Sawing Process Research Articles

Dynamic model and machining mechanism of wire sawing

During the wire sawing process, the wire usually undergoes large deformation, which leads to changes in the sawing force and the contact state between wire and workpiece, and in turn affects the material removal rate (MRR) and the workpiece quality. This paper presents a general dynamic model for the wire sawing. The model aims to describe the coupling relations among the contact state of wire and workpiece, the sawing force and the material removal. An iterative simulation flow was designed by the proposed model. The experiment of wire sawing with rocking and reciprocating (WSRR) was carried out to validate the proposed model. The comparison results indicated that the proposed model replicated the entire sawing experiment well. On this basis, the influences of wire speed, feed rate, rocking angle, preload force, guide rollers distance and workpiece size on sawing force, contact length and MRR were systematically analyzed. The results show that the wire reciprocating is the root cause of saw marks. Workpiece rocking causes the wire bow angle to change periodically and significantly reduces the contact length. Wire speed and feed rate has great influence on the value of normal force. The force fluctuation is affected by the maximum rocking angle and wire preloading force. MRR is mainly determined by the feed speed. The feed rate, maximum wire speed, maximum rocking angle, and preloading force could influence on the fluctuation range of the MRR. This work provides a general model for a better understanding of the wire sawing.

A predictive approach for enhancing outcomes performance in SAW process

Welding processes are the most common manufacturing solution that frequently complete the final steps of an industrial production. Their large use makes these techniques worth of attention of the scientific community, so that several efforts are spent for optimising and improving the way the processes are executed.Submerged Arc Welding is widely used in the industrial scenario being semi-automatic but it cannot be ignored that this joining technique is far from the full automatization and is still dependent by the operator expertise.In this study, an experimental investigation has been performed to build a robust data set for the subsequent application of seven machine learning classifier. The aim of the work is the definition of a suitable classifier able to detect and predict invalid process conditions which could lead to failed joint.

Comparative study of SAW and ASAW process on ASTM A709 Grade 36 steel welds

Welding is a versatile fabrication process used in manufacturing industries for joining structural components. The welded structure's capacity to carrying loads is affected by bead characteristics and process parameters. In this research work, the influnce of the Submerged Arc Welding and Advanced Submerged Arc Welding process on heat input, area of penetration, reinforcement, and heat affected zone, electrode melting rate, electrode and plate melting efficiencies, flux consumption, metal deposition rate, the microhardness of weld metal and HAZ, the microstructure of weld metal zone and power consumption have been studied. The experiments were carried out with the bead on plate (BOP) technique in ASTM A709 Grade 36 steel. The Advanced Submerged Arc Welding process reduces the heat input and area of heat affected zone. At the same time, it increases the area of reinforcement height, electrode melting rate, electrode melting efficiency, metal deposition rate and flux consumption. The microhardness of both zones of the Advanced Submerged Arc Welding process is higher than the Submerged Arc Welding process. Moreover, the microhardness of the heat affected zone is higher than the weld metal zone. The microstructures show the ferritic structure with columnar grains, whereas the column size reduces in the Advanced Submerged Arc Welding process. The Advanced Submerged Arc Welding process reduces the power consumption by 20.59% compared to the Submerged Arc Welding process.

Modeling for prediction of sawing force based on the maximum undeformed chip distribution in the granite sawing

Sawing by circular saw blades is predominant in the mechanized treatment of natural stone. The predictive sawing force is crucial for optimizing, controlling, and monitoring the sawing process. In this work, a novel model for predicting sawing force, which is based on the distribution of the undeformed chip thickness at the sawing contact arc, was proposed. Based on the analysis of the undeformed chip geometry of the circular saw blade, the segment surface was divided into the front end and rear end according to the contact pattern between the segments and granite, and the models of the maximum undeformed chip thickness of diamond particles on the front end and rear end were established. Results showed that the new proposed force model fully considered the distribution of undeformed chips compared with the current model. The novel model has higher prediction accuracy, the mean maximum absolute error is within 3.77%, and the maximum absolute error is within 7.83%. Through theoretical analysis, the ratio of the maximum undeformed chip thickness of the front segment to the rear segment is 1.67, which can fully explain the wear non-uniformity of the segment. The proposed model is of great significance to the optimization of the saw blade structure and process parameters.

