after the dressing process. For this reason, the cutting speed offers the potential to further increase the productivity of the process. The microgeometry of the cutting edge of the ground milling tool is mainly affected by the feed and the macro geometry by the feed and radial depth of cut.

Wear Behavior of Metal Bonded Grinding Tools When Grinding Ti-6Al-4V in an Oxygen-Free Atmosphere

In the current study, the wear behavior of bronze-bonded grinding tools when grinding the titanium alloy Ti-6Al-4V was explored. In this process, oxidation plays a key role since both the bronze bond and the titanium workpiece chemically react with oxygen. The oxidation effect is intensified further due to increased temperatures during grinding and can cause tribo-oxidation. This wear effect can be reduced or even eliminated by grinding in an extreme high-vacuum (XHV) adequate atmosphere. This atmosphere is nearly oxygen-free and is generated using a silane-doped argon gas that chemically reacts with oxygen. This reaction is able to decrease the oxygen partial pressure (pO2 ≤ 10−12 mbar) down to an XHV-adequate atmosphere. The aim of this paper is to investigate the influence of oxygen in the atmosphere on the application and wear behavior during grinding and to demonstrate the potential of this novel approach. The results presented show that during grinding with cBN, the process forces are significantly influenced by the atmosphere. Depending on the process parameters, a reduction of up to 93% is thus possible. This force reduction correlates with radial tool wear. When grinding under oxygen-free conditions, it can be reduced by up to 64%.

Fabrication of PCD face grinding wheel with positive rake angle by femtosecond laser and its performance evaluation in cemented carbide grinding

Super-hard abrasive grinding is considered to be the main approach to realize precision and ultra-precision machining of difficult-to-machine materials such as cemented carbide, engineering ceramics, titanium alloys and superalloy materials encountered. However, heavy grinding force, high grinding temperature and poor surface integrity are prone to be encountered in conventional negative rake angle grinding of difficult-to-machine materials. In response to these problems, a novel concept of positive rake angle grinding is first proposed and an abrasive grain regularly arranged binder-less polycrystalline diamond face grinding wheel with positive rake angle has been designed and fabricated by femtosecond laser ablation. To evaluate the grinding performance of the face grinding wheel with positive rake angle, grinding experiments of YG8 cemented carbide are conducted and compared with the traditional electroplated diamond grinding tool with equivalent abrasive grain dimension and distribution. The results show that compared with the conventional negative rake angle grinding, the normal and tangential forces in positive rake angle face grinding are reduced by 30.3 % ∼ 36.4 % and 21.1 % ∼ 29.3 %, respectively, and the ratio of normal to tangential force is reduced by 12.6 % ∼ 20.3 %. The surface roughness and average depth of subsurface metamorphic layer are also significantly smaller. The laser fabricated polycrystalline diamond face grinding wheel also has better wear resistance in the grinding of cemented carbide. Therefore, it can be concluded that better ground surface quality is obtained by the novel grinding wheel with positive rake angle. The innovative grinding method can fill the research gap on the grinding mechanism of positive rake angle grinding and further enrich the grinding theory of difficult-to-machine materials.

Robotic compliant grinding of curved parts based on a designed active force-controlled end-effector with optimized series elastic component

High-accuracy, fast-response, and low-overshoot force control are important to guarantee the material removal accuracy and surface quality of robotic compliant grinding. In order to achieve the above target, this study develops an active compliant force-controlled end-effector based on a series elastic actuator for the robotic grinding of curved parts. Firstly, a decoupled robotic grinding system composed of an industrial robot and an end-effector is developed, and a novel force-controlled end-effector is designed by adding an elastic component between the servo motor and the load to improve compliance. Secondly, the influences of the elastic component and grinding tool stiffness on the stability of the force-controlled end-effector system are analyzed by establishing a contact model of the compliant end-effector and the transfer function of the entire force control system. Then, the stiffness of the grinding tool and the elastic component are optimized with full consideration of the system cutoff frequency and the end-effector compliance. To improve the force tracking accuracies of the developed compliant end-effector, a proportional-integral (PI) controller with first-order differential force feedforward control is designed. Finally, grinding experiments are conducted for verification. The effects of spring stiffness and grinding tool stiffness on the force control system are tested, which match well with the theoretical analysis. Grinding results show that the maximum force control error of the compliant force-controlled end-effector is decreased by 70% compared to that of the rigid force-controlled end-effector, and the overshoot of the force control is reduced from 30% to almost 0 under the same response speed. The maximum and average absolute grinding depth errors using the designed end-effector are reduced by 57.2% and 58.6%, respectively, compared with those of the traditional rigid end-effector, and the average surface roughness of the finished part is reduced by 19.2%. Which demonstrates the effectiveness and advantages of the proposed compliant force-controlled end-effector.

Utilisation Potential of Mechanical Material Loads during Grinding by Means of a Novel Tool Concept

The objective of this work is to improve the surface and subsurface properties of steel parts by means of a new grinding tool concept featuring nearly spherical grains in an elastic bonding system and to uncover the underlying mechanisms leading to the intended improvement of surface integrity. The resulting workpiece topography and subsurface properties, such as residual stresses, are evaluated to characterise and assess the potential of this novel tool concept. Micrographs and EBSD images are also analysed. The results show increased mechanical process loads and resulting favourable subsurface properties in terms of mechanically induced plastic deformation and compressive residual stresses, revealing the high potential of spherical grains in an elastic bonding system.