Sawing Process Research Articles

Optimization of Scots pine (Pinus sylvestris) management with the total net return from the value chain

Constant unit prices for sawlogs and pulpwood are commonly used in the valuation of a forest stand. We analyzed the optimal management strategy at the stand level in even-aged pine stands in the case where stems are valued based on the prices and predicted quantities of the end products of the sawing process at the stand level (QualityPremiumCase). The QPC was then compared to the base case (BC) in which quality indifferent unit prices are used.We used a simulation-optimization system OptiFor in which a process-based growth model PipeQual provides growth predictions that include input variables for models that predict the lumber grades and by-products percentages of the total volume of stems. Growth model predictions, harvesting cost function, and models for predicting the yield of various sawn wood grades and by-products of the sawing process, in addition to exogenous unit prices and processing costs were used for calculation of the bare land value as a function of the decision variables. Numerical optimization, by Osyczka’s direct and random search algorithm was used to determine the management regime that maximized the bare land value for both cases.Fewer thinnings in the QPC were optimal compared to the BC. Thinnings were heavier, and time intervals between thinnings were longer in the QPC than in the BC. The yield of sawn wood was significantly higher and the quality distribution of sawn wood better in the QPC. It was also found that optimal management regimes obtained by constant unit prices may lead to raw material supply, which is not profitable for sawmills to process.

Analysis of bead wear in diamond wire sawing considering the rock properties and production rate

Predicting the wear rate of diamond beads in the diamond wire sawing process is one of the most important factors in the optimized design and cost estimation of quarrying. This paper aims to predict the wear rate of diamond beads as one of the principal performance criteria in dimension stone quarrying. Saw operating parameters and mechanical and physical properties of rock are the most effective factors on diamond bead wear. In the same working conditions (at constant operating parameters), the wear rate of diamond wire saw is strongly affected by the production rate, and the characteristics of rock. In this study, the uniaxial compressive strength, Schmiazek abrasivity factor, Mohs hardness, and Young’s modulus were selected as the main physical and mechanical properties of rock. The 11 types of igneous rocks were cut in the laboratory using a diamond wire saw and a fully instrumented cutting platform. During the cutting process, the wear rate of diamond beads were determined after each cutting test. The wear rate of diamond bead and rock characteristics were evaluated using simple and multiple curvilinear regression analysis, and prediction models were developed. The developed models were validated by considering the t-test, F-test, correlation coefficient and the plots of predicted versus actual values. The results indicated that the wear rate of diamond beads can be reliably predicted using the developed model.

Characterization of the Diamond Wire Sawing Process for Monocrystalline Silicon by Raman Spectroscopy and SIREX Polarimetry

A detailed approach to evaluate the sub-surface damage of diamond wire-sawn monocrystalline silicon wafers relating to the sawing process is presented. Residual stresses, the presence of amorphous silicon and microcracks are considered and related to diamond wire velocity and cutting ability. In particular, the degree of amorphization of the wafer surface is analyzed, as it may affect the etching performance (texturing) during solar cell manufacture. Raman spectroscopy and Scanning Infrared Stress Explorer (SIREX) measurements are used independently as non-destructive, contactless optical characterization methods to provide stress imaging with high spatial resolution. Raman mappings show that amorphous silicon layers can occur inhomogeneously across the surface of diamond wire-sawn wafers. The Raman and SIREX results reveal a connection between a higher fraction of the amorphous phase, a more inhomogeneous stress distribution and a lower peak maximum of the stress difference on wafers, depending on both the wire wear and the wire velocity. SIREX line scans of the in-plane difference of the principal stress components ∆σ taken across the sawing grooves show significant differences in magnitude and periodicity. Furthermore, the results are compared with the microcrack depth from the same investigation areas. The possibility to optimize the diamond wire sawing processes by analyzing the sub-surface stress of the wafers is offered by complementary use of both Raman and SIREX measurements.

Innovation in Granite Industry: Chittoor, Andhra Pradesh

Business innovation is possible through waste management. The main objective of waste management system is to maximise economic benefits and, at the same time, to protect environment. Granite processing industry generates a large quantities of wastes mainly in the form of stone powder during sawing and polishing processes, which pollute and damage the environment. The present study focuses on granite waste recycling and depends on participant observation method. It aims to characterise and evaluate the possibilities of using the granite wastes generated by the processing enterprises and quarries in the Chittoor district of Andhra Pradesh, as alternative raw materials in the production of bricks, chips, road metals, seating sheets, base stones, close to wells, landscaping pavers, split stone veneer tiles, mosaics, backsplashes, paper weights, table tops, pen and land phone stands, and a wide variety of hand-crafted products. If the available granite waste is re-used by producing the above items through advanced technology machines, it would provide employment, increase gross domestic product, increase foreign currency, reduce environmental problems, reduce poverty, etc. Hence the government should encourage prospective entrepreneurs who want to establish granite waste recycling enterprises not only in Chittoor district but anywhere in India.

