Small Kerf Research Articles

Influence of cutting parameters on wear of diamond wire during multi-wire rocking sawing with reciprocating motion

Multi-wire cutting with diamond wire saw has gradually become the main processing method for hard-and-brittle materials due to its small kerf loss and high machining accuracy. However, the diamond wire saw will inevitably suffer wear during the process of machining, and hence affects the quality of the cut surface. In this paper, a wire saw wear model was established, and the wear at different positions on the wire saw was theoretically calculated by correlating the volume of the workpiece removed by the unit wire saw to the wire saw wear. The iteration method was used to calculate the wear of the wire saw after cutting by superimposing the wear caused by every monolithic wafer. Based on this wear year model of the wire saw, the influence of multi-wire cutting parameters and the shapes of the workpiece on the wire saw wear was discussed through numerical simulation. The simulation results showed that the feed speed of the workpiece and the length of the wire saw had an obvious effect on the maximum wear of the wire saw, and the maximum rocking angle, wire speed, and reciprocating times had little effect on the maximum wear of the wire saw. The wear curve of the circular workpiece wire saw is unstable in the whole process, and the wear curve of the rectangular workpiece wire saw changes at the beginning and end, and the middle is stable.

Parametric optimization of material removal rate, surface roughness, and kerf width in high-speed wire electric discharge machining (HS-WEDM) of DC53 die steel

Dies are widely used in various manufacturing processes and are considered one of the important aspects of manufacturing industries. DC53 die steel is a recently developed and improved die steel which has good material characteristics as compared with D2 die steel and is replacing D2 die steel due to its improved material characteristics. The wire electric discharge machining is widely used for its machining, because conventional machining is not suitable for its machining. The demand for shorter lead time with improved quality and precision has made die making a challenging task for die makers, and this becomes more challenging with new die steel such as DC53 die steel. For this reason, the Taguchi method is employed and the effect of various factors of high-speed wire electric discharge machining (HS-WEDM) on the machining characteristics such as material removal rate (MRR), kerf width, and surface roughness (SR) of DC53 die steel is investigated. The factors such as pulse on time (Pon), current intensity (C), pulse off time (Poff), and wire speed (WS) are selected. Taguchi L27 orthogonal array is selected for experimenting. Analysis of variance (ANOVA) is used to find the significant factor on each machining characteristic, while analysis of means (ANOM) of signal to noise (S/N) ratio is used to find the optimal value of factors for improving each machining characteristic. It is concluded that current intensity is most significant on MRR and SR, while pulse on time is most significant on kerf width. The optimal value of factors identified for achieving maximum material removal rate is 3-μs Pon, 5-μs Poff, 3-A C, and 11-m/s WS, while for achieving low surface roughness, optimal value of factors are 4-μs Pon, 9-μs Poff, 2-A C, and 9-m/s WS. Moreover, for achieving small kerf width, the factors should be set at the optimal value of 4-μs Pon, 9-μs Poff, 1-A C, and 7-m/s WS.

Diamond slicing using ultrashort laser-induced graphitization and additional nanosecond laser illumination

Single-crystal diamonds exhibit properties consistent with semiconductor substrates. However, they are hard and brittle, making them difficult to slice. Therefore, this study demonstrates diamond slicing by applying femtosecond laser internal processing, which converts diamond to graphite. Additionally, the use of nanosecond lasers for further modification is also demonstrated. This method enables diamond slicing with only a small kerf loss. A femtosecond laser beam (pulse energy of 2 μJ, pulse duration of 550 fs) was tightly focused using an objective lens with a numerical aperture (NA) of 0.5. The focus was scanned parallel to the optical axis towards the light source (i.e., backward). The scanning speed was set to 100 μm/s. A continuous modified line of 12–15 μm diameter was formed in the diamond. In addition, adjacent single lines were formed with a spacing of 5 μm, and a planar modified layer (15–20 μm thick) was generated in the bulk diamond. The differences in crystal orientation in the texture of the modified layer were also clarified.In addition, the first modified layer was reheated using a nanosecond pulsed laser to convert it into a separable layer. A diamond of size approximately 1 × 1 mm2 was separated, and the separated surface and cross section were observed. Furthermore, the separation of the diamond depended on a crack generated in the front of the modified layer during additional laser illumination. Raman spectroscopy showed that the modified layer contained graphite.

Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0J/cm2 (±0.3) and Fth,∞=2.5J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500mW power, 100mm focal length, 2000µm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143µm/s – more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

Effect of laser beam scanning mode on material removal efficiency in laser ablation for micromachining of glass

This study investigated the influence of laser beam scanning mode on material removal efficiency through evaluation of cut-through time for a 5 mm length inside a glass substrate. The parameters related to the scanning mode covered scanning speed, focus position, number of lines and shifting pitch in one kerf, scanning under raster, merge or group mode, and scanning at fixed or nonfixed parameter mode. Picosecond, near infrared laser pulses were used to ablate a 700 μm thick, nonion exchanged Gorilla glass at fluence of 9.0 J/cm2 using a galvanometer scanner. It has been found that the optimal scanning speed for ablation without cracks and debris was above 200 mm/s, namely, only a few overlapped pulses in a single line scan. When ablation started from glass bottom, the ejected materials could efficiently escape from the ablation kerf and no ejected materials would disperse the laser energy deposition to the glass unlike ablation from the top surface. The cut-through time was 1.36 times and 24.5 times longer when focus was placed at the middle and top of the glass, respectively, compared to at bottom surface. The optimal number of lines was determined by the required kerf width of approximately half the glass thickness for high ablation efficiency. Ablated materials were not ejected out of the kerf efficiently at smaller kerf with fewer lines. Cut-through time was also increased at larger kerf with more lines due to more material removal. The optimal shifting pitch was found to be approximately a scanned line width which was close to the spot size in this study. Scanning under raster mode could achieve minimal cut-through time of 31.42 s. The cut-through time was increased by a factor of 1.51 times and 13.43 times, respectively, for merge and group mode. Merge and raster mode allowed layer by layer scanning with high material removal and the ablation was further enhanced by continuous line scanning in one ablation layer under raster mode. Ablation under fixed parameter mode could eliminate the call-procedure of laser parameters used in individual line scanning. The cut-through time was reduced by 86% compared to nonfixed parameter mode.

An Investigation of Abrasive Water Jet Machining on Graphite/Glass/Epoxy Composite

In the present research work, the effect of abrasive water jet (AWJ) machining parameters such as jet operating pressure, feed rate, standoff distance (SOD), and concentration of abrasive on kerf width produced on graphite filled glass fiber reinforced epoxy composite is investigated. Experiments were conducted based on Taguchi’s L27 orthogonal arrays and the process parameters were optimized to obtain small kerf. The main as well as interaction effects of the process parameters were analyzed using the analysis of variance (ANOVA) and regression models were developed to predict kerf width. The results show that the operating pressure, the SOD, and the feed rate are found to be significantly affecting the top kerf width and their contribution to kerf width is 24.72%, 12.38%, and 52.16%, respectively. Further, morphological study is made using scanning electron microscope (SEM) on the samples that were machined at optimized process parameters. It was observed that AWJ machined surfaces were free from delamination at optimized process parameters.

Dicing of SiC Wafer by Atmospheric-Pressure Plasma Etching Process with Slit Mask for Plasma Confinement

Silicon carbide (SiC) is a promising semiconductor material for high-temperature, high-frequency, high-power, and energy-saving applications. However, because of the hardness and chemical stability of SiC, few conventional machining methods can handle this material efficiently. A plasma chemical vaporization machining (PCVM) technique is an atmospheric-pressure plasma etching process. We previously proposed a novel style of PCVM dicing using slit apertures for plasma confinement, which in principle can achieve both a high removal rate and small kerf loss, and demonstration experiments were performed using a silicon wafer as a sample. In this research, some basic experiments were performed using 4H-SiC wafer as a sample, and a maximum removal rate of approximately 10 μm/min and a narrowest groove width of 25 μm were achieved. We also found that argon can be used for plasma generation instead of expensive helium gas.

Comparative Study of Remote Fiber Laser and Water-Jet Guided Laser Cutting of Thin Metal Sheets

Abstract This article presents a comparison between remote laser cutting with a fiber laser and water-jet guided laser cutting using a 532 nm solid state laser. Complex contours are processed in stainless steel and brass sheets (thickness ≤ 100 μm), respectively. Results for achievable quality and productivity as well as possible applications for both systems are shown and discussed. We sustained dross free cuts with almost no heat affected zone and small kerf width for the water-jet guided process, whereas small dross, notable heat affected zone and varying kerf width where observed for remote cutting. However, process times for the water-jet guided process where considerably higher than those for remote cutting.

UV laser microprocessing and post chemical etching on ultrathin Al 2O 3 ceramic substrate

In this study, an Nd:YVO 4 UV laser was used for microprocessing ultrathin (125 μm) ceramic plates for use as a multi-layer microchip substrate. The effects of the UV laser microprocessing parameters, including laser power density, frequency, laser scanning speed, and pass delay on microprocessing accuracy and quality (kerf width and arithmetic average roughness R a on the kerf sidewall) were investigated by means of a 4 × 4 orthogonal design. The key processing parameters were determined and optimized for small kerf width and minimal R a of the kerf sidewall while retaining high production efficiency. Subsequent chemical etching of the laser processed areas was performed to reduce the kerf surface and kerf sidewall roughness by removing debris and the thin recast layer for the required size precision and post gilding treatment. The results showed that a clean surface and crack-free kerf sidewall with roughness R a of 0.16 μm could be achieved by laser microprocessing and chemical etching.

