Workpiece Feed Speed Research Articles

Surface characteristics of precision as-cut NdFeB magnet considering diamond wire wear

NdFeB is the highest output value permanent magnet material at present, which has extremely high magnetic properties and is widely used. In the production process of NdFeB, cutting is an indispensable process, and high precision as-cut surface characteristics can reduce the cost of subsequent processes. In this paper, the single factor sawing experiment of NdFeB was carried out by using the range of processing parameters in industrial production. The effects of workpiece feed speed, saw wire speed, workpiece processing size and diamond saw wire wear on sawing surface morphology, surface material brittleness removal ratio, roughness and waviness were studied. The research shows that the surface characteristics of the workpiece sawed in the stable wear stage of the diamond saw wire are the best. In all service stages of the saw wire, reducing the feed speed and workpiece processing size, and increasing the wire speed will reduce the surface roughness and waviness, reduce the number and size of pits, and reduce the proportion of brittle removal areas. The research results provide an experimental reference for the optimization of diamond wire saw cutting parameters of NdFeB.

Influence of Diamond Wire Saw Processing Parameters on the Sawn Surface Characteristics of Silicon Nitride Ceramics.

For the slicing of superhard silicon nitride ceramics, diamond wire sawing technology has great potential for application, and its slicing surface characteristics are an important indicator of cutting quality. In this paper, the sawing experiments of silicon nitride ceramics were carried out within the range of industrial processing parameters of diamond wire sawing (saw wire speed: 800-1600 m/min, workpiece feed speed 0.1-0.4 mm/min). The effects of cutting parameters on the surface morphology, surface roughness and waviness of the as-sawn slices were analyzed. The results show that within the range of sawing parameters for industrial applications, the material on the diamond wire as-sawn surface of silicon nitride ceramics is removed mainly in a brittle mode, with the slice morphology showing brittle pits and regularly distributed wire marks in the 20-55 μm scale range. The surface roughness of the slices along the workpiece feed direction ranges from 0.27 to 0.38 μm and decreases with increasing saw wire speed and decreasing feed rate. The surface waviness ranges from 0.09 to 0.21 μm, which is in good agreement with the changing trend of the sliced-surface roughness. The results of the study provide an experimental reference for promoting the engineering application of diamond wire sawing technology to the processing of silicon nitride ceramic slices.

Analysis and Prediction of Grind-Hardening Surface Roughness Based on Response Surface Methodology-BP Neural Network

Surface morphology and surface roughness are very important properties used to assess the quality of grind-hardening surfaces. In this study, grind-hardening tests for 42CrMo steel were designed using the response surface methodology to reveal the surface morphological characteristics of the grind-hardening surface and the effects of grinding parameters on its roughness. The results showed considerable grinding damage in both the cutting-in and cutting-out areas of the grind-hardened surface, while the middle area was more stable. More specifically, the cutting-in area showed much bonding and damage, while the cutting-out area showed more microcracks. Under the conditions of this test, the surface roughness tended to increase with the increase in cutting depth and workpiece feed speed. The effect of grinding line speed on the grind-hardening surface roughness was not significant. The significance of the effects of grinding parameters on surface roughness ranked as: cutting depth > workpiece feed speed > grinding speed. In turn, a response surface methodology-BP neural network prediction model for the surface roughness of grind-hardening was developed, whose feasibility and validity were confirmed by the experimental results. The model achieved surface roughness prediction of the grind-hardening process with a mean relative error of 2.86%.

