Bottom Kerf Width Research Articles

Dimensional accuracy improvement by parametric optimization in pulsed Nd:YAG laser cutting of Kevlar-29/basalt fiber-reinforced hybrid composites

Laser cutting proves its suitability for cutting of single fiber-reinforced polymer (FRP) composites compared with conventional cutting techniques due to reduced fiber delamination, matrix cracking and fiber pullout. However, the performance of the laser cutting process of hybrid FRP composites is yet to be revealed, which paves the way of the present study. In this article, an experimental investigation of the laser cutting process is carried out on 1.35-mm-thick Kevlar-29 and basalt fiber-reinforced polymer (KBFRP) hybrid composite laminates using 250 W pulsed Nd:YAG laser system. The performance of laser cutting was evaluated by quantifying different kerf quality characteristics such as top and bottom kerf width, top and bottom kerf deviation and kerf taper. These kerf quality characteristics define the geometrical accuracy of the laser cut. Response surface methodology-based Box–Behnken design was adopted for conducting the experiments with varied settings of laser cutting parameters, viz. lamp current, pulse width, pulse frequency, compressed air pressure and cutting speed. Second-order regression models of each response were developed and validated by using standard error plots. A parametric effect analysis was carried out by using the variation of performance measures predicted through developed mathematical models. In order to achieve the optimal levels of the process parameters for all kerf quality characteristics, a self-developed python language-coded TLBO algorithm was used. Finally, the confirmation experiments were performed at obtained optimal levels of laser cutting parameters. An overall improvement of 22.23% in multiple kerf quality characteristics was achieved through optimal settings of laser cutting parameters. The individual improvement of 11.44%, 8.47%, 17.65%, 15.22% and 58.87% was recorded in top kerf width, bottom kerf width, top kerf deviation, bottom kerf deviation and kerf taper, respectively. The developed mathematical models and suggested optimal conditions are able to provide direction to the researchers for obtaining higher-dimensional accuracy in Nd:YAG laser cutting of KBFRP hybrid composites.

Prediction of optimal cut quality characteristic of Inconel 718 sheet by genetic algorithm and particle swarm optimization

Selection of an appropriate optimal range of cutting parameters during the machining of Inconel-718 is quite essential to achieve the high-quality cut and is a challenging task within this domain of study. The aim of this research is to develop a robust prediction model which can suggest the desired range of cutting parameters for accomplishing better cutting quality, precision, and geometrical accuracy. Experiments have been performed on a 300 W (CNC-PCT 300) pulsed Nd: YAG laser cutting system at various levels of input cutting parameters, viz., gas pressure, standoff distance, cutting speed, and laser power. Thereafter, the artificial neural network technique has been adopted to develop mathematical models in terms of aforementioned input cutting parameters for geometrical quality characteristics: Top Kerf Width, Bottom Kerf Width, and Kerf Taper. These developed models have been validated by comparing the predicted values with the experimental ones. Furthermore, these models have been optimized using a multiobjective genetic algorithm and particle swarm optimization techniques, in order to ascertain the optimal range of cutting parameters pertaining to better quality cut with high precision and geometrical accuracy.

Prediction of geometric quality characteristics during laser cutting of Inconel-718 sheet using statistical approach

Machining of advanced material like Inconel-718 with accuracy and precision is an emerging need. Selection of an appropriate optimal range of cutting parameters is quite essential to achieve high-quality cut and is a challenging task within this domain of study. The aim of this research is to develop a robust prediction model which can suggest the desired range of cutting parameters for accomplishing better cutting quality, precision, and geometrical accuracy. Experiments have been performed on a 300-W (CNC-PCT 300) pulsed Nd:YAG laser cutting system at various levels of input cutting parameters, viz. gas pressure, standoff distance, cutting speed and laser power. Thereafter, response surface methodology has been adopted to develop mathematical models in terms of aforementioned input cutting parameters for geometrical quality characteristics: Top Kerf Width (TKW) and Bottom Kerf Width (BKW). The percentage error in the prediction models has been found as 1.981% and 1.511% for TKW and BKW, respectively. These developed models have been validated by comparing the predicted values with the experimental ones. Further, these models have been used to determine the dependency of responses on input parameters and to ascertain an optimal range of cutting parameters pertaining to better quality cut with high precision and geometrical accuracy. Moreover, it has also been found that the dependency of input parameters on output is non-monotonous in nature.

