Wire Wear Research Articles

Performance evaluation of SiC powder mixed electrical discharge machining: a case of wire cut mode with re-circulating molybdenum wire

A review of the available literature on powder mixed electrical discharge machining (PMEDM) indicates that most of the research has been done for “die sinking machining mode” whereas the “wire cut machining mode” has not received due attention despite being an important process variant. This work employs silicon carbide (SiC) powder mixed dielectric fluid for machining of AISI D2 in “wire cut” mode with re-circulating molybdenum wire (an economic and chemically stable proposition as a tool). The effect of five process parameters (powder concentration, peak current, pulse on time, nozzle flushing pressure and stand-off distance) has been evaluated on surface roughness, kerf width, material removal rate, and wire wear ratio using Taguchi’s approach followed by analysis of variance (ANOVA) for determining statistically significant factors at 95% confidence level. It is found that for surface roughness, higher current and low to moderate concentration levels (2 to 4g/l) deteriorate surface quality; higher values of pressure and stand-off distance are also seen to adversely affect it. For material removal rate, pulse on time as well as its interactions with powder concentration and current, are statistically significant. A higher pulse on with smaller and moderate powder concentrations (2g/l and 4g/l) reduces MRR. For the wire wear ratio, the current is the sole significant factor (PCR of ~65%). SEM analysis of the machined workpiece for the maximum MRR condition quantifies the recast layer as ~19microns. An indirect comparison with the reported values for non-powdered EDM process indicates that for the similar wire (molybdenum), the use of SiC powder maintains the surface roughness and kerf values, for a much harder D2 material used in this work.

Study on Damage Tests Based on Structure and Operating Parameters of Wire Ropes Used by Conveyors in Orchards

Abstract The regularity of wire rope breakage of new-type rail conveyors used in orchards is not clear yet. The breakage may be mainly associated with the diameter and material of pulleys, wire rope tension, and linear speed, as well as exposure to acid rain and sandy soil. This paper took wire rope structure and operating parameters as the research object, designed and built a simulation conveyor wire rope winding test platform based on programmable logic controller (PLC), and verified the feasibility of the system to automatically control wire rope tension, and then conducted the wire rope winding test. According to the tests, a wire rope will have earlier wire breakage and faster wear if it works at a higher speed or in greater tension—a wire rope reached the scrapping criterion after 2,000 cycles of working at the speed of 29.35 m/s or at the tension of 6,500 N. Sandy soil and acid rain are also great contributors to wire breakage, and finer sandy soil or greater acidity of acid will cause more severe wire breakage—a wire rope reached the scrapping criterion after 3,300 cycles of work if exposed to acid rain with pH value of 2.0. Pulley diameter also counts: the smaller the pulley diameter is, the less wear the pulley will cause; and pulley material also plays a part—Q235 steel pulley may cause greater wear than a nylon pulley. Wear and plastic deformation of outer wires lead to surface material loss of a wire rope, thereby resulting in crack or even fracture of single wires, greater tension of other unbroken wires, and accelerated wear of the whole wire rope to the scrap criterion. The study aims to provide a reference for optimizing the safety performance of conveyors in orchards, as well as for maintenance and care of wire ropes in other applications.

Experimental Investigation of a Cryogenically Cooled Oxygen-mist Near-dry Wire-cut Electrical Discharge Machining Process

In this paper, a novel method of cryogenically cooled (low-temperature nitrogen gas) wire tool is used during the oxygen-mist near-dry wire-cut electrical discharge machining (NDWEDM) process to cut Inconel 718 alloy material. The current, pulse-width, pulse-interval, and flow rate are the controllable variables for response characteristics, such as the material removal rate (MRR) and wire wear ratio (WWR). The Box-Behnken method is applied to design the experiments to collect the observations from experiments. The mathematical models for each response were developed using significant individual, interaction, and quadratic terms by the sequential sum of the square test. The response surfaces were developed. It was revealed from the analysis that 52.92 % of current, 24.63 % of Pulse-width, 12.81 % of pulse- interval and 5.75 % of flow rate contributed to MRR, while 14.89 % of current, 9.75 % of pulse-width, 62.20 % of pulse-interval, and 5.44 % of flow rate contributed to WWR. The pulse-width has more contribution on MRR due to the long period of spark between the wire and work materials. It was also observed that the pulse-interval has more effect on WWR due to the more ideal period (high spark-pause-time) between two consecutive high-temperature sparks in the wire tool. The wear of the wire tool has been analysed using scanning electron microscopy (SEM) photographs. The desirability principles were first applied to obtain multi-objective solutions with a combination of process parameters to achieve the optimal values of both responses. The predicted combination of results has been validated by data that were collected from confirmation experiments.