The Diamond Wire Saw with a Nonmetallic Core

Diamond wire saw is the leading technology for use in cutting hard brittle material. Its smaller kerf and faster cutting time make it replacing the conventional slurry technology for those materials. Turned over the traditional router, this paper presents a novel approach that replaces the typical metallic core with a nonmetallic core, for manufacturing of ultraviolet curing resin fixed-abrasive diamond wire saw (DWS). The experiments show that the diamond wire saw made by this manufacturing method can obtain a good performance as well as taking many other advantages.

Techniques de découpage télé-opérées dans le domaine du déclassement nucléaire

Remote disassembly of radiologically burdened large components is among the most sophisticated and complex activities in the dismantling of nuclear installations. High local dose rates and contamination levels in combination with poor accessibility and complex geometries of parts imply major challenges.In many cases the design of nuclear reactors makes use of the shielding effect of water during operation. Hence, also in the later nuclear decommissioning it is possible to make benefit of this effect by dismantling/cutting of equipment under water. In the opposite, in some other cases of nuclear reactor design no shielding water is used during operation, and thus, also decommissioning activities have to focus exclusively on dry dismantling techniques to avoid, amongst others, the production of wet secondary waste.These and several other parameters entail the application of different cutting technologies thoroughly adjusted to the particular requirements.This article describes three thermal and one nonthermal cutting technology which have been effectively applied in nuclear decommissioning projects. The thermal cutting technologies addressed are “Autogenous Flame Cutting”, “Plasma Arc Cutting” and “Contact Arc Metal Cutting”. The non-thermal cutting technology addressed is “High Pressure Water Jet Cutting”.With the exception of Contact Arc Metal Cutting, all of these technologies are well known and prooven in the field of manufacturing. Nevertheless, to cope with the challenges in the field of nuclear decommissioning, it is also very important to combine the cutting technology/cutting equipment correctly with the remote controlled handling systems.At first the basic functioning will be described for understanding of the technologies themselves. The functioning accounts different fields of application and the particular technological limits. Adaptations for nuclear decommissioning requirements will be described presenting the most important modifications.At second applications and gained experience in particular nuclear decommissioning projects will be present by pictures and/or short videos.As conclusion details and data of all addressed cutting technologies will be presented in a matrix, giving a hand to concerned engineers in the selection of best matching technologies for particular nuclear decommissioning activities.<b>Short description of the different cutting technologies<b/>Autogenous Flame CuttingThe Autogenous Flame Cutting Technology has been introduced more than 100 years ago and has been developed to a standard method for the cutting of mild steel. A high pressure oxygen jet oxidises the material in a small kerf. Nevertheless, not all metal types are appropriate for the autogenous cutting process.Which are the limiting factors of the Autogenous Flame Cutting Technology? How can normally non-suitable material be cut anyhow? What is the maximum achievable cutting speed? Which peripheral equipment is necessary?Plasma Arc CuttingIn the nineteen-fifties the Plasma Arc Cutting Technology has been introduced as a complementary technology, to cope also with material unsuitable for flame cutting (for example stainless steel, copper, etc.).In contrast to Autogenous Flame Cutting, the Plasma Arc Cutting uses an electronically induced plasma arc to melt a kerf in the material. Inside the plasma arc temperatures up to 30.000 Kelvin exist. In theory, this temperature is sufficient to cut all materials. But where are the limits in practise?For nuclear decommissioning the Under-Water Plasma Arc Cutting Technology is important. Special equipment allows cutting under water, reducing the radiation impact to the concerned staff. Also the release of dust and particles to the air is reduced by 99.4 %.Contact Arc Metal CuttingContact Arc Metal Cutting is a new thermal cutting technology for under-water cutting jobs. In opposite to the previously introduced cutting technologies, here a carbon blade cuts the components. An electric arc between cutting blade and component melts the kerf into the material like a hot knife into a piece of butter.With the Contact Arc Cutting Technology it is now possible to cut also complex structures (structures with hollows and undercuts).How exact is the technology? Which applications are possible and where are the limits? The article will answer this and other questions.Water Jet Cutting(High Pressure) Water Jet Cutting can be distinguished in Pure Water Jet Cutting and Water Jet Cutting with additional abrasive particles. Both cutting principles use high pressure pumps to create the required high water pressure. In a special nozzle the water pressure is transformed into a high speed water jet (achieving speeds of several hundred meters per second). Nevertheless, cutting of metal or concrete requires the adding of abrasive particles to the water jet.There are two different technical solutions of Water Jet Cutting with additional abrasive particles. The Water Abrasive Injection Jet Cutting technology and the Water Abrasive Suspension Jet Cutting technology.The technological differences between the two technologies will be explained. Advantages for nuclear decommissioning projects and required peripheric equipment are explained in the article.