Influences of hard inclusions on processing stress in diamond multi-wire sawing multi-crystalline silicon

There are SiC and Si3N4 hard inclusions in photovoltaic mc-Si, which will lead to stress concentration in the sawing process and reduce the fracture strength of as-sawn wafers. In this paper, a finite element model of diamond multi-wire sawing mc-Si with hard inclusions is established. The influence of the type, size, location of the hard inclusions, the coupling effect between adjacent inclusions and the sawing process parameters on the thermal mechanical coupling sawing stress and stress concentration factor was analyzed. The research results show that the greater the thermal expansion coefficient of the inclusions, the greater the stress concentration. The larger the size of the hard inclusions, the greater the sawing stress. The inclusions distributed at the saw wire outlet and the center of the saw kerf will produce greater sawing stress. The smaller the distance between adjacent inclusions, the greater the coupling sawing stress. Increase the wire speed and the workpiece feed speed, and the sawing stress caused by the influence of inclusions increases. The research results of this paper provide a theoretical reference for understanding the influence of hard inclusions inside mc-Si on the sawing stress and optimizing process parameters.

Study on the cutting mechanism of randomly deflected truncated cone shape single abrasive grain

Based on the random distribution characteristic of abrasive grains for the grinding wheel circumferential surface during the manufacturing process, considering the grinding parameters and deflection parameters comprehensively, a randomly deflected truncated cone shape single abrasive grain cutting simulation model was established. Then, studying its cutting mechanism, i.e., the trajectory length value by numerical method and formula method was compared, the consequence indicates that the error is extremely small; this demonstrates the accuracy of the numerical method. The calculation and analysis of the workpiece cutting surface topography and the undeformed chip shape were carried out; it shows that the cutting surface topography and the undeformed chip shape are coincident. And the calculation results of the model were compared to verify. The influence laws of each grinding process parameter on the material removal volume (MRV) and material removal rate (MRR) were investigated; the results display that the grinding method affects the changing pattern of MRV and MRR; when the grinding method was up-grinding, a high wheel speed or a small wheel diameter is able to enhance the MRR; the MRV and MRR are increments with the increasing workpiece feed speed or abrasive grain cutting depth; and the MRV and MRR decrease with the raising of the absolute value of single abrasive grain deflection angle. The situation is a similar or opposite trend in down grinding. This work can provide a theoretical reference for the selection and optimization of parameters and further lay a foundation for the research in the grinding mechanism of the grinding wheel.

Analysis of crack-free surface generation of photovoltaic polysilicon wafer cut by diamond wire saw

At present, diamond wire sawing technology has been widely used in slicing photovoltaic polysilicon. Improving the surface quality of the slices to obtain a sawn surface without microcrack damage can greatly increase the fracture strength of polycsilicon wafers and reduce the cost of wet black silicon texturing, which is beneficial to improve the final photoelectric conversion efficiency of solar cells. In this paper, a mathematical model of diamond wire sawing was established based on the machining mechanism of brittle material removal and surface generation, and the numerical calculation of the sawing process was carried out. The validity of the model was verified by sawing experiments. The critical ratio of workpiece feed speed to saw wire movement speed was obtained when generating a crack-free slice surface under the combination of different process parameters and saw wire parameters. Based on the established theoretical model of sawing, the influence of saw wire movement speed, abrasives density and abrasives size on the critical speed ratio was analyzed, and the critical speed ratio (CSR) corresponding to the finer diameter wire and the higher wire speed which will be gradually applied in industry in the future was analyzed. The research results show that it is more conducive to obtaining a crack-free sawn surface by reducing the workpiece feed speed or increasing the saw wire movement speed, and the workpiece feed speed has a greater impact on the sawn surface quality. The CSR will slightly decrease within a small change range when increasing the saw wire movement speed. Increasing the density of abrasives on the saw wire surface within a certain range or decreasing the abrasives size is more inclined to obtain a crack-free sawn surface. The CSR will decrease slightly in a small range when decreasing the abrasives density or increasing the abrasives average size.