Experimental Investigation of a Cryogenically Cooled Oxygen-mist Near-dry Wire-cut Electrical Discharge Machining Process

In this paper, a novel method of cryogenically cooled (low-temperature nitrogen gas) wire tool is used during the oxygen-mist near-dry wire-cut electrical discharge machining (NDWEDM) process to cut Inconel 718 alloy material. The current, pulse-width, pulse-interval, and flow rate are the controllable variables for response characteristics, such as the material removal rate (MRR) and wire wear ratio (WWR). The Box-Behnken method is applied to design the experiments to collect the observations from experiments. The mathematical models for each response were developed using significant individual, interaction, and quadratic terms by the sequential sum of the square test. The response surfaces were developed. It was revealed from the analysis that 52.92 % of current, 24.63 % of Pulse-width, 12.81 % of pulse- interval and 5.75 % of flow rate contributed to MRR, while 14.89 % of current, 9.75 % of pulse-width, 62.20 % of pulse-interval, and 5.44 % of flow rate contributed to WWR. The pulse-width has more contribution on MRR due to the long period of spark between the wire and work materials. It was also observed that the pulse-interval has more effect on WWR due to the more ideal period (high spark-pause-time) between two consecutive high-temperature sparks in the wire tool. The wear of the wire tool has been analysed using scanning electron microscopy (SEM) photographs. The desirability principles were first applied to obtain multi-objective solutions with a combination of process parameters to achieve the optimal values of both responses. The predicted combination of results has been validated by data that were collected from confirmation experiments.

Grain flash temperatures in diamond wire sawing of silicon

Diamond wire sawing has obtained 90% of the single-crystal silicon–based photovoltaic market, mainly for its high production efficiency, high wafer quality, and low tool wear. The diamond wire wear is strongly influenced by the temperatures in the grain-workpiece contact zone; and yet, research studies on experimental investigations and modeling are currently lacking. In this direction, a temperature model is developed for the evaluation of the flash temperatures at the grain tip with respect to the grain penetration depth. An experimental single-grain scratch test setup is designed to validate the model that can emulate the long contact lengths as in the wire sawing process, at high speeds. Furthermore, the influence of brittle and ductile material removal modes on cutting zone temperatures is evaluated.

Extreme wire electrical discharge machining based on semiconductor characteristics

To meet the increasing demand for wire electrical discharge machining (WEDM) under extreme conditions such as ultra-high thickness cutting, micro-wire cutting, micro-energy finishing, and ceramic composites machining, a concept of multichannel discharge WEDM under semiconductor characteristics was proposed. The essence of this conception is that under these extreme machining conditions, the electrode wire or workpiece — or even both of the two electrodes — cannot be treated as electrically conductive materials of the conventional WEDM due to their high electrical resistance. However, they can exhibit electrical discharge behavior like semiconductors, which is defined as semiconductor characteristics. The conventional WEDM theory and related technologies cannot be applied to extreme WEDM because conventional WEDM only has one discharge channel per pulse, whereas multiple discharge channels can be generated by each pulse in extreme WEDM. Therefore, a suitable theory needs to be developed for extreme WEDM under semiconductor characteristics. Based on the multichannel discharge behavior of semiconductors, experiments were conducted on high-efficiency machining with multichannel discharge by stacking several workpieces as an assembly with semiconductor characteristics. It was proved that the multichannel discharge WEDM is capable of achieving high machining efficiency, as well as enhanced surface quality and lower wear of electrode wire. The proposed multichannel discharge WEDM sets up the foundation for the establishment of the theoretical system of EDM under semiconductor characteristics.

