Plasma Arc Cutting Research Articles

Parametric investigation and optimisation of plasma arc cutting of structural steel St.52-3 using grey-based fuzzy algorithm.

This paper reports parametric optimisation of air plasma arc cutting (PAC) of structural steel St.52-3, which is widely used in bridge construction and ship building. Response variables considered are material removal rate, a surface roughness (Rz5-mean height of profile) as well as a size of heat affected zone (HAZ) which are critical for corresponding fatigue life. Screening experiment showed pressure, current, arc voltage and speed as factors having an influence on responses of interest. The experimental runs were planned by using Box-Behnken response surface design, and the grey-based fuzzy algorithm was employed to predict the optimal process parameter setting combination. The confirmation test conducted shows an improvement in grey-fuzzy relational grade by about 19%. This highlights the usefulness of grey-fuzzy algorithm as a multi-objective optimiser for plasma arc cutting. The effect of process parameters on performance characteristics has also been discussed resulting in better understanding of the plasma arc cutting process. [Submitted 29 July 2017; Accepted 15 April 2018]

Measurement and optimization of multi-response characteristics in plasma arc cutting of Monel 400™ using RSM and TOPSIS

Plasma arc cutting (PAC) is well recognized non-conventional machining processes widely used to fabricate intricate part profiles for diverse electrically conductive materials including superalloys and composites. The dimensional accuracy and surface quality of PAC surface are critical elements for specific applications especially in aerospace and manufacturing industries. Material removal rate (MRR), kerf taper (KT) at top and bottom surface and heat affected zone (HAZ) are very important attributes which influences the quality and performance of plasma cut surfaces. Present study investigates the effect of PAC parameters such arc current, cutting speed, stand-off distance and gas pressure on evaluating the part quality characteristics such as MRR, KT and HAZ of Monel 400 superalloy. Box-behnken design approach is incorporated to formulate the experiments and rigorous experimental analysis is performed. The quadratic models are developed and assessed for its performance using analysis of variance (ANOVA). Statistical and response surface analysis are accomplished to identify the most influencing PAC parameters. Multi-objective optimization studies are carried out using Multi-criteria decision making methodology (MCDM) to determine the optimal cutting conditions of PAC through employing technique for order of preference by similarity to ideal solution (TOPSIS). The optimal PAC process parameters such as cutting speed of 2400 mm/min, gas pressure of 3 bar, arc current of 45 A and stand-off distance of 2 mm are determined. Microstructure analysis is conducted to ascertaining the morphologies of cut surface at various cutting conditions.

Experimental investigation and optimization of PAC parameters on Monel 400™ superalloy

ABSTRACTNickel-based superalloys are predominantly used to manufacture marine, automotive, and aerospace parts due to its excellent corrosion resistance in acidic environments and high-strength characteristics. Machining of these alloys are extremely difficult through conventional process because of their tendency to quickly work harden and poor thermal conductivity. Plasma arc cutting (PAC) is a disruptive metal-cutting process to perform cutting of difficult to cut materials even for intricate profiles. The present work examines the effect of PAC process variables such as arc current, gas pressure, cutting speed, and stand-off distance on evaluating the surface roughness, kerf width, and micro hardness of Monel 400™ superalloy. Experiments are designed and conducted using Box–Behnken design (BBD) of response surface methodology. The quadratic models are developed and assessed for its performance using analysis of variance (ANOVA). Optimal machining process conditions, cutting speed of 2427.08 mm/min, gas pressure of 3.83 bar, arc current of 45 A, and stand-off distance of 2.14 mm are obtained through multiobjective desirability approach. From the confirmation experiments, the relative error is found to be 2.68% for surface roughness, 4.45% for kerf width, and 4.36% for micro hardness which confirms the feasibility and efficiency of proposed methodology.

Developments in Plasma Arc Cutting (PAC) of Steel Alloys: A Review

The Plasma Arc Cutting (PAC) process was developed for difficult-to-machine materials in order to overcome the inefficiency and ineffectiveness of conventional machining methods when it comes to complex shapes and tool wear due to the contact between the tool and the workpiece. PAC consumes ionized gas, known as the heat source, and a high energy stream, known as the plasma. Many researchers have examined the PAC of steel alloys by considering the cutting power, scanning speed, cutting height and plasma gas pressure as the process parameters, and analysing the effects on the edge roughness, the kerf taper angle (conicity), burr formation, Heat Affected Zone (HAZ), Material Removal Rate (MRR), surface quality after cutting, and the metallurgical effects of the cut. A comprehensive review was carried out on developments in the analysis and optimization of PAC for steel alloys. It is observed that, the feed rate and edge roughness have a significant effect on the machining characteristics; however, less consideration was given by the researcher to these parameters. In addition, a critical comparison was made of the process parameters involved and the methods of analysis used, with the aim of providing the status of current research and guidance for future research.

