Pulse Electrochemical Machining Process Research Articles

Multi-time scale simulation of pulse electrochemical machining process with multi-physical model

To determine the relationship between the pulse current and the physicochemical properties of multi-time scales, a method of multi-time scale simulation is introduced to investigate multi-time scale evolution of temperature and void fraction in PECM process. A multi-time scale iterations method is introduced to reduce computation time of multi-time scale simulation. Simulation results indicate that the method is efficient and pulse current can make the PECM process more stable. Experimental results show that the multi-time scale simulation results can well match the actual machining results, especially in the middle section of the workpiece.

Optimal design of cathode based on iterative solution of multi-physical model in pulse electrochemical machining (PECM)

In pulse electrochemical machining (PECM), the control of pulse parameters would result in designing the cathode shape according to a given anode shape more complexly than in direct current electrochemical machining (DC-ECM). To solve the problem, a numerical approach is proposed to achieve optimal design of cathode. A gap model is proposed to describe the influence of pulse parameters on gap size and a multi-physical model is introduced to describe the influence of pulse parameters on the distribution of electrolyte conductivity which can reflect the distribution of gap. An optimization method based on iterative solution of multi-physical model is presented to improve design accuracy of cathode shape. The experiments are conducted to illustrate the method of cathode design in PECM process. The results show that the proposed method can effectively improve processing accuracy.

Multiphysics simulation of the material removal process in pulse electrochemical machining (PECM)

For the time scale of the applied pulses is orders of magnitude smaller than the time scale on which the workpiece is machined, simulation of the temperature evolution and the changes of the workpiece shape in pulse electrochemical machining (PECM) process would be a computationally very expensive procedure. A multi-physics model and the quasi steady state shortcut (QSSSC) approach are presented for modeling the temperature evolution in PECM process. By defining a critical upper limit, a simplified algorithm is introduced to simulate the changes of workpiece shape in PECM process. The assumption is made that geometry structure is fixed before the system reaches the quasi steady state (QSS) and the material removal is calculated by current density when the QSS is reached. Simulation results indicate that the simplified algorithm is convenient for the calculation of the shape change of the electrodes. The validity of the simplified algorithm is verified by the comparison of workpiece profiles obtained by simulation prediction and experiments.

Process Design in Pulse Electrochemical Machining Based on Material Specific Data – 1.4301 and Electrolytic Copper as an Example

The Pulse Electrochemical Machining Process is an innovative, non-conventional process, based on the Electrochemical Machining process. Herein, pulsed current instead of constant current and a feed overlaid mechanical vibration of the tool electrode allows a higher precision and copying accuracy in contrast to the well-established ECM process. Yet, in this context the pulse-pause time and the length of the pulse on-time used in the process cause changes in the material removal while processing and therefore influences the processing result as well as cycle times and other industry relevant criteria. Understanding these pulse- and process specific changes is a key to the process design for industrial applications, since different sets and variations in parameters also change the final form and surface topography. This contribution shows, at the example of two materials 1.4301 and electrolytic copper, how a machining process can be designed and calculated based on material specific data. The way to acquire the necessary material data sets using industrial equipment, as well as the use and information which can be drawn from the data will be addressed.

Investigating the Energy Consumption of the PECM Process for Consideration in the Selection of Manufacturing Process Chains

The initial planning of manufacturing process chains provides the opportunity to sustainably influence the energy requirement for the manufacturing of industrial products by selecting the process chain with the lowest energy consumption. However, the task is still challenging due to the need for energy consumption data of manufacturing equipment. In this paper, the analysis of the energy consumption of a manufacturing process is illustrated by the example of the Pulse Electrochemical Machining (PECM) process. A comparison of two machine tool generations of the same manufacturer shows the improvement in energy consumption. Based on the information gained from the analysis, an approach for the provision of energy consumption data is presented.

The Heat-affected Zone in EDM and its Influence on a Following PECM Process

EDM (Electrical Discharge Machining) and PECM (Pulse Electrochemical Machining) provide unique possibilities for the machining of many different materials. Whereas EDM is able to machine any material above a minimal electrical conductivity, though with a certain degree of tool wear and heat influence, PECM has difficulties machining materials that build a passive layer or have chemically indissoluble contents. However, PECM has the advantage of working nearly wear-free. Based on this fact, a process chain can be built up that first structures copper electrodes by PECM and then uses them in EDM. When worn out, the electrodes can be restructured by PECM to keep a high reproducibility and constant quality of the machined geometry. In this contribution, the heat-affected zone of the tool electrode resulting from an EDM process and its potential influence on the machinability in the following PECM process are investigated for different copper alloys.