Transmit antenna selection for multiple antenna systems with stall avoidance

This paper presents an analysis of the performance of transmit antenna selection in multiple-input multiple-output (MIMO) systems with N Stop and Wait (N-SAW) at the data link layer. The impact of packet size, number of SAW processes and the stalling of packets inside the receiver reordering buffer, due to N-SAW, on transmit antenna selection is investigated. Antenna selection is implemented as a signal processing technique that enhances the performance of the MIMO system; two schemes, throughput and capacity based transmit antenna selection are considered. Results show that under similar conditions, throughput maximization outperforms capacity maximization in terms of throughput, transmission latency and dropped packets when stall avoidance is implemented. The results further show that throughput and dropped packets increase with increase in SAW processes and decrease with increase in packet size. Transmission latency increases with increase in packet size and remains unchanged with increase in number of SAW processes.

Modeling the Effect of Plate Thickness on Dilution and Bead Height in SAW Process

Objectives: Dilution and bead height model generation for submerged arc welding and variable plate thickness Methods/Statistical Analysis: Central composite design (rotatable) technique used with Design Expert® software. 32 beads on plate specimen welded with submerged arc welding process. Current, voltage, plate thickness, travel speed and nozzle to plate distance taken as variable to identify the direct and interaction effects of these parameters on dilution and bead height. All weld samples cut from the specimen, polished and etched with 2% Nital solution to observe bead profile on high resolution microscope with 10 X image enhancement for quality measurement of bead parameters. Findings: Plate thickness along with other welding parameters affects the bead profile due to change in heat flow conditions. Variable plate thickness model for bead parameters help us to understand that how the changed heat flow conditions affects bead profile when plate thickness changes. Bead height increase with current and reduce with travel speed. The maximum bead height has been observed with 14 mm plate where bead height is observed 2.94 mm at 325 amperes current and 21.25 m/hr of travel speed while minimum is 1.79 mm for 12 mm plate at 250 Ampere current and 22.50 m/hr travel speed. Higher bead height is observed with thicker plate due heat sinking effect in thickness direction. Percentage dilution is affected by plate thickness along with other parameters, especially when we work with faster travel speed. Application/Improvements: Variable plate thickness model for bead height and dilution for Submerged arc welding represented which can be helpful to identify bead characteristics over a wide range of thicknesses for SAW welded carbon steels.

Modular Multi-Process Welding System Used for HSLA Materials Joining

The development of welding technologies and techniques used for advanced materials joining should be closely linked with the design and development of equipment and also with the expectations of end-users involved in the cutting-edge manufacturing engineering. In order to reach this objective, the researchers, developers and producers should work together for designing new welding processes, technologies and equipment that meet the requirements of productivity and cost-effective manufacturing processes. Combining the multiple-arc & multi-process welding solutions, the system presented in this paper was designed to perform longitudinal butt and fillet welds of high-strength low-alloy (HSLA) steels plates of medium and large thickness, frequently encountered in shipbuilding, oil and gas onshore and offshore industries. The welding system can be easily used for achieving long seams specific to complex ship blocks or sections, pipelines sections, beams, girders and stringers for railway wagons. Based on the modularity concept, the architecture of this innovative welding system was designed as a structure of multiple interchangeable slides, used for positioning and assembling the welding heads typical for gas metal arc welding, submerged arc welding and Laser welding processes. Due to its versatility, adaptability and functionality, the system allows end-users to select the suitable combination of welding processes, in order to obtain butt and fillet HSLA steels welded joints. By controlling and monitoring the process parameters in real time, significant advantages such as weld geometry, high deposition rate and high penetration and, consequently, improved productivity, controlled cooling rate and, hence, reduced stress and strain are achieved. Due to its modularity and versatility, the system can be successfully used in different industrial applications, in several combinations of GMAW, SAW and LASER-hybrid welding processes, for joining of similar and dissimilar materials.