Experimental and parametric evaluation of cut quality characteristics in CO2 laser cutting of polystyrene

Cutting characteristics such as heat affected zone (HAZ), top and bottom kerf widths, ratio of top kerf width to bottom kerf width, and dross height are so reliant on process condition in the laser cutting of polymer materials. In the present research, a 60 (W) continuous wave CO2 laser cutting machine was used for cutting the extruded samples of Polystyrene sheet with the thickness of 3 mm. The experiments were designed based on the statistical method, design of experiments. Three variables considered as process parameters including laser power (in three level of 60, 70 and 80 W), cutting velocity (in three level of 6, 10, 14 mm/s) and cutting with covering gas or without gas. The results indicated that the maximum feasible laser power and increasing cutting velocity using compressed air resulted in decreasing HAZ width. By gradual increase of the laser power the cutting mechanism converts from melting to evaporation. Increasing laser power and cutting velocity individually made the dross height smaller. The process parameters were optimized to achieve minimum top kerf width, minimum HAZ width, and ratio equal to 1.

Geometrical quality evaluation in laser cutting of Inconel-718 sheet by using Taguchi based regression analysis and particle swarm optimization

The Inconel-718 is one of the most demanding advanced engineering materials because of its superior quality. The conventional machining techniques are facing many problems to cut intricate profiles on these materials due to its minimum thermal conductivity, minimum elastic property and maximum chemical affinity at magnified temperature. The laser beam cutting is one of the advanced cutting method that may be used to achieve the geometrical accuracy with more precision by the suitable management of input process parameters. In this research work, the experimental investigation during the pulsed Nd:YAG laser cutting of Inconel-718 has been carried out. The experiments have been conducted by using the well planned orthogonal array L27. The experimentally measured values of different quality characteristics have been used for developing the second order regression models of bottom kerf deviation (KD), bottom kerf width (KW) and kerf taper (KT). The developed models of different quality characteristics have been utilized as a quality function for single–objective optimization by using particle swarm optimization (PSO) method. The optimum results obtained by the proposed hybrid methodology have been compared with experimental results. The comparison of optimized results with the experimental results shows that an individual improvement of 75%, 12.67% and 33.70% in bottom kerf deviation, bottom kerf width, and kerf taper has been observed. The parametric effects of different most significant input process parameters on quality characteristics have also been discussed.

A feasibility study on wire electrical discharge machining of carbon fibre reinforced plastic composites

This paper details preliminary experimental work to investigate the wire electrical discharge machining (WEDM) of unidirectional carbon fibre reinforced plastic (CFRP) composites using a high tensile strength zinc rich coated brass wire (0.25 mm diameter). A fractional factorial L18 Taguchi experimental design was employed to evaluate the influence of varying open gap voltage (120 and 140 V), ignition current (3 – 5 A) as well as pulse on-time (0.8 – 1 µs) and off-time (4 – 8 µs) on material removal rate (MRR), top (Wt) and bottom (Wb) kerf widths as well as workpiece edge damage. The ignition current and pulse off-time were found to be statistically significant factors affecting MRR based on an analysis of variance, with percentage contribution ratios (PCR) of 48.5% and 24.3% respectively. It was observed that MRR, which ranged between 0.43 and 2.41 mm3/min, increased with both ignition current and pulse on-time due to the higher discharge energy generated in the machining gap. No signs of workpiece damage in terms of delamination or surface burning was apparent, despite the higher MRR. Conversely, the larger open gap voltage surprisingly led to reductions in MRR, which was likely due to unstable gap conditions caused by greater levels of residual melted resin within the gap or re-deposition on the workpiece surface. In terms of kerf width, ignition current was revealed as the sole significant factor with respect to the top surface (up to ~ 0.28 mm) having a PCR of 56.6%, while none of the variable parameters had a major effect on the bottom kerf width.

