EDM simulation: finite element-based calculation of deformation, microstructure and residual stresses

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.

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

A thermal–electrical model was developed for sparks generated by electrical discharge in a liquid media. A cylindrical shape has been used for the discharge channel created between the electrodes. The discharge channel being an electrical conductor will dissipate heat, which can be explained by the Joule heating effect. The amount of heat dissipated varies with the thermal–physical properties of the conductor; as a result, the maximum temperature reached is different. In the present model, the radii value of the conductor is a function of the current intensity and pulse duration. The thermal–physical values used in the model are the average of both the ambient and melting value. Copper and iron are the materials used for anode and cathode, respectively. The Finite Element Analysis (FEA) results were compared with the experimental values of the table of AGIE SIT used by other researchers [D.D. DiBitonto, P.T. Eubank, M.R. Patel, M.A. Barrufet, Theoretical models of the electrical discharge machining process—I: a simple cathode erosion model, Journal of Applied Physics, 66(9) (1989) 4095–4103; M.R. Patel, M.A. Barrufet, P.T. Eubank, D.D. DiBitonto, Theoretical models of the electrical discharge machining process—II: the anode erosion model, Journal of Applied Physics, 66(9) (1989) 4104–4111; P.T. Eubank, M.R. Patel, M.A. Barrufet, B. Bozkurt, Theoretical models of the electrical discharge machining process—III: the variable mass, cylindrical plasma model, Journal of Applied Physics, 73(11) (1993) 7900–7909]. In order to show the universality of the model it was obtained results for all current intensity values of the table. The Tool Wear Ratio (TWR) and Material Removal Rate (MRR) as well as surface roughness results agree reasonably well with the researcher's values found for that table and itself.

A finite element model of EDM based on the Joule effect

The electrical discharge machining (EDM) process is, by far, the most popular amongst the non-conventional machining processes. The technology is optimum for accurate machining of complex geometries in hard materials, as those required in the tooling industry. However, although a large number of EDM machines are sold every year, scientific knowledge of the process is still limited. The complex nature of the process involves simultaneous interaction of thermal, mechanical, chemical and electrical phenomena, which makes process modelling very difficult. In this paper a new contribution to the simulation and modelling of the EDM process is presented. Temperature fields within the workpiece generated by the superposition of multiple discharges, as it happens during an actual EDM operation, are numerically calculated using a finite difference schema. The characteristics of the discharge for a given operation, namely energy transferred onto the workpiece, diameter of the discharge channel and material removal efficiency can be estimated using inverse identification from the results of the numerical model. The model has been validated through industrial EDM tests, showing that it can efficiently predict material removal rate and surface roughness with errors below 6%.

A numerical model of the EDM process considering the effect of multiple discharges

Numerical simulation of powder mixed electric discharge machining (PMEDM) using finite element method

The high temperature gradients generated at the gap during electrical discharge machining (EDM) result in large localized thermal stresses in a small heat-affected zone. These thermal stresses can lead to micro-cracks, decrease in strength and fatigue life and possibly catastrophic failure. A finite element model has been developed to estimate the temperature field and thermal stresses due to Gaussian distributed heat flux of a spark during EDM. First, the developed code calculates the temperature in the workpiece and then the thermal stress field is estimated using this temperature field. The effects of various process variables (current and duty cycle) on temperature distribution and thermal stress distribution have been reported. The results of the analysis show high temperature gradient zones and the regions of large stresses where, sometimes, they exceed the material yield strength.

Thermal stresses due to electrical discharge machining

Constitutive modeling for the tear fracture of rubber with filler particles

This paper presents the static modeling and analysis of a novel cylindrical tube actuator subjected to a rotation about longitudinal axis with an internally applied air pressure under an electromagnetic field. The current tube actuator belongs to a smart actuator category and is made of an electro-magneto-active polymer filled with a particular volume fraction of suitable fillers. A continuum mechanics-based electro-magneto-mechanical model is developed to predict the response of the actuator for a combined pressure and electromagnetic field loading. To validate the same, the model is compared with the outputs of an existing spring roll actuator. Parametric studies are subsequently performed for varying input pressure, electric field, magnetic field, fillers content, and actuator’s rotational speed. The output sensitivity in terms of strain intensity at inner and outer surfaces of the actuator is also checked at different controlling inputs. In addition, various electro-magneto-mechanical instability curves are drawn to examine the critical inflation of the tube actuator. In general, the developed model provides initial steps toward the modern actuator designs for applications where a precise control with high load-carrying capability of the actuator plays a significant role.

Modeling and analysis of an electro-magneto-elastic rotating cylindrical tube actuator

ABSTRACT Electrical discharge machining (EDM) has recently become popular in manufacturing industries but numerous issues are associated with it like recast layer, surface roughness, and overcut (OC) that result in poor quality and rejection by customers. To overcome these issues, manufacturers are looking for precise methods of machining. In this line, current study aims to investigate the effect of machining input characteristics upon OC during machining of nickel-based alloy, i.e., Inconel 718 by means of EDM. This will help in reduction of OC and improvement in precision. Test experiments were designed as per Taguchi’s DOE approach and conducted by varying different machining input characteristics namely tool diameter discharge current, pulse-on time, pulse-off time tool rotation and depth of hole. Rotary copper tool electrode is used as the drilling tool. Microstructure of drilled hole over the work piece is observed and distinguished through scanning electron microscopy (SEM) images and same was used for OC measurement. Further analysis of variance has been applied for discovering optimum factors for minimum OC. It can be concluded from the test results that discharge current and pulse on time are most influencing factors affecting OC. This study will help the industry to improve precision in manufacturing which can enhance the quality of products.

Vinod Yadav

Papers

Thermal stresses due to electrical discharge machining

Constitutive modeling for the tear fracture of rubber with filler particles

Modeling and analysis of an electro-magneto-elastic rotating cylindrical tube actuator

Analysis of over cut in electrical discharge machining of nickel-based alloy using Taguchi approach

Dynamic modelling and analysis of smart cantilever beam using FEM