Effect of grit shape and crystal structure on damage in diamond wire scribing of silicon

AbstractFundamental understanding of the fixed abrasive slicing of photovoltaic silicon wafers is crucial for producing low‐cost wafers with superior surface quality and mechanical strength. With the goal of understanding the diamond wire sawing process, this paper investigates the scribing of mono‐ and multi‐crystalline silicon by the abrasive grits on an actual diamond wire. Specifically, the effects of grit shape and silicon crystal structure on the resulting surface morphology, subsurface damage, and the critical depth of cut at which ductile‐to‐brittle transition occurs are investigated. Results show that surface cracking depends on the grit shape. Scribing across the grain and twin boundaries in multi‐crystalline silicon impacts the resulting surface morphology, with grit shape producing a greater effect than crystallographic orientation in the grain interior relative to the grain boundary. Subsurface damage depends on the grit shape and crystal structure. Differences in the critical depth of cut for ductile‐to‐brittle transition in scribing of mono‐crystalline silicon are explained via analysis of the stress state produced by idealized grit shapes.

An artificial neural network for real-time hardwood lumber grading

Computerized grading of hardwood lumber according to NHLA rules would permit fast assessment of sawn lumber and the evaluation of potential edging and trimming operations to improve lumber value. More importantly, to enable optimization of the hardwood lumber sawing process, a fast means of evaluating the potential value of boards before they are sawn is necessary. As log and lumber scanning systems become prevalent and common, these needs become more pressing. From an automation perspective, the NHLA lumber grades are difficult to implement efficiently in a computer program. Exhaustive approaches that examine every potential cutting size and combination to determine the grade give accurate grading solutions, at the cost of computation time. Other approaches have examined heuristic methods that implement key parts of the grading rules, or used artificial neural network methods, both with the loss of accuracy. Here, a different approach to computerized grading is examined that takes a hybridized approach using projected yield from cut-up simulation and neural network methods. This new hybrid approach has the advantage of both accuracy and high-processing speed. Such an approach lends itself to log sawing optimization with respect to NHLA grades and market values when internal log defect information is known.

Subsurface crack damage in silicon wafers induced by resin bonded diamond wire sawing

In order to optimize the process of wire sawing, this work studied the subsurface crack damage in silicon wafers induced by resin bonded diamond wire sawing using theoretical and experimental methods. A novel mathematical relationship between subsurface crack damage depth and processing parameters was established according to the indentation fracture mechanics. Sawing experiment using resin bonded diamond wire saw was performed on a wire saw machine. The validity of the proposed model was conducted by comparing with the experimental results. At last, the influences of processing parameters on subsurface damage depth were discussed. Results indicate that the median cracks are mainly oblique cracks which generate the subsurface crack damage. On the diamond wire saw cross section, the abrasives with the position angle 78° between abrasive position and vertical direction generate the largest subsurface damage depth. Furthermore, abrasives, generating the subsurface damage, tend away from the bottom of diamond wire with the increase of wire speed or decreases with the increase of feed rate. However, the wire speed and feed rate have opposite effects on the subsurface crack damage depth. In addition, the subsurface crack damage depth is unchanged when the ratio of feed rate and wire speed does not change.

Edge trimming for surface activated dielectric bonded wafers

The impact of the edge trimming process on permanently bonded wafers is described. The edge trimming process is a blade sawing process applied on the Si wafer edge and bevel, removing the fragile edge of the wafer prior to grinding. We investigated two routes for the integration on permanently bonded Si wafers, edge-trim before bonding and edge-trim after bonding. The impact on the subsequent processes for both integration routes is assessed. For the case of edge-trim before bonding, a combination of functional water cleaning such as ozone dissolved in water and ammoniac scrub cleaning shows a significant effect to remove Si residues, enabling void free dielectric bonding. For the case of edge-trim after bonding, utilizing a small grit diamond blade shows no mechanical failures into the dielectric bonding interface. These proposed processes are a very promising for the fabrication of extreme thinned Si without mechanical failure at wafer edge.

Simulation Research for the Effect of KDP Crystal Defect and Initial Internal Stress on Sawing Stress

KDP (KH2PO4) crystal is a kind of excellent nonlinear optical crystals, which has been widely used in nonlinear optical and Inertial Confinement Fusion (ICF) engineering. KDP crystal with the characteristics of low hardness, high brittleness, easy deliquescence and temperature-sensitive is easy to crack during the crystal growth, taken out from crystallizer, and the process of slicing. Stress concentration caused by the initial internal stress redistribution and the growth defect in KDP crystal is an important reason of KDP crystal cracking during sawing process. The numerical simulation model of the KDP crystal containing spherical cavity defect and sawing with fixed abrasive wire saw is established by finite element method in this paper. The effects of initial internal stress, spherical cavity defect on sawing stress are investigated. The maximum tensile stress near the defect during the sawing process is simulated and analyzed. The results show that sawing stress changes smoothly during sawing process, and the fixed abrasive wire saw slicing belongs to low stress cutting way. The sawing stress at sawing kerf is increased obviously. The crystal defect leads to local stress concentration during sawing process. The coupling effect of sawing stress with initial internal stress and the effect of stress concentration are enhanced when the sawing kerf approaches to the defect.