Optimization of CO2 Laser Cutting of Stainless Steel Sheet for Curved Profile

Laser cutting is one of the most widely used thermal energy based non-contact type advance machining process. In recent years, considerable experimental investigations have been carried out aiming at improving laser cutting process performance. In this work CO2 laser cutting parameters on stainless steel 304 width 2.5 mm thickness were studied. The cut quality achieved minimum kerf width to cut stainless steel sheet depends on appropriate selection process parameters was investigated. The parameters consider to include laser output power, cutting speed, gas pressure. The effect of cutting parameter on the cut quality was further investigated by monitoring top kerf width, and bottom kerf width using box –behnken designing the response surface methodology. And finally optimized best CO2 laser cutting parameters are selected by using genetic algorithm approach.

Abrasive Water Jet Machining of Multidirectional CFRP Laminates

Abrasive water jet machining (AWJM) is widely used in aerospace, marine and automotive industries for trimming composites. However, AWJM demonstrates some challenges when cutting carbon fibre reinforced plastic (CFRP) composites materials such as cut accuracy and quality. More experimental work is needed to provide sufficient machinability databases for manufacturing engineers. This paper presents an experimental study and statistical analysis for cutting 2 lay-up configurations of multidirectional CFRP laminates. Different AWJM conditions including jet pressure, feed rate, and standoff distance are experimented using full factorial design of experiments. Machining process responses such as top and bottom kerf width, kerf taper, machinability and surface characteristics have been evaluated using analysis of variance (ANOVA) technique. A process cost model for the AWJM is presented.

Enhancement of low power CO2 laser cutting process for injection molded polycarbonate

Laser cutting technology is a non-contact process that typically is used for industrial manufacturing applications. Laser cut quality is strongly influenced by the cutting processing parameters. In this research, CO2 laser cutting specifications have been investigated by using design of experiments (DOE) with considering laser cutting speed, laser power and focal plane position as process input parameters and kerf geometry dimensions (i.e. top and bottom kerf width, ratio of the upper kerf to lower kerf, upper heat affected zone (HAZ)) and surface roughness of the kerf wall as process output responses. A 60 Watts CO2 laser cutting machine is used for cutting the injection molded samples of polycarbonate sheet with the thickness of 3.2mm. Results reveal that by decreasing the laser focal plane position and laser power, the bottom kerf width will be decreased. Also the bottom kerf width decreases by increasing the cutting speed. As a general result, locating the laser spot point in the depth of the workpiece the laser cutting quality increases. Minimum value of the responses (top kerf, heat affected zone, ratio of the upper kerf to lower kerf, and surface roughness) are considered as optimization criteria. Validating the theoretical results using the experimental tests is carried out in order to analyze the results obtained via software.

The Effect of Traverse Speed on Kerf Width in AWJ Cutting of Ceramic Tiles

This article describes experiments performed to assess the effectiveness of abrasive waterjet (AWJ) traverse used to cut ceramic tiles. As the process does not involve high forces, it is important to select the correct traverse speed to obtain the required kerf width while keeping the efficiency of the cutting process high. The study focused on determining the influence of the traverse speed on the kerf width in ceramic tiles. The kerf width is one of the crucial parameters in AWJ cutting. Cutting with a high traverse speed can create tapered edges on the kerf. The experiments involved measuring the kerf width to determine the most suitable process parameters in the AWJ cutting of ceramic tiles. The top and bottom kerf widths were measured using optical microscopy images.

Investigation of the effect of nanofillers on the quality of CO2 laser cutting of FRP nanocomposites

This paper reports the experimental results of the influence of nanofillers on CO2 laser cutting of vinylester/glass based on L18 orthogonal array technique and grey relational analysis. Nickel nanopowder and carbon black as nanofillers were investigated. Top kerf width, bottom kerf width and surface roughness were measured by varying scanning speed, air pressure and nanofiller content at a constant laser power of 400 W. A grey-Taguchi method was adopted for the optimisation. Burning of matrix and formation of caves were dominant in vinylester/glass laser cut surfaces. Nickel nanopowder effectively reduced cave formation and improved quality of cut. But, char formation in the form of globules was observed in case of carbon black dispersed in vinylester/glass. Scanning speed significantly influenced kerf width. The addition of nanofillers improved the surface roughness of the cut profile. Optimal scanning speed 500 mm/min, air pressure 0.15 MPa and nanofiller 4 wt% corresponded to the multiple responses as per grey relational analysis. The responses were predicted using multiple regression with good accuracy.