Optimization of Dimensional accuracy in plasma arc cutting process employing parametric modelling approach

Plasma arc cutting (PAC) is a high temperature thermal cutting process employed for the cutting of extensively high strength material which are difficult to cut through any other manufacturing process. This process involves high energized plasma arc to cut any conducting material with better dimensional accuracy in lesser time. This research work presents the effect of process parameter on to the dimensional accuracy of PAC process. The input process parameters were selected as arc voltage, standoff distance and cutting speed. A rectangular plate of 304L stainless steel of 10 mm thickness was taken for the experiment as a workpiece. Stainless steel is very extensively used material in manufacturing industries. Linear dimension were measured following Taguchi’s L16 orthogonal array design approach. Three levels were selected to conduct the experiment for each of the process parameter. In all experiments, clockwise cut direction was followed. The result obtained thorough measurement is further analyzed. Analysis of variance (ANOVA) and Analysis of means (ANOM) were performed to evaluate the effect of each process parameter. ANOVA analysis reveals the effect of input process parameter upon leaner dimension in X axis. The results of the work shows that the optimal setting of process parameter values for the leaner dimension on the X axis. The result of the investigations clearly show that the specific range of input process parameter achieved the improved machinability.

Plasma Arc Cutting Dimensional Accuracy Optimization employing the Parameter Design approach

Plasma Arc Cutting (PAC) is a thermal manufacturing process used for metal plates cutting. This work experimentally investigates the influence of process parameters onto the dimensional accuracy performance of the plasma arc cutting process. The cutting parameters studied were cutting speed (mm/min), torch standoff distance (mm), and arc voltage (volts). Linear dimensions of a rectangular workpiece were measured after PAC cutting following the full factorial design experimental approach. For each one of the three process parameters, three parameter levels were used. Analysis of means (ANOM) and analysis of variances (ANOVA) were performed in order for the effect of each parameter on the leaner dimensional accuracy to be assessed.

Application of MCDM-Based TOPSIS Method for the Optimization of Multi Quality Characteristics of Modern Manufacturing Processes

Optimization of non-conventional machining (NCM) processes viz. AJM, AWJM, EDM, WEDM, ECM, ECMM, LBM, PAC, etc. has always been an open research area for researchers. In recent manufacturing environment, almost all the NCM processes consist of a number of input and output to be considered together. The purpose of the present article is to highlight the application of a multi-criteria decision making (MCDM) based method called Technique of Order Preference by Similarity of Ideal Solution (TOPSIS) in optimization of some modern manufacturing processes (MMPs). In the present paper, seven different MMPs namely Electro Chemical Honing (ECH), Abrasive Water Jet Machining (AWJM), Abrasive Jet Machining (AJM), Laser Beam Machining (LBM), Plasma Arc Cutting (PAC), Laser Cutting (LC) and Electric Discharge Machining (EDM) were exemplified. The multiple outcomes of all the illustrated MMPs have been optimized simultaneously by using TOPSIS method. It is a simple, systematic, and logical technique which can be employed to obtain the best parametric combination of cutting parameters. It was observed that the results attained by using TOPSIS method were almost tie with those derived by past researchers. This proves the applicability and adaptability of the TOPSIS method while solving different MCDM-based problems in a real manufacturing system.

Parametric Optimization of Some Non-Conventional Machining Processes Using MOORA Method

Non-conventional manufacturing techniques are most widely used in industries in order to achieve high accuracy and desirable product quality. Therefore, the selection of an appropriate machining parameter has become a crucial job before starting the operation. Several optimization methods are available to resolve the upstairs situation. The current study explores a novel technique namely multi-objective optimization on the basis of ratio analysis (MOORA) to solve different multi-objective problems that are encountered in the real-time manufacturing industries. This study focuses on the application of MOORA method for solving some non-conventional machining processes that have multiple criteria problems. Wire-Electric Discharge Machining (WEDM), Plasma Arc Cutting (PAC), Electro Chemical Micro Machining (ECMM), Electro Chemical Machining (ECM), Abrasive Jet Machining (AJM), Abrasive Water Jet Machining (AWJM), Ultrasonic Machining (USM), Laser Beam Machining (LBM) and Laser cutting process are the major attentions in the current study. Total nine NTM multi-criteria problems which include selection of proper machining parameters have been studied. The optimal settings of input variables obtained by using MOORA method nearly tie with those derived by the earlier investigators.