Analysis of diamond wear morphology and segment wear evolution during the process of hard granite sawing

Diamond circular sawblade has been widely used in hard granite processing. In this study, the wear mechanism and wear evolution of the diamond segment were investigated. The wear morphologies of diamond grits were classified as emerging diamond, whole diamond, crack diamond, blunt diamond, micro-fractured diamond, macro-fractured diamond, wear flat diamond, and pull-out diamond, which is based on sufficient observation data. The main form of diamond wear is fracture. The fracture morphology of diamond grit dominates by cleavage, which is brittle transgranular fractures, and the microscopic features are fracture steps and river-like patterns. Since the {111} crystal plane has the largest interplanar spacing among all the crystal planes, cleavage fractures tend to occur on this crystal plane. Through the scratches and pitting on the diamond grit surface, it proved that the wear process is a mixed type of two-body wear and three-body wear. However, some diamond grits exhibit special fracture morphology and are without the typical characteristics of cleavage fracture. Combined with internal factors (including microstructures and internal defect) and external factors (including chip flow, thermal load and mechanical load), the mechanism of various diamond wear morphologies and segment wear phenomena observed in the sawing experiment is clarified. Finally, the evolution process of the diamond failure and segment wear are described. The research systematically revealed the mechanism of segment wear and the fracture morphology characteristics of diamond grits in the sawing granites, which can further improve the understanding of segment wear and provide theoretical guidance for segment design.

Breakage Ratio of Silicon Wafer during Fixed Diamond Wire Sawing.

Monocrystalline silicon is an important material for processing electronic and photovoltaic devices. The fixed diamond wire sawing technology is the first key technology for monocrystalline silicon wafer processing. A systematic study of the relationship between the fracture strength, stress and breakage rate is the basis for thinning silicon wafers. The external vibration excitation of sawing machine and diamond wire lead to the transverse vibration and longitudinal vibration for silicon wafers. The transverse vibration is the main reason of wafer breakage. In this paper, a mathematical model for calculating breakage ratio of silicon wafer is established. The maximum stress and breakage ratio for as-sawn silicon wafers are studied. It is found that the maximum amplitude of the silicon wafers with the size of 156 mm × 156 mm × 0.2 mm was 160 μm during the diamond wire sawing process. The amplitude, maximum stress and breakage rate of the wafers increased with the increase of the cutting depth. The smaller the silicon wafer thickness, the larger of silicon wafer breakage ratio. In the sawing stage, the breakage ratio of the 156 mm × 156 mm section with a thickness of 0.15 mm of silicon wafers is 6%.

Beads‐milling of waste Si sawdust into micro‐flakes and applied in UV‐curable polystyrene composites for anticorrosion coatings

AbstractIn this study, the waste Si sawdust (WSS) obtained from the silicon wafer sawing process was applied in polymer composite for anticorrosion application for the first time. The WSS powder was processed through a beads‐milling (BM) procedure using Zr beads. Subsequently, WSS‐based polystyrene (PS) composite coatings were prepared by photo‐polymerization of styrene monomers in the presence of a specific amount of WSS powder with UV radiation. The as‐prepared WSS‐based PS composite coatings were subsequently investigated and characterized by a series of tests. Anticorrosion performance of sample‐coated cold‐rolled steel (CRS) electrodes were investigated by a series of electrochemical corrosion measurements (e.g., Tafel, Nyquist, and Bode plots) in saline conditions. Gas permeability analysis (GPA) study of these membranes were also determined to support the anticorrosion data of coatings. It should be noted that the WSS‐based PS composite coatings were all found to exhibit better corrosion resistance than that of neat PS. Moreover, the composite coating with higher loading of WSS was found to show better anticorrosion performance than of lower loading of WSS. This may be attributed to the dispersion of WSS particles in PS can effectively prolong the diffusion path of corrosive factors, as evidenced by the corresponding GPA results.

Application of Unconstrained Cobalt and Aluminium Metal Powders in the Alloying of Carbon Steel in Submerged Arc Welding: Thermodynamic Analysis of Gas Reactions

The application of cobalt and aluminium powders in unconstrained format, not as metal powder in tubular wire nor as pre-alloyed powder, is used in this work to simplify weld metal alloying. The objective of this study is to demonstrate the application of unconstrained cobalt and aluminium powders in Submerged Arc Welding SAW to alloy the weld metal and to control the weld metal oxygen content. Aluminium powder is used to control the oxygen potential at the weld pool-slag interface in order to prevent oxidation of cobalt. The results presented here show that with the addition of Aluminium powder, 70% yield of Cobalt was achieved from the cobalt powder to the weld metal. The carbon steel base-plate material and weld wire materials combination were alloyed to 5.3% Co and 4.2% Al, whilst controlling the weld metal total oxygen content to 230 ppm. Thermodynamic analysis is applied to investigate the possible chemical interaction reactions between Co and Al compounds, as well as the role of the reactions on Co yield to the weld pool. The application of unconstrained metal powders ensures productivity gains in the overall SAW process because the time consuming and expensive manufacturing of alloyed wire and alloyed powder are eliminated.