On the tribology and grinding performance of graphene-modified porous composite-bonded CBN wheel

In order to provide the effective reinforcement and lubrication for reducing the friction on the interface of the grinding wheel and workpiece during the high-efficiency deep grinding of difficult-to-machine materials, an in-house developed porous composite-bonded (Cubic Boron Nitride) CBN wheel with graphene nanoplatelets was explored to meet the increasing demand for industrial purpose. It can be found from experimental study that by adding the appropriate concentration of graphene, 0.01 wt%, both of the flexural strength and tribology performance have been enhanced in the graphene-modified porous composite-bonded CBN wheel, and then the related grinding wheel was fabricated to perform the grinding experiments on the Ti–6Al–4V titanium alloy (TC4). It has been found that by adding the graphene the sharpness of the abrasives on the surface of the grinding wheel always keeps at a certain range and the grinding wheel may have self-sharpening ability which can guarantee the stability during the high-efficiency deep grinding process. Finally, by considering process parameters in this study the graphene-modified porous composite-bonded CBN grinding wheel could be used to achieve the high-efficiency deep grinding of TC4 as well as guarantee its surface quality under the grinding wheel speed of 80 m/s, grinding depth of 0.1 mm and workpiece feed speed of 0.6 m/min.

Study on cutting PV polysilicon with a new type of diamond abrasives-helix-distribution saw wire based on controlling the subsurface microcrack damage depth

There are large brittle fracture pits on the surface of photovoltaic polysilicon wafer cut by diamond wire saw, because of the problems such as poor flow of cutting fluid and difficulty in chip discharge. At the same time, the anti-corrosion amorphous layer on the wafer surface can obviously block the subsequent acid etching and texturing reaction. In order to solve these problems, a new type of diamond abrasives-helix-distribution saw wire is used as the sawing tool to obtain the surface characteristics of photovoltaic polysilicon wafer suitable for acid texturing, then research on wire sawing photovoltaic polysilicon based on controlling subsurface microcrack damage depth control is carried out. The concept of high-quality cutting abrasives (HQCA) is defined, and the cutting process of polycrystalline silicon is numerically calculated based on the established new type diamond wire model, the influence of the process parameters and the structural parameters of the saw wire on the cutting characteristics is analyzed, and the reasonable matching between the process parameters and the saw wire parameters is discussed. The study results show that the number and proportion of HQCA in all abrasive grains involved in sawing can be increased by increasing the workpiece feed speed or reducing the moving speed of saw wire, properly reducing the abrasive concentration on the saw wire surface or increasing the abrasives size, or setting the ratio of axial distance between the abrasive area on wire surface and the bare wire area as 1:1. In this case, the formation of the wafer surface tends to be removed in the way of material microbrittleness, and the subsurface crack depths are in the optimal etching depth range. The number and proportion of HQCA remain basically unchanged when the workpiece feed speed changes in constant proportion to the wire speed, and the screw pitch of the abrasive groups on the surface of the saw wire has little effect on it.

The influence of selected treatment parameters with atmospheric plasma on the treatment process and wood wettability

The paper presents the use of low-temperature plasma, generated in the air at atmospheric pressure, for treatment of wood surfaces to improve their wettability. For this purpose, a dielectric barrier discharge plasma device with a floating electrode configuration was used. The density and homogeneity of the plasma discharge, formed between the isolated high voltage electrodes and the surface of the spruce (Picea abies (L.) Karst.) and beech (Fagus sylvatica L.) wood, was shown to be highly dependent on the size of the gap between the electrode and wood. Topography measurements using a confocal laser microscope showed that exposure of wood to plasma causes changes on its surface at the sub-microscopic level. Measurements of the contact angles of water droplets and water-based coating showed the improved susceptibility to wetting of treated surfaces. Differences in surface wettability were also detected depending on the selected machining parameters: type of wood, workpiece feed speed, the distance between the electrodes, the distance between the electrodes and workpiece, and workpiece thickness.