Experimental study of magnetic arc blow for plasma arc cutting

Oxygen plasma arc cutting (PAC) is widely used in various industrial fields. In the case of cutting magnetized plates, the magnetic field is concentrated around the cutting front according to the progress of the cutting, and the electromagnetic force induced by leakage magnetic field deflects the plasma jet. The deflected plasma jet causes poor cutting quality and sometimes causes fatal damage on the electrode and the nozzle by a double arc as abnormal discharge. This phenomenon is called magnetic arc blow, and it is a critical issue of applying plasma cutting on magnetized plates. The purpose of this study is to investigate the arc blow behaviour and to devise a method to prevent it. We examined the relationship between operating conditions and double arc with external magnetic fields on the plasma jet. We found criteria of operation conditions that induce the arc blow. In addition, we have succeeded in suppressing the double arc generation attributed to the external magnetic field with a mild steel shield cap attachment around the nozzle tip.

Application of Grey Taguchi-based response surface methodology (GT-RSM) for optimizing the plasma arc cutting parameters of 304L stainless steel

Plasma arc cutting (PAC) is a highly promising thermal cutting process because of its wide industrial applications involving cutting of different materials at high speeds. The competing abilities of PAC with laser cutting combined with its less polluting nature have shifted the research attention towards the process. The cutting parameters like arc current, torch stand-off, cutting speed and gas pressure play an important role in determining the quality of a cut surface. In the present work, the quality characteristics of the cut surface were assessed by measuring the surface roughness and kerf width while cutting the 304 L stainless steel. The experimental trials were designed by Taguchi’s L18 orthogonal array unlike the central composite design used with traditional response surface methodology (RSM), and an integrated approach of Grey Taguchi-based response surface methodology (GT-RSM) was disclosed for predicting the optimal combination of cutting parameters. The GT-RSM approach was found to improve the quality characteristics studied in the work significantly. The results will offer a good cutting database for the textile, chemical and pharmaceutical processing industries.

Parameter design in plasma arc cutting of galvanised iron sheet using desirability function-based response surface methodology

Plasma arc cutting (PAC) is a widely used industrial process for cutting different materials at higher speeds. The capability of PAC to compete with laser cutting has created a significant amount of research attention. The present study was focused towards assessing the quality of cut obtained under different cutting conditions by varying the process parameters like cutting speed, arc current and stand-off distance. The quality of cut was monitored by measuring the surface roughness and kerf width. A new integrated approach of desirability function-based response surface methodology (DRSM) was disclosed for modelling and predicting the optimal cutting condition. The effectiveness of DRSM technique was proved by conducting a confirmation test. A significant improvement was observed in the quality characteristics and an overall P-profile plot of the cut surfaces was also examined to study the enhancement in surface finish. [Received 20 August 2014; Revised 15 April 2015; Accepted 25 April 2015]

Optimization of Process Parameters in Plasma arc Cutting of EN 31 Steel Based on MRR and Multiple Roughness Characteristics Using Grey Relational Analysis

This paper investigates the effects and parametric optimization of process parameters for plasma arc cutting (PAC) of EN31 steel using grey relation analysis. Three process parameters viz. gas pressure, arc current and torch height are considered and experiments are conducted based on L27 orthogonal array (OA). Process responses viz. material removal rate (MRR) and surface roughness parameters (centre line average roughness: Ra, root mean square: Rq, skewness: Rsk, kurtosis: Rsk and mean line peak spacing: Rsm) of the machined surface are measured for every experimental runs. For maximum MRR and minimum surface roughness characteristics process parameters are optimized based on Taguchi method coupled with grey relational analysis. Analysis of variance (ANOVA) is performed to get the contribution of each process parameters on the performance characteristics and it is observed that gas pressure is significant process parameter that affects the responses. Confirmation test using optimal setting shows good agreement to the predicted value. This indicates utility of the grey-Taguchi technique as a multi-objective optimizer in the field of PAC. Finally, using scanning electron microscopy, the surface morphology is studied.

