Abrasive Sawing Research Articles

Абразивные пилы Среднего Зауралья и некоторые аспекты их использования в древности

In the Middle Transurals, stones started to get sawed with abrasive saws in the Neolithic era and was widely used in the Eneolithic. The author studied 129 abrasive saws and 153 items with traces of sawing. They respectively originate from 26 and 22 archaeological sites. Usually there are one or two saws at the site (11 and 5 sites, respectively). But some sites appeared to have dozens of them (Shaitanskoye Lake I – 13; Ust-Vagilsky hill – 19; Yurino IV – 22). They are found both in settlements, sites, and in sanctuaries. Saws are mainly represented by fragments from 1.5 to 24.5 cm long. Moreover, they were broken intentionally. There are few whole saws preserved, usually their length is 10–20 cm. The thickness of the saws ranges from 0.5 to 2.5 cm. Saws up to 0.6 cm thick predominate and constitute 46.3 %. Fifteen saws have two working blades each. 30 abrasive saws are made of fragments of grinding plates and are both one-sided and two-sided. The saws cut into the processed material from 0.2 to 2.5 cm deep. Most often (56.8 %) the items were sawed 0.2 to 0.5 cm deep. The most intense deterioration (3.6 and 4.4 cm) is found in two saws. The working edges of abrasive saws were usually formed by grinding. At the same time, the opposite edge of the saws nearly always remained untreated. The deterioration of stone saws and sawing traces in various objects were analyzed and showed that sawing boiled down to mostly splitting thin blanks used to make knives and arrowheads. There are very rare traces of saws on polished chopping tools such as axes (1) and adzes (5). Abrasive saws were also used to design teeth on comb stamps or grooves on so-called ironings. Besides, saws could be used to cut out patches out of fragments of richly ornamented broken vessels. Saws were made of 8 types of mineral raw materials. It appeared possible to identify mineral raw materials for102 saws. Two-thirds of them are made of slate (41.2 %) and granodiorite (35.3 %). The next most popular material is mica slate which constitutes 11.8 %. The remaining saws are made of sandstone (5 items), quartzite, carbonaceous shale, brown ironstone (2 items each) and quartzite sandstone (1 item). The experiments made it possible to determine the sawing speed and the deterioration rate of the saw material. It is established how long and how much workforce it took to saw. The research managed to compare the efficiency of sawing different types of stone with saws made of materials with different hardness. The experiment results reveal the peculiarities of abrasive sawing of stone. The peculiarities were the methods for securing the blank and securing the saw in the intended cutting line. Sawing with a two-handed saw, as well as using fine-grained abrasive, significantly increased the processing efficiency.

Slurry pressure at the cutting zone in multi-wire sawing: An experimental study

Multi-wire sawing has been widely used in the processing of semiconductor material wafers employed in integrated circuits, solar cells, etc. Recently, free abrasive multi-wire sawing has been gradually replaced by solid abrasive multi-wire sawing technology in the domain of solar wafers. However, free abrasive sawing still plays an important role in the processing of electronic-grade monocrystalline silicon wafers, where the requirements on the wafer quality are continuously increasing. Because the free abrasive multi-wire sawing process is very complex, its material removal mechanisms are not fully understood. In this study, experiments were designed to measure the slurry pressure at the cutting zone during a free abrasive multi-wire sawing process to fabricate monocrystalline silicon wafers, and the pressure distribution condition throughout the cutting zone was obtained. Two sets of micropores of 0.17 mm diameter were processed on the experimental workpiece to transmit the cutting zone fluid pressure to the sensor. Each group of micropores consisted of 17 small pores, divided into three rows, with the row spacing consistent with the pitch width of the wire guide. During installation, the center line of each row of micropores was aligned with the center line of the steel wire. The pressure at the cutting zone was measured using the micropores to transfer the slurry pressure to the sensor. Calibration experiments were conducted by considering the capillary effects of the micropores, and the actual pressure at the cutting zone was obtained. Experimental results show that the slurry pressure was 0.16 bar at 40 mm near the slurry inlet. As the distance from the slurry inlet increased, the pressure fluctuated around 0.14 bar. Furthermore, at a distance of 160 mm from the slurry inlet, the sensor was not able to detect the pressure at the cutting zone. The experimental results from the free abrasive multi-wire sawing pressure measurement showed that material removal involves a three-body action comprising the metal wire, abrasive grains, and workpiece. At the cutting zone far from the location of the slurry inlet, forming a stable and continuous film with the slurry is difficult. The experimental results confirm that the force of material removal during the sawing process mainly comes from the wire tension of the steel wire. The film thickness of the slurry in the cutting zone is determined by the diameter of the abrasive between the wire and ingot. The experimental conclusion is of great significance for understanding the complex material removal process in the cutting zone for multi-wire sawing.