The Effect of Log Position Accuracy on the Volume Yield in Sawmilling of Tropical Hardwood

This study investigated the effect of the positioning of the log before sawing on the volume yield of sawn timber from tropical hardwood species. Three positioning parameters were studied, the offset, skew, and rotation, combined with two sawing patterns of cant-sawing and through-and-through sawing. A database consisting of two tropical hardwood species with very different outer shapes, jambirre (Millettia stuhllmannii Taub.) and umbila (Pterocarpus angolensis DC.), was used to simulate the sawing process. The result of the simulation revealed that, according to the combined effect of offset, skew, and rotation positioning, the positioning of the log before sawing is extremely important to achieve a high volume yield of sawn timber. The positioning parameter that has the highest effect on the volume yield is the rotation, and the variation in the volume yield associated with a deviation in the positioning can reduce the volume yield of sawn timber by between 7.7% and 12.5%.

Efecto del sistema de aserrío tradicional en las características de la madera de encinos

El proceso de aserrío de encinos se considera una fase importante de su industrialización y de la calidad de la madera generada. Se analiza el control de calidad del proceso de aserrío, el sistema de corte tradicional con el radial y su efecto en los coeficientes de aprovechamiento, en los tiempos de procesamiento y en la proporción de dimensiones en anchos de la madera generada. Se utilizaron trozas de Quercus laurina, Q. candicans y Q. acutifolia, que se procesaron en un aserradero banda de 8 plg de ancho, con sierras tradicionales para pino. La variación del corte (St) fue de 3,93 mm, que se considera alta y refleja una mala calidad del aserrío, la media fue de 25,36 mm y la dimensión óptima de corte de 28,71 mm, la diferencia indica que un porcentaje considerable de las tablas producidas (80 %) no se puede clasificar en el espesor de la categoría de 3/4 plg. Los coeficientes de aserrío del sistema tradicional fueron de 55,83 % y en el radial de 52,31 %. El tiempo de aserrío para procesar 1 000 pies tablas en el sistema tradicional fue de 73 minutos y en el radial de 103 minutos, lo que representa un 41 % más del tradicional. Con el sistema se aserrío radial, se generó una proporción alta (77 %) de tablas angostas (4 plg y 6 plg), y un porcentaje bajo (23 %) de tablas con anchos mayores de 8 plg. Con el aserrío tradicional, las proporciones se invierten significativamente, para los anchos mayores a 8 plg representaron un 88 %.

Efeitos da Pulsação Ultrassônica da Corrente sobre a Geometria da ZF e ZAC na Soldagem Arco Submerso

Resumo: O presente trabalho propõe investigar a aplicação da técnica de excitação ultrassônica do arco no processo SAW com o intuito de avaliar a influência dos principais parâmetros associados a pulsação da corrente, como a frequência e a amplitude da corrente de excitação ultrassônica, sobre os cordões de solda produzidos. Para tanto, foi montada uma bancada experimental constituída por duas fontes de energia: uma convencional de soldagem e outra capaz de pulsar a corrente em frequências ultrassônicas. Durante a realização dos ensaios foram empregadas duas amplitudes de corrente de excitação ultrassônica, 25 A e 50 A, cada qual em três frequências de pulsação diferentes, 20 kHz, 50 kHz e 80 kHz. A partir de macrografias foram realizadas análises dimensionais dos cordões obtidos com foco na largura, penetração e área fundida, assim como a área da zona afetada pelo calor (ZAC). Como resultado, contrariando as informações disponíveis na literatura, não foi possível identificar alterações consideráveis na geometria do cordão de solda, assim como, na ZAC que pudessem ser atribuídas à pulsação da corrente nas frequências estudadas.

Influence of Saw Blade Tension on the Stability of Sawing Processes

Sawing with bandsaws is a fast and efficient process for cutting semi-finished parts out of bar stock in the metalworking industry. However, the produced surface quality on the workpiece is low due to the unguided length of the saw blade during the engagement in the workpiece. The kinematic correlation between the thin, unstable structure of the saw blade, only pre-stressed in the cutting direction, and the distance of the two saw blade guides according to the workpiece dimensions leads to an indefinite behaviour of the saw blade in the kerf. Apart from the surface quality, this cutting behaviour also causes a great wear of the tool. With increasing wear of the tool, the process becomes more and more unstable and the cutting loss increases. For an optimization of the sawing process, the influences on the stability of the process are investigated by experiment on a test bandsaw equipped with extensive measurement equipment. This paper examines how the saw blade tension influences the stability of sawing processes subject to tool wear. For this purpose, the saw blade tension is varied in a wide range and the stability of the process is assessed. The results obtained show a great influence of the saw blade tension on the sawing process and form the basis for developing a stand-alone stability control system to automatically adjust the sawing parameters.