Measurement and analysis of molybdenum wire erosion and deformation during wire electric discharge machining of Ti-6Al-4V alloy

With growing demands of manufacturing sector, wire erosion and breakage act as major challenges during wire electric discharge machining (WEDM) process. This paper reports an experimental investigation on the measurement and analysis of molybdenum wire erosion after WEDM of Ti-6Al-4V alloy at varying input levels viz. discharge voltage, discharge current, pulse duration, pulse off-time, and wire speed. A wire surface quality index for the tolerable limit of wire surface erosion was estimated using image processing technique. The mean of wire image histogram was used as an indicative tool to correlate the intensity of wire wear and the workpiece quality. The wire surface damages were analyzed with optical microscope and Field emission scanning electron microscope. The eroded wire surfaces reported damages in the form of craters, globules, microholes. It was observed that as the mean of image histogram decreases, the intensity of wire surface erosion increases.

Parametric optimization of wire-EDM machining of nimonic 80a using response surface methodology

Wire electrical discharge machining (WEDM) can machine hard materials with ease. Nimonic 80A is hard and high temperature resistant material which is widely used in the power plant boiler tubes, gas turbines, exhaust valves. This work involves in developing a models for correlating the dependency of various WEDM process parameters of Nimonic 80A like gap voltage, duty factor and feed rate on response factors like rate of material removal (MRR), wire wear ratio and surface roughness (SR). This experiment was carried out on the basis of Response Surface Methodology (RSM) and Grey Relational Analysis (GRA). Using the design of experiments, 20 experiments were conducted. The duty factor of 0.8771, gap voltage 17V and wire feed rate of 17m/min was found to be the optimized process parameter while machining Nimonic 80A.

Thermal modes of operation of power-current contact of electric transport during conduct of bench tests

Purpose. Analysis of the results of bench tests of sliding electrical contacts of electric vehicles, in order to determine the thermal regime of the sliding contact.
 Methodology. The initial data were obtained during field experiments on a specialized stand in the laboratory, which were carried out to determine the wear of the contact wire inserts of different types for pantographs of electro-rolling stock of railways. To determine the contact wire temperature at the place of sliding contact, a non-destructive non-contact method of control using a thermal imager was used.
 Findings. During the experimental part of the research, the thermal imaging photographs were obtained, they recorded the temperatures at the place of sliding contact between the insert of the pantograph of the electric rolling stock and the contact wire installed on the test disk. These temperature values were recorded with a certain time interval, which allowed to build the dependences of changes in thermal regime over time, to determine the heating time constant of the "insert-contact wire" of the test bench and to obtain the final temperature value at the end of tests. Accepting the insert sample in which the minimum temperature in the area of sliding contact is as a reference, it becomes possible by the value of the temperature of the contact wire in the area of sliding contact to predict the final test result of other types of pads.
 Originality. Indicators of temperature modes of sliding contact of electric vehicles during bench tests are obtained for the first time, the proposed relative temperature indicator allows to predict the results of bench tests of qualitative indicators of sliding contact of electric vehicles..
 Practical value. Bench tests of inserts of current collectors of electric vehicles are a long procedure, the normative indicator of the number of passes of the current collector on the stand is equal to 500 thousand passes, which requires significant expenditure of time, energy, human resources and others. The indicators proposed according to the test results, namely the heating time constant and the relative temperature index, allow to carry out two-stage tests. At the first stage, with a duration of 10 thousand revolutions of the test bench disk, the proposed indicators are determined and compared with the corresponding reference, in case of their compliance it becomes possible to predict the final test result as successful (contact wire wear less than normal) or unsuccessful. In the latter case, the need for the second stage of testing up to 500 thousand revolutions is questionable, because the end result will be negative, and the significant resources will be involved in the test, and therefore these tests are impractical.

