Thermal modeling of the material removal rate and surface roughness for die-sinking EDM

The die-sinking electrical discharge machining (EDM) process is characterized by slow processing speeds. Research effort has been focused on optimizing the process parameters so as for the productivity of the process to be increased. In this paper a simple, thermal based model has been developed for the determination of the material removal rate and the average surface roughness achieved as a function of the process parameters. The model predicts that the increase of the discharge current, the arc voltage or the spark duration results in higher material removal rates and coarser workpiece surfaces. On the other hand the decrease of the idling time increases the material removal rate with the additional advantage of achieving slightly better surface roughness values. The model’s predictions are compared with experimental results for verifying the approach and present good agreement with them.     

Modeling and analysis of white layer depth in a wire-cut EDM process through response surface methodology

A white layer is considered a major flaw on a workpiece surface machined with wire-cut electrical discharge machining (WEDM). In this paper, an attempt has been made to model the white layer depth through response surface methodology (RSM) in a WEDM process comprising a rough cut followed by a trim cut. An experimental plan for rotatable central composite design of second order involving four variables with five levels has been employed to carry out the experimental investigation and subsequently to establish the mathematical model correlating the input process parameters with the response. Pulse on time during rough cutting, pulse on time, wire tool offset, and constant cutting speed during trim cutting are considered the dominant input process parameters whilst the white layer depth is the response. An insignificant lack of fit term indicated a curve with a good fit. Also, an extensive analysis of the influences of all the individual input parameters on the response has been carried out and presented in this research study.     

Experimental investigation and 3D finite element prediction of the white layer thickness, heat affected zone, and surface roughness in EDM process

An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand, an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.     

Modeling and analysis of electrode wear and white layer thickness in die-sinking EDM process through response surface methodology

In this study, an attempt has been made to model electrode wear (EW) and recast layer thickness (WLT) through response surface methodology (RSM) in a die-sinking EDM process. A central composite rotatable design (CCRD) involving three variables with five levels has been employed to establish a mathematical model between input parameters and responses. Pulse on-time, pulse off-time and pulse current were changed during the tests based on the CCRD. The results of analysis of variance (ANOVA) indicated that the proposed mathematical models obtained can adequately describe the performances within the limits of factors being studied. The experimental and predicted values were in a good agreement.     

Experimental investigation of burr reduction during EDM end-milling hybrid process

Burrs are always generated during the end-milling process of ductile materials and have become a common challenge because a large plastic flow of the material is generated during cutting. In this research, a combination method of the end-milling and electrical discharged machining (EDM) process is proposed to suppress the generated burrs during machining; this process is called the EDM end-milling process. EDM end-milling was performed for side milling of AISI 1045 alloy steel (HRC = 28). The height of the generated burrs was measured and compared between ordinary end milling and EDM end-milling, and the experimental results indicate that the generated burrs are suppressed effectively by EDM end-milling owing to the effect of reduced plastic flow. The experimental results also indicate that the height of the generated burrs decreases when the capacitance values are increased during EDM end-milling. Furthermore, the results show that the height of the generated burrs remains unchanged by EDM end-milling when the axial depth of cut is increased.

     

液体喷射抛光技术材料去除机理的有限元分析

实验研究了液体喷射抛光技术的材料去除量分布特征,并利用有限元分析方法,分析了抛光头(液体柱)与工件表面相互作用时流场的分布特点。实验结果及计算机模拟的结果表明,材料去除量与射流碰撞工件后流体沿工件表面的速度有关,即材料去除量的分布与抛光液在工件表面速度场的分布有关,速度分布最大的边缘部分,材料去除量最大;相互作用区外,速度逐渐减小,材料去除量也随之渐少。该现象说明,抛光液中磨料粒子的径向流动对工件产生的径向剪切应力是材料去除的关键。     

基于ST14材料冲压工艺有限元分析应用

以ST14材料的左右后门窗框前支架工件为载体,以AutoForm冲压工艺有限元分析软件为平台,针对ST14材料的经验结构工艺模拟材料的成形过程,分析了工件冲压成形工艺过程中的缺陷问题,通过工件工艺结构的反复修正,实现了解决冲压工艺缺陷问题的目的.     

