Tool Profile Research Articles

High-speed micro electrical discharge machining with fine surface quality in atmospheric pressure nitrogen plasma jet

Characteristics of dielectric significantly influence machining performance of micro electrical discharge machining (EDM). A high material removal rate and large tool wear are obtained in micro EDM in liquid dielectric. Tool wear in gas dielectric is small, but the material removal rate is extremely low. In previous study, it was found that micro EDM in atmospheric pressure nitrogen plasma jet (APPJ) obtained a higher material removal rate than that in gas dielectric. However, material removal rate is still much lower than in liquid dielectric. To improve the machining performance of micro EDM in APPJ, this paper proposes micro EDM in APPJ assisted with coaxial mist (APPJ + mist). Effects of both flow rate of mist and discharge pulse energy on the critical breakdown distance, material removal rate, tool electrode wear ratio, surface roughness and profile are investigated. Experiments in nitrogen with coaxial mist (nitrogen + mist), deionized water and pure mist are also conducted for comparison. Experimental results indicate that critical breakdown distances in APPJ + mist, nitrogen + mist and mist are larger than in APPJ and deionized water. To understand the effect of misted droplets on critical breakdown distance, electric field intensity of the gap in deionized water and mist were simulated. Theoretical analysis reveals that electric field intensity on the surface of water droplet is much larger than that of tool electrode rim, resulting in the easy breakdown of gap with misted droplet. Material removal rate increases from 200 μm3/s (without mist) to 1252 μm3/s (with 5 mL/min mist) in APPJ in the case of open voltage of 100 V and capacitance of 8200 pF, which is higher than material removal rate in deionized water (1096 μm3/s) under the same discharge parameters. There is almost no tool electrode wear in APPJ + mist. The surface roughness of machined groove in APPJ + mist is 538 nm much lower than that in deionized water (672 nm), nitrogen + mist (627 nm) or pure mist (691 nm). Straighter side walls and flatter bottoms of micro grooves were obtained in APPJ + mist and nitrogen + mist than those in deionized water and mist. A micro cavity is also generated by using the proposed method without compensation of tool electrode wear.

Tracing sub-surface swept profiles of tapered toroidal end mills between level cuts

Abstract Development of closed-form solutions and algorithms for constructing sub-surface swept profiles (SWP) of toroidal and conical bodies is presented in this paper. While the problem of identifying the entire SWP of such surfaces has been extensively investigated in extant studies, construction of subsurface SWPs has rarely been addressed despite the subject being of great significance to machining process employing nonstandard-shaped NC tools. Torus shapes considered in extant literature are restricted to the fourth quadrant of a tube cross section. In industrial applications, however, profile cutters contain different regions of a toroidal surface. To identify SWP elements in the proposed study, a single analytical expression in one variable has been deduced using two moving frames. The basic idea behind such a formulation is to employ the one-to-many strategy, which greatly reduces the computational cost and effort. Algorithms to identify feasible domains of SWP parameters at each level cut, where toroidal and conical surfaces meet, have also been proposed in this study. This is important, since cutting a tool surfaces along the rotation axis divides SWP-parameter domains into non overlapping sets of intervals that must be addressed for each tool posture. In addition, this study demonstrates that for certain tool postures, while C1 continuity between sub-surfaces is satisfied, the SWP connectivity is lost at some points. To locate these so called singular-characteristic points, some precomputation steps have been performed. Lastly, several factors affecting the smoothness of SWPs have been identified and discussed. Highlights Closed form solutions have been derived for constructing the sub-swept profiles of toroidal tools. Three algorithms have been presented to identify the feasible domains of swept profile parameters. In order to locate the singular-characteristic points some precomputation steps have been carried out. Finally, several factors, affecting the smoothness of the swept profiles, have been identified.

Three-Linear-Axis Grinding of Small Aperture Aspheric Surfaces

A novel approach of three-linear-axis ultra-precision grinding with wheel path generation, tool interference checking and profile compensation is proposed and systematically investigated for fabricating aspheric surfaces. The performance of the proposed techniques is evaluated by grinding an aspheric mould insert on bindless tungsten carbide. The experimental results demonstrate that the profile error can be reduced to 0.1 μm or a lower value in peak to valley (PV) after two compensation cycles. The on-machine measurement results show agreement with the off-machine measurement results when commercially available profilometers are employed. The study confirms the feasibility of the proposed wheel path determination method and the developed profile compensation approach. A mirror surface with roughness less than 8 nm in Sa is achieved.

Prediction of Bioactive Peptides from Chlorella sorokiniana Proteins Using Proteomic Techniques in Combination with Bioinformatics Analyses.