О критериях и нормах браковки канатов пассажирских канатных дорог

The criteria for the rejection of ropes of Passenger cable cars are considered, the main defects of load-bearing, traction and load-bearing cables, possible causes of their occurrence and the criteria for rejection are described. The theoretical substantiation of defects associated with plastic deformations of the rope wire (extrusion of wires, stratification, twisting of the rope, kinks, breaks, basket shape) is given. The methods of monitoring the state of ropes in the process of operation of passenger cable cars are considered. Recommendations are given to improve the level of security by using remote monitoring systems based on modern digital information technologies. The criteria for rejecting the ropes of passenger cable cars are proposed: according to the undulation, wear and breakage of the outer wires of the ropes, which are absent in the current Federal Norms and rules «Rules for the safety of passenger cable cars and funiculars».

Improvement of Video Measuring Systems for Electric Traction Network Diagnostics

Purpose. The purpose of the article is system analysis of the state of electric traction networks, as well as methods of complex diagnostics of the contact network from a moving laboratory car to increase the resolution capability of the systems for monitoring the quality of interaction between the contact network and current collectors. Methodology. The problem was solved by theoretical analysis and experimental studies of the current collection parameters, a generalized model of the device for monitoring the wear of the overhead wire and its functional units in order to determine the factors affecting the control error, as well as the development of methods that reduce the specified error. The apparatus of factor analysis, the theory of optoelectronic circuits and methods of statistical information processing were used. Findings. Innovative approaches and qualitatively new diagnostic tools are proposed that allow expanding the functionality of the laboratory cars for testing the contact network for power supply enterprises of electrified railways, industrial and urban electric transport. Hardware and software have been developed to improve the system for measuring the parameters of the overhead wire and other components of the contact network. Originality. The theoretical maximum permissible, from the point of view of the contact network operation, error in monitoring the wear of the overhead wire and other components of the electric traction network has been determined. A method for increasing the resolution capability of a stereo television system and an adaptive lighting system is proposed. It consists in preliminary image transformation and expansion of the dynamic range of image measurement. The ways of introducing a high-speed real-time compression algorithm and using LED backlighting are proposed. Practical value. The quality of the contact network diagnostics in difficult conditions for video surveillance has been improved. A camera with a built-in image compression module without losing its performance is proposed, which allows capturing and transmitting full-frame images to a computing complex for the application of new diagnostic algorithms for contact network components. The modernized video measuring systems for the wear of the overhead wire for monitoring the grounding of the contact network supports are proposed, as well as elements of track facilities located in the visibility zone of specialized cameras, which ensure the operability of the systems at any time of the day at speeds up to 160 km/h. An air curtain subsystem was implemented to protect the cameras.

Experimental stand and researches on pantograph-catenary contact force control using chaos theory

Due to the oscillating behaviour of the pantograph and the catenary during the movement of the locomotive, the contact force changes to wide limits, resulting in electrical sparks with consequences: premature wear of the contact wire, electromagnetic disturbances, energy loss. Suitable control of the contact force at speeds exceeding 160 km/h may diminish these effects. Due to the particularities of the pantograph-catenary system and many random external factors, existing control methods do not always give the best results. The authors’ research has shown that the contact force signal contains a chaotic component that can be offset by chaos theory methods. Their own studies have demonstrated theoretically and by simulation that this approach can largely eliminate the separating the pantograph from the catenary and will lessen excessive forces. Experimental research, conducted by the authors and presented in this article, has been done in laboratory conditions on a specially built test stand and confirms that this new approach to active pantograph control produces superior results to existing methods.

Sustainability improvement of WEDM process by analysing and classifying wire rupture using kernel-based naive Bayes classifier

The current work aims to improve the sustainability of wire electric discharge machining by predicting the wire breakages. Wire breakages are process interruptions which increase the machining time, energy wastage and material consumption. The study is a novel approach to predict process continuity by binomial classification of machining outcomes using kernel-based naive Bayes algorithm. The two classes are labelled as wire breakages and continuous machining. Training dataset consists of 31 experiments according to central composite design of response surface methodology, and wire breakage instances are recorded as response. The input dataset contains four machining parameters, namely pulse on time, pulse off time, servo voltage and wire feed rate, whereas mean gap voltage variation is derived from in-process data. The trained model was 96.7% accurate in wire breakage predictions. Further, nine confirmation tests were conducted to check model adequacy in real-world situations. The model predicted all instances of wire breakages accurately. The stages of wire wear up to wire rupture were studied by conducting microstructural analysis.

