A.K.M. De Silva

New Developments in Electro-Chemical Machining

Abstract Electrochemical machining (ECM) has traditionally been used in highly specialized fields such as those of the aerospace and defense industries. It is now increasingly being applied in other industries where parts with difficult-to-cut materials and complex geometry are required. In this paper the latest advances are discussed, and the principal issues in ECM development and related research are raised. Developments in tool design, pulse current, micro-shaping, finishing, numerically controlled, environmental concerns, hybrid processes, and recent industrial applications, are covered.

Electroforming process and application to micro/macro manufacturing

Abstract Electroforming is the highly specialised use of electrodeposition for the manufacture of metal parts. This paper describes the process principles and mechanisms of electroforming, outlining its advantages and limitations. A review of modelling and simulation of electroforming and experimental analysis work is also presented. The metals that can be electroformed successfully are copper, nickel, iron or silver, thickness up to 16 mm, dimensional tolerances up to 1 μm, and surface finishes of 0.05 μm R a . The ability to manufacture complex parts to close tolerances and cost effectively has meant that electroforming has applications both in traditional/macro manufacturing and new micromanufacturing fields. These include tooling; mould making; fabrication of microelectromechanical systems (MEMS) and the combination of lithography, electroforming and plastic moulding in the LIGA process. Applications in micro-optics and medicine are included.

Precision ECM by Process Characteristic Modelling

Abstract Electrochemical machining (ECM), which is not normally considered as a precision process, is used to achieve accuracy better than 5 urn and surface finish 0.03 μm R a by using pulsed power of relatively short durations (1–10 ms) and narrow inter-electrode gaps (10–50 μm). The narrow gaps, however, make the control and prediction of the process much more complex than normal ECM. An empirical model is developed based on the characteristic relationships of ECM to predict and optimise the process parameters such as dissolution efficiency, current density, electrolyte concentration and pulse duration, in narrow gaps. This model is then used to facilitate new applications of high precision ECM without recourse to the lengthy trial-and-error approach, by predicting selective dissolution of the workpiece and tool design.

Influence of Electrolyte Concentration on Copying Accuracy of Precision-ECM

Abstract A precision ECM process, dimensional accuracy ± 2 μm, surface finish 0.01 μm Ra has been developed using narrow inter-electrode gaps (

Process monitoring of electrochemical micromachining

Abstract Electrochemical micro-machining (ECμM), utilises very small inter-electrode gaps (

Computer applications in unconventional machining

Abstract The progress of unconventional machining through the application of computer-aided technology is presented. The processes of ECM, EDM, LBM, AWJM are discussed in relation to the influence of CAD, CAM, CAE, CNC, CIM and on their acceptance by manufacturing industry. EDM and LBM can readily be integrated onto the machine shop floor today. Other processes have lesser degrees of automation, mainly because their applications tend to be more specialised. All processes need to be able to be fully automated and integrated if they are to remain competitive.

CDT Analysis is Used as a Condition Monitoring Parameter to Study the Tribological Behavior of Bearing Lubricant Under Different Operating Pressure

The deceleration and running down operation of any rotating system when analysed would lead to useful input function for condition monitoring. When the power supply to any rotor system is cut off, total momentum gained through the sustained operation will dissipate and the system will come to halt. The time elapsed between the power cutoff and the complete stop of the system is defined as CDT (Coast Down Time). The tribological behaviour could be effectively monitored through this parameter (CDT), which has been conducted on a horizontal rotor system with a full journal bearing at different speed and lubrication pressures. The characteristics are compared with steady state vibration in order to emphasize the potential benefit of using CDT as a useful diagnostic parameter for condition monitoring.Copyright

Shell Assisted Layer Manufacturing (SALM)

This paper presents the technology and some experiments results of a novel Rapid Prototyping/Tooling/Manufacture (RP/RT/RM) process, Shell Assisted Layer Manufacturing (SALM), which is based on layer manufacturing technology (LMT). The SALM process executes two essential steps to develop one layer of the part. Initially, it develops the outer shell (boundaries) of the particular layer of the part using the Fused Deposition Modelling (FDM) technique and then the shell is filled with UV (Ultraviolet) curable resin. The deposited resin layer is then cured using a UV light source. This procedure is repeated until the complete part is built. The process has the potential to give improved quality, productivity and process speed.

A Fuzzy Logic Approach for the Pulse Classification of Electro Chemical Discharge Machining (ECDM)

This paper presents the pulse classification of the ECDM process using Fuzzy Logic (FL). An Electro Discharge Machining (EDM) machine was modified by incorporating an electrolyte system and by modifying the control system. Gap voltage and working current waveforms were obtained. A fuzzy rule base was designed and simulated to classify pulses. Different ECDM process variables were considered to design the pulse classification rule base. The performances were compared by changing the process variables and by changing rules in the fuzzy rule base. The classification accuracy was measured in the classification system. A quantitative analysis was performed to evaluate the fuzzy pulse classifier with different process variables and with different fuzzy rules for the ECDM machine.

Laser Assisted Jet Electrochemical Machining of Hard to Cut Alloys

Laser Assisted Jet Electrochemical Machining (LAJECM) is a hybrid process which combines electrolyte jet and low power laser beam (375mW) to facilitate material removal. The main purpose of the laser is to enhance dissolution from the workpiece in the specific area giving faster dissolution in axial rather in lateral direction and in result higher dimension precision. Experimental analysis using stainless steel, titanium alloy and high carbon alloy has proved that laser assistance can yield up to 33% higher volumetric rate and up to 65% better dimensional accuracy. It has been also proved that laser enhances current efficiency during the machining process.