Chlorella is one of the most nutritionally important microalgae with high protein content and can be a good source of potential bioactive peptides. In the current study, isolated proteins from Chlorella sorokiniana were subjected to in silico analysis to predict potential peptides with biological activities. Molecular characteristics of proteins were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and proteomics techniques. A total of eight proteins were identified by proteomics techniques from 10 protein bands of the SDS-PAGE. The predictive result by BIOPEP’s profile of bioactive peptides tools suggested that proteins of C. sorokiniana have the highest number of dipeptidyl peptidase-IV (DPP IV) inhibitors, with high occurrence of other bioactive peptides such as angiotensin-I converting enzyme (ACE) inhibitor, glucose uptake stimulant, antioxidant, regulating, anti-amnestic and antithrombotic peptides. In silico analysis of enzymatic hydrolysis revealed that pepsin (pH > 2), bromelain and papain were proteases that can release relatively larger quantity of bioactive peptides. In addition, combinations of different enzymes in hydrolysis were observed to dispense higher numbers of bioactive peptides from proteins compared to using individual proteases. Results suggest the potential of protein isolated from C. sorokiniana could be a source of high value products with pharmaceutical and nutraceutical application potential.

Corrosion behavior of Friction stir welded aluminum alloys: A review

A review on corrosion behavior of Friction Stir Welded aluminum alloys has been presented. Objective of the work is to discuss the behavior of Friction Stir Welded aluminum alloys under chloride environment. The variation of corrosion potential and corrosion rate for the welded portion and base metal and within the welded region for various zones like weld nugget, HAZ and TMAZ has been studied. Alloys of series 2XXX, 5XXX, 6XXX & 7XXX are considered and a comparison is made in between heat treatable and non-heat treatable alloys on basis of their response to chloride atmosphere. The effect of tool rotational speed, traverse speed & tool profile on and are investigated. It is concluded that 5XXX series alloy exhibit better corrosion resistance compared to other series whereas 2XXX & 7XXX are most susceptible to corrosion. It is found that except for hexagonal tool profile corrosion rates of welded joints are higher than the parent metal for both heat treatable as well as non-heat treatable alloys.

Effect of Eye Shield versus Massage on Preterm Infants’ Pain Response during Venipuncture

Background: Evidence demonstrates that controlling pain in the preterm infants during the neonatal periods is improving physiological, behavioral and hormonal outcomes. Eye shield and massage may play an important role as a non-pharmacological pain management during venipuncture. Aim: Is to investigate effect of eye shield and massage on preterm infants’ pain response during venipuncture. Patients and Methods: Time seriesquasi experimental research design was carried out on a randomized sample of 100 newborn infants attending the Neonatal Intensive Care Unit (NICU) of El Manial University Hospital (Kasr Al Ainy), (30control group,30 eye shield group and 30 massage group). Neonatal assessment tool and Preterm Infant Pain Profile (PIPP) were utilized for data collection. Results: There was a significant mean difference between control, eye shield and massage groups regarding PIPP pain assessment scores in three time frames (before venipuncture T0, during T1 and after T2) at P? 0.00 but there wasn’t a significant mean differences after 5 min (T3). Massage group had the fewest mean PIPP score during four time frames (3.50±0.97 before venipuncture, 8.16±1.91 during venipuncture, 4.30±4.30 after venipuncture and 3.22±0.81 after 5 minutes of venipuncture). Conclusion: ANOVA indicated that massage and eye shield groups showed a significant reduction in preterm infant’s pain response than control group during venipuncture but massage was more effective than eye shield. Recommendations: Further studies needed to evaluate the effect of massage in combination with eye shield on preterm infant pain response.

Probing defects in friction stir welding process using temperature profile

Detection of defects in friction stir welding process is a challenging task since most of the defects are internal or subsurface. An attempt has been made to explore the methodologies based on temperature signal for possible detection of defects in friction stir welding process using different tool profiles. The presence of defect is affected by temperature diffusion and is better reflected by the change of temperature over time. Temperature signals are acquired using thermocouples inserted in specific locations on advancing and retreating side of the welds. The rate of change of temperature and wavelet-analysis-based indicator computed from temperature signal against each experiment reveal appreciable difference for defective and defect-free welds. Threshold values are computed that clearly set a boundary for classifying the defective welds from defect-free welds. The proposed approaches can effectively reduce the post-processing steps essential for other non-destructive evaluation of the welds and can work as a first level of safeguard in the identification of defects during friction stir welding process. The methodologies can be extended towards monitoring of the process in industrial applications.