Properties of coatings obtained by electric arc spraing for renovation of parts of machines and vehicle mechanisms

The robots present the results of investigating the power of coatings, excluding electric arc (EAS) filings, and their comparison with the powers of coatings, excluding gas-flame filings. The porosity of the coating, taken from electric arc filings, was in the range of 8-10%. the adhesion strength was 80…100 MPa. The results of the investigations show the advantages and purpose of using electric arc sawing to improve and move the capacity of machine parts and transport mechanisms. In the work, the following factors are added to the process of electric arc sawing: storage of fuel sum, distance of sawing, dispersion of sawing and other. on authority cover. In the course of the investigation, the increase in resistance, adhesive strength, coating thickness, the term for the coating thickness, was determined by the parameters of the electric arc filing. The robots have considered the possibility of securing the necessary authorities influencing the surface with the method of advancing the resource of machine parts by way of regulation by the factors of EAS. Regulating the smoothness and temperature of the stream of transporting gas and particles, you can change the diameter of the droplet, increase the width and reduce the oxidation of the coating. The results of comparative analysis of the properties of coatings applied by electric arc spraying (EAS) using the products of combustion of propane-air mixture and gas-flame spraying (FSP) using gas-air mixture are presented. Under optimal conditions of the spraying process, the porosity of the coatings obtained by electric arc spraying is much lower compared to gas-flame spraying: 8-10% and 20-30%, respectively. Adhesion strength of coatings obtained by electric arc spraying increased by 1.8-2.2 times (from 30-40 MPa in gas-flame spraying to 100 MPa in electric arc), wear resistance increased by 2-2yu5 times.

Mathematical models for the use, processing, and optimized utilization of natural arc‐shaped bamboo laminated lumber

AbstractThe natural arc‐shaped bamboo laminated lumber (ABLL) maintained the natural structure of bamboo material. It had significance for its various applications in bamboo industry. This article took the thickness (T) and width (W) of the ABLL as the research object. The first mathematical model determined the relationship among the size of the bamboo tubes, the number of divisions and the thickness (T) of the ABLL. In order to avoid forming incomplete arc‐shaped bamboo corners during the process of sawing of ABLL into square lumber, we used Mathlab analysis to obtain the appropriate numbers of divisions were 4–6 parts. Moreover, the thickness (T) of ABLL was found to be 37–62 mm. The second mathematical model determined the relationship between the size of the equal‐arc shaped bamboo split and the width (W) of ABLL. The proposed mathematical models provided a grading basis for the material selection in the processing of ABLL, optimized the utilization of bamboo, and was of great significance for high‐quality preparation of ABLL.

Corrosion susceptibility behavior in 12Cr–1Mo martensitic stainless steel welded by SAW process and the effect of δ-ferrite in the HAZ

Pitting corrosion in stainless steel (SS) is a punctual defect that promotes fatigue and cracks propagation. Martensitic steel of steam turbine is exposed to the thermal cycle of welding, high pressures, and corrosive environments in the heat-affected zone (HAZ). The presence of δ-ferrite in HAZ causes crystalline grain boundaries sensitization and reduces corrosion resistance. This research evaluated the corrosive effect of NaCl, NaOH, and H2SO4 in critical welding regions (BM, HAZ, FZ) by analyzing potentiodynamic curves, EIS, and mass loss calculation. The δ-ferrite in the HAZ promotes an increase in the corrosion rate in the NaCl and H2SO4 derivatives of the corrosion products formed. Furthermore, the mass loss in the HAZ was more significant than that in the BM and FZ. Despite having a lower Cr content in the FZ.

Measurement and simulation calculation of wire bow angle during the diamond wire saw process

The wire bow angle is an important factor that affects the shape precision of an ingot after the diamond wire sawing process. In this research, the wire bow angles of the inside and outside of an ingot were recorded with a high-speed camera. The effects of the processing parameters such as the wire tension force, feed speed, and wire velocity on the wire bow angles inside and outside the ingot were analyzed. A numerical simulation model of the wire bow in the wire sawing process is presented in this paper to describe the wire bow angle inside the ingot. It was shown that the wire bow angle inside the ingot was smaller than that of outside the ingot for all of the processing parameters. The wire bow angles improved with the increase of the feed speed and decrease of the wire velocity and the wire tension force. The results of the wire bow angle measurement of the inside ingot and the simulation calculation were similar for the process parameters.

