Asfana Banu

Dimensional accuracy of micro-electro discharge milling

This paper investigates the dimensional accuracy and tool wear rate (TWR) in micro electro discharge (micro-ED) milling of stainless steel (S304) workpiece and tungsten as the tool electrode with control parameter; voltage and feed rate. Dimensional accuracy is represented by the difference of micro-channel width between the two ends of the channel. The TWR and the micro-channel width data are analyzed and empirical model are developed. The optimum values for minimum TWR and minimum micro-channel width are found to be 91 V voltage and 10 μm/s feed rate.

Process Capability of High Speed Micro End-Milling of Inconel 718 with Minimum Quantity Lubrication

The demand for micro-parts is expected to grow and micro-machining has been shown to be a viable manufacturing process to produce these products. These micro-products may be produced from hard-to-machine materials such as superalloys under little or no metal cutting fluids to reduce machining cost or drawbacks associated with health and environment. This project aims to investigate the capability of micro end-milling process of Inconel 718 with minimum quantity lubrication (MQL). Microtools DT-110 multi-process micro machine was used to machine 10 micro-channels with MQL and 10 more under dry condition while maintaining the same machining parameters. The width of the micro-channels was measured using digital microscope and used to determine the process capability indices, Cp and Cpk. QI Macros SPC for Excel was used to analyze the resultant machining data. The results indicated that micro end-milling process of Inconel 718 was not capable under both MQL and dry cutting conditions as indicated by the Cp values of less than 1.0. However, the use of MQL helped the process to be more stable and capable. Results obtained showed that the process variation was greatly reduced by using MQL in micro end-milling of Inconel 718.

Micro Electro Discharge Machining of Non-Conductive Ceramic

Electro discharge machining (EDM) as a die sinking process has taken off in 1943. Since then it was known as a non-conventional machining process and its application was limited for processing only electrically conductive materials. Later on, due to the widespread applications, this EDM process is considered conventional as usual. However, in the recent years EDM has gone through considerable changes especially with dielectric fluids, simple to complex geometry, meso to micro sized structures, nanometric surface finish, and so on. In addition, the application of EDM has also been extended for processing electrically semi-conductive and non-conductive materials like ceramics and composites. This paper discussed micro electro discharge machining of non-conductive ceramic materials. It includes detail process development, modelling of material removal rate and surface finish which include the effect of multi spark and random spalling conditions.

Precision Control of Kerf in Metal Cutting Using Dry Micro WEDM: Issues and Challenges

Micro dry wire EDM is a process where gas is used as the dielectric fluid instead of a liquid. In this process certain modifications of a wire EDM are needed during the machining operation to achieve stable machining. Optimizing kerf to get high dimensional accuracy is one of the critical issues in micro dry wire EDM. The fundamental modelling for optimum kerf using micro dry wire EDM has not been formulated yet. Due to the complex phenomenon, the prediction of optimum kerf in a micro dry wire EDM process is rather difficult. Hence, the main objectives of this research are to improve the micro dry wire EDM process and to develop mathematical models for optimum kerf using micro dry wire EDM. During the process improvement of micro dry wire EDM, various machining setup will be involve in order to achieve the most stable process. The most stable machining process will be used to prove the developed mathematical models. A mathematical relationship between kerf and process parameters is anticipated. The mathematical models in conjunction with experimental data will eventually produce the desired theory. The developed process and mathematical model of kerf is a breakthrough in fabricating products such as micro tools, molds etc. with optimum kerf and high dimensional accuracy. The successful completion of this research will contribute to the environmental friendly micromachining process.

Investigation of Accuracy in Microdrilling with Minimum Quantity Lubrication

Cutting fluid plays an important role in machining processes to achieve dimensional accuracy, reduce tool wear, and improve tool life. Use of flood cooling conventionally used in machining is not cost effective and consumption of huge amount of cutting fluids is not health and environmental friendly. Therefore, one of the alternatives is to use minimum quantity of lubrication (MQL) in machining process. MQL is eco-friendly and has economical advantage on manufacturing cost. Study of the effects of MQL on burrs and aspect ratio should be carried out because burrs and aspect ratio are important issues in microdrilled parts used as microfluidic channels in bio-medical applications. In case of micromachining, flood cooling is not recommended to avoid any possible damage of the microstructures. As a result alternative solutions are sought. This paper investigates and compares burrs and aspect ratio in dry microdrilling and microdrilling with the presence of MQL on aluminium alloy 1100. The relationship among tool diameter, feed rate, and spindle speed on the area affected by burrs and drilled hole aspect ratio are analysed. The values of aspect ratio for both conditions show that there is slight improvement on aspect ratio in MQL over dry drilling. MQL has significant influence on affected area by burrs. It is observed that low spindle speed, high feed rate, and bigger drill diameter should be used along with MQL to reduce burrs.

Investigation of Kerf in Micro Wire Electro Discharge Machining

Precision and accuracy are among those of the most important factors in the field of machining processes. Micro wire electro discharge machining (micro-WEDM) is used widely in the machining process to fabricate micro parts with high precision and accuracy. However, in micro-WEDM, minimal kerf remains as a critical issue. This paper investigates the kerf in micro-WEDM of stainless steel (S304). Experimental investigation is carried out with 70 μm diameter tungsten electrode wire with two varying parameters voltage and capacitance. The kerf data are analyzed and an empirical model is developed using Design Expert software. The optimum parameters for minimum kerf are found to be 10nF capacitance and 90V voltage.

High Aspect Ratio Micro-EDM Drilling with Nano Surface Finish

This paper presents the issues related to high aspect ratio in micro drilling on metallic materials using micro electro discharge machining (Micro-EDM). Experimental investigation is carried out by drilling high aspect ratio micro holes on copper workpiece with 1 mm diameter tungsten carbide tool electrode using micro-EDM DT 110 with two varying parameters voltage and capacitance. For the measurement and observation of aspect ratio, roundness, and surface roughness were performed by scanning electron microscope, optical microscope, and WYKO NT1100 optical profiler respectively. The purpose of this paper is to achieve high aspect ratio, accurate roundness, and low surface roughness with the minimum wear of tool electrode within machining time. The data were analyzed by Design Expert software. Emperical models for aspect ratio, roundness, and surface roughness are developed. The analysis revealed that the most influential parameter is capacitance. Multiple optimization of responses showed that the optimum parameter values are 90 V gap voltage and 0.26 µF capacitance which provide 2.4 aspect ratio, 44 µm roundness, and 6.0 µm Ra surface roughness. The desirability achieved by optimization is 73.9%. The models are validated by experiments.