A Methodology for Generating a Variable-Pitch Rotor of Twin-Screw Vacuum Pump

The twin-screw vacuum pump is widely used in low and medium-low vacuum applications. Its core element consists of a pair of rotors rotating in opposite direction on parallel axes. Screw rotors with uniform pitch are usually finished by the form grinding method, but the rotors with variable pitch are not. In this paper, a manufacturing process for generating the tooth profile of the screw rotor with variable pitch by CNC lathe turning is proposed. The initial position of turning tool and normal profile error of the manufactured screw rotors are derived and verified numerically. Numerical examples are presented to validate the proposed method. The simulation results reveal that the proposed CNC turning process is feasible and flexible.

Thermo-mechanical interaction between aluminum alloy and tools with different profiles during friction stir welding

Abstract The influence of the tool profiles on the thermo-mechanical interaction between AA6061-T6 workpiece and tool during friction stir welding was investigated. A customized experimental setup was employed to measure the feature points temperature and tool spindle torque in the process of FSW. Microstructure and tensile properties of stir zone (SZ) were characterized. Results indicate that the shoulder and pin geometries were responsible for the heat generation, tool torque variation at the plunging stage as well as the cross section contour of SZ, respectively. Finer grains in SZ resulted from flutes on shoulder and grooves on pin. Flat faces on the pin resulted in inhomogeneous grain size. Weld with higher 0.2% yield strength of 173 MPa was obtained by using the cylindrical pin tool while higher elongation weld of 32.0% was produced with triflat threaded pin tool.

A profile-adaptive compliant polishing tool for aero-engine blade finishing process

As a key role in the precision finishing of aero-engine parts, polishing tools strongly affect the surface quality of finished parts. In this paper, a novel profile-adaptive compliant polishing tool with a controlled and movable sleeve was developed for aero-engine blade finishing process. The profile of the polishing tool’s end can be changed to fit well with the profile of workpiece surface by adjusting the tool’s rotational speed and the length of its protrusion. The control and implementation of the profile-adaptive polishing for aero-engine blades was proposed. Then, the approximate curvature prediction model of polishing tool’s end was experimentally established. Finally, polishing experiments with the unimproved polishing tool and the proposed compliant polishing tool were carried out for TC4 aero-engine blades. Through comparing and analyzing the measurement results of surface texture, three-dimensional surface topography, and surface roughness, the feasibility and effectiveness of the proposed profile-adaptive compliant polishing tool for aero-engine blade finishing process were proved.

Dynamics of tapping process

Abstract Dynamic problem of tapping process, which is widely used to create internal threads, has never been studied before. Existing theories on explaining the generation mechanism of regenerative chatter occurring in metal cutting process did not consider the varying tool profiles, complicated process geometries and multi-direction vibrations, and thus, they cannot be directly used to reveal the underlying cause of the chatter phenomena in tapping process. This article makes the first attempt to investigate the dynamic problem in tapping process. Expressions of the dynamic uncut chip thickness are derived first by considering the regenerative effect of lateral, torsional and axial vibrations. Coupling between the lateral vibrations and the torsional/axial vibrations as well as the dynamic cutting forces is modelled along the tapping path, and it is theoretically proven that the effects of lateral vibrations and torsional/axial vibrations on the dynamic cutting forces are decoupled. Based on this finding, the lateral and torsional/axial chatter stability of the tapping process is separately predicted in frequency domain. Besides, a strategy for measuring and modifying the FRFs of tapping system is also established by using an additive adapter. A series of rigid tapping experiments, in which the possible feed error (also called synchronization error) is firstly reduced by conducting a Fanuc servo guide-based adjustment, are carried out to validate the proposed model.

Single and Multi-Response Optimization and Validation of Mechanical Properties in Dissimilar Friction Stir Welded AA2219-T87 and AA7075-T73 Alloys Using T-GRA

A study of dissimilar friction stir welding of two aerospace aluminum alloys AA2219-T87 and AA7075-T73 is carried out with five friction stir welding (FSW) parameters namely rotational speed, welding speed, tool profile, tilt angle and position of material. The welding was performed as per the L16 Orthogonal array formed by Taguchi mixed factorial design matrix. Taguchi and Grey Relational Analysis was used for single and multiple response optimizations respectively for optimizing tensile strength, yield strength and percentage elongation. Tensile testing was carried out and analysis was done for getting the optimum setting parameters level. Then the results for L16 was ranked and the optimized parameter set was predicted to be A1B1C2D1E1. Further experimental validation weld was performed and the results correlate with the predicted value. A joint efficiency of 71.8% which is even higher than the predicted values was obtained. Microstructural and hardness studies were performed on the validated welds. Fractography was done to understand the mode of failure occurs in the weld region and most fracture occurs with an offset towards AA2219 side. The presence of intermetallic is found in EDS analysis and XRD further validates the intermetallic composition.