Experimental investigation on the machining characteristics of fixed-free abrasive combined wire sawing PV polycrystalline silicon solar cell

At present, the fixed abrasive wire sawing (FAWS) technology is gradually used in the photovoltaic industry to cut polycrystalline silicon slices. However, there are obvious directional wire marks, parallel grooves, and amorphous silicon layer on the surface of the slices formed by the FAWS, which leads to a high optic reflectivity of the textured surface obtained after the mature acid etching texturization technology. So the slices cannot meet the requirements of the photovoltaic cell. In the paper, a novel fixed-free abrasive combined wire sawing (FFACWS) technology for cutting PV polycrystalline silicon is presented to solve this problem, by adding loose SiC abrasives to cooling lubricant during the fixed abrasive wire sawing. A single-factor and orthogonal experimental study on sawing characteristics was carried out. The effect of size and mass fraction of SiC abrasives in the slurry, workpiece feed speed and wire speed on the surface morphology, roughness, and kerf loss were studied. The results show that within the range of the processing parameters in the paper studied, the obvious wire marks, parallel grooves, and ductile layers on the surface of the slices can be removed by the FFACWS. The surface roughness of the slices along the wire movement direction and the workpiece feed direction increases with the increase of the mass fraction of SiC abrasives in the slurry and workpiece feed speed and it decreases with the increase of wire speed. But the effect of the size of SiC abrasives is related to the matching of the protruding height of the fixed abrasives on the wire surface along the workpiece feed direction. In the wire movement direction, it increases with the size of SiC abrasives. The kerf loss increases with the increase of size and mass fraction of SiC abrasives in the slurry and the wire speed but has little effect with the change of workpiece feed speed.

Experimental study on slicing photovoltaic polycrystalline silicon with diamond wire saw

At present, polycrystalline silicon photovoltaic cells play a dominant role in silicon-based solar cells because of its advantages such as relatively simple preparation process and relatively low cost. Slicing is the first mechanical processing procedure for battery cells, the quality of sawn surface affects the cost of subsequent processes such as texture making, also affects the breaking strength of battery cells and the photoelectric conversion efficiency and other performances. In this paper, polycrystalline silicon sawing experiments are carried out, and the effects of main process parameters, such as the workpiece feed speed, the wire moving speed, the ratio of the workpiece feed speed to the wire moving speed, and the sawn workpiece size, on the surface morphology and roughness Ra of the photovoltaic polycrystalline silicon slice are analyzed. Orthogonal experimental method was used to analyze the primary and secondary order and positive and negative effects of various factors on surface morphology and surface roughness, the optimum process parameters were obtained, and the wear morphology and mechanism of wire were analyzed. The research results show that: within the range of process parameters studied in this paper, the surface morphology of polycrystalline silicon slices shows a comprehensive effect of material ductility and brittleness removal. Reducing the workpiece feed speed and size, increasing the wire moving speed will increase the proportion of the ductile smooth area on the slice surface and decrease the surface roughness Ra value, the slice surface roughness Ra value is basically unchanged when workpiece feed speed and wire speed change at the same time but the ratio of them remains constant. Compared with the wire moving speed and the workpiece size, the workpiece feed speed has the greatest influence on the surface morphology and roughness. Abrasive falling off and coating wear are the main wear forms of the wire.

Three-dimensional topography simulation research of diamond-wire sawing based on MATLAB

PurposeThe purpose of this paper is to study the influence of the processing parameters of diamond wire sawing on surface morphology and roughness.Design/methodology/approachFirst, a wire saw cutting model is established to determine the positional relationship between a wire saw and the machined surface of the workpiece, and the abrasive grain cutting trajectory is generated. Through the data processing of the cutting trajectory, the simulation of the three-dimensional surface topography of the slice and the calculation of the surface roughness are realized by using the GUI programming of MATLAB. Finally, different surface roughness values are obtained by changing the machining parameters (saw wire speed and workpiece feed speed).FindingsThe conclusion is that the surface roughness of the slice is larger when the feed speed is higher and smaller when the linear speed is higher.Originality/valueDiamond wire saw cutting is the first process of chip processing, and its efficiency and quality have an important impact on subsequent processing. This paper will focus on the influence of the sawing wire cutting processing parameters (sawing wire speed and workpiece feed speed) on the surface roughness to optimize the processing parameters and obtain smaller surface roughness values. Through MATLAB three-dimensional simulation, the surface morphology can be observed more intuitively, which provides a theoretical basis for improving the processing quality.