Separation of silicon carbide and silicon powders in kerf loss slurry of loose abrasive sawing by means of phase transfer separation method with mixed cationic-anionic surfactant collectors addition

Kerf loss slurry generated from the slicing process of silicon wafer by using loose abrasive sawing method contains silicon carbide (SiC) and silicon (Si) powders. This study attempted to separate SiC and Si powders in kerf loss slurry through phase transfer separation method with mixed cationic-anionic surfactant collectors addition. Isooctane and water were employed as the two phases. Dodecylamine acetate (DAA) and sodium oleate (NaOL) was used as the cationic and anionic surfactant collector, respectively. The effects of single surfactant collector addition (DAA/NaOL) and mixed cationic-anionic surfactant collectors addition (DAA + NaOL) on the transfer of individual SiC and Si powders from the water phase to the isooctane phase, as well as on the separation of SiC and Si powders in kerf loss slurry, were investigated and compared.The results indicated that DAA could improve the transfer of both SiC and Si powders to the isooctane phase, and the improvement for SiC powder was higher than for Si powder. In contrast, NaOL could only improve the transfer of SiC powder to the isooctane phase, and the improvement for SiC powder was less than DAA did. Compared to single DAA/NaOL addition, mixed DAA + NaOL addition could improve the separation of SiC and Si powders in kerf loss slurry at lower surfactant collector dosages. In addition, the dosage of NaOL in mixed DAA + NaOL addition had more significant effect on improving their mutual separation than that of DAA did. The optimal separation results were obtained with mixed surfactant collectors addition of 0.01 kg/ton DAA and 0.05 kg/ton NaOL at pH 5. The purity and recovery of SiC powder recovered from the isooctane phase was 90.0% and 92.0%, respectively, and those of Si powder recovered from the water phase was 89.5% and 87.0%, respectively. The total dosage of surfactant collectors was 40% reduced.

A material removal coefficient for diamond wire sawing of silicon

Diamond wire sawing (DWS) of silicon wafers has replaced loose abrasive sawing (LAS) within a very short time, mainly due to the enormous cost pressure in the photovoltaic industry. However, the LAS process is still much better investigated and understood from a mechanics point of view. This lack of micromechanically substantiated process knowledge is a major challenge in optimisation for a reliable process and the associated improvement in the quality of the products. The present work aims to contribute to this field by deriving a material removal coefficient that can be used at the process level in well-established material removal laws such as the Preston or Archard equation. The results show that the removal coefficient calculated on the basis of finite element simulations indicates a significant increase in material removal for common DWS sawing conditions in comparison to LAS, which is in good agreement with experimental findings.

Experimental and numerical analysis of scratching induced damage during diamond wire sawing of silicon

Diamond wire sawing (DWS) is the dominant manufacturing process for thin silicon substrates. The understanding of micromechanical damaging and material removal mechanisms is essential for improving the reliability of the processes and the quality of the products. Due to the lack of models that are capable to predict subsurface damage during diamond wire sawing of silicon, process analyses are so far only possible on the basis of models originally developed for loose abrasive sawing (LAS). However, the application of LAS models to the DWS process does not seem appropriate, because of the different underlying deformation mechanisms. Within this work a three-dimensional Finite-Element analysis is conducted in order to investigate the cracking mechanisms during the sawing process. Experimental as well as numerical studies concerning median and lateral cracking are carried out using a Vickers indenter scratching on silicon. The results show that the numerically predicted dimensions of damage zones are in good agreement with the experimental results and that the new model is suitable for the analysis of subsurface damage during diamond wire sawing of silicon.

Evaluation of take-home exposure to asbestos from handling asbestos-contaminated worker clothing following the abrasive sawing of cement pipe

Although industrial uses of asbestos have declined since the 1970s, in recent years there has been a renewed interest in para-occupational (“take-home”) exposure to these fibers. The aim of this study was to quantify the release of asbestos fibers, if any, during the shaking out of crocidolite- and chrysotile-contaminated clothing in a simulated at-home setting. An exposure study was conducted in which personal and area air samples were collected during the handling (i.e. shake-out) of work clothing (shirt and pants) previously worn by an operator who had cut asbestos-containing cement pipe. During eight “loading” events, the operator cut a historically representative asbestos-containing cement pipe (10% crocidolite and 25% chrysotile) using a powered abrasive saw. Subsequently, 30-minute air samples were collected during four “shake-out” events, each of which consisted of the handling of two complete sets of contaminated work clothes. Samples were analyzed in accordance with NIOSH methods 7400 and 7402. The mean phase contrast microscopy equivalent (PCME) airborne concentrations were 0.52 f/cc (SD = 0.34 f/cc) for total asbestos fibers, 0.36 f/cc (SD = 0.26 f/cc) for chrysotile and 0.17 f/cc (SD = 0.096 f/cc) for crocidolite. Based on likely estimates of the frequency of laundering activities, and assuming that the dusty clothing (1) is not blown off in the occupational setting using compressed air and (2) is not shaken out before entering the home, a family member handling the clothing could potentially have a lifetime cumulative exposure to chrysotile and crocidolite of approximately 0.20 f/cc-year and 0.096 f/cc-year, respectively.