Orthodontic Brackets and Wires Wear in Different Conditions: A Review

Metallic ions release from orthodontic brackets and wires mostly depends on quality (chemical composition) and the medium to which it is exposed, e.g. acid, alkali, substances with high fluorine concentration, etc. Among a heterogenous group of research, it was reported that stainless steel, which is used in orthodontic stuff, is the material that suffers most wear. It was apparent that dissolutions with acid pH, alcohols, fluorides, and chlorides aggravate the orthodontic material corrosion. Otherwise, nickel release from brackets and wires can cause allergic reactions to patients. This review addressed corrosion and wear of orthodontic brackets, wires and arches exposed to different media: beverages (juices), mouthwashes, artificial saliva, etc., and the possible health effects that can be caused by releasing of metallic ions under several conditions.

Research on the Elastic Properties of Discontinuous Contact Wire Rope for WR‐CVT

This study mainly conducts the research on the discontinuous contact elastic properties of wire rope based on WR‐CVT. The geometry model and finite element model of continuous contact and discontinuous contact of 2/3 lay pitch wire rope are established. And the contact stress distribution of the steel wire is analyzed through 5 sections and 5 contact points. The results show that on the C‐C plane, the contact stress of the discontinuous contact model is 229.4 MPa higher than that of the continuous contact, but this difference is not obvious on the D‐D plane. The contact stress nephogram is elliptical, but in the noncontact area, the shape of the contact trace shows a distinct noncomplete ellipse, and the contact trace is distributed along the spiral trajectory of the steel wire. Point 4 due to the reduction in contact area, compared with continuous contact, discontinuous contact shows a higher stress value. The geometric dimensions of the wear scars of continuous contact and discontinuous contact indicate that regardless of the length of the wear scar or the width of the wear scar, the geometric characteristics of steel wire wear mark in discontinuous contact are larger than that in continuous contact, so the discontinuous contact aggravates the surface wear of wire. This research lays a theoretical foundation for the discontinuous contact wear and fatigue of WR‐CVT wire rope and other components.

An Investigation on the Current Collection Quality of Railway Pantograph-Catenary Systems With Contact Wire Wear Degradations

In railway pantograph-catenary systems, the contact surfaces undergo wear in long-term operations, directly affecting interaction performance and potentially deteriorating the current collection quality. The effect of contact wire wear (CWW) on the current collection quality should be evaluated to understand the system’s health status in operations. This article presents a stochastic analysis of the pantograph–catenary interaction performance with different levels of CWW based on four years of measurement data. The power spectral density (PSD) estimation is carried out on the measured CWW to obtain their frequency representations. The random time histories of CWW are generated based on the PSDs. A nonlinear finite element model of catenary with a lumped-mass pantograph is built. Using the Monte Carlo method, the stochastic analysis of pantograph-catenary contact force is carried out to investigate the distribution and dispersion of assessment indices with different levels of CWW. The results indicate that the CWW mainly affects the maximum and minimum contact forces instead of the contact force standard deviation. The optimal pantograph–catenary interaction performance is observed certain years after CWW is formed, depending on the traffic density of the railway line, which is at the second year in the presented case study. Then, the performance declines with an increase in service time. Also, higher operating speed causes a more significant dispersion in assessment indices representing a lower current collection quality, particularly at the maximum operating speed (70% of the catenary wave propagation speed).