Integration of tool error identification and machining accuracy prediction into machining compensation in flank milling

In a flank milling process, the tool rotation profile error induced by its radial dimension error, setup error, tool deflection, and wear has a great influence on the dimensional accuracy of the machined components. In this paper, we present an integrated identification of tool error, prediction of machining accuracy, and compensation methodology for tool profile error to improve the machining accuracy. Firstly, the tool errors are divided into static and dynamic errors based on the error characteristics and the corresponding error identification methods are established to recognize the tool error parameters. Secondly, the machining accuracy is predicted by a prediction model, and the tool error parameters are input into this model. Thirdly, a new tool error compensation method is developed and incorporated in the corresponding NC codes. Finally, some machining experiments have been carried out to validate the proposed identification-prediction-compensation methodology, and the results show that this methodology is effective.

Challenges in the detection of weld-defects in friction-stir-welding (FSW)

ABSTRACTFriction-Stir-Welding (FSW) involves many critical process variables that affect the overall quality of the weld produced; consequently, it is difficult to accurately predict the most favourable process parameters to acquire high-quality defect-free welds. Quality of an FSW joint is influenced by several crucial factors including welding process parameters, and many others. Since the new invention of FSW process, investigators have researched the influence of process parameters and pin tool profiles on microstructures and mechanical properties with a view to optimise FSW process, thereby keeping the degradation of the weld strength to a minimum. In this study weld defects in Friction-Stir (FS) welded thick (8.13 mm) aerospace grade aluminium alloy (AA 2219-T87) are correlated with weld process parameters from an assortment of a large matrix of weld schedules. In this investigation, a novel FSW process parameter window was established for the effective joining of aerospace grade aluminium which could successfully distinguish several types of weld schedules with characteristic and intrinsic weld-defects. Using experimental results obtained from various schedules, an empirical force index (Effective Force Index), which is a function of the critical weld process parameters is proposed to identify regions of weld schedules.

Prediction of Responses in FSW Processed Hybrid Composites Using Soft Computing Technique

In this research a proper step taken to predict friction stir welding process parameters for the aluminium hybrid composites. In FSW Weld quality is influenced by welding input parameters. The welding parameters taken for this work are axial load, tool profile, spindle speed and material composition. In the present work different combination of aluminium hybrid composite of 6 mm thick is attempted to weld using vertical milling machine. By taking the input parameters such as axial load, tool profile, spindle speed and material composition whereas the response of the model tensile strength and hardness is calculated. The ANN was trained with experimental data. Testing of the ANN is carried out using experimental data not used during training. The result shows the comparison of experimental values of tensile strength and hardness and predicted value using ANN. This indicates that the developed neural network can be used as alternative way for calculating mechanical properties for given process.

Equations of heat generation during friction stir welding for tapered polygonal tools

ABSTRACTOwing to the complex nature of heat generation in friction stir welding, equations are required to understand the effect of process parameters and tool geometry on heat generation. In this study, simplified equations for straight tool profiles have been extended to treat tapered tool profiles for triangular, square, pentagonal and hexagonal geometries. New equations have been implemented to model heat generation in a finite element software package for welding aluminium alloy. The calculated thermal profiles agree better with experimental data than those calculated using the simplified equations. It was also demonstrated that the amount of heat generation increases with increasing number of flats on the tapered tool profile, with a hexagonal tapered tool profile generating the highest temperature.

PENGEMBANGAN ALAT EVALUASI PEMBELAJARAN IPA YANG MENDUKUNG KETERAMPILAN ABAD 21

This study aims to develop learning devices, especially in the evaluation section of science learning in junior high school, which in turn after being implemented in the classroom is expected to develop 21st century skills of students. In particular, this study aims to, 1) identify science learning evaluation tools made by teachers so that they obtain a clear picture of the profile of the evaluation tool, 2) develop a junior high school science learning evaluation tool that supports 21st century skills. This research includes development research in four stages, namely: decide, design, develop, and evaluate. The results of this study indicate that the tools developed by the teacher are in complete category, the learning objectives are clear, although the stages in part still need to be improved. Learning evaluation instruments developed by the teacher have met the principles of assessment, the presentation is in accordance with the curriculum, the sentence in the question is quite communicative, uses good and correct language and does not cause multiple interpretations. However, the majority of questions made by teachers still measure low-level thinking skills. This is because teachers have not been trained in developing questions that measure high-level thinking skills. An evaluation tool that was then developed together with the teacher was intended to perfect the shortcomings of the previous evaluation toolKeywords: 21st Century Skills, Learning Evaluation Tools, Middle School Science

ANN Modeling and Analysis of Friction Welded AA6061 Aluminum Alloy

The present investigation, the ANN method is applied using MATLAB software. An AA6061-T6 Aluminium alloy mixture to measure the tensile strength for FSW joint with a 6 mm thickness. In the first phase of the project, the FSW process is carried out on Al alloy plates using a CNC vertical milling apparatus. The significant parameters of FSW consists are weld speed rate, tool rotation speed, and tool profile. Then the welded joint is tested in UTM to measure tensile strength. The model's input parameters are filtered speed and tool revolution speed (TRS). Emissions of ANN Model property parameters are the tensile strength. The ANN models are good performance has been achieved. This type model can be used to determine the tensile strength for Al plates, which are welded by welding speed and the function of rotation speed. The united influence of weld rate also tool rotational speed on the engineering properties of welded Al plates was simulated. Compared measured values and determined data, the calculated results are a good deal with the measured data.

A Reliability Statistical Evaluation Method of CNC Machine Tools Considering the Mission and Load Profile

Reliability of the CNC machine tool (abbreviated as machine tool) relates to the product's reliability and has great influence on the manufacturing process. The traditional reliability statistical evaluation method of the machine tool neglects the influence of the mission profile and load profile (M&L), it causes that the evaluation result is not accurate enough to provide accurate references for the reliability-related works under specific M&Ls such as the preventive maintenance, product improvement, etc. To address these defects, this paper proposes an improved reliability statistical evaluation method considering the M&L. Firstly, the machine tool is decomposed by the meta-action decomposition method, and the mission profile of the machine tool is represented by the meta-action chain (MC). Secondly, load profile representation indicators of the machine tool are extracted based on the load composition and cutting force calculation. Then, the mapping model between the M&L and the machine tool's reliability is established using the radial basis function (RBF) neural network. Finally, the improved reliability statistical evaluation method is illustrated and validated by the engineering practical application. Comparing the evaluation results of the two statistical evaluation methods, it shows that the improved reliability statistical evaluation method is more accurate than the traditional reliability statistical evaluation method, under specific M&Ls, so that it can provide more accurate references for the reliability-related works.

Clinical profile and comparison of causality assessment tools in cutaneous adverse drug reactions

Background:Cutaneous adverse drug reactions (CADRs) are probably the most frequent of all manifestations of drug sensitivity. As a considerable number of new drugs are periodically introduced into the market, the incidence of CADR is likely to increase. The pattern of CADR and the causative drugs is likely to change accordingly. There is no uniformly accepted and reliable method of objectively assessing the causal link between drug and adverse reaction.Aim:To study the clinical patterns and causative drugs and compare causality assessment [World Health Organization (WHO) and Naranjo algorithm] of CADR among patients attending the dermatology department.Materials and Methods:This is a cross-sectional hospital-based study in which all patients with suspected CADR attending the dermatology department of a tertiary care center over a 9-month period were evaluated using the causality assessment criteria recommended by the WHO-Uppsala Monitoring Centre (UMC) and Naranjo scale. The severity of the reaction was assessed using Adverse Drug Reaction Severity Assessment Scale (modified Hartwig and Siegel scale).Results:A total of 200 consecutive patients with CADR were evaluated. The causality assessment for a drug as per WHO scale yielded 63 (31.5%) cases as certain, 12 (6%) as probable, and 125 (62.5%) as possible, whereas Naranjo scale showed 26 (13%) cases to be definite, 138 (69%) as probable, and 36 (18%) as possible. There was poor agreement between the two scales. Fixed drug eruption was the most common pattern of CADR (82.41%). The average number of drugs received by patients was 2.09. The most common suspected drug group was antimicrobials (n = 170; 40.5%), followed by nonsteroidal anti-inflammatory drugs (n = 148; 35.3%) and antiretroviral drugs (n = 41; 9.7%). Fixed drug eruption was most commonly caused by paracetamol. Antiepileptics and antimicrobials were the most common suspects among severe cutaneous adverse reactions.Limitations:Multiple concomitant drug usage by patients and inability to provoke all patients/measure drug levels in blood resulted in higher number of drugs with causal association as probable/possible.Conclusion:WHO-UMC scale was found to be easier to apply and evaluate, with greater practical utility. Poor agreement between the two commonly used scales emphasizes the need for a consistent and uniform causality assessment tool.