Machinability of glass by abrasive waterjet

Thin glass plate is usually used to make some important components such as glass substrate, coated glass plate and so forth. However, glass is known as one of the difficult-to-machine materials using conventional machining processes because of its high hardness and brittleness. The Abrasive Water Jet (AWJ) is a non-conventional machining technology, which has been used for cutting a variety of difficult-to-machine materials such as ceramics and composites. In the present study, a kind of thin glass plate was machined with an abrasive waterjet to investigate its machinability under varying cutting conditions. Machinability was evaluated in terms of kerf width and the process parameters were optimised for obtaining a small kerf width.

Modelling and analysis of pulsed Nd:YAG laser machining characteristics during micro-drilling of zirconia (ZrO 2)

Pulsed Nd: YAG laser beam has great ability for micro-machining of ceramic materials because of high laser beam intensity at low mean beam power, good focusing characteristics due to very small pulse duration, small kerf widths and narrow heat effected zones. In the paper, experimental investigations into CNC pulsed Nd:YAG laser micro-drilling of zirconium oxide (ZrO 2) have been carried out. Influence of laser machining parameters on the HAZ thickness and phenomena of tapering of the machined micro-holes has been experimentally investigated. Response Surface Methodology-based optimal parametric analysis has been performed to determine the optimal setting of process parameters such as pulse frequency and pulse width, lamp current, assist air pressure for achieving minimum HAZ thickness and taper of the micro-hole machined by pulsed Nd:YAG laser. Minimum HAZ thickness has been obtained as 0.0675 mm when the lamp current, pulse frequency, assisted air pressure and pulse width are set at optimal parametric setting i.e. 17 amp, 2.0 kHz, 2.0 kg/cm 2 and 2% of the duty cycle, respectively. Minimum taper has been achieved as 0.0319 at optimal parametric setting i.e. the lamp current of 17 amp, pulse frequency of 2.0 kHz, assisted air pressure of 0.6 kg/cm 2 and pulse width of 2% of the duty cycle. Analysis has also been carried out for multi-optimisation of both the responses i.e. HAZ thickness and taper during pulsed Nd:YAG laser micro-drilling on ZrO 2.

Cutting of 1.2 mm thick austenitic stainless steel sheet using pulsed and CW Nd:YAG laser

Stainless steel is an important engineering material that is difficult to be cut by oxy-fuel methods because of the high melting point and low viscosity of the formed oxides. However, it is suitable to be cut by laser. This work aims to evaluate the optimum laser cutting parameters for 1.2 mm austenitic stainless steel sheets by using pulsed and CW Nd:YAG laser beam and nitrogen or oxygen as assistant gases, each one separately. It was shown that the laser cutting quality depends mainly on the laser power, pulse frequency, cutting speed and focus position. The optimum cutting was achieved during pulsed mode at applied power 210 W, frequency 200–250 Hz, speed 1–1.5 m/min, focus position −0.5 to −1 mm, nitrogen pressure 9–11 bar and oxygen pressure 2–4 bar. Increasing the frequency and cutting speed decreased the kerf width and the roughness of cut surface, while increasing the power and gas pressure increased the kerf width and roughness. Comparing with oxygen, nitrogen produced brighter and smoother cut surface with smaller kerf, although it did not prove to be economical. In CW mode, the speed can be increased to more than 8 m/min with equivalent power and gas pressure (limited by the laser system). Pulsed mode was also not economical, especially in limited frequency laser systems, where the pulse overlap should be controlled by both frequency and speed. In CW, the speed can be increased to the maximum system limit. The results should be included in computerized database for the automatic implementation of laser process.

Basic Mechanisms and Models of Multi‐Wire Sawing

AbstractMore than 80 % of the current solar cell production requires the cutting of large silicon crystals. While in the last years the cost of solar cell processing and module fabrication could be reduced considerably, the sawing costs remain high, about 30 % of the wafer production. At present the large crystals are cut using the multi‐wire slicing technology[2] which has the advantage of a high throughput (several hundred wafers per day and machine), a small kerf loss of about 200 μm and almost no restrictions on the size of the ingots. Basic knowledge about the microscopic details of the sawing process is required in order to slice crystals in a controlled way. In the following the principles of the sawing process will be described in this review article as far as they are understood today.