Biomass from Wood Processing Industries as an Economically Viable and Environmentally Friendly Solution

Biomass is seen as an economically viable and environmentally friendly solution to energy generation. Biomass is a financially viable investment as well as being environmentally friendly. The development and implementation of biomass technologies could bring many environmental, energetically and economic benefits, solving important problems such as waste disposal and renewable energy supply. The different countries clearly have chosen very different approaches in developing and deploying various bio–energy options. Partly this is caused by the natural conditions (type of resources and crops, climate) and the structure of the energy system, and also by the specific political priorities linked to the agricultural and forestry sectors in those countries. Romania has a significant potential in organic waste, including waste generated in forestry sector, agro–food industry or municipal biodegradable wastes. Biomass is an emerging renewable fuel that can help to heat homes and buildings at lower impact to the environment and lower costs than fossil fuels. The fuel (usually in the form of biomass pellets) is made from sustainable materials, such as wood, which is easily replaced and in abundance, at a relatively cheap price. As people are becoming more and more conscious about their individual impact on the environment and looking into greener, more efficient alternatives, biomass is slowly becoming one of the nation’s favorite renewable heat technologies. Actually, sawdust as by–product from wood sawing process, doesn’t have much application because of its low burning efficient. However, by pressing the saw dust into pellets, it becomes a kind of high quality biofuel product – sawdust pellets or wood pellets.

Estimation of the Ampere Consumption of Dimension Stone Sawing Machine Using of Artificial Neural Networks

Nowadays, estimating the ampere consumption and achieve to the optimum condition from the perspective of energy consumption is one of the most important steps to reduce the production costs. In this research it is tried to develop an accurate model for estimating the ampere consumption by using the artificial neural networks (ANN).In the first step, experimental studies were carried out on 7 carbonate rock samples in different conditions at particular feed rates (100, 200, 300and 400) and depth of cuts (15, 22, 30and 35mm) using a fully instrumented laboratory rig that is enable to change the machine parameters and measure the ampere consumption. In next step, a back propagation neural network was designed for modelling the sawing process for predicting the ampere consumption. The input network consisting of two parts: machine, work piece characteristics and the output of neural network was ampere consumption. This research evaluated the competencies of neural networks to estimate the ampere consumption in sawing process. The correlation coefficient between measured and predicted data in training and testing data is 0.95 and 0.97 respectively. The root mean square error (RMSE) for train and test data is 1.2 and 0.7 respectively. The results of this study showed that the ANNs can be used to estimate the ampere consumption with high ability and low error for industrial applications. Moreover, the cost of sawing machine ampere consumption can be accurately estimated using this neural model from some important physical and mechanical properties of rock.

Indirect measurement of high grid strip densities over Nyquist sampling rate based on the moiré pattern analysis for quality assurance in grid manufacturing

Abstract We have recently developed very precise carbon-interspaced antiscatter grids having a wide range of grid strip densities ( i.e. , 85–234 lines/in.) by adopting the sawing process, depending on the demands of specific imaging modalities. However, because grid strips of the recently developed grids are mostly invisible through X-ray nondestructive testing due to their high strip densities, quality assurance in the manufacturing has not yet satisfactorily made. In this work, we proposed a pragmatic method to measure actual grid strip densities over the Nyquist sampling rate based on the moire pattern analysis. We prepared several samples of the carbon-interspaced grids having nominal grid strip densities of 85, 103, 130, 150, 178, 203, 215, and 234 lines/in. and measured their strip densities by using the proposed method to demonstrate its viability assessment. The differences between the nominal and the measured grid strip densities were less than about 1.8%, indicating the proposed method is useful for the quality assurance in grid manufacturing.

The impact of wafering on organic and inorganic surface contaminations

Beside the silicon feedstock material, the crystallization process and the cell processing itself, the wafer sawing process can strongly determine the final solar cell quality. Especially surface contamination is introduced in this process step because impurities from sawing meet with a virgin silicon surface which is highly reactive until the oxide layer is formed. In this paper we quantitatively analysed both, the organic and inorganic contamination on wafer surfaces and show that changes of process parameters during wafering may cause dramatic changes in surface purity. We present powerful techniques for the monitoring of wafer surface quality which is essential for the production of high efficiency and high quality solar cells.