Grey-Taguchi-Based Optimization of Wire-Sawing for a Slicing Ceramic

Slicing ceramic (SC) is well-known as difficult-to-cut material. It is a hard and brittle material. The Grey-Taguchi method, which converts multiple response problems into a single response, is used to determine the effect of the process parameters for wire-sawing on multiple quality characteristics. The wire-sawing parameters include the wire tension (T), the slurry concentration (C), mixed grains mesh size (G), the wire speed (S), and the working load (P). The machining quality characteristics include a material removal rate (MRR), machined surface roughness (SR) of SC, kerf width (KW), wire wear (WW), and flatness (FT). An analysis of variance (ANOVA) is used to identify the mixed grains and slurry concentration that have a significant effect on multiple quality characteristics. The results of the ANOVA using the Grey-Taguchi method show that the optimum conditions are T2C1G1S2P1 (wire tension of 24 N, slurry concentration of 10% wt., mixed grains of #600 + #1000 mesh size, wire speed of 2.8 m/s, and working load of 1.27 N). The respective improvement in MRR, machined SR of SC, KW, WW, and FT is 2.43%, 2.36%, 1.08%, 2.33%, and 14.27%. The addition of #600 + #1000 mixed grains mesh size to the slurry improves the machined SR of SC, KW, and WW. An increase in wire speed and working load and the use of appropriate mixed grains mesh size and slurry concentration increases the MRR for wire-saw machining.

An overview of major research areas in Wire cut EDM on different materials

WEDM (Wire electrical discharge machining) is a precision machining method for cutting electrically conductive materials. It is an unconventional machining process that produces precision parts that match the dimensional tolerances of our designs within the range of ±0.0001mm. As the residual stress results in premature failure of parts, the WEDM is preferred for hard to machine materials such as Inconel, Nickel, and other Super alloys. In the present paper, earlier and recent work was reviewed, segregated and evaluated on the effect of wire material, diameter, dielectric fluid, wire wear, pulse on and off times and machining characteristics such as kerf size, machining efficiency, material surface characteristics, etc. This paper also focused on hybrid and ultrasonic-assisted WEDM used for machining of different materials. This paper discussed the major research studies in WEDM.

ANFIS modelling of mean gap voltage variation to predict wire breakages during wire EDM of Inconel 718

The study aims to correlate the mean gap voltage variation and wire breakage occurrences during the wire EDM of Inconel 718. A novel approach to predict the wire breakage is introduced by considering the mean gap voltage variation (ΔVm) as an indicator of the instabilities in the spark gap. Such instabilities are regarded as the primary reason for wire breakages and inferior part quality of wire electric discharge machined components. The parameter ΔVm is a process data obtained as the difference between servo voltage and mean gap voltage (Vm). It was found experimentally that if the value of ΔVm crosses a threshold limit, the process interruptions through wire breakages were observed. In order to predict the wire breakage situations, the study models ΔVm using adaptive neuro fuzzy inference system (ANFIS). Based on central composite design (CCD) of response surface methodology (RSM), 31 experiments were conducted and ΔVm is recorded as the response. The input parameters considered were pulse on time, pulse off time, servo voltage and wire feed rate. The ANFIS model was found very accurate in predicting ΔVm, based on which wire breakage alerts can be given. The capability of the model is further confirmed by verification experiments. EDS and microstructural analysis further revealed the effect of ΔVm on wire wear and part quality. Higher value of ΔVm resulted in greater wire wear and inferior part quality. The surface finish and flatness error of machined parts were measured to compare the part quality.

The Effects of Different Slurry Concentrations and Wire Speeds for Swinging and Non-Swinging Wire-Saw Machining

Slurry concentration and wire speed affect the yield and machining quality of ceramics (Al2O3) that are produced using wire-saw machining (WSM). This study determines the effect of slurry concentration and wire speed on the material removal rate (MRR), the machined surface roughness (SR), the kerf width, the wire wear and the flatness for swinging and non-swinging WSM. The experiments show that swinging WSM results in a higher machining efficiency than non-swinging WSM. WSM with swinging also achieves a peak MRR at a medium slurry concentration (25 wt%) and a higher wire speed (5.6 m/s) using the cutting conditions for the experimental region. However, slurry concentration and wire speed have no significant effect on the machined SR, the kerf width, the wire wear or the flatness for WSM with swinging mode.