Prediction and verification of wafer surface morphology in ultrasonic vibration assisted wire saw (UAWS) slicing single crystal silicon based on mixed material removal mode

Monocrystalline silicon slicing is the first step in making chips, and the surface quality of silicon wafers directly affects the quality of later processing and accounts for a large proportion in the chip manufacturing cost. Ultrasonic vibration assisted wire saw (UAWS) is an effective sawing process for cutting hard and brittle materials such as monocrystalline Si, which can significantly improve the surface quality of silicon wafers. In order to further study the formation mechanism of the surface morphology of single crystal silicon sliced by UAWS, a new model for prediction of wafer surface morphology in UAWS slicing single crystal silicon based on mixed material removal mode is presented and verified by experiments in this paper. Firstly, the surface model of diamond wire saw tool is established by equal probability method. Then, the trajectory equation of arbitrary abrasive particles on the surface of wire saw is derived and analyzed. Thirdly, a new model for prediction of the wafer surface morphology based on mixed material removal mode is presented. Finally, the prediction model is verified by UAWS slicing experiment, and the effects of slicing parameters such as wire saw speed, feed speed, and workpiece rotate speed on the surface quality of silicon wafer were studied. It shows that the predicted wafer surface morphology and the experimental wafer surface morphology are similar in some characteristics, and the average error between the experimental and the theoretical values of the wafer surface roughness is 11.9%, which verifies the validity of the prediction model.

Modelling of sawing processes with internal coolant supply

The circular sawing process is an important step in the preparation of intermediate parts in industrial manufacturing. A particular characteristic of the sawing process is that the cutting process takes place in a chip space in the closed cutting gap. As part of an ongoing research project, the application of an internal coolant supply for the sawing process is being investigated. The long-term goal of the project is to develop a highly efficient and resource-saving circular sawing process through optimised internal coolant supply. Since the cutting zone during sawing with a fluid is difficult to access using measurement equipment, simulation is used in addition to experimental investigations to examine the thermo-mechanical and thermo-fluid processes in the internal cutting gap. This paper presents a first proof of concept of a FEM - model for sawing with internal coolant supply using the CEL approach. The aim was to show the opportunities and limitations of the current model with respect to the research project. The validation of orthogonal cutting of the material AISI 1045 with the CEL approach showed a 15% deviation in the cutting force and a 17% deviation in the chip compression. The state of the interaction of the fluid with the hot chip showed a physically imperfect behaviour due to insufficient models of the complex thermo-fluid heat transfers. However, the model can be used in its first design to investigate the mechanical interaction of an internal coolant supply between chip and fluid and serves as a starting point for the simulative investigation of the complex thermo-mechanical and thermo-fluid processes during sawing, considering a cooling fluid.

Experiment and theoretical prediction for subsurface microcracks and damage depth of multi-crystalline silicon wafer in diamond wire sawing

Diamond wire saw slicing is an important process of multi-crystalline silicon (mc-Si) solar cell substrate processing. In wire sawing of silicon crystal, the brittleness removal of materials will lead to subsurface microcrack damage, reduce the fracture strength, increase the breakage probability of the as-sawn wafer and affect the subsequent surface etching texture of wafer. In this paper, a mathematical model calculating subsurface damage depth (SSD) of mc-Si is established based on the analysis of subsurface crack system in diamond wire sawing process. The correctness and rationality of the model are verified by experiments. Then, the model is used to predict the variation trend of the microcracks number (CN) and subsurface damage depth under different process parameters and saw wire parameters. The results show that the SSD decreases and CN increases with the increase of wire speed and decrease of feed speed; With the increase of abrasive density on wire surface, the SSD decreases and CN increase. The change of abrasive average size has little effect on the SSD and CN; a smaller abrasive size range is beneficial to reduce the SSD and increase CN.