Material removal and surface generation mechanisms in diamond wire sawing of silicon crystal

Silicon crystal is usually first cut into wafers in the applications of electronic devices and photovoltaic solar cells. At present, fixed abrasive wire sawing technology has been widely used in slicing. The mechanism of material removal and surface generation during wire sawing is the key basic problem to study the surface quality of sliced wafers, which is important to realize high-precision slicing. This paper presents theoretical analysis on the relationship between the average cutting depth of abrasives distributing in different positions along the wire circumferential surface and the process parameters. The wire sawing experiments of single crystal silicon were carried out, then the morphologies of sawn surface and swarf were observed, the surface roughness was measured and analyzed, the material removal and surface generation mechanism of single crystal silicon cut by electroplated diamond sawing wire were addressed. Research results show that there is an approximate non-linear increasing relationship between the average cutting depth of the abrasives and the ratio of the workpiece feed speed to the wire speed, and the abrasives cutting depth and surface roughness of sliced wafers increases with the increasing of ratio value. It is difficult to obtain the sliced surface in a fully ductile mode of material removal in the actual wire sawing process because there are always a small amount of abrasives with high protrusion on the wire surface whose cutting depths are greater than the critical ductile regime cutting depth, but adopting a low ratio can make the generation of the sliced wafer surface in near-ductile or local-ductile material removal mode which can produce high quality wafer surface. This research is expected to be useful in optimizing the combination of process parameters in fixed abrasive diamond wire saw precision slicing of silicon wafers.

Study on force distribution and its location in granite sawing

The present work proposed a model of the location of resultant force based on tangential force distribution. Afterwards, the actual location of resultant force was calculated based on the analysis of the force components in the sawing contact zone. Based on the experimental results, it is found that the distribution coefficient and the location of the resultant force are both great influenced by depth of cut and workpiece feed speed except sawblade speed. The value of the distribution coefficient ranges from 1.375 to 0.416, and the location of the resultant force ranges from 0.727 to 0.568, which both decrease with the increase of depth of cut and workpiece feed speed. Furthermore, a good corresponding relationship between the location of resultant force and the distribution coefficient was obtained, which not only validates the force location model but also further reveals the characteristics of force distribution and its location in the contact zone.

Characteristics of sawing force location in the unsteady stage

Although the unsteady sawing stage, an integral part of the complete sawing process, contains the characteristics of the sawing process, few studies have been carried out due to the complexity of processing. In the present work, the varying characteristics of sawing force location were studied based on the cut-in and cut-out unsteady stages. Through using kinematic method, the force location can be calculated based on the measured horizontal and vertical force components converted to the tangential and normal force components. Corresponding experiments were undertaken on a precision sawing machine at a large range. Based on the experimental results and analysis, it is found that the force location increases with the increase of the instantaneous length of contact zone, but it decreases with the increase of depth of cut. The workpiece feed speed and sawblade speed have an influence on the force location. When the instantaneous length of contact zone is close to that of the maximum contact zone, the force location basically acts at 0.6 apart from the bottom of the contact zone, which is due to the shifting behaviour of sawing swarf.

Experimental Study on Grinding Force of Zirconia Ceramics in Dry/Wet Grinding Environment

The impacts of different linear speed of grinding wheel, grinding depth and workpiece feed speed with or without grinding fluid on grinding force were studied by plane grinding machining of zirconia ceramics. The impacts of different machining environment and grinding parameter on normal and tangential grinding forceswere studied by testing the grinding force during grinding with a force measuring device. The studies showed that the normal and tangential grinding forces decrease with the increase of the linear speed of grinding wheel and increase with the improvement of grinding depth and workpiece feed speed. The grinding depth has the greatest impacts on the normal and tangential grinding forces in dry grinding environment; while in wet grinding environment, the grinding depth exerts the greatest impacts on the normal grinding force and the linear speed of grinding wheel imposes the greatest impacts on the tangential grinding force. In addition, it was found that the normal grinding force in dry grinding is minor than that in wet grinding, that the tangential grinding force in dry grinding is greater than that in wet grinding, and that the grinding force ratio in dry grinding is lower than that in wet grinding.