Video based Process Observations of the Pulse Electrochemical Machining Process at High Current Densities and Small Gaps

Pulse Electrochemical Machining (PECM), a nontraditional process, using pulse-lengths in the low millisecond range as well as feed overlaid mechanical vibration, allows more precise tolerances and geometric precision through narrowing the working gap compared to conventional sinking ECM. With small working gaps in ranges down to 10μm, the anodic shape evolution during machining is getting difficult to monitor. Therefore understanding the shaping phenomena during the PECM process is key factor in achieving precision during the manufacturing of dies and molds, as well as precision parts in e.g. automotive or aircraft industry. In this contribution an experimental approach towards visual in-process observations of the PECM shaping process during the use of mechanical vibrations up to 50Hz and high pulsed current densities will be presented. Recording the process with a precisely clocked high speed camera system allowing precise μs shutter times, visual observations are conducted and being used as input for detailed downstream data analysis. The experimental study incorporates one of the most widely used flushing conditions in PECM as well as an outlook into the comparison between recorded in-process data and a static FEM simulation based on the monitored shape are given. In all experiments stainless steel of type AISI 304 (X5CrNi18–10) is used as anode and cathode material and for all PECM experiments a commercially available PEMCenter8000 with sodium nitrate as electrolyte was used. The concept presented will help to better link experiment and modelling of the PECM process, by simultaneously providing process relevant electrochemical data as well as the directly corresponding geometric shaping information during experiments.

Possibility of Pulsed Electrochemical Processes to Nanofabrication Using Scanning Probe Oxidation

This study demonstrates nano-scale lithography process on localized (100) silicon (p-type) surface using modified AFM apparatuses and controlling methods. AFM-based experimental apparatuses are connected the customized pulse generator that supplies electricity between conductive tip and silicon surface maintaining constant humidity during processes. Then pulse durations are controlled according to various experimental conditions. The pulsed electrochemical reaction within the gap between conductive tip and silicon surface induces the formation of oxide with nano-scale topographies. Various heights and widths of oxides can be created by AFM surface modification according to various pulse durations and applied electrical conditions under humidity environment. In addition, it can be known that oxides are completely removed after sample surface is etched in diluted HF solution, which shows micro/nano-scale grooves can be fabricated after predefined chemical treatment. They are wider than oxides widths and have several nanometer depths. Nano patterning technique from this experiment suggests that pulse electrochemical machining process has bright potential for advancing nano machining technologies.

Modelling and Monitoring Interelectrode Gap in Pulse Electrochemical Machining

Pulse electrochemical machining (PECM) provides an economical and effective method for machining high strength, heat-resistant materials into complex shapes such as turbine blades of titanium alloys. The dimensional accuracy of PECM can be improved if a small interelectrode gap is maintained. This paper presents an interelectrode gap model for estimating machining parameters for the minimum gap size under the limit of electrolyte boiling. A specially-built PECM cell and a high speed data acquisition system are used to acquire the pulse current signal for developing an on-line monitoring strategy. A stochastic analysis of the current signal indicates a linear correlation between the gap size and the variance of the filtered current signal. An on-line monitoring system based on this correlation is proposed for the PECM process.

Modelling and Analysis of Pulse Electrochemical Machining (PECM)

A small interelectrode gap in Electrochemical Machining (ECM) results in improved dimensional accuracy control and simplified tool design. However, using a small gap with conventional ECM equipment adversely affects the electrolyte flow or mass transport conditions in the gap, leading to process instability. The most remarkable breakthrough in this regard is the development of ECM using pulsed current. Pulse Electrochemical Machining (PECM) involves the application of a voltage pulse at high current density in the anodic dissolution process. PECM allows for more precise monitoring and control of machining parameters than ECM using continuous current. Small interelectrode gap, low electrolyte flow rate, gap state recovery during the pulse-off times and improved anodic dissolution efficiency features encountered in PECM lead to improved workpiece precision and surface finish when compared with ECM using continuous current. This paper presents mathematical models for the PECM process which take into consideration the nonsteady physical phenomena in the gap between the electrodes, including the conjugate fields of electrolyte flow velocities, pressure, temperature, gas concentrations, current densities and anodic material removal rates. The principles underlying higher dimensional accuracy and simpler tool design attainable with optimum pulse parameters are also discussed. Experimental studies indicate the validity of the proposed PECM models.

Study of Pulse Electrochemical Machining Characteristics

The Pulse Electrochemical Machining (PECM) promises to improve dimensional accuracy control and to simplify tool design in machining hard, high strength, and heat resistant materials into complex shapes such as turbine blades. This paper presents a mathematical model for the PECM process which takes the non-steady physical phenomena in the gap into consideration. A specially-built PECM cell and a high-speed data acquisition device are used to obtain accurate experimental results in the gap for the model verification. The interelectrode gap characteristics, Including pulse current, metal removal rate, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analyzed based on the model and experiments.