Experimental investigation and analytical modelling of the effects of process parameters on material removal rate for bonnet polishing of cobalt chrome alloy

Cobalt chrome alloys are the most extensively used material in the field of total hip and total knee implants, both of which need highly accurate form and low surface roughness for longevity in vivo. In order to achieve the desired form, it is extremely important to understand how process parameters of the final finishing process affect the material removal rate. This paper reports a modified Preston equation model combining process parameters to allow prediction of the material removal rate during bonnet polishing of a medical grade cobalt chrome alloy. The model created is based on experiments which were carried out on a bonnet polishing machine to investigate the effects of process parameters, including precess angle, head speed, tool offset and tool pressure, on material removal rate. The characteristic of material removal is termed influence function and assessed in terms of width, maximal depth and material removal rate. Experimental results show that the width of the influence function increases significantly with the increase of the precess angle and the tool offset; the depth of the influence function increases with the increase of the head speed, increases first and then decrease with the increase of the tool offset; the material removal rate increases with the increase of the precess angle non-linearly, with the increase of the head speed linearly, and increases first then decreases with the increase of the tool offset because of the bonnet distortion; the tool pressure has a slight effect on the influence function. The proposed model has been verified experimentally by using different Preston coefficients from literature. The close values of the experimental data and predicted data indicate that the model is viable when applied to the prediction of the material removal rate in bonnet polishing.     

Experimental investigation of laser transformation hardening of low alloy steel using response surface methodology

In this research, a systematic investigation on laser transformation hardening (LTH) process is carried out on high-strength low-alloy medium carbon steel, EN25 using design of experiments (DOE). The effect of input process parameters like laser power, travel speed over the response hardened width (HW), hardened depth (HD), and hardened area (HA) are analyzed. The experimental trials are conducted based on the design matrix obtained from the 3^k full factorial design (FFD) using a 2 kW continuous wave Nd:YAG laser power system. A quadratic regression model is developed to predict the responses using response surface methodology (RSM). Based on the developed mathematical models, the direct and interaction effects of the process parameters on LTH are investigated. The optimal hardening conditions are identified to maximize the HW and minimize the HD and HA. The results of the validation test show that the experimental values quite satisfactorily agree with the predicted values of the mathematical models and hence, the models can predict the response adequately.     

Experimental investigation of brittle material removal fraction on an optical glass surface during ultrasound-assisted grinding

The proposed work addresses the problem of placing safety stock under the guaranteed-service model when a set of supplying, manufacturing and delivery stages model the production system. Every stage has a set of options that can perform the stage and every option has an associated cost and time. Hence, the problem is to select an option per stage that minimises the safety stock and lead time at the same time. We proposed solving the problem using two swarm intelligent meta-heuristics, Ant Colony and Intelligent Water Drop, because of their results in solving NP-hard problems such as the safety stock problem. In our proposed algorithm, swarms are created and each one selects an option per stage with its safety stock and lead time. After that, the Pareto Optimality Criterion is applied to all the configurations to compute a Pareto front. A real-life logistic network of the automotive industry is solved using our proposed algorithm. Finally, we provided some multi-objective performance metrics to assess the performance of our approach and carried out a statistical analysis to support our conclusions.     

Development of an inversion model for establishing EDM input parameters to satisfy material removal rate, electrode wear ratio and surface roughness

Electro-discharge machining (EDM) has grown tremendously over the last few decades. Due to its extensive capabilities, this technique has been increasingly adapted to new industrial applications within the field of aerospace, medical, die and mould production, precision tooling, etc. The novelty of the research presented in this paper lies in solving an inversion model, based on the least squares theory, which involves establishing the values of the EDM input parameters (peak current level, pulse-on time and pulse-off time) to ensure the simultaneous fulfilment of material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR). The inversion model was constructed from a set of experiments and the equations formulated in the forward model described in the first part of this paper. In the forward model, the well-known ANOVA and regression models were used to predict the EDM output performance characteristics, such as MRR, EWR and SR in the EDM process for AISI 1045 steel with respect to a set of EDM input parameters.     

Surface roughness and material removal rate of lapping process on ceramics

Lapping is a widely used surface finishing process for ceramics. An experimental investigation is conducted into the lapping of alumina, Ni−Zn ferrite and sodium silicate glass using SiC abrasive to study the effect of process parameters, such as abrasive particle size, lapping pressure, and abrasive concentration, on the surface roughness and material removal rate during lapping. A simple model is developed based on the indentation fracture and abrasive particle distribution in the slurry to explain various aspects of the lapping process. The model provides predictions for the surface roughness,R _a andR _t , on the machined surface and rough estimation for the material removal rate during lapping. Comparison of the predictions with the experimental measurements reveals same order of magnitude accuracy.     

Modelling of surface finish and material removal rate in rough honing

In the present work influence of different parameters of the rough honing process on surface roughness and material removal rate were studied. Specifically, second order mathematical models are presented for mean average roughness Ra (μm), maximum peak-to-valley roughness Rt (μm) and material removal rate Qm (cm min⁻¹), obtained by means of regression analysis.     