Experimental investigation on diamond wire sawing of Si3N4 ceramics considering the evolution of wire cutting performance

When diamond wire saw is used in machining silicon nitride ceramics (Si3N4 ceramics), the ultra-hardness of Si3N4 causes the saw wire to wear out, which leads to the saw wire cutting performance constantly changing during its life cycle, and thus the machined quality of Si3N4 ceramics is affected. Surface roughness and topography are important indicators of the quality of the machined surface. In this paper, the diamond wire saw cutting experiment of Si3N4 ceramics was carried out, the effect of the evolution of saw wire cutting performance on the surface roughness and topography of Si3N4 ceramics as-sawn slices was investigated based on the analysis of the changes of saw wire wear topography, breaking force, bow angle and kerf loss during the sawing process. The results show that the surface roughness along the saw wire motion direction and the workpiece feed direction tends to decrease and then increase with the evolution of the cutting performance of the saw wire, which accords well with the trend of the as-sawn slices surface morphology. The results of the study can provide experimental reference for the development of high precision diamond wire saw cutting technology for Si3N4 ceramics.

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.

Photocatalytic H2 evolution by AgNP@PSi/SiNS composite derived from diamond-wire sawing silicon waste

Diamond-wire sawing silicon waste (DSSW) from photovoltaic silicon wafer sawing process represents a resource worth recovery and recycling. In this contribution, in order to utilize DSSW with low cost and high value, composite Si nanostructures for photocatalytic H2 evolution were innovatively synthesized by a simple, one-pot metal-assisted chemical etching (MACE) method from DSSW. The morphologies, phase structure, elemental composition and optical properties of the composite were characterized by XPS, BET, XRD, SEM, TEM, HRTEM and UV–vis. DRS, the photocatalytic performance was evaluated by water splitting under visible light. The results indicated that a visible light responsive Ag nanoparticles/porous silicon/silicon nanosheets ([email protected]/SiNS) composite was obtained. Owing to the porous and nanosheets features, the specific surface area of the composite is as high as 377.968 m2 g−1 and quantum confinement effects is successfully triggered to broaden the band gap of silicon from 1.12 eV to 1.31 eV, which allows an excellent hydrogen evolution amount of 367.65 μmol g−1 in the initial 1 h. In addition, the effect of Ag amount on the morphologies and photocatalytic performance of the composite was investigated. This study presents a promising route for the fabrication of composite silicon nanostructured photocatalysts from industrial silicon waste for solar hydrogen generation, demonstrating the potential for waste recovery and energy conversion.

Formaldehyde Deodorization Effect and Far-Infrared Emission Characteristics of Ceramics Prepared with Sawdust, Risk Husk, and Charcoal: Effect of Material Mixing Ratio

Indoor air quality is a very important environmental factor in modern society. However, air pollutants generated from various interior construction materials significantly affect the human body, including formaldehyde (HCHO) and volatile organic compounds that threaten public health by deteriorating indoor air quality. Effective in removing these harmful substances are porous materials, such as woodceramics. In this study, charcoal, a porous material, was added to rice husk, an agricultural by-product, and sawdust generated during the sawing process to prepare boards and ceramics at different mixing ratios, and the HCHO deodorization performance and far-infrared emission characteristics were measured. As the mixing ratio of charcoal increased, the deodorization rate of the boards and ceramics tended to increase. Overall, the deodorization rate was measured to be 80% to 90%, indicating that the boards and ceramics prepared with charcoal are suitable to be used for the purpose of deodorization. The effect of the material mixing ratio on far-infrared emissivity and emission power was insignificant.

Lateral forces determine dimensional accuracy of the narrow-kerf sawing of wood

The shrinking global forest area limits the supply of industrially usable raw resources. This, in combination with the ever-increasing consumption of timber due to population growth can lead to the lack of a positive balance between the annual volumetric growth and consumption of wood. An important innovation toward increasing environmental and economic sustainability of timber production is to reduce the volume of wood residues by minimizing the sawing kerf. It results in higher material yield but may impact the dimensional accuracy of derived products. Therefore, the cutting tool geometry as well as the sawing process as a whole must be carefully optimized to assure optimal use of resources. The goal of this study is to better understand the causes of machining errors that occur when sawing wood with saws of varying thickness of kerf, with a special focus on re-sawing thin lamellae performed on the gang saw. Numerical simulations were tested against experimental results, considering influence of diverse components of cutting forces, in addition to the initial and operating stiffness coefficients of the saw blade. It has been demonstrated that asymmetric loads from the cutting process for the scraper saw blade can cause sawing inaccuracies. The simulation methodology developed in this research can be straightforwardly extended towards determination of optimal geometry of other cutting tools, particularly with the reduced sawing kerf. This may lead to more sustainable use of natural resources as well as an increase in economic gain for the wood processing industries.