Optimization of Machining Parameters of SiC Single Crystal Cut by Diamond Wire Saw

For the process of optimizing the process parameters in the process of cutting the hard and brittle materials such as single-crystal SiC by diamond wire saw, the process parameters such as wire saw speed, workpiece feed speed and workpiece rotation speed are the design variables, and the sawing force and surface roughness are the processing targets by orthogonal experimental design. The grey system theory is introduced to optimize the multi-objective cutting process. According to the experimental data, the grey correlation resolution coefficient is determined. The significant relationship between the processing parameters and the target characteristics is analyzed. The optimal combination of process parameters under multi-target conditions is obtained, namely the workpiece feed rate is 0.025mm/min, the wire saw speed is 1.6m/s, and the workpiece rotating speed is 16r/min.

Development of EDT Equipment Using Wire Tool Electrode

Whirling electrical discharge texturing (WEDT) was developed to process microstructures on the inner surface of cylindrical parts made of high hardness materials. However, the minimum processable diameter of the cylindrical parts was φ 5 mm and the equipment could not feed the new tool electrodes. Therefore, the authors devised a novel method of WEDT using a straight wire tool electrode for a cylindrical surfaces with a small diameter. It was confirmed that microstructures could be created on the inner surface of a cylinder of φ 1.1 mm diameter, and that the texture-area ratio could be controlled by the workpiece feed speed. Moreover, new EDT equipment with a feeding system for a wire tool electrode and a bending system for the tip of a wire tool electrode was developed. As a result, the equipment that can process microstructures on the inner surface of a cylinder with a small diameter and feed a wire tool electrode during texturing was successfully developed.

Study on Surface Quality and Machining Efficiency of Diamond Wire Saw Slicing SiCp-Al Composites

In order to study the basic rule of diamond wire saw slicing SiCp-Al composites, the theoretical analysis and experiments were carried out. The influences of diamond wire saw slicing speed and workpiece feed speed on surface quality and machining efficiency were discussed. The analysis results show that the machined surface gets smoother when diamond wire saw slicing speed changes from 2m/s to 3.5m/s, but gets rougher when diamond wire saw slicing speed changes from 3.5m/s to 4m/s. And the surface gets rougher when workpiece feed speed changes from 0.5m/s to 1m/s.The machining efficiency gets higher when diamond wire saw slicing speed and workpiece feed speed increase. These results provide guidance for selecting reasonable parameters in future research.

Investigation on the grinding temperature field of nano-ZrO<SUB align="right">2 dental ceramics with a nanoparticle jet of MQL

The heat-transfer model of a surface grinding temperature field with a nanoparticle jet flow of minimum quantity lubrication (MQL), as well as the proportionality coefficient model of the energy input workpiece, was established. Numerical simulation of the surface grinding temperature field of a nano-ZrO2 dental ceramic workpiece material was conducted. With increased cut depth, the peak values of grinding temperature rocketed. With increased workpiece feed speed, grinding temperature on the finished surface decreased. With increased wheel peripheral speed, a high amount of heat energy accumulated on the surface because of the low heat-transfer coefficient of the ceramic material, and a large temperature gradient appeared in the temperature distribution layer. Under the same cooling and lubrication conditions, grinding temperature insignificantly changed along the direction of grinding width. Conversely, under different cooling conditions, the temperature variation was significant. MQL grinding conditions with additive nanoparticles significantly affected the weakening of temperature effect on the grinding zone.