Optimization of MRR and Surface Roughness in PAC of EN 31 Steel Using Weighted Principal Component Analysis

Abstract In this paper, an attempt has been made to optimize the process parameters for multi-responses (material removal rate, MRR and surface roughness) in plasma arc cutting (PAC) of EN 31 steel using weighted principal component analysis (WPCA). For surface roughness characteristics, five different surface roughness parameters (centre line average roughness: R a , root mean square: R q , skewness: R sk , kurtosis: R ku and mean line peak spacing: R sm ) are considered. Three process parameters viz. gas pressure, arc current and torch height are considered. The experimental plan is based on Taguchi L 27 orthogonal array (OA). To convert the multi-responses problem to a single response optimization problem, WPCA is applied to compute a multi-response performance index (MPI) and then MPI has been optimized using Taguchi method. The optimum combination of process parameters has been found for maximum MRR and minimum surface roughness and verified through a confirmation test. Also, ANOVA is carried out and it is seen that the gas pressure is the most significant factor followed by arc current.

Reactor Vessel Internals Segmentation Experience using Mechanical Cutting Tools

Abstract Some commercial nuclear power plants have been permanently shut down to date and decommissioned using dismantling methods. Other operating plants have decided to undergo an upgrade process that includes replacement of reactor internals. In both cases, there is a need to perform a segmentation of the reactor vessel internals with proven methods for long term waste disposal. Westinghouse has developed several concepts to dismantle reactor internals based on safe and reliable techniques, including plasma arc cutting (PAC), abrasive waterjet cutting (AWJC), metal disintegration machining (MDM), or mechanical cutting. Mechanical cutting has been used by Westinghouse since 1999 for both Pressurized Water Reactors (PWR’s) and Boiling Water Reactors (BWR’s) and its process has been continuously improved over the years. The complexity of the work requires well designed and reliable tools. Different band saws, disc saws, tube cutters and shearing tools have been developed to cut the reactor internals. All of those equipments are hydraulically driven which is very suitable for submerged applications. Westinghouse experience in mechanical cutting has demonstrated that it is an excellent technique for segmentation of internals. In summary, the purpose of this paper will be to provide an overview of the Westinghouse mechanical segmentation process, based on actual experience from the work that has been completed to date.

High-speed imaging investigation of transient phenomena impacting plasma arc cutting process optimization

In this work, we report on the investigation of selected transient phenomena taking place in plasma arc cutting (PAC) that are relevant for process optimization. High-speed imaging diagnostics is exploited for the characterization of different technological solutions in order to provide deeper insights into torch and process design. In particular, the pilot arc start-up phase is analysed for a 250 A automatic dual-gas torch equipped with electrodes with different shapes of the initial insert recess, revealing that there is no influence of the recess depth on the time for the stabilization of the pilot arc attachment on the cathode insert. The influence of different insert materials, including Ag–Hf and Cu–Zr binary alloys, on erosion during the shut-down phase is investigated at 120 A and reduced emission of material and faster shut-down is found for alloy inserts compared with standard Hf inserts. The start-up and shut-down transients are also investigated during transferred arc operation using a modified nozzle that comprises a viewing port on one side of the nozzle, and pulsing arc behaviour inside the plasma chamber that is correlated with cathode-nozzle voltage oscillations at a frequency of 7.7 kHz is found. Finally, results regarding the influence of different plasma gas diffusers on the arc stability during the cutting initiation phase in a 100 A mono-gas manual torch are reported.

Experimental study of anode processes in plasma arc cutting

Anode processes taking place during pilot arc and cutting phases of plasma arc cutting (PAC) are experimentally studied. The experiments are carried out on commercial equipment so as to bring the studied conditions close to real operating conditions in application areas. The obtained results show the significant role of anode attachment in both process phases. In the pilot arc phase long residence time of the anodic spot results in electrode wear. An increase in the flow rate of the plasma medium facilitates anodic spot movement. In the cutting phase, the anode attachment significantly affects the kerf shape and surface morphology. Lack of its movement deeper inside the kerf leads to different heat transfer conditions at the top and bottom of the material and results in different surface roughness values. Facilitating the anodic spot movement towards the plate bottom is desirable to improve the cut quality.