Selection of the most influential factors on the water-jet assisted underwater laser process by adaptive neuro-fuzzy technique

Water-jet assisted underwater laser cutting has shown some advantages as it produces much less turbulence, gas bubble and aerosols, resulting in a more gentle process. However, this process has relatively low efficiency due to different losses in water. It is important to determine which parameters are the most important for the process. In this investigation was analyzed the water-jet assisted underwater laser cutting parameters forecasting based on the different parameters. The method of ANFIS (adaptive neuro fuzzy inference system) was applied to the data in order to select the most influential factors for water-jet assisted underwater laser cutting parameters forecasting. Three inputs are considered: laser power, cutting speed and water-jet speed. The ANFIS process for variable selection was also implemented in order to detect the predominant factors affecting the forecasting of the water-jet assisted underwater laser cutting parameters. According to the results the combination of laser power cutting speed forms the most influential combination foe the prediction of water-jet assisted underwater laser cutting parameters. The best prediction was observed for the bottom kerf-width (R2=0.9653). The worst prediction was observed for dross area per unit length (R2=0.6804). According to the results, a greater improvement in estimation accuracy can be achieved by removing the unnecessary parameter.

An investigation on cutting quality by adding polymer in abrasive water jet

ABSTRACTAn experimental investigation is presented to improve the cutting quality in abrasive water jet (AWJ) cutting of marble by an addition of polyacrylamide (PAM). Considering experimental data, the kerf widths have a remarkable change when the PAM concentration approaches to 400 ppm. The deviation between top and bottom kerf width reaches the minimal value when PAM concentration is equal to about 600 ppm. In addition, the surface topography analyses illustrate that an addition of PAM can broaden the cutting wear zone and make the cutting quality better. Furthermore, the effects of PAM on the surface roughness are assessed by a profilometer. It is eventually found that the surface roughness decreases initially and then increases greatly with the increase of the depth of cut. Additionally, the minimum surface roughness occurs when the PAM concentration is 600 ppm, which agrees well with the experimental result of kerf width. An increasing stand-off distance or traverse speed produces a higher surface roughness.

MACHINING OF D2 HEAT TREATED STEEL USING ABRASIVE WATER JET: THE EFFECT OF STANDOFF DISTANCE AND FEED RATE ON KERF WIDTH AND SURFACE ROUGHNESS

This paper discusses the machining of D2 heat treated steel using Abrasive Water Jet (AWJ). D2 steel is an alloy of high-carbon, high-chromium, air-hardened steel, which has high wear resistance and toughness, and is generally used in tool and die making. The experimental investigation has been carried out to find the effect of process parameters such as standoff distance and the feed rate on the kerf width and on the surface roughness (Ra) value of the kerf generated by AWJ. It has been observed that, in single pass machining, for the same increase in standoff distance, the top kerf width increases (≈18%) whereas the bottom kerf width decreases (≈25%). The results also show that, the increase in standoff distance and feed rate increases the surface roughness (Ra) value. However, in multi-pass (two) machining, it has been observed that, at the same feed rate the difference between top and bottom kerf widths is considerably less (≈27%) which results in the reduction of kerf taper, also similar reduction is observed in surface roughness (Ra) value

Predictive modelling of surface roughness and kerf widths in abrasive water jet cutting of Kevlar composites using neural network

Abrasive water jet cutting (AWJC) is one of the important non-traditional machining processes used for cutting of difficult-to-cut materials and intricate profiles. Cutting of Kevlar fibre reinforced polymer composites is a complex process, making it difficult to model, predict and improve the cut surface quality. This paper presents a detailed approach of the usage and effectiveness of a back-propagation neural network (NN) for modelling and prediction of three cut surface characteristics namely top kerf width, bottom kerf width and surface roughness (Ra) in AWJC of aerospace grade Kevlar-epoxy composites. Statistically designed full factorial experiments based on three process parameters [water jet pressure (WJP), abrasive flow rate (AFR) and quality level (QL)] at three levels each were conducted to generate the NN training database. The results demonstrate that the NN model was able to successfully model and predict the two kerf widths and surface roughness closely matching the experimental results.

Monitoring of plasma arc cutting process by cutting sound

Plasma arc cutting sound containing useful information about the cutting process has close relation with cut quality. The present paper investigates quality diagnosis method of plasma arc cutting by the cutting sound. In the present study the cut quality is divided into three types based on bottom kerf width and dross attached state. There are attached dross state (type 1), free dross state (type 2) and uncut through state (type 3). It is shown that a peak about 20 Hz appears obviously at cut quality type 2 and as cut quality becomes the type 3 the value of ∼40 kHz decreases remarkably. And influence of the emitted area of molten metal from plasma arc cutting on the cutting sound also has been revealed. At last corresponding relationship between the cutting sound and the cut quality has been discussed as cutting condition such as arc current and torch standoff height varied suddenly during the cutting process. Experimental results also suggest the possibility to make an acoustic based monitoring system for plasma arc cutting process by the cutting sound.

A study on the use of single mesh size abrasives in abrasive waterjet machining

This paper details the studies on the use of single mesh size garnet abrasives in abrasive waterjet machining for cutting aluminum. The influence of three different single mesh size abrasives, pressure, traverse rate, and abrasive flow rate; on depth of cut, top kerf width, bottom kerf width, kerf taper, and surface roughness are investigated. Experiments designed using standard L9 orthogonal array and the analysis of variance helped in the determination of highly significant, significant and weakly significant cutting parameters. Single mesh size abrasives are found to yield decreased surface roughness than multi mesh size abrasives. Based on these studies, response equations are developed to predict the target parameters. Using single mesh abrasives, a practitioner not only can cut faster but also achieve reduced surface roughness.

Relationship between plasma arc cutting acoustic and cut quality

The tremendous acoustic signal exiting during the plasma arc cutting process includes a lot of information about this process and has a close relation with cut quality. To investigate the relationship between the plasma arc cutting acoustic and cut quality, a number of experiments have been carried out. In the present study, cut quality by plasma arc is described by top and bottom kerf widths, bevel angle, and attached dross state, and the relationship between the evaluation items for cut quality and the SPL (sound pressure level) of the cutting acoustic is investigated in detail. It is shown that the SPL reaches a maximum as the bottom kerf width equals the diameter of the plasma arc potential core. The attached dross and kerf widths in a state of free dross obviously affect the low and high frequency components of the plasma arc cutting acoustic, respectively. These results also suggest the possibility of designing an acoustic-based monitoring system for the plasma arc cutting process.

Measurement and Analysis of Plasma Arc Cutting Acoustic Signal

Plasma arc cutting sound has close relation with cutting conditions, so it contains useful information about this cutting process. In order to analyze the relationship between the plasma arc cutting acoustic signal and cut quality (including top and bottom kerf widths, bevel angle and dross attached level), a number of experiments under various cutting speeds have been carried out. It is shown that SPL (sound pressure level) of cutting acoustic signal shows mountain-shaped distribution with an increase of bottom kerf width. Experimental results also suggest the possibility to make an acoustic-based quality monitoring system for plasma arc cutting process.

STUDIES ON ABRASIVE WATERJET MACHINING OF BLACK GRANITE THROUGH DESIGN OF EXPERIMENTS

Abrasive waterjet machining is emerging as an effective machining technique. In this context, optimizing the process parameters for effective utilization is essential. This paper discusses the machining of black granite with the use of a design of experiments approach and includes establishing the response equations. The influence of P, TR, and AFR for specially formulated abrasive samples having three different abrasive particle size distributions are analysed on the target parameters namely top kerf width, bottom kerf width, and kerf taper. At the 1% significance level, the top kerf width is influenced by high traverse rate and includes an interaction effect P × AFR. The bottom kerf width is influenced by abrasive sample AS3, and a high traverse rate TR3. Fragmentation of abrasives at the nozzle exit is higher due to the presence of larger size particles in the sample AS3. The interaction effects P × AS, AFR × AS, and PL × ASL are also found to yield minimum kerf width at the bottom. This is in addition to the jet instability influencing the bottom kerf width considerably. In the case of kerf taper, no parameters are clearly dominant at the 1% significance level, though kerf taper appears to be affected by a combination of all the independent parameters taken together. However, TR, TRL, and TRq are found to be significant at the 5% level. The response equations developed in this study will be useful to the manufacturing engineers to select a suitable combination of parameters for a specific application of black granite cutting. The numerical values reported in this study are specific to the cutting of black granite. Research with other types of granite is planned.