Numerical modelling of silicon melt purification in induction directional solidification system

Solar grade silicon production is an energy intensive and harmful to the environment process. Yet 40% of this valuable product material is lost into sawdust (kerf loss) during wafering. The kerf waste from Fixed Abrasive Sawing of PV silicon wafers is pelletized and then remelted in an induction furnace. The furnace has a square cross-section quartz crucible, surrounded by graphite susceptors and heated by an induction coil that enables directional solidification of the new ingot. Top and bottom 'pancake' coils provide additional temperature control. Once melted, silicon becomes electrically conductive and subject to stirring by induction. To recycle the silicon, particulate impurities (due to the sawing, condensed silicon oxides or carbides) need to be removed. Flow control and the electromagnetic Leenov-Kolin force are used to expel particulates, through a novel dual frequency induction scheme. Three-dimensional, multi-physics numerical modelling captures the electromagnetic, fluid-flow and heat-transfer effects in this process. The presented results show it is possible to retain the impurity particles on the sides of the solidified ingot where they can be sliced off and removed.

Analysis of the Sub-surface Damage of mc- and cz-Si Wafers Sawn with Diamond-plated Wire

The usage of diamond-plated wire to produce silicon wafers for the photovoltaic industry is still a new and highly investigated wafering technology. The requirements regarding the quality of the wafer surface are very high and they have to compete with the cost effectiveness and quality of wafers produced by the established loose abrasive sawing technology. Hence, the wafer topography, the fracture stress and the corresponding sub-surface damage have to be investigated and improved.This paper discusses the topographic parameters, the crack depths and the fracture stress of mono- and multi-crystalline silicon wafers that were produced on multi-wire saws using diamond-plated wire and comparable process parameters. Especially multi-crystalline silicon (mc-Si) wafers exhibit lower fracture stress values compared to mono-crystalline silicon (cz-Si) wafers. We investigated the relations between crack depth and fracture stress. In detail, we determined a 15% higher median and a 40% increased interquartile range of the crack depth of mc-Si wafers in comparison to similar produced cz-Si wafers. That correlates with lower fracture stress values of textured mc-Si wafers compared to cz-Si wafers. In the following, we studied the sub-surface damage as a function of crystal orientation in detail. It was found that the crack depths increases from the {100} plane over the {111} plane to the {101} plane. However for the {101} plane two grains were investigated, resulting in a discrepancy of 4μm. This may be related to the unknown rotation angle between the corresponding {111} cleavage planes and the wire direction and requires further investigations.

Slot Machining Effects on Residual Stress Measurements Using the Crack Compliance Method

Abstract The main aim of this paper was to evaluate the practical aspects and compare two of the most common machining techniques employed in the crack compliance (incremental slitting) method for the determination of residual stresses, namely wire electrodischarge machining (WEDM) and circular abrasive saws. For the circular saws, the effect of the rotational speed and blade thickness was also evaluated. Results show that the associated level of errors introduced during thin saw machining can be as low as the results obtained by WEDM machining. However, for practical reasons, WEDM machining offers a better control of cut increment length than sawing techniques. Additionally, higher rotational saw speeds are likely to introduce larger errors in strain readings probably due to higher frictional heat and plasticity generation ahead of the slot tip.

Observations of Dislocations in Ammonium Dihydrogen Phosphate: Production of Dislocation-Free Crystals

The results of etch-pit and diffraction topographic studies on ammonium dihydrogen phosphate (ADP) are reported. These studies were carried out on specimens sectioned by abrasive wheel and string-saw from large single crystals grown from aqueous solution. The two characterization methods are shown to be in approximate one-to-one correspondence in the case of sections produced by abrasive sawing. Absence of both etch pits and topographic images in sections made by string-sawing of material well removed from the seed region is taken to indicate that this material is dislocation-free. Preliminary results on the plasticity of ADP are reported.

Cutting glass by abrasive saws

Cutting glass by abrasive saws