Investigation Analysis of Plasma Arc Cutting Parameters on the Unevenness Surface of Hardox-400 Material

Plasma arc cutting (PAC) is a thermal cutting process that makes use of a constricted jet of high-temperature plasma gas to melt and separate (cut) metal [2]. In this study 12mm plate thickness Hardox-400 has been cut by high tolerance voltage, cutting speed, and plasma gas flow rate included as main parameters in the analysis and their effect on unevenness of cut surface is evaluated. The design of experiments (DoE) techniques is used in order to outline the main parameters which define the geometry of the cut profile, as well as its constancy for Hardox-400 material plate. Despite the value selected for these parameters, the analysis shows that Hardox-400 plates can have different profiles, depending on the specific side considered. Unevenness can be obtained as a result of an experimental investigation aimed at selecting the proper values of process parameters of PAC system. Results of this screening step are analyzed by means of the Analysis of Variance (ANOVA) technique with use of design expert 8.0.7.1 software in order to clearly identify the main parameters, which define the unevenness quality attribute. The operating conditions have been carefully optimized through parameters adjustment like cutting speed, plasma gas and arc voltage in order to obtain good surface quality for all the sides of Hardox-400 plate.

プラズマ切断における磁気吹き現象の実験的考察

Oxygen plasma arc cutting (PAC) is widely used in various industrial fields. In case of cutting magnetized plates, the magnetic field is concentrated around the cutting front according to the progress of the cutting, and the electromagnetic force induced by leakage magnetic field deflects the plasma jet. The deflected plasma jet causes poor cutting quality and sometimes makes fatal damages on the electrode and the nozzle by double arc as abnormal discharge. This phenomenon is called Magnetic Arc Blow and it is critical issue of applying plasma cutting on magnetized plate. The purpose of this study is to investigate the arc blow behavior and to devise a method to prevent it.We examined the relationship between operating conditions and double arc with external magnetic fields on the plasma jet. We found out criteria of operation conditions that induces the arc blow. In addition, we have succeeded to suppress the double arc generation attributed to the external magnetic field with a mild steel shield cap attachment around the nozzle tip.

The Study of Surface Roughness and MRR of Mild Steel Using Manual Plasma Arc Cutting Machining

Manufacturing companies define the qualities of thermal removing process based on the dimension and physical appearance of the cutting material surface. Therefore, the roughness of the surface area of the cutting material and the rate of the material being removed during the manual plasma arc cutting process was importantly considered. Plasma arc cutter Selco Genesis 90 was used to cut the specimens made from Standard AISI 1017 Steel manually based on the selected parameters setting. Two different thicknesses of specimens with 3mm and 6mm were used. The material removal rate (MRR) was measured by determining the weight of the specimens before and after the cutting process. The surface roughness (SR) analysis was conducted to determine the average roughness (Ra) value. Taguchi method was utilized as an experimental layout to obtain MRR and Ra values. The results reveal that for the case of manual plasma arc cutting machining, the SR values are inversely proportional to the MRR values. The quality of the surface roughness depends on the dross peak that occurred during the cutting process.

Experimental Study of Consumption of Hafnium Electrode in Oxygen Plasma Arc Cutting

An experimental study was conducted on the consumption of hafnium electrodes during oxygen plasma arc cutting (PAC). Hafnium (Hf) is used as a refractory cathode material for thermionic emission in a high-temperature region. The consumption of an Hf electrode was investigated by measuring the concavity depth on the Hf electrodes after operations. These measurements were performed under several operating conditions. The consumption properties are separated into two consumption rates: Hf consumption during transient periods, when the arc current is increasing or decreasing such as at start-up and shut-off; and Hf consumption during the stable arc phase, when the arc current is held at the operating current. The consumption rates are estimated from the experimental data. Spectroscopic measurements of the arc plasma jet coming from a nozzle were conducted to study the consumption behaviour of Hf electrodes. A line of Hf at λ = 340 nm was observed using a monochromator. Characteristic intermittent Hf radiations in addition to the background continuum were observed in transient periods when the arc current or gas pressure changed. The intermittent radiation is considered to arise from droplets of Hf electrode from the surface of a molten electrode. The ejection of droplets is thought to be caused by rapid consumption during transient periods, and to be induced by a disruption in the balance of the fluid dynamics on the melted electrode.