Application of Six-Sigma DMAIC methodology to sand-casting process with response surface methodology

This paper deals with the application of Six-Sigma methodology to the flywheel casting process in foundry to minimize the defects in this process. The primary tools used in this interventionist process were the process map, cause-and-effect matrix and the failure mode effective analysis. The present study proposes to measure the performance criteria of the process through investigating the effect of working parameters, namely, moisture content, green strength, permeability, and loss on ignition on sand preparation. The experimental results were statistically analyzed and modeled through response surface methodology (RSM). Based on the findings, the optimized process parameters were taken for experiment and better performance obtained in the production process was confirmed. The comparison between the existing process and the proposed process has been attempted in this paper and the results have been discussed in detail.     

Static analysis of nanobeams including surface effects by nonlocal finite element

In reality, there are two phenomena should be considered to describe behaviors of nanostructures adequately and accurately. The first one is the surface properties, especially for a relatively high ratio of the surface area to the volume of structural. The second phenomenon is the information about bulk material, which contains the forces between atoms and the internal length scale. Therefore, the objective of the current work is to study the coupled effects of surface properties and nonlocal elasticity on the static deflection of nanobeams. Surface elasticity is employed to describe the behavior of the surface layer and the Euler-Bernoulli beam hypothesis is used to state the bulk deformation kinematics. Both, the surface layer and bulk volume of the beam are assumed elastically isotropic. Information about the forces between atoms, and the internal length scale are proposed by the nonlocal Eringen model. Galerkin finite element technique is employed for the discretization of the nonlocal mathematical model with surface properties. The present results are compared favorably with those published results. The effects of nonlocal parameter and surface elastic constants are figured out and presented.     

Optimization of drawbead design in sheet forming using one step finite element method coupled with response surface methodology

In a sheet forming process, drawbead plays an important role on the control of the material flow. In this paper, a numerical procedure for the design of forming processes is described. It is based on the coupling of an optimization technique and the simplified one step finite element method (also called inverse approach). The optimization technique allows adjustment of the process parameters so that specified criteria are fulfilled. Response surface methodology (RSM) is a global approximation method, which is ideally suited for solving highly nonlinear optimization problems. The finite element method, in addition to predicting the response of the process to certain parameters, allows assessment of the effect of a variation in these parameters on this response. The authors utilize the one step method at the preliminary design stage to supply stress or strain information for the following optimization using RSM. The procedure for this optimization process is fully described. The front fender for Numisheet 2002 is presented and the real defect free workpiece is produced to demonstrate the usefulness of the proposed optimization procedure. A comparison between the two forming limit curves (FLC) before and after optimization and results obtained using the precise incremental commercial software DYNAFORM based on the explicit dynamic approach verify that the optimization design method of drawbead could be successfully applied in designing actual tools of auto body cover panels.     

Experimental investigation and prediction of optimum process parameters of micro-wire-cut EDM of 2205 DSS

Micro-wire-cut electrode discharge machining (EDM) is an emerging manufacturing process in the field of micro-manufacturing to fabricate the complex profiles of micro-components. It is a complex process involving various process parameters such as pulse on time, pulse off time, wire speed, wire tension and current. In addition to micro-fabrication, this process can also be extended in the field of tool design and developments such as dies, moulds, precision manufacturing, contour cutting, etc., where complex shapes need to be generated with high-grade dimensional accuracy and surface finish. In this research work, an attempt is made to investigate the effect of process parameters on the output variables such as material removal rate (MRR), surface finish and the cutting width (kerf) of wire-cut EDM for duplex stainless steel (DSS). Scanning electron microscopy (SEM) has been used to capture the images of the kerf width, and the measurements are taken with the help of the welding expert system and software. An optimization technique (Taguchi method) has been employed to identify the optimum parameters of the micro-wire-cut EDM process for cutting 2205 grade duplex stainless steel. The effect of each control parameter on the performance measure is studied individually using the plots of signal to noise ratio.     

Numerical investigation of bolt fitting and fastening forces by elastoplastic finite element analysis

The bolt–flange fitting and detaching processes are numerically investigated by the updated Lagrangian elastoplastic finite element analysis. The elastoplastic behavior of the flange is modeled by the power-law plastic model with the isotropic strain hardening, while assuming the bolt to be rigid by virtue of the big difference in the material stiffness between bolt and flange. Through the parametric numerical analyses of the bolt–flange fitting and detaching processes with respect to the shape of the bolt cross-section, the characteristics of the bolt fitting and fastening forces are investigated. The validity of the simplified 2-D axisymmetric finite element model is examined through the comparison with the numerical results obtained by 3-D full finite element model. As well, the effects of the bolt petal number on these forces are investigated, and the experiment is